EP0935695B1 - Paper with a layer for ink-jet printing - Google Patents

Abstract

A paper, particularly suitable for use in an ink-jet printing procedure, has a printing layer with a pigment mixture which, for 100 parts by weight of the total pigment mixture, has 10 to 30 weight % of an organic pigment made of amide resin, the rest being formed of inorganic pigment, and the binding agent consisting of a mixture of starch ether and polyvinyl alcohol.

Description

The invention relates to a paper with a applied to at least one of its sides Recording layer containing a Pigment mixture of organic and inorganic Pigment, binder and cationic auxiliary. Furthermore, the invention relates to a method for the production of the paper as well as the use.

Papers of the type specified above become Use as a print carrier for the so-called inkjet process (Inkjet printing process) used. An overview of the z. Currently usual Types of paper used for the various inkjet processes be used Hentzschel / Pelzer in the DE reference: Weekly paper production 18 (1996): "Improving the printability of inkjet papers by polyvinyl alcohol and others Components ". Accordingly, between the surface glued papers for the usual Office use and high quality painted Papers, especially for color prints be used, differentiated.

While with the simpler and for office use suitable varieties for pigmentation is dispensed with and as a surface sizing agent Starch, possibly cationic starch, is used, contain the coated papers in addition to pigment and binder a cationic additive.

DE-A-43 22 178 discloses as a binder Polyvinyl alcohol, polyvinyl pyrrolidone, Vinyl acetate homopolymer and / or vinyl acetate copolymer. One becomes a cationic substance quaternary ammonium compound indicated. As Amorphous silicas, clay and Zeolite revealed.

EP-A-0 514 633 describes a recording material for the inkjet process in which the recording layer contains polyvinyl alcohol, an amorphous silica with a large specific surface area, a particle size of 2 to 12 μm and a cationic polymer without crosslinking groups. Cationic polyamides, polyacrylamides or polyamines are disclosed as the cationic component. In addition to good print image quality, this known recording material is said to have improved light and water resistance.

The production of a primarily transparent recording sheet - using a plastic film as a coating carrier - is described in EP-A-0 671 282. Two layers are applied, of which the recording layer contains a hydrophilic binder and hollow spherical pigments or solid plastic particles as filler in the form of spheres with an average diameter of 0.1 to 50 μm . In addition, further fillers can be added in an amount of up to 60% by weight, with colloidal silicates, titanium dioxide, calcium carbonate, aluminum hydroxide and bright white types of clay being proposed.

As a cationizing agent in the EP-A-0 602 326 a quaternary salt compound of a dimethylamine-epichlorohydrin adduct suggested. With the specified cationic The aim is to create a paper for the connection To make that available even under inconvenient climatic conditions producing a satisfactory printed image. It will a variety of inorganic and organic Pigments revealed. As a binder both synthetic as well as natural binders specified u. a. also polyvinyl alcohol and Starch ether, but without specific instructions for mixing the individual pigment or Binder components are given. Examples are synthetic amorphous Silicon dioxide as pigment and polyvinyl alcohol or starch is disclosed as a binder.

A coating color is known from DE-A-195 34 327 Manufacture of an inkjet paper known for Solution to the problem is using a coating color high pigment concentration and relative to provide low viscosity, so that a well covering line can be applied can, in short, the generation of a satisfactory typeface guaranteed. As preferred binders are copolymers of Styrene-butadiene or styrene-acrylate with functional cationic groups and / or cationic polyvinyl acetates, cationic Polyvinyl alcohol and their copolymers are disclosed. In addition, starch, methyl cellulose, Hydroxymethyl cellulose, carboxymethyl cellulose, Alginates, proteins and polyvinyl alcohols, if necessary can also be used in cationic form. To the pigments suitable according to that document almost all in the field of paper coating usual pigments, such as. B. like and natural calcium carbonate, precipitated or pyrogenic silica, kaolin, calcined kaolin, Talc, titanium dioxide, but also organic Pigments such as B. melamine-formaldehyde resin, disclosed. If possible, pigment mixtures are disclosed, these relate to the mixing of calcium carbonate / calcium silicate hydrate, fumed silica / calcium carbonate, precipitated Silicic acid / calcium carbonate, kaolin / titanium dioxide. In addition to a mixture, the mixture of binders made of polyvinyl alcohol and cationic starch Mixture of cationic starch and cationic Plastic binder or a mixture of cationic starch / polyvinyl alcohol and cationic plastic binder disclosed. The The specified proportion of binder is 10 to 30 % By weight, based on pigment.

