WO2013107764A1 - Ink-jet recording material - Google Patents

Description

 Ink jet recording material

The present invention relates to an ink jet recording material, as shown in its basic structure in Figure 1, comprising at least:

^■ a flat substrate (1) having a front (a) and a front (a) opposite rear side (b),

^■ an undercoat (2), positioned above the front side (a) of the substrate (1) and / or below the rear side (b) of the substrate (1),

^■ an upper coating (3), positioned above the at least one undercoat (2) on sides of the front face (a) of the substrate (1) and / or below the at least one sub-coating (2) on the side of the back (b) of the substrate (1 ).

The invention also relates to a method for producing such an ink jet recording material.

Inkjet recording materials, especially those with a paper substrate, are well known in the art.

For the most part, the known ink jet recording materials have a multi-layered coating, which is then formed, for example, of at least one or more ink-receiving layers and at least one protective layer, wherein the at least one protective layer is formed over the at least one ink-receiving layer. Quite often, an intermediate layer connected to the ink-receiving layer is additionally provided directly on the substrate.

The essential components of the known ink receiving layers are inorganic pigments and binders, of which as pigments in particular silica and the hydroxides and oxides of aluminum and as a binder polyvinyl alcohol are widely used.

An ink-jet recording paper having an ink-receiving layer and a topsheet covering the ink-receiving layer is known from EP-A-0 806 299. While the ink-receiving layer contains no pigments, the top layer comprises inorganic pigment particles, in which case, for example, aluminum hydroxide of the boehmite type with a pore structure is used. Radius distribution of 10 to 35 Ängström, corresponding to 1 to 3.5 nm, is listed. The substrates used are in particular baryth-coated or polyolefin-coated papers.

DE-A-19 952 356 also describes an ink jet recording paper having a plurality of coating layers. The known paper has on at least one side of its support as a first layer an ink-receiving layer with fine inorganic particles and a binder resin. The ink-receiving layer is then coated or impregnated with a coating liquid in the form of a topcoat and then dried. The coating liquid contains at least one specific tetraalkoxy titanium dissolved in an organic solvent.

 As the inorganic particles in the ink-receiving layer, it is possible to use, among others, those of synthetic amorphous silica, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, aluminum hydroxide, alumina and alumina hydrate (pseudoboehmite sol) alone or in combination of two or more. As preferred, the use of alumina hydrate or colloidal silica as fine inorganic particles is described, with an alumina hydrate having a pseudoboehmite structure being particularly preferred.

EP-A-0 732 219, which is considered as the closest prior art, proposes a printing medium in which an ink-receiving layer, which in turn is covered by a surface layer, is provided on a liquid-absorbent paper base material. While the ink-receiving layer comprises a binder and a cationic substance, the surface layer is intended to contain cationic ultrafine particles of alumina or alumina hydrate having a particle diameter in the range of 1 nm to 500 nm. For the surface layer, a gloss of 45% or more at a viewing angle of 75 ° is disclosed.

 As inorganic pigments of the ink-receiving layer, among a variety of other pigments, there are mentioned, inter alia, alumina and alumina hydrate. In addition, organic particles may still be present. As a suitable range for the particle sizes are 0.1 to 20 microns, corresponding to 100 to 20,000 nm.

EP-A-0 803 375 discloses a recording material, in particular for ink-jet printing, whose porous recording layer applied to a substrate contains not only nonionic or cationic water-insoluble resin particles but also aluminum oxide hydrate particles, in which case boehmite having a secondary particle size of from 100 to 200 nm is preferred. In the production of the recording layer, their drying takes place in contact with a smooth surface. Optionally, the recording layer may be covered with a silicon dioxide layer to improve the scratch resistance.

[0010] EP-A-0 810 101 discloses a recording material having a porous ink-receiving layer which may contain both the pure hydroxides of aluminum and pure alumina, including boehmite alumina hydroxide wherein the microcrystals of the alumina hydroxide are in one certain degree of parallelism. One of its objects is that invention to provide a high gloss recording material. By way of example, values in the range from 51% to 68% are mentioned.

