EP1126081B1 - Support for recording layers - Google Patents

Abstract

A support material comprises a raw paper that may be coated on at least one side with a synthetic resin, and the raw paper or the resin coating on the raw paper is provided at least on the front side with a pigment layer wherein the pigment layer contains at least about 5% by weight of a pigment with a narrow grain size distribution, whereby at least about 70% of these pigment particles feature a size of less than 1 mum and at least 40% by weight of these particles feature a grain size of 0.35 to 0.8 mum, or in that the pigment coating is a structured calcium carbonate, for example surface-modified, and both embodiments feature improved surface properties.

Description

The invention relates to a layer support for Recording materials, a method for the same Production and its use as a photographic Support and as a support for an ink jet recording material and a thermal Recording material.

Polyolefin coated photographic substrates usually consist of a glued base paper, the with polyolefin on both sides, usually by extrusion is coated.

The extrusion coating of paper creates the polymer surface depending on the Coating speed of crater-shaped disturbances, so-called pits. At high rotation speeds of the cooling cylinder can be in fine recesses the surface of the cooling cylinder enclosed Do not air bubbles before contact with the hot resin escape so that the trapped air only after the Coating the paper to form crater-shaped Wells on the polymer surface escape. This Surface defects have a negative impact on those of one Backing material required and for the image quality decisive surface properties such as gloss and Smooth out.

The surface can be improved by Increase in the amount of resin applied this measure is not sufficient for high extrusion speeds and also causes high material costs.

US 5 861 209 describes a pigment-coated Paper for gravure printing, being a pigment aragonitic precipitated calcium carbonate with a so-called bimodal particle size distribution used becomes. Through this pigment line, the so-called "missing dot performance" in engraving printing and the Ink absorption improved in this printing process become. US 5 312 484 describes a composite pigment made of titanium dioxide and at least one pigment extender a low refractive index. US 5,605,568 describes a modified calcium carbonate pigment for Coating paper for relief printing Offset printing and engraving printing. EP 0 296 866 A2 discloses a process for making a kaolin pigment with improved optical and Printing properties for coating paper. The US 6th 020 051 relates to an ink from an interference pigment and a water-soluble and / or water-dispersible Binder for printing on the back of for Papers provided with photo base paper bright golden lettering or logos. After this The paper is printed as with photographic Layers usually with a polyolefin resin coated. US 5 759 258 relates to a method for Recycling of mineral pigment fillers Papers.

EP 0 285 146 A2 proposes to suppress the Occurrence of pits before, a gas that is lighter than air and can escape through the extruded film to apply the cooling cylinder surface to the To displace air bubbles. The disadvantage of this, however, is the high technical effort.

US 4,994,357 proposes the pressure with which the polyethylene coated paper on the cooling cylinder is pressed to suppress the occurrence of pits to increase. Because of the high contact pressure is only a low production speed possible because at higher speeds the polyethylene from the paper can replace.

EP 0 952 483 A1 describes a photographic support (base paper), the polyethylene surface of which is of high quality and which is not impaired even by production at high extrusion speeds. For this purpose, EP 0 952 483 A1 proposes to provide the base paper with a layer containing clay, the amount of the clay not exceeding 3.3 g / m ² . A disadvantage of this carrier material is the insufficient adhesion between the pigment-containing layer and the polyethylene layer extruded thereon.

A uniform surface of the carrier material is not only for photographic recording materials from Importance. To get a photo-like look become more non-photographic in the production Recording materials, for example ink-jet papers, papers coated with polyolefin. A uneven or flawed surface of the Backing material is made up of shiny spots on the recorded image is noticeable and is therefore also at these recording materials undesirable.

It is therefore an object of the invention to provide a layer support for recording materials with more even, smoother Provide surface at low pits level that excellent cockle behavior has and at high Extrusion speeds can be coated with resin.

