Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H19/00—Coated paper; Coating material
  • D21H19/36—Coatings with pigments
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/50—Recording sheets characterised by the coating used to improve ink, dye or pigment receptivity, e.g. for ink-jet or thermal dye transfer recording
  • B41M5/502—Recording sheets characterised by the coating used to improve ink, dye or pigment receptivity, e.g. for ink-jet or thermal dye transfer recording characterised by structural details, e.g. multilayer materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M2205/00—Printing methods or features related to printing methods; Location or type of the layers
  • B41M2205/34—Both sides of a layer or material are treated, e.g. coated
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/50—Recording sheets characterised by the coating used to improve ink, dye or pigment receptivity, e.g. for ink-jet or thermal dye transfer recording
  • B41M5/52—Macromolecular coatings
  • B41M5/5218—Macromolecular coatings characterised by inorganic additives, e.g. pigments, clays
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/50—Recording sheets characterised by the coating used to improve ink, dye or pigment receptivity, e.g. for ink-jet or thermal dye transfer recording
  • B41M5/52—Macromolecular coatings
  • B41M5/5236—Macromolecular coatings characterised by the use of natural gums, of proteins, e.g. gelatins, or of macromolecular carbohydrates, e.g. cellulose
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/50—Recording sheets characterised by the coating used to improve ink, dye or pigment receptivity, e.g. for ink-jet or thermal dye transfer recording
  • B41M5/52—Macromolecular coatings
  • B41M5/5254—Macromolecular coatings characterised by the use of polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds, e.g. vinyl polymers
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
  • D21H11/14—Secondary fibres
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H19/00—Coated paper; Coating material
  • D21H19/80—Paper comprising more than one coating
  • D21H19/84—Paper comprising more than one coating on both sides of the substrate