For the generation of typefaces with increased Storage stability is described in EP-A-0 739 747 Inkjet recording sheet proposed in the as pigment silicon dioxide and as Binder component in a proportion of 5 to 55 % By weight of a butadiene / styrene latex are used, which is 20 to 45% by weight of butadiene monomer should be preserved. As another binder polyvinyl alcohol is being considered.

While the simpler papers for office use, d. H. only surface-sized Papers, mostly easy to manufacture and are printable is the manufacture of the higher quality varieties, especially if it is for recording papers for multicolour inkjet printing acts, not completely without problems.

The DE literature reference discussed at the beginning: Wochenblatt für Papierfabrikation references in this context on the big Binder requirements due to the high specific Surface of silica, so when choosing a compromise of polyvinyl alcohol as a binder must be searched between a sufficient Pigment adhesion on the paper sheet and the Coating color viscosity. In this context is also used on failed attempts Cellulose derivatives and oxidatively degraded starch referred.

It has also been proposed for the Inkjet printing suitable recording papers the casting process. On the corresponding proposal can be found in the EP-A-0 634 283. What is known from this document Paper is said to have a high surface gloss, Surface smoothness and good inkjet recording properties feature. It's about it one applied to a base paper pigmented primer provided, the then coated with a cast coating layer being a polymer with a glass transition point of at least 40 ° C and by Polymerization of an ethylenically unsaturated Monomers is formed. A cationic substance is added to the pre-coat while the Cast coating layer in its simplest Embodiment only from the polymer, if necessary with the addition of the usual coating aids, consists. The admixture is also exemplary colloidal silicon dioxide for cast coating specified. From the addition of cationic substances according to this script, the cast coating layer becomes a less surface gloss and less Ink absorption expected.

Another time is an inkjet recording paper, that after one Cast coating process is produced in the EP-B-0 529 308. According to this script comes from calcium carbonate and silicon dioxide composite pigment for use, which in an amount of at least 50% by weight, preferably at least 80% by weight in the recording layer is present.

kontrollierte An- und Aufnahme insbesondere von wäßrigen Druckfarben,

kontrollierte Absorption der Druckfarben und gute Trennung der darin enthaltenen Farbstoffe und Dispergier- oder Lösemittel,

geringe Eindringtiefe der Druckfarben zur Erzielung hoher Farbdichte und -brillianz, Ausbildung der Bildpunkte mit glatten Begrenzungslinien und hohe Bildschärfe, kontrollierte schnelle Farbtrocknung und hohe Wischfestigkeit des Bildes.

The object of the present invention is to provide a paper with an inexpensive recording layer which is particularly suitable for use in multicolor inkjet printers and which fulfills the following requirements:

controlled acceptance and absorption, especially of aqueous printing inks,

controlled absorption of the printing inks and good separation of the dyes and dispersing agents or solvents contained therein,

low penetration depth of the printing inks to achieve high color density and brilliance, formation of the image points with smooth boundary lines and high image sharpness, controlled fast color drying and high smudge resistance of the image.

In particular, the task was also seen in to develop a recording layer under Recourse to those from the general area of

Paper coating known pigments and binders the waiver of those previously considered necessary, but cost-driving pyrogenic and precipitated Allows silicas.