The object of the invention is also to solve problems in the To suppress adhesion of the resin layer on the base paper and a carrier material with high whiteness and To provide rigidity.

This task is solved by at least one one side coated with synthetic resin, containing one with at least one on the front Base paper provided with pigment layer, the Pigment layer at least 5 wt.%, Based on the Weight of the total pigment in the pigment layer, one Contains pigments with a narrow grain size distribution, at least 70% by weight of these pigment particles Have a size of less than 1 µm and at least 40 % By weight of these particles has a particle size of 0.35 to 0.8 μm have, the resin layer at least on the pigment layer is applied.

As far as ink jet applications are concerned, this will Task achieved by using a layer support, the one at least on the front with a pigment layer Raw paper, the pigment layer at least 5 % By weight, based on the weight of the total pigment in the Pigment layer, a pigment with a narrow Contains grain size distribution, at least 70% by weight these pigment particles have a size of less than 1 µm have and at least 40% by weight of these particles Have grain size of 0.35 to 0.8 microns. This Layer supports for an ink jet recording layer no resin layer (polyolefin layer) on the base paper on.

Preferably 50 to 80% by weight of the particles are present a grain size of less than 1µm 0.35 to 0.8 µm. The percentage of pigment with the narrow distribution can be 10 to 90% by weight, especially preferably 30 to 80% by weight of the total pigment of the Pigment layer.

Under a pigment with a narrow grain size distribution pigments with a Grain size distribution understood at least about 70% by weight of the pigment particles are smaller than has about 1 micron and at 40 to 80 wt.% This Pigment particles the difference between the pigment with the largest grain size (diameter) and the pigment of the smallest grain size is less than about 0.4 µm.

The layer supports according to the invention differ from the layer supports of EP 0 952 483 A1 by the use of a pigment with a specific particle size distribution or by the use of a selected surface-modified calcium carbonate. The layer support according to the invention is not subject to the restriction with respect to an upper limit of 3.3 g / m ^{2 of} the clay contained in the pigment layer. The pigment selection according to the invention achieves a number of surprising advantages.

So it was surprising that a much better one Adhesion of the polyolefin layer on the pigment layer of the Raw paper is achieved as in EP 0 952 483 A1. The Roughness values and thus also the smoothness of the Layer supports have been improved. Compared to EP 0 952 483 A1, consequently the roughness probably due to liability problems the value of 0.5µm should not fall below, a good one according to the invention Adhesion even with roughness of less than 0.5 µm reached.

The extrusion coating was able to increase without Liability problems or increasing the level of pits too at high speeds of up to 600 m / min 200 to 250 are currently common m / min. At the same time there was a saving in polyolefin achieved from 15 to 30%.

The pigment can be selected from the groups of metal oxides, silicates, carbonates, sulfides and sulfates. Kaolins, talc, calcium carbonate and / or barium sulfate are particularly suitable. Calcium carbonate with ad _50% value of approximately 0.7 μm, for example, has proven to be particularly advantageous. According to a further preferred embodiment, a pigment mixture of calcium carbonate and kaolin (clay) is used. The mass ratio calcium carbonate / kaolin is preferably 30:70 to 70:30. Surprisingly, it was found that, despite the high proportion of the kaolin which tends to yellow, only an insignificant negative effect on the whiteness of the support was observed. The surface of the calcium carbonate in the pigment layer can be modified with a platelet-shaped inorganic substance.

As a binder in the pigment layer in the Paper industry usual natural and synthetic Polymers are used. Are particularly suitable such as starch, gelatin, styrene / butadiene latex, Styrene / acrylate latex, polyvinyl alcohol or their Mixtures. It turned out to be particularly well suited Mixture of starch and styrene latex in a ratio from 2: 1 to 1: 2.

The mass ratio pigment / binder in the Pigment layer is 30:70 to 90:10, in particular 85:15.

