Classifications

• • 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
  • B41M5/508—Supports
• • 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
• • 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
  • B41M5/5227—Macromolecular coatings characterised by organic non-macromolecular additives, e.g. UV-absorbers, plasticisers, surfactants
• • 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

Definitions

• the invention relates to a method for producing a print carrier for the contactless inkjet printing method according to the preamble of claim 1.
• the invention further relates to a paper produced by such a method according to the preamble of claim 24 and the use of such paper.
• the non-contact inkjet printing process has undergone a rapid development in recent years and is increasingly being used for printers, especially recently multicolor printers for personal computer systems, in order to print the screen content of a computer as hard copy onto a print medium with the highest possible image resolution.
• small droplets of ink are shot onto the print carrier at speeds between 3 and 30 m / sec. These droplets are either generated in a jet with a constant droplet sequence, which is deflected electrostatically when not required, or individually as required (so-called drop-on-demand method).
• the print carrier for the inkjet process does not need to be specially prepared for the process, such as for example in the thermal printing process, but it has to meet a whole series of requirements in order to produce high-quality images.
• the defined ink droplets should be fixed on the print carrier without splashing and must result in a dot diameter that can be controlled via the drop diameter.
• the point spread factor characterizing the difference between the pressure point diameter and the diameter of an ink drop producing it depends both on the ink properties (e.g. rheology, surface tension, charge character, solids content, liquid retention capacity and evaporation tendency, solidification point) and on the properties of the print medium.
• Papers that are attempted to meet these high requirements are usually not natural papers but coated papers.
• Known inkjet papers therefore consist of a base paper which is additionally surface-sized on both sides and at least on one side which is coated with a pigmented coating color on the side serving as the printing surface.
• Known base papers are wood-free papers, in the production of which short-fiber eucalyptus pulp is often used because of its good sorption properties.
• the ash content of known base papers is up to about 20 to 35%, with kaolin, calcium carbonate or various silicates being used as fillers.
• Known base papers often have a mass sizing and are produced with a mass per unit area of between 45 and 90 g / m 2 .
• polyvinyl alcohols in particular serve as surface strengthening agents to form a barrier layer between the base paper and the pigment coat to be applied thereon. Pigments can also be added to the surface sizing in the manner of a primer.
• the actual functional layer on the surface of the paper that interacts with the printing ink is the top coat applied to known high quality papers.
• Its essential components are in known inkjet papers highly adsorptive pigments such as precipitated or pyrogenic silicas and silicates with specific surfaces of approx. 50 to 400 m 2 / g, which are used to achieve a fast ink adsorption and smudge resistance.
• calcium carbonate serves as a blending pigment and is used in proportions of up to about 30% of the total coating pigment.
• urea-formaldehyde pigments which, despite their relatively small specific surface area of 14-20 m 2 / g, are able to meet the special requirements for inkjet paper.
• the binder used in the top coats is, above all, highly saponified polyvinyl alcohols in a binder / pigment ratio of 3: 1 to 1: 3. This high proportion of binder is required to limit diffusion of the ink in all directions within the pigment line. It is also known to add cationic monomeric or polymeric agents to the coating color, such as polyethyleneimine or polydadmac in amounts of about 0.5 to 10%, based on the total coating pigment. These agents support the fixation and solidification of the inks and also have a positive influence on the color density.
• the top coat generally has a basis weight between 10 and 20 g / m 2 .
• the inks used in the inkjet printing process are usually made on an aqueous basis.
• Representatives of the azo group are mainly used as dyes, whose good water solubility can be controlled by incorporating hydrophilic side chains.
• An essential requirement for the inks is to mount them well on the print carrier and to crystallize them out, and to give light-fast, chemical-resistant and waterproof images.
• water-soluble glycols in an amount of up to 30% as so-called "humectants" Incorporate ink compositions.
• the inks also contain surface-active substances to control the surface tension that is important for the drop size and shape.
• Inkjet papers are assumed to have great future potential.
• the development which is mainly driven on in Japan, shows that the focus is on coated but essentially only coated paper.
• the binders used for the coating color are diverse, in addition to latices and hydroxyethyl cellulose, polyvinyl alcohol is predominantly used.
• the coating colors are partly Cationic agents added, which in addition to those mentioned above also include cationic hard and quaternary ammonium compounds. Silicon oxides in various forms, silicates and also aluminum oxide and aluminum hydroxide are predominantly used as pigments for the coating. Calcium carbonate is usually only used as an extender pigment.