Another object of the invention is Development of methods for applying the recording layer for the production of the invention Paper.

The existing task is accomplished by the invention a paper with at least one of his Sides of the recording layer applied, which is a pigment mixture of organic and inorganic Pigment, binder and cationic auxiliary contains, the recording layer is characterized in that the pigment mixture - based on 100% by weight of total pigment mixture - 10 to 30% by weight of an organic amide resin Contains pigment and 40 to 90 wt.% Talc and that Binder a mixture of starch ether and Contains polyvinyl alcohol.

The organic pigment preferably consists of Melamine-formaldehyde resin, urea-formaldehyde resin or a mixture of these organic pigments.

According to a further embodiment, the organic pigment has an internal pore volume of 1.5 to 4.5 cm ³ / g.

15% < 2 µm

47% < 5 µm

83% < 10 µm

98% < 20 µm

In addition to talc and amide resin as pigment components, the pigment mixture of the recording layer can contain, as further inorganic pigments, precipitated or very finely ground calcium carbonate, titanium dioxide, calcined clay, aluminum oxide, aluminum hydroxide, modified bentonite or a mixture of these pigments, an amount of more than 50% by weight % of these pigments should not be exceeded. In the context of the present invention, coarsely ground calcium carbonate, customary coating clay and satin white have proven unsuitable. A relatively coarse type with the following grain size distribution has proven suitable as a suitable talc:

15% <2 µm

47% <5 µm

83% <10 µm

98% <20 µm

As modified bentonites are under the Invention the three-layer silicates suitable as they disclosed in DE-A-44 38 305 and DE-A-44 38 306 are.

A proportion of binder in the Range from 35 to 70% by weight based on 100 parts by weight Total pigment mixture, proven.

Surprisingly, this makes the Recording quality not negatively affected and on the other hand arise despite the compared to State of the art higher proportion of binder, based on 100 parts by weight of pigment, so far none too high material costs because the share of inexpensive starch ether at the Binder mixture is relatively high. Preferably there is the binder mixture - calculated as Dry weight parts - from 12 to 25 parts by weight Polyvinyl alcohol and 88 to 75 parts by weight Starch ether. In particular, a mixture preferred, in which the proportion of polyvinyl alcohol in the range from 14 to 22% by weight and the proportion of Starch ether is in the range from 78 to 86% by weight.

Possibly. can the binder mixture in addition Starch ether and polyvinyl alcohol as others Component one or more latices contain. The latex portion should however less than 12% by weight, based on the Binder mixture.

An application weight of the recording layer in the range from 10 to 30 g / m ² and side has proven to be particularly suitable; in particular an application weight of 18 to 24 g / m ² and side is preferred.

Quaternary agents come as cationic aids Ammonium compounds into consideration, preferably Polydiallyldimethylammonium chloride (Polydadmac) and dimethyldistearylammonium chloride and Benzyldimethylstearylammonium chloride. Furthermore has quaternized polymethacrylate resin as proven suitable as it is called Polycat L 452 from the company CTP paper auxiliaries GmbH & Co. KG in Bobingen, Germany, will be produced. Suitable amounts are used in the range of 2 to 18 parts by weight / 100 parts by weight Pigment mixture (preferably 2 to 7 parts by weight).

For setting a wet abrasion resistant Surface of the recording layer can this in an expedient embodiment an aid contain for crosslinking the binder mixture. An addition of 0.1 to 3.5 has proven suitable % (Otro), based on pigment, proven. Ammonium zirconium carbonate is preferred and / or an epoxy resin is used. A suitable one Epoxy resin is specified in WO 95/05505.

As coating base paper for the order of Recording layer in particular comes full bulk glued base paper is used, in particular such a base paper that additionally a surface sizing, especially from starch in combination with a synthetic surface sizing agents, e.g. B. an acrylic styrene dispersion.