The pigment-containing layer between the base paper and resin can be applied to the base paper as a single layer or in multiple layers. The coating composition can be applied with all customary application units, the amount being chosen so that after drying the application weight per layer is at most 20 g / m ² , in particular 8 to 17 g / m ² .

In a special embodiment of the invention, the base paper is provided with an additional pigment-containing preliminary layer before it is coated with the pigment layer according to the invention. All common white pigments, such as precipitated calcium carbonate, titanium dioxide, kaolin, talc or barium sulfate with a particle size of 0.1 to 10 μm, in particular 0.1 to 2 μm, are suitable as the pigment. The application weight of the preliminary layer must not exceed about 20 g / m ² . The pigment layer according to the invention is preferably applied only after the preliminary layer has dried.

All types are suitable for the production of the base paper of cellulose fibers as well as synthetic fibers. For the Sizing is suitable for all known in the paper industry Sizing agents and wet strength agents. The base paper can Pigments and fillers such as kaolin, calcium carbonate or Titanium dioxide and other auxiliary substances such as defoamers, contain optical brighteners and dyes.

The base paper can be produced on a Fourdrinier or cylinder paper machine. The basis weight of the base paper can be 50 to 250 g / m ² , in particular 80 to 170 g / m ² .

A less qualitatively high-quality paper can also be used for the production of the layer support according to the invention, for the production of which, for example, recycled cellulose fibers were used. The base paper can be used in uncompressed or compacted form (smoothed). Uncompressed base papers with a density of less than 0.9 g / cm ³ are particularly suitable in terms of saving material costs

The surface of the pigment layer according to the invention is coated with a synthetic resin, for example polyolefin such as polyethylene, polypropylene or polybutene, and with copolymers of two or more olefins by extrusion. Low-density polyethylene types (LDPE), high-density polyethylene types (HDPE), ethylene / α-olefin copolymers (LLDPE) and mixtures thereof are particularly suitable. The polymer layer can contain white pigments such as titanium dioxide and other auxiliaries such as optical brighteners, dyes or dispersing agents. The application weight of the polymer layer is 5 to 30 g / m ² , in particular 10 to 25 g / m ² . It was found that a comparable pit level is achieved even with a reduction in the application weight of 15 to 30%. The polymer layer can be extruded in one layer or coextruded in multiple layers.

In a preferred embodiment of the invention the back of the base paper with a clear, i.e. pigment-free polyolefin, especially polyethylene, coated. The back of the carrier material can also further functional layers such as antistatic or anticurl layers exhibit.

The layer support according to the invention can be used as a support for photographic emulsions, ink jet recording layers and for recording layers for so-called thermal Dye transfer process (D2T2) can be used.

The following examples are provided for further explanation the invention.

Examples Examples 1 to 10

A photographic standard base paper with a basis weight of 162 g / m ^{2 was used} , which was made from a pulp suspension containing 100% by weight of hardwood sulfate pulp as well as 0.5% by weight of alkyl ketene dimer and 0.7% by weight of polyamide-polyamine-epichlorohydrin resin and was surface-sized with oxidized starch.

The base paper was used in an uncompressed form, ie not smoothed, and had a density of 0.84 g / cm ³ .

Various coatings according to the invention were applied to this base paper with the aid of a “bent blade” application unit and dried. The compositions of the pigment layers produced are shown in Table 1. component 1 2 3 4 5 6 7 8th 9 10 CaCO ₃ (d _50% = 0.7 µm) 30 30 30 100 - - 30 50 - 70 Modified CaCO ₃ - - - - - - - - 30 - Kaolin 1 70 70 70 100 - - - 70 30 Kaolin 2 - - - - - - 70 - - - talc - - - - - 100 - 50 - - Styrene / butadiene latex 8th 8th 8th 8th 8th 8th 8th 8th 8th 8th Strength 6 6 6 6 6 6 6 6 6 6 calcium stearate 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 Application weight g / m ² 5 11 17 10 10 10 10 10 10 10