Definitions

• the invention relates to a paper, in particular for multicolor printing processes.
• This paper can be processed in the form of sheets or roll paper.
• Paper is composed of a carrier or base paper whose surface is treated or painted. It is used, for example, as printer paper for business papers, catalogs or advertising.
• Digital printing processes use toner or ink, such as B. be used in laser printers or inkjet printers. Conventional printing methods such.
• B. Offset printing processes use inks. Whereas inkjet printers were previously only suitable for smaller print jobs, a new generation of inkjet printers achieves outputs of more than 2,000 sheets per minute and is thus starting to displace offset printing.
• Toner is applied as a solid, but ink and ink consist of a solid phase (pigment and / or dyes) and a liquid phase (water and / or solvent).
• a solid phase pigment and / or dyes
• a liquid phase water and / or solvent.
• the aim is to achieve the best possible separation of solid and liquid phases in order to achieve a color-intensive printed image, especially in multicolor printing. This is especially difficult with the ink used by inkjet printers since it contains a high proportion of liquid compared to printing ink.
• the carrier or base paper must be sufficiently strong and have a given volume.
• the fibers of the backing paper cause the strength.
• Fillers are inexpensive, they bring the opacity, so that a paper can be printed on both sides. A high use of fillers reduces costs.
• a significant cost factor of digital printing paper are the fibers used to make the backing paper.
• the carrier paper of the digital printing paper has to absorb high loads. In particular, it must carry the fillers and the coating application and must not tear when conveying the paper by printers or printing presses.
• z. B. in the EP 0 785 307 or the DE 197 45 082 is sought to use high amounts of cheap filler, but the least possible amounts of coating order, since pigments that have a higher tinctorial strength than fillers, significantly more expensive than fillers. To get along with the least possible coating order, even the backing paper should be as light as possible or white.
• the backing paper is particularly bright, it shows a whiteness of usually 80 to 110% ISO.
• the coating application ensures a uniform bright, as white as possible surface, the trouble-free processing of the paper, z.
• the delivery systems of an inkjet or laser printer as well as the precise acquisition and recording of the ink or the toner or the ink.
• the ink or ink must be recorded smoothly.
• pigments or mixtures of pigments are used, which are optionally mixed with binder and to give the paper as uniformly bright surface that is well suited for receiving toner, ink or ink and gives a color-intensive, high-contrast print image
• Pigments are among the cost-intensive constituents of printing paper. They are according to the disclosure of EP 0785 307 or the DE 197 45 082 be used sparingly.
• the paper according to the invention shows an above-average color intensive, high-contrast print image, although the whiteness of the paper is at least 60% ISO to a maximum of 80% ISO much lower than common.
• the paper according to the invention ensures contour-sharp, low-gradient printing.
• the paper according to claim 1 is coated with a maximum of 8 g / m 2 coating order per side of the paper thinly.
• the fibers of the backing paper are not completely covered by the coating application.
• the secondary fibers which are not completely covered by the coating application, absorb the liquid phase of the ink of an offset printer or the ink of the ink jet printer extremely fast.
• the pigments contained in the ink therefore probably settle in the majority on the surface of the paper according to the invention, which is formed from coating application and fibers or fiber sections.
• the deposition of the dyes and / or pigments from the ink or ink takes place as sharply and completely on the surface of the paper, which is formed by the coating order, but also by the fibers of the backing paper that produces an extremely colorful, high-contrast and brilliant print image becomes.
• the paper according to the invention is wiped fast by the rapid absorption of the liquid phase immediately after printing and can, for. B. at speeds of 2000 sheets / minute and more in inkjet printers are printed without causing the blur of the printed image.
• the paper according to the invention can therefore be used in particular in high-performance ink jet printers with a capacity of more than 500 sheets per minute, in particular more than 1,000 sheets per minute, preferably more than 2,000 sheets per minute, with unchanged print quality.
• Fresh or primary fibers are wood or annual plants mechanically or chemically produced fibers. They are used for the first time (fresh) for the production of paper, cardboard or cardboard.
• secondary fibers are in particular fibers that have already been processed once into paper or paperboard. The paper or the cardboard were dissolved, if necessary, ink or paint was removed and the fibers are re-processed into paper or paperboard.
• Paper, paperboard, dissolving and reprocessing make paper secondary fibers, less firm and, above all, darker than paper made from primary long-fiber pulps.
• the typical gray tone of recycled paper is well known.
• Secondary fibers, mostly recycled paper fibers, are cheaper to buy and more environmentally friendly in terms of reprocessing, since important resources such as energy, water and chemicals can be significantly reduced.
• a paper for digital printing in which the fibers of the backing paper are at least 50% by weight secondary fibers is, with unchanged composition of filler and coating application and a coating application of a maximum of 8 g / m 2 per side of the backing paper significantly darker than typical offset or laser printing papers.
• Such a paper lowers the cost of materials and is environmentally friendly.
• This advantage can be better utilized, as well as the printability properties of the invention, if at least 60% by weight, preferably at least 75% by weight, advantageously at least 90% by weight, of the fibers of the carrier paper are secondary fibers.
• the backing paper can also be made entirely from secondary fibers without further ado.
• All types of secondary fibers are suitable for the production of the backing paper.
• waste paper but also rags can be used.
• the carrier paper other fibers added, it may be fresh or primary fibers, but also be synthetic fibers.
• a paper which has a more than 50% fraction of secondary fibers based on the total amount of fibers used for the carrier paper and in whose coating application no optical brighteners are contained. Such a paper is particularly economical and environmentally friendly to produce.