From EP-A-0 875 394 it is known to treat aluminum oxide hydroxide with the rare earth salts and to use it for the production of the recording layer of an ink jet recording material.

Finally, a recent proposal according to EP-A-1 512 544 provides for the addition of polynuclear aluminum hydroxo complexes to nanocrystalline inorganic compounds contained in the recording layer for the purpose of improving the shelf life and increasing the printing speed of ink jet recording materials. These compounds, which according to the statements in this document are to have a pore volume of> 20 ml / 100 g, are particularly preferably pseudoboehmite and silicon dioxide having a particle size of not more than 20 nm. In addition to the nanocrystalline, nanoporous inorganic compounds, others may be used , as defined above, non-nanoporous nanocrystalline inorganic inorganic compounds may be included in the recording layer. In addition to one or more recording layers disclosed, that invention also contemplates auxiliary layers. In particular, polyester films are proposed as suitable substrates and, if paper is considered, preferably baryta-coated or polyolefin-coated paper. Uncoated papers of various types may also be used, but their composition and properties are not specified. At this point it is merely stated that they can vary greatly.

The objectives of the known from the prior art recording materials are mostly aimed at the high-price sector with very high surface standards, which is explained by the fact that due to the rapidly increasing digital photography a growing demand for high-quality print media for multicolor photo printing has arisen , In addition, however, there is also an increasing demand for such inkjet recording materials which find use, for example, in everyday business life, which means that they have to be less expensive to produce than the print media for digital photography mentioned above, but on the other hand have a much higher quality standard as, for example, the still widely used plain copying papers. In the present case, the higher quality standard, which is obviously also visible, in direct comparison with plain copy paper, is in particular a silk-matt surface. Furthermore, the ink jet recording materials to be used successfully in business should be printable at very high printing speeds by means of inkjet printers and in parallel also in offset printing. The area of application "business area" demands in any case for rather subdued costs, which are appropriate for the operational area. This requires both the quantitative use of raw materials to limit as well as to minimize manufacturing costs.

The well-known from the prior art multistage process for the application of a variety of layers are opposed to this goal as well as the use of high-priced materials that often require a costly preparation prior to their processing.

The object of the present invention is to provide the public with an ink jet recording material which meets the above-mentioned requirements and in particular comprises:

 a sufficient resistance of the ink-jet print image to moisture and water, which is of vital importance for the intended area of application "business area",

 - a silk-matt appearance,

 - good value for money and

 - A high-speed printability by means of inkjet printers and in parallel also in offset printing.

The object is achieved, according to the inventors, with an ink jet recording material, at least comprising:

A planar substrate (1) having a front side (a) and a rear side (b) opposite the front side (a), A sub-coating (2), positioned above the front side (a) of the substrate (1) and / or below the rear side (b) of the substrate (1),

 An upper coating (3) positioned above the at least one undercoating (2) on the side of the front side (a) of the substrate (1) and / or below the at least one undercoating (2) on the side of the back side (b) of the substrate (1 )

the inkjet recording material proposed hereby being characterized in that

 both the at least one undercoat (2) and the at least one top coat (3) each have an inorganic pigment,

 the at least one sub-coating (2) also has an organic hollow-body pigment in addition to the inorganic pigment.

In order to produce such an ink jet recording material, a novel process for the production of an ink jet recording material is proposed in an inventive manner, the process comprising at least the following process steps:

 (i.) preparing a first coating composition, said first coating composition comprising at least:

 a first inorganic pigment,

 an organic hollow body pigment.

 (ii.) preparing a second coating composition, said second coating composition comprising at least one second inorganic pigment.

(iii.) forming a planar substrate (1) having a front side (a) and a rear side (b) opposite the front side (a),

 (iv) applying the prepared first coating composition to form a subcoating (2), positioned above the front side (a) of the substrate (1) and / or below the back side (b) of the substrate (1),

 (v.) drying the first coating composition,

 (vi.) applying the prepared second coating composition to form a topcoat (3) positioned above the at least one undercoating (2) on the front (a) side of the substrate (1) and / or below the at least one undercoating (2) Sides of the back side (b) of the substrate (1),

(vii.) drying the second coating composition. The method steps (iii.) To (vii.) Disclosed above can, for example and in the context of a first preferred variant, be executed in exactly this order. Absolutely conceivable and insofar as a preferred variant is to combine process steps,

 for example, the method steps (iv.) and (vi.) for one side (a, b) of the substrate (1),

 - And as then, for example, the process steps (v.) And (vii.) Each for one side (a, b) of the substrate (1).