Examples 11 to 18

The base paper used in Example 1 was in-line with Using a film press with the coating according to Example 1 coated and dried. The

Application weight was 10 g / m ² . The compositions of the pigment layers produced are shown in Table 2. component 11 12 13 14 15 16 17 18 CaCO ₃ (d _50% = 0.7 µm) 30 70 100 - - 30 50 - Modified CaCO ₃ - - - - - - - 30 Kaolin 1 70 30 100 - - - 70 Kaolin 2 - - - - 70 - - talc - - - - 100 - 50 - Styrene / butadiene latex 8th 8th 8th 8th 8th 8th 8th 8th Strength 6 6 6 6 6 6 6 6 calcium stearate 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 Application weight [g / m ² ] 10 10 10 10 10 10 10 10

Example 19

The base paper used in Example 1 was first coated "in-line" with the aid of a film press with a coating solution containing 30% by weight of a conventional calcium carbonate. The application weight was 12 g / m ² . After drying, a pigment layer according to Example 1 (Tab. 1) was applied in the next step with an application weight of 10 g / m ² .

The base papers coated according to Examples 1 to 19 were mixed with a mixture of 72% by weight of a low density polyethylene (LDPE, 0.923 g / cm ³ ), 15% by weight of a titanium dioxide masterbatch (50% by weight LDPE and 50% by weight). % TiO ₂ ) and 13% by weight of other additives such as optical brighteners, calcium stearate and blue pigment with different application weights (28 g / m ² , 23 g / m ² , 18 g / m ² and 13 g / m ² ). The coating was carried out at extrusion speeds of 250 m / min and 350 m / min.

Example 20

The CaCO ₃ coated paper of Example 4 was coated with an ink receiving layer of the following composition: Al ₂ O ₃ (average particle size 1.2 µm) 25% by weight Silica (average particle size 6.5 µm) 40% by weight Polyvinyl alcohol (fully saponified) 21% by weight quaternary polyammonium salt 14% by weight

The coating weight of the recording layer was 20 g / m ² . This recording material was tested for its Cockle index. The results are shown below.

Comparative Example 1

The surface-sized base paper from Examples 1 to 10 was on the front with a polyethylene blend according to Examples 1 to 19 at one Extrusion speeds of 200 m / min and 250 m / min coated.

Comparative Example 2

A base paper according to Example 1 of EP 0 952 483 A1 with a mass sizing with starch was coated with a solution of clay and polyacrylic acid. The amount of clay in the layer was 1.9 g / m ² . The pigment-containing layer was then coated with a mixture of TiO2 and LDPE at an application weight of 29 g / m ² and an extrusion speed of 300 m / min.
The back of the base paper was coated with a clear polyethylene.

Comparative Example 3

For comparison with the ink-jet recording material from example 20, the base paper from example 4 without pigment coating was used. The ink-receiving layer of Example 20 was applied to the base paper at a coating weight of 20 g / m ² .

Comparative Example 4

For comparison with the ink jet recording material from Example 20 was tested on conventional copy paper. Such conventional copy papers have one Pigment coating.

Checking according to the examples and the Comparative examples produced substrate

Determination of the number of pits

The surface of the polyolefin coated paper becomes magnified with a microscope and with a CCD camera sampled. Using an image processing program created a profile of the pit level from 30 measuring points. The results are shown in Table 3.

From Table 3 it can be seen that the inventive Samples have a smaller number of pits than the sample of comparative example V1. The pits level of the examples 1 to 10 is comparable to that of V2. The pits level the samples of Examples 11 to 19 only fall slightly compared to that of Examples 1 to 10.

gloss measurement

The measurement was carried out using a three-angle gloss meter DIN 67 530 at an angle of 60 °. The results are compiled in Table 3.

The smoothness of the samples of Examples 1 to 19 is the same Except for those of Examples 4, 10 and 11 improved compared to V1 as well as V2.