• the paper according to the invention contains fillers. These are partly introduced via the secondary fibers, which frequently carry up to 20% by weight of filler.
• the secondary fibers are obtained by dissolving paper in water or alkaline liquor, de-inking the fibers if necessary, and removing ink and contaminants from the suspension.
• the thus prepared secondary fibers are then either used directly as a suspension for the production of the paper according to the invention or they are dried, stored or transported and then suspended again before processing in aqueous solution. Deinkening does not always remove all fillers, so the secondary fibers carry up to 20% by weight of fillers. This is to be taken into account when setting a predetermined filler content for the paper for digital printing. Also applies to the filler used for the paper according to the invention, that the use of optical brightener is not required because according to a preferred embodiment, no high degrees of whiteness for the paper are required.
• the fillers used are light white particles, most commonly calcium carbonates, both natural (GCC) and precipitated (PCC) calcium carbonates, or kaolin. Typically, mixtures of different fillers are used. Overall, the content of filler in the base paper may be 50% by weight for the paper.
• the paper according to the invention is provided on one or both sides with a coating application of up to 8 g / m 2 per side of the carrier paper.
• the application is at least 0.5 g / m 2 per side.
• up to 2 g / m 2 to 6 g / m 2 preferably about 4 g / m 2 coating application per side applied to the carrier paper.
• a dispersion is usually prepared from white pigments or mixtures of pigments on the one hand and binders or mixtures of binders on the other hand, which is applied in liquid form to the backing paper. So usually white coated paper is then dried and possibly the surface is compacted, for. B. by calendering.
• coating pigments such as PCC, GCC, kaolin, titanium dioxide can be used singly or in admixture.
• binders known binders can be used. Starch is preferably used as a binder, but also latex or polyvinyl alcohols are well suited.
• the coating application can be designed to achieve whiteness for the finished high performance ink jet printer paper of 60% ISO or 70% ISO or more, if desired also at least 75% ISO maximum but 80% ISO.
• these values are achieved without the use of optical brighteners.
• the digital printing paper according to the invention can have a sheet weight of 50 g / m 2 up to 180 g / m 2 . In this area, it is particularly well suited for use in high-speed inkjet printers.
• the paper of the present invention is particularly suitable for use in high speed ink jet printers which print more than 500 sheets per minute, typically more than 1,000 sheets or even 2,000 sheets per minute.
• the suitability of papers for the respective printer or printing equipment such as offset, laser or inkjet printer is checked by printing with a uniform standard.
• These standards or test images are designed so that parameters such as acutance, color density, color intensity, print gloss and the like are verifiable.
• the following evaluations of various parameters relate to the printing of a sheet of paper with such a test pattern or standard.
• An essential property of the paper according to the invention relates to the application of printing ink or ink.
• the surface of the paper according to the invention and the composition of the carrier paper of 50% or more secondary fibers determine the Speed at which the applied ink or ink will dry; in other words, how fast the liquid phase of the ink or ink is absorbed by the respective paper.
• the drying takes place in the paper according to the invention in a preferred embodiment of the invention in less than 0.1 seconds, preferably less than 0.06 seconds, advantageously less than 0.03 seconds. A lower limit is noticeable at 0.001 seconds.
• the drying time was determined in practical tests by printing in each case 5,000 sheets or a corresponding amount of the paper to be tested by means of a high-performance inkjet printer with a test pattern, optionally cut at the end of the printing process and after the stacking, which takes place automatically at the output of the printer, be examined visually for clarity of the printed image or blurring.
• Typical high-performance inkjet printers suitable for testing the drying time are z.
• the device Océ Jetstream 2200, InfoPrint 5000 of IBM / Ricoh and HP T 300 which can print each about 2,700 sheet A4 per minute in color. These inkjet printers are about to replace offset printing equipment because they have comparable performance.
• the rapid drying is probably due to the good fluid conduction through the thin coat application and the good absorbency of the secondary fibers in the backing paper. Again, it should be noted that the moisture introduced by the ink or ink does not adversely affect the strength of the base paper or its dimensional stability.
• the acutance (or line sharpness or gradient) of a paper is determined by detecting the extent of a printed line versus a reference line. Tested with the measuring device of the company ImageXpert "Full Motion System", a scanner system, the paper according to the invention exhibits a contour sharpness of up to 280 ⁇ m, preferably with an imprinted pixel size of 5 pixels of up to 240 microns, in particular of up to 220 microns. The contour sharpness is z.
• the good contour sharpness described above can not be achieved with known printing papers for digital printers. It is also unexpected because professionals do not consider secondary fibers suitable for reproducing good contour sharpness due to their good suction power.
• the paper according to the invention for digital printing has according to a preferred embodiment, despite the thin coating application and a possibly smoothed, z.
• the calendered surface has a uniform surface that uniformly accepts toner or printer ink.
• the surface of the paper hardly shows any mottling.
• Mottling refers to highly compressed surface sections that are color-coded from the surface. They give the paper a dirty appearance. In addition, they take ink, toner or printer ink differently than the rest of the paper surface, creating an uneven print image.
• the mottling which is visually determined by viewing the surface, is less than 3% of the paper surface tested in the paper of the invention. As a rule, it is less than 1% of the tested paper surface.
• the paper according to the invention for digital printing has a high optical density.
• the optical density indicates to what extent or intensity applied Ink, toner or printer ink is recorded and reproduced on or through the paper surface.
• the scale for the measure of the rendering is dimensionless and is 0 to 2, where 2 represents the 100% representation.