The inventive method initially provides the training and the provision of a flat substrate (1) with a front side (a) and one of the front side (a) opposite back (b) before. Such a planar substrate (1) may be a plastic film preferably with a further coating facilitating corona coating. For the purposes of the present invention, very particular preference is given to paper, for example an untreated base paper, as a flat substrate (1).

The formation of paper as a sheet substrate (1) is done for example and in a preferred embodiment on a paper machine in which in at least one upstream Mischbütte a paper pulp of different pulps, optionally groundwood, fillers and water is applied and where to this Paper pulp before being fed to the paper machine prefers further constituents, for example resin glue for engine sizing, as well as other customary additives, such as pigments, shading dyes and / or optical brighteners. Thus prepared is then an untreated base paper as a sheet substrate (1) before. In one possible embodiment, the paper as a flat substrate (1) before its application with the generic term to be provided undercoat (2) and top coat (3) nor a surface sizing on at least one preferably on both sides (a, b).

[0022] According to the invention, the method proposed here provides for the preparation of a first coating composition, this first coating composition comprising at least

 a first inorganic pigment,

an organic hollow body pigment. As the first inorganic pigment, precipitated calcium carbonate is considered to be preferred, either or particularly preferably being included as the sole pigment in the first coating composition or in combination with further inorganic pigments, especially selected from the list, comprising kaolin and silica dioxide. In the case of a combination of precipitated calcium carbonate with further inorganic pigments, it is preferable to set a ratio based on% by weight (calcium carbonate: further inorganic pigments) in a range from 4: 1 to 10: 1. Likewise, it is absolutely essential, within the first coating composition, to have a ratio by weight (inorganic pigment: organic hollow body pigment) in a range of 19: 1 to 2: 1, more preferably in a range of 1: 5 : 1 to 4: 1 or more restricted in a range of 1 1, 5: 1 to 6.5: 1 set. In this case, as stated above, that inorganic pigment may be formed either exclusively by the precipitated calcium carbonate or by a combination of precipitated calcium carbonate with further inorganic pigment. The preferred ratio ranges disclosed above are intended to apply both to the first coating composition prepared for application and to the at least one undercoat (2) formed therefrom.

Further constituents of the first coating composition include:

- crosslinker,

 - defoamer,

 - Nuancierfarbstoffe,

 Ink fixative,

 which are all to be integrated according to individual needs in the first coating composition, and

 - In particular, binders selected from the list, comprising: polyvinyl alcohol, partially or fully saponified, starch, gelatin, polyacrylates, Vinylestermischpolymere, Polyvi- nylacetatmischpolymere, polystyrene-butadiene latices and cellulose derivatives. These binders can be incorporated alone or else, and preferably in combination with one another, into the first coating composition, with a combination of polyvinyl alcohol with a further binder in particular being considered to be very particularly preferred.

The application of the prepared first coating composition for forming a subcoating (2) on the front side (a) and / or on the back side (b) of the planar substrate (1) is preferably carried out by means of a coating apparatus selected from the list, including curtain coater and spray coater, film press and roller applicator, air brush coater, knife and roller blade coater. In the context of the invention proposed here, the curtain coater is very particularly preferred both in its design as a slot caster and in its embodiment as a sliding surface caster.

Drying of the first coating composition for forming a subcoating (2) on the front side (a) and / or on the back side (b) of the planar substrate (1) is usually carried out by a method in which heat is supplied, as happens by hot-air floatation dryer or contact dryer, usually in the form of drying cylinders. Proven is also a combination of the listed dry processes. The ink jet recording material proposed on this side then has a respective surface-related mass, preferably from 2 to 15 g / m ² and very particularly preferably from 6 to 10 g / m ^2, with respect to the undercoat (2) applied on one or both sides.