The process of producing the paper according to the invention has proven to be particularly suitable for the cast coating process, in particular a cast coating process in which an aqueous coating color is applied to the paper web, leveled and contacted with a heated high-gloss cylinder with simultaneous drying to form the recording layer. The aqueous coating slip preferably contains a pigment mixture which, based on 100% by weight of the total pigment mixture, contains 10 to 30% by weight of organic pigment consisting of amide resin and 40 to 90% by weight of talc and also a binder which comprises a mixture of starch ether and Contains polyvinyl alcohol. The production of the paper according to the invention is, however, not tied to the casting process described above; rather, the production can also be carried out by the re-wet method or the coagulation process.
The coating color according to the invention with the specified pigment and binder mixture can also be applied to a paper web, leveled by means of a knife coating device or a doctor blade, and then dried and calendered. In addition to the pigment mixture, binder mixture and cationic auxiliary agent provided according to the invention, the coating color for producing the recording layer can also contain other auxiliary agents such as optical brighteners, shading dye, dispersing and wetting agents, thickening aids and, in the case of production by the casting process, still releasing agents such as the stearates of Contain sodium and calcium and / or suitable oils. Defoamers and agents for regulating the pH can also be present. Overall, it is preferred that the auxiliaries be present in the coating in an amount of no more than 4 to 7 parts by weight, based on 100 parts by weight of total solid. The starch ethers known from WO 95/05505 can be used in the context of the present invention. Low-viscosity types with a high degree of hydrolysis are preferably used as polyvinyl alcohol.

Another option is to use a Film press with the one according to the invention coating components provided intended components on both sides of the paper web if necessary applied and then dried. The term film press is one Understand device in which the coating color first applied to transfer rollers and equalized there and the pre-dosed coating color then from the transfer rollers to the is applied to both sides of the paper web. The Predosing / leveling of the coating color can thereby both of knife coaters, of rotating squeegees or rotating Dosing rollers are made.

The paper according to the invention is used preferably for printing in an inkjet printer, especially in a multi-color inkjet printer.

The following examples illustrate the invention:

Production of the coating color example 1

An aqueous slurry of 78 parts by weight of talc and 22 parts by weight of a urea-formaldehyde pigment with a specific surface area of 20 m ² / g and an internal pore volume of 2.6 cm ³ / g is made using 17 parts by weight. Parts of a 20% Polydadmac solution are dispersed and then 127 parts by weight of a 24% solution of a hydroxypropyl starch ether with a degree of substitution of 0.07 and 45 parts by weight of a 20% solution of a low-viscosity polyvinyl alcohol with a high degree of hydrolysis are added.

18 parts by weight of a 35% calcium stearate dispersion and overall 10.3 parts by weight of a 10% solution optical brightener and shading dyes admitted. The coating color has after setting to a pH of 8.1 a solids content of 39% by weight.

Example 2

It becomes an aqueous pigment slurry produced, consisting of 81 parts by weight of talc and 19 parts by weight of a urea-formaldehyde pigment. About this slurry become 17.3 parts by weight of a 20% Polydadmac solution added. As a binder 131 parts by weight of those given in Example 1 Starch ether solution and 46 parts by weight of the in Example 1 indicated polyvinyl alcohol solution admitted. 19 parts by weight are used as the release agent a 35% calcium stearate and further 17 parts by weight of a 15% solution of optical brightener and shading dye. Finally, 21 parts by weight of a 20 % solution of quaternized polymethacrylate resin added. The finished coating color is on a solids content of 44.3% by weight and a pH set from 7.8.

Production of the recording paper Example 3

With the coating color specified in Example 1 or 2, a coating base paper with a basis weight of 55 g / m ² , which is fully glued in the mass and is provided with a surface preparation of starch, is coated on one side on a cast coating machine. The application weight is 25 g / m ² . The cast coating method used is the so-called direct method, in which the coating color is applied to the paper and the wet coating color is pressed against a heated high-gloss cylinder. A very smooth surface is achieved. The recording papers produced can be printed excellently in multicolor printing using the inkjet printing process.