Determination of the roughness

The roughness was on papers before Extrusion coating with a UBM measuring device according to DIN 4768 with a cut-off setting of 0.8 mm carried out.

Here too, the samples according to the invention clearly show better roughness values than the samples from V1 and V2, whereby the sample of V1 drops significantly compared to the Sample of V2.

Color value determination

The L, a, b values were determined using the Elrepho 2000 colorimeter in single sheet measurements (D65, 10 °, UVI) carried out.

Adhesion of polyethylene

The measurements were made right after the extrusion coating with a tensile strength tester from the company Lorentzen & Wettre on paper samples with a width of 10 mm with a trigger angle of 180 ° and one Peeling speed of 50 mm / min carried out. The Measured values are given in N / 15mm and in Table 3 compiled.

The samples according to the invention clearly show one improved adhesion of the resin to the pigment layer both compared to the sample of V1 and V2.

rigidity

The stiffness values were compared with the Flexural strength tester from Lorentzen & Wettre according to the standard SCAN-P 29.69 determined. The values are given in mN and reflect the longitudinal stiffness.

Compared to comparative example V1, all samples show a significantly improved stiffness. The show samples of Examples 1 and 2 according to the invention a slight compared to the sample of V2 Improvement.

Cockleindex

The cockle behavior of the samples was carried out visually according to a process developed at the Technical University of Darmstadt. For the examination, the paper to be tested was placed on a flat surface and illuminated under obliquely incident light. A cockle index of less than 10 means no cockle, 10 to 16 means low to moderate cockle, 16 to 20 means strong cockle, more than 20 means very strong cockle. The sample according to the invention shows an excellent Cockle index (10.7) compared to the comparative examples V3 (24.3) and 4 (20.7).

Claims (9)

1. Support material coated on at least one side with a synthetic resin, containing a raw paper provided at least on the front side with a pigment coating, characterized in that the pigment coating contains at least about 5 % by weight of a pigment with a narrow grain distribution, whereby at least about 70 % of these pigment particles feature a size of less than about 1 µm and at least 40 % by weight of these particles feature a grain size of 0.35 to 0.8 µm, whereby the resin coating is applied at least on the pigment coating.
2. Support material according to claim 1 or 2, characterized in that the pigment is a calcium carbonate.
3. Support material according to claim 1 or 2, characterized in that the coating contains a pigment mixture which contains at least about 30 % by weight kaolin.
4. Support material according to one of the claims 1 to 4, characterized in that the application weight of the coating amounts to a maximum of about 20 g/m².
5. Support material according to one of the claims 1 to 5, characterized in that the raw paper is a slightly compressed paper with a density of less than about 1 g/cm³.
6. Support material according to one of the claims 1 to 5, characterized in that the pigment coating contains a structured calcium carbonate.
7. Process for the manufacture of a support material coated on at least one side with a synthetic resin, containing a raw paper provided at least on the front side with a pigment coating, characterized in that the coating containing at least one pigment is applied on the front side of a raw paper, and the pigment features a narrow grain size distribution, that the pigment coating contains at least about 5 % by weight of a pigment with a narrow grain distribution, whereby at least about 70 % of these pigment particles feature a size of less than about 1 µm, and at least 40 % by weight of these particles feature a grain size of 0.35 and 0.8 µm, and a synthetic resin is applied at least on the pigment, coating by extrusion, at a speed of up to 600 m/min.
8. Process according to claim 7, characterized in that the synthetic resin is extruded onto the pigment coating of the raw paper at a speed of 350 to 600 m/min.
9. Process according to claim 7 or 8, characterized in that the coating of the raw paper is applied in two stages in such a way that first a preliminary layer containing pigment is first applied with an application weight of up to about 20 g/m² onto the raw paper, and then a coating containing a pigment with a narrow grain size distribution is applied, in which about 50 % of the pigment particles feature a diameter of 0.7 µm.