According to the invention, the method proposed here provides for the preparation of a second coating composition, this second coating composition comprising at least one second inorganic pigment. This second inorganic pigment is preferably aluminum hydroxide, which is either and very particularly preferably included as the sole pigment in the second coating composition or in combination with other inorganic pigments, in particular selected from the list, comprising silicon dioxide and in particular pyrogenic silica. In the case of a combination of aluminum hydroxide with further inorganic pigments, it is preferable to set a ratio based on% by weight (aluminum hydroxide: further inorganic pigments) in a range from 3: 1 to 8: 1. The preferred ratio range disclosed above is intended to apply both to the second coating composition prepared for application and to the at least one top coating (3) formed therefrom.

Other components of the second coating composition include:

 - crosslinker,

 - defoamer,

 and

- In particular binders selected from the list, comprising: polyvinyl alcohol, partially or fully saponified, but also: starch, gelatin, polyacrylates and styrene-acrylate Copolymers, polyvinyl acetate mixed polymers, polystyrene-butadiene latexes and cellulose derivatives. These binders may be incorporated alone or else, and preferably in combination with one another, into the second coating composition, with a combination of polyvinyl alcohol with a further binder in particular being considered to be very particularly preferred.

Applying the prepared second coating composition for forming an upper coating (3) on the at least one sub-coating (2) on the front side (a) of the substrate (1) and / or below the at least one sub-coating (2) on the side of Back side (b) of the substrate (1) is preferably done by means of a coating device selected from the list comprising curtain coater and spray coater, film press and roller applicator, air brush coater, doctor blade and roller doctor coater. In the context of the invention proposed here, the curtain coater is very particularly preferred both in its design as a slot caster and in its embodiment as a sliding surface caster.

The drying of the second coating composition for forming an upper coating (3) on the at least one sub-coating (2) on the side of the front side (a) of the substrate (1) and / or below the at least one sub-coating (2) on the back side (B) of the substrate (1) is usually done by a method in which heat is supplied, as is done by hot-air floating dryer or contact dryer, usually in the form of drying cylinders. Proven is also a combination of the listed dry processes. It represents a possible variant of the presently proposed method for producing an inkjet recording material, when the drying of the first coating composition to form a subcoating (2) and the drying of the second coating composition to form an upper coating (3) occur simultaneously and thus sub and top coating ( 2, 3)

 for example, wet-on-wet by means of two successive process steps (iv., vi.)

 or alternatively

- At the same time by means of a combined process step (iv. + vi.) Implemented very particularly preferably by means of a Gleitflächengießers be applied with multiple coating head. With regard to the topcoat (3) applied on one or both sides, the inkjet recording material proposed here has a respective basis-related mass of preferably from 1 to 15 g / m ² , further limited from 3 to 8 g / m ² and very particularly preferably from 4 to 6 g / m ² on.

In order to meet the requirements for a semi-matt appearance of the ink jet recording material proposed herein, the ink jet recording material having the sheet substrate (1), the at least one undercoat (2) and the at least one top coat (3) preferably undergoes calendering a surface compaction with concomitant friction to provide gloss on the underside (2) and topcoat (3) side in a most preferred range of 10 to 40%, and most preferably in the range of 20 to 40% as measured by Tappi 450 or ISO 2813 with a 60 ° angle of reflection.

When smoothing with concomitant friction is very particularly preferably a calender with at least one press nip used, in which one pressing surface has a high hardness, while the other pressing surface is formed elastically. If the ink-jet recording material proposed here carries only one undercoat (2) and one top coat (3) on one side, this side with top and bottom coat (2, 3) is preferred for contacting the press face with high hardness. It is a most preferred embodiment of this method of making an ink jet recording material, when at least one of the two pressing surfaces - most preferably the high hardness pressing surface, ideally formed as a heatable press roll - has a surface temperature in a range of 50 ° C to 200 ° C, further limited in a range of 90 ° C to 135 ° C, and most preferably in a range of 95 ° C to 1 15 ° C. Also, a preferred compression pressure in a range of 60 kN / m to 220 kN / m, most preferably in a range of 100 kN / m to 140 kN / m and more particularly in a range of 1 10 kn / m to 135 kn / m proved particularly suitable. If, by means of the method proposed here, an inkjet recording material is produced which has both an undercoating (2) and an uppercoating (3) on both sides, it is particularly preferred if