• the norm to be applied is ISO / CD 5-3, status T, status I or status E, with status T predominantly used in the US. Here was measured with the usual E status for Europe.
• the values listed below were recorded with the Gretag Macbeth D 19 D Densitometer, filter set type 47 B / P, 0 ° / 45 ° ring optics according to DIN 16536 "Testing of Printing and Inks of Printing Techniques - Color Density Measurement on Prints".
• the paper according to the invention surprisingly reaches a value of at least 0.4, preferably more than 0.8, preferably more than 1.0, despite the low whiteness of 60% ISO to 75% ISO.
• These good values for paper may be explained by the fact that the good absorbency of the secondary fibers absorbs the liquid from the ink jet ink so quickly and completely that there is a sharp separation of pigments or dyes and liquid, so that more pigments are present on the surface of the printing paper remain as in known papers. There, slow picking up of inkjet ink may cause enough time for settling effects, which causes pigments to be dragged through the liquid to or into the fiber. They are therefore no longer available on the surface of the paper.
• the paper according to the invention has a high color fidelity or color fastness, which is also measured and designated as color tone reproduction.
• the measuring specification here is DIN 6174 "Colorimetric determination of color dimensions and color distances in approximately uniform CIELAB color space.” Measured here was a spectrophotometer Elrepho SE 070, diffuse illumination, 0 ° measurement, standard illuminant D65. The measurement correlates the brightness and readings for the red-green axis and the blue-yellow axis of the object being inspected and indicates the total color distance. The measured values are dimensionless and can reach up to 6-digit values, easily up to more than 200,000.
• the paper having a whiteness of only 60% ISO to 80% ISO has a color intensity of at least 100,000, preferably of at least 120,000, advantageous of at least 150,000.
• the printed paper has a much higher gloss than the unprinted paper.
• the print gloss gloss of the printed paper
• the print gloss is more than 5, preferably more than 10, advantageously more than 15 based on the gloss of the unprinted paper.
• the print gloss is determined by the surface of the paper according to the invention. This paper is printed with a given standard or test pattern and the print gloss is measured. Although the printed paper is measured, this parameter relates to a property of the unprinted paper of the present invention, since the color rendition is directly dependent on the substrate on which it is applied. For the paper according to the invention, the measured values are unusually high; Experts had suggested lower levels given the higher proportion of secondary fibers compared to known digital printing papers.
• the paper for digital printing on a high pick resistance which makes it suitable for use in digital printers.
• the picking strength - measured according to ISO 3783 - records how much the printers use the surface of the paper when applying printing ink or toner or printing ink. As by fibers or particles from the surface of the paper dissolved out (plucked).
• the paper for digital printing according to the invention has a picking strength of less than 4.0.
• the pick resistance is less than 2.0, more preferably less than 1.0.
• the low pick resistance is astonishing since the paper according to the invention has a high proportion of secondary fibers or consists of secondary fibers which are shorter than primary fibers and can therefore be more easily leached out of the fiber composite of the carrier paper.
• the coating is very thin, so that the applied pigments or the mixture of pigments and binders can cover and protect the fibers only little. The good pick resistance was therefore unexpected.
• Backing paper A has 55% secondary fibers and 45% primary fibers, each based on the total amount of fibers.
• Carrier paper B has 75% secondary fibers and 25% primary fibers.
• Backing paper C has 90% secondary fibers and 10% primary fibers.
• Carrier paper D has 100% secondary fibers.
• the primary fiber used is chemically produced softwood pulp bleached to whiteness 80% ISO.
• filler is also added to the aqueous suspension.
• the suspension contains 30% by weight of filler based on the dried paper.
• Half of the filler is introduced by the secondary fibers.
• the other half of the filler is kaolin.
• the suspension is dewatered and Papers A, B, C and D are produced with a sheet weight of 80 g / m 2 each and dried to a moisture content of 2% by weight. These papers are then each provided with a coating order.
• a slurry of PCC, GCC and kaolin in equal parts, containing no optical brightener, is applied to both sides of the support papers in an amount of 3 g / m 2 .
• the coated papers are again dried and smoothed. The smoothing is done with a calender with a line pressure of about 100 N / m.
• the finished sheets have a whiteness of 70% ISO.
• Table 1 parameter Paper reference Paper A Paper B Paper C Paper D White (% ISO) 95 70 70 70 70 70 drying time (Seconds) 0.2 0.06 0.04 0.03 ⁇ 0.02 Contour sharpness ( ⁇ m) 300 270 255 235 220 Optical density 0.4 0.65 1.0 1.1 1.2 color intensity 95,000 120000 145000 150000 165000 print gloss 5 7 9 11 10 pick resistance 4 1.7 1.1 0.9 0.7 Mottling (% of surface) 5 2 1.5 2.5 1.0
• the paper according to the invention shows, in the parameters which are important for the evaluation of the printed image, in particular in multicolor printing, ie color intensity, optical density, acutance and gloss, despite the lower whiteness of 70% ISO of the paper according to the invention, values which are significantly better are attainable as with the reference paper with a whiteness of 95% ISO.
• drying time of the paper according to the invention is much lower than the drying time of the commercial reference paper. It is assumed that the greatly shortened drying time also leads to sharpness of contour and color intensity as well as optical density showing markedly improved values compared with the prior art or the reference paper.
• the rapid separation of liquid and solid phase (pigments) of the inkjet ink on the paper according to the invention can lead to these parameters showing better values than in the case of the reference paper. The differences are significant and show significantly better print results than in the prior art.

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• Ink Jet Recording Methods And Recording Media Thereof (AREA)

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Citations (8)

• 2011
  • 2011-01-11 EP EP11150547A patent/EP2474668A1/fr not_active Withdrawn

Patent Citations (8)

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