Unless expressly stated otherwise, all weights refer to the otro weight, d. H. oven dry.

Claims (15)

1. Paper having a recording layer applied to at least one of its sides, which recording layer comprises a pigment mixture of organic and inorganic pigments, binder and cationic auxiliary, characterised in that the pigment mixture comprises - based on 100 % by weight total pigment mixture - from 10 to 30 % by weight organic pigment consisting of amide resin, and from 40 to 90 % by weight talcum, and the binder comprises a mixture of starch ether and polyvinyl alcohol.
2. Paper according to claim 1, characterised in that the organic pigment consists of melamine-formaldehyde resin, urea-formaldehyde resin or of a mixture of those organic pigments.
3. Paper according to either claim 1 or claim 2, characterised in that the organic pigment has an internal pore volume of from 1.5 to 4.5 cm³/g.
4. Paper according to either claim 1 or claim 3, characterised in that the recording layer comprises as a further inorganic pigment precipitated or finely ground calcium carbonate, titanium dioxide, calcined clay, aluminium oxide, aluminium hydroxide, modified bentonite or a mixture of those pigments in an amount not exceeding 50 % by weight - based on the total pigment mixture.
5. Paper according to either claim 1 or claim 4, characterised in that the recording layer comprises from 35 to 70 % by weight binder - based on 100 parts by weight of total pigment mixture.
6. Paper according to either claim 1 or claim 5, characterised in that the recording layer comprises a crosslinking agent for the binder.
7. Paper according to either claim 1 or claim 6, characterised in that the crosslinking agent is present in the recording layer in an amount of from 0.1 to 5 % by weight, based on pigment.
8. Paper according to either claim 1 or claim 7, characterised in that the crosslinking agent is selected from the group comprising ammonium zirconium carbonate and epoxy resin.
9. Paper according to any one of claims 1 to 8, characterised in that the recording layer is applied in an amount of from 10 to 30 g/m²/side.
10. Process for the production of a paper according to any one of claims 1 to 9, characterised in that the recording layer, which comprises a pigment mixture comprising - based on 100 % by weight total pigment mixture - from 10 to 30 % by weight organic pigment consisting of amide resin, and from 40 to 90 % by weight talcum, as well as a binder comprising a mixture of starch ether and polyvinyl alcohol, is applied by means of cast coating.
11. Process for the production of a paper according to claim 10, characterised in that an aqueous coating colour, which comprises a pigment mixture comprising-based on 100 % by weight total pigment mixture - from 10 to 30 % by weight organic pigment consisting of amide resin, and from 40 to 90 % by weight talcum, as well as a binder comprising a mixture of starch ether and polyvinyl alcohol, is applied to a paper web to form the recording layer, is evened and is brought into contact with a heated high-gloss cylinder while simultaneously being dried.
12. Process for the production of a paper according to any one of claims 1 to 9, characterised in that an aqueous coating colour, which comprises a pigment mixture comprising - based on 100 % by weight total pigment mixture - from 10 to 30 % by weight organic pigment consisting of amide resin, and from 40 to 90 % by weight talcum, as well as a binder comprising a mixture of starch ether and polyvinyl alcohol, is applied to a paper web, is evened by means of a knife coating device or a revolving doctor, is dried and is calendered.
13. Process for the production of a paper according to any one of claims 1 to 9, characterised in that an aqueous coating colour, which comprises a pigment mixture comprising - based on 100 % by weight total pigment mixture - from 10 to 30 % by weight organic pigment consisting of amide resin, and from 40 to 90 % by weight talcum, as well as a binder comprising a mixture of starch ether and polyvinyl alcohol, is applied to the paper web by means of a film press.
14. Use of a paper according to any one of claims 1 to 9 in an inkjet printer.
15. Use of a paper according to any one of claims 1 to 9 in a colour inkjet printer.