- Both the front (a) of the substrate (1) with undercoating (2) and upper coating (3) undergoes a smoothing with concomitant friction, in which this front of the Inkjet recording material gets in contact with a heated pressing surface with high hardness,

 - As well as the back (b) of the substrate (1) with undercoat (2) and topcoat (3) undergoes smoothing with concomitant friction, in which this back of the inkjet recording material gets in contact with a heated pressing surface with high hardness.

 It is possible that in the process only a calender is used that is used twice by means of two machine runs, it is equally possible and is particularly preferred if the method two calenders are used, which is a smoothing with smoothing concomitant friction of front side (a) of substrate (1) with undercoating (2) and topcoating (3), the other smoothing unit with smoothing friction from back side (b) of substrate (1) with undercoating (2) and topcoating (3 ).

The friction during smoothing results on the one hand already by the walking of both the recording material and the elastic pressing surface in the middle of the press nip in contact with the hard pressing surface, the friction can be further increased by a moderate speed difference between recording material and hard pressing surface in the press nip.

The information given in the description and claims for basis weight,% by weight (% by weight) and parts by weight (parts by weight) are based on the "atro" weight, ie, absolutely dry parts by weight In the comments on the organic pigments, the relevant figures are based on the "lutro" - weight, ie air-dry parts by weight, minus the proportion by weight of water around and inside the pigments in their form of delivery.

The invention will be further clarified by means of the following example according to the invention:

To form a paper web as a flat substrate (1) for an inkjet recording material proposed on this side, a paper pulp of eucalyptus pulp and other pulp fibers with fillers and water is applied in a mixing chest. Further constituents of the pulp to be added are rosin size for engine sizing with an amount of 0.6% by weight (atro), based on the total weight of the pulp, and other customary additives. fe, such as pigments and / or optical brighteners. After completion of the pulp this is then fed to a fourdrinier paper machine, where it is processed into a paper web with a basis weight of 69 g / m ² .

To form a first coating composition, a formulation with the following main components is used:

The first coating composition is applied to the substrate (1) both front and back on the substrate (1) using a curtain coater as a slot caster to form an undercoating (2), each having a basis weight of 8.0 when dry g / m ² for the undercoating (2) is measured. Then, the second coating composition for forming a top coat (3) is applied here only on the undercoat / (2) previously applied to the front side of the substrate (1) by using a curtain coater as a slot caster Drying a surface mass of 6.0 g / m ² for the top coat (3) is measured. The recording material thus prepared is carried out by a calender with a press nip at set line pressure of 120 kN / m, the one press roll elastic and the other press roll are hard and heatable. The latter has a heated surface temperature of 100 ° C. in the press nip, which is brought into contact with the side of the ink jet recording material to be smoothed, which has both lower and upper coating (2. 3). In the ink jet recording material prepared as described above, a gloss value of 30% can be determined on the side having both the undercoat and topcoat (2, 3) measured according to Tappi 450 or ISO 2813 with a reflection angle of 60 ° , At the same time, such an ink jet recording material has a good resistance to moisture and water of the ink jet print image, and is printable at high speed by ink jet printers and also by offset printing. The tasks could be fulfilled so well.

Terms list:

 (1) Substrate

 (a) Front side of the substrate (1)

(b) Back side of the substrate (1)

(2) Undercoating

 (3) top coat

Claims

Claims 1.) An ink jet recording material comprising at least:  A planar substrate (1) having a front side (a) and a rear side (b) opposite the front side (a),  A sub-coating (2), positioned above the front side (a) of the substrate (1) and / or below the rear side (b) of the substrate (1),  An upper coating (3) positioned above the at least one undercoating (2) on the side of the front side (a) of the substrate (1) and / or below the at least one undercoating (2) on the side of the back side (b) of the substrate (1 ), characterized in that  both the at least one undercoat (2) and the at least one top coat (3) each have an inorganic pigment,  the at least one sub-coating (2) also has an organic hollow-body pigment in addition to the inorganic pigment. 2.) An ink jet recording material according to claim 1, characterized in that the ratio by weight of inorganic pigment: organic hollow body pigment in the at least one sub-coating (2) in a range of 19: 1 to 2: 1. 3.) An ink jet recording material according to claim 1, characterized in that the ratio by weight of inorganic pigment: organic hollow body pigment in the at least one sub-coating (2) in a range of 1 1, 5: 1 to 4: 1. 4.) Ink jet recording material according to one of the claims 1 to 3, characterized in that the inorganic pigment of the at least one sub-coating (2) comprises precipitated calcium carbonate. 5.) An ink jet recording material according to any one of claims 1 to 4, characterized in that the inorganic pigment of the at least one top coat (3) comprises aluminum hydroxide. 6.) An ink jet recording material according to claim 5, characterized in that the upper coating (3) in addition to aluminum hydroxide comprises at least one further inorganic pigment. 7.) An ink jet recording material according to any one of claims 1 to 6, characterized in that the ink jet recording material at least on the side with the undercoat (2) and the top coat (3) has a gloss in a range of 10 to 40%, measured according to Tappi 450th or ISO 2813 with a 60 ° reflection angle. 8.) Ink jet recording material according to one of the claims 1 to 7, characterized in that the flat substrate (1) is an untreated paper base paper. 9.) A process for producing an ink jet recording material, the process comprising at least the following process steps:  (i.) preparing a first coating composition, said first coating composition comprising at least  a first inorganic pigment,  an organic hollow body pigment.  (ii.) preparing a second coating composition, said second coating composition comprising at least one second inorganic pigment.  (iii.) forming a planar substrate (1) having a front side (a) and a rear side (b) opposite the front side (a),  (iv) applying the prepared first coating composition to form a subcoating (2), positioned above the front side (a) of the substrate (1) and / or below the back side (b) of the substrate (1), (v.) drying the first coating composition,  (vi.) applying the prepared second coating composition to form a topcoat (3) positioned above the at least one undercoating (2) on the front (a) side of the substrate (1) and / or below the at least one undercoating (2) Sides of the back side (b) of the substrate (1), (vii.) drying the second coating composition. 10.) A process for producing an ink jet recording material according to claim 9, characterized in that the application of the prepared first coating composition for forming a sub-coating (2) by means of a curtain coater happens. 1) A method for producing an ink jet recording material according to any one of claims 9 and 10, characterized in that the application of the prepared second coating composition for forming an upper coating (3) by means of a curtain coater happens. 12.) A process for producing an ink jet recording material according to any one of claims 9 to 1 1, characterized in that the ratio by weight of inorganic pigment: organic hollow body pigment in the at least one sub-coating (2) in a range of 1 1, 5 : 1 to 4: 1. 13.) A process for producing an ink jet recording material according to any one of claims 9 to 12, characterized in that the inorganic pigment of the at least one sub-coating (2) comprises precipitated calcium carbonate. 14.) A process for producing an ink jet recording material according to any one of claims 9 to 13, characterized in that the inorganic pigment of the at least one top coat (3) comprises aluminum hydroxide. 15.) A process for producing an ink jet recording material according to any one of claims 9 to 13, characterized in that the ink jet recording material with the sheet substrate (1), the at least one undercoat (2) and the at least one top coat (3) by means of a calender to achieve a gloss on the side with the undercoat (2) and the top coat (3) in a range of 10 to 40%, measured according to Tappi 450 or ISO 2813 with a reflection angle of 60 °. 16.) A process for producing an ink jet recording material according to claim 15, characterized in that the calendering treatment comprises pressing the ink jet recording material with the planar substrate (1), the at least one undercoat (2) and the at least one top coat (3) at least between see two pressing surfaces provides, of which the one pressing surface has a surface temperature in a range of 50 ° C to 200 ° C.