• the invention has for its object to show a method for producing an inkjet paper or to provide such paper, the functional layer, namely the top coat, according to its formulation allows an application to the base paper on modern production units at high production speeds, this top coat While fulfilling the requirements for an inkjet paper explained at the beginning as far as possible, it is also possible, if desired, to use more cost-effective raw materials, namely wood pulp and other wood materials in the base paper and also to produce this base paper cost-effectively on large production units. In a preferred embodiment of the invention, it should be possible to use inexpensive raw materials also for the top coat.
• this object is basically achieved according to the invention in that a coating color is applied as the top coat, which overall has a cationic behavior, i.e. is cationic from the outset.
• the cationic ionogenicity of a line can also be determined with modern measuring methods on the finished paper or on samples of the line which have been removed from the paper. According to the invention, therefore, a paper is also claimed which has a cationic top coat.
• each stroke application that forms the outer surface of the paper is referred to as the top coat, even if, in special embodiments, it is the only stroke on the paper should act. This is done on the one hand to include both single and double-coated papers with the same term, which have a stroke of the same type as the single or last stroke, and on the other hand to distinguish the top coat from the pre-coat in double-coated papers.
• a spontaneous interaction at the paper / printing ink interface in the sense of rapid ink pigment aggregation and / or agglomeration on the surface can be achieved by means of a cationically adjusted coating color.
• the interrelation of such a coating color with the inkjet inks is so positive that other negative influences such as fraying of points, wicks, penetration, etc. can be covered by them.
• the coating color used should be cationic in such a way that it has a zeta potential between +5 and +70 mV.
• a completely cationically adjusted coating color essentially means that the coating pigment suspensions are already cationically adjusted before further substances, essentially the binders for producing the actual coating color, are added to them.
• Common coating pigments essentially kaolin, are originally anionic in nature. In order to change their ionogenicity, they can already be treated with certain cationic agents during a grinding process at the manufacturer, but at the latest when they are dispersed into an aqueous slurries for coating color preparation, which lead to a charge reversal of the pigment particles. It has long been known to use ionogenic agents, but mostly anionic agents to disperse pigment slurries. They are intended to promote the separation of the particles in the suspension and to prevent re-agglomeration. Such measures are also possible on the basis of a cationic ionogenicity.
• cationic binders are also used for the coating color according to the invention. These can be cationic starches and / or cationic plastic dispersions. Once the pigment slurrie is in a cationic form, non-ionic additives can also be used to produce the coating color. In particular, the use of commercially available polyvinyl alcohol, which is inherently non-ionic, has also proven to be advantageous in the system according to the invention. Other additives common in smaller quantities in coating colors such as Lubricants, crosslinking agents, defoamers, thickeners and / or optical brighteners must be checked to ensure that their ionogenicity is compatible with the cationic system. If such means are not available in a suitable design, they may also need to be changed in ionogenicity.
• a pigment that fulfills this requirement according to the invention is a ground natural calcium carbonate, which is also still available indefinitely and is accordingly inexpensive. In addition, it has a relatively high whiteness.
• This ground calcium carbonate must also be treated with cationic grinding or dispersing agents to produce a cationic pigment dispersion. While known coating colors for inkjet papers generally require a very high amount of binder, the limited surface hydrophilicity of the calcium carbonate means that the proportion of binder can be considerably reduced compared to known papers. Depending on the basic and surface finish of the base paper, the binder requirement is less than 11%, based on the total coating pigment, even less than 9%.
• At least 50% calcium carbonate, which has a fineness of should have at least 60% ⁇ 2 ⁇ m.
• the fineness of the total pigment in the coating color should be at least 75% ⁇ 2 ⁇ m. It is entirely possible to use up to 100% calcium carbonate as a coating pigment.
• blending pigments include kaolin, talc, aluminum hydroxide, mica and / or gypsum, the proportion of kaolin, talc, mica and gypsum in each case being limited to 50% and the proportion of aluminum hydroxide to 20% of the coating pigment.
• These blending pigments should also be cationic in their dispersion.
• the top coat can develop its interaction according to the invention with the printing ink as best as possible, it should form a closed layer on the paper surface as far as possible and knock as little as possible into the base paper.
• a coating color holdout This can be achieved by sizing the base paper in the conventional sense. According to the invention, therefore, in a preferred embodiment, sizing of the base paper is provided either in its mass or on its surface. Which route is chosen may depend on the equipment of the paper making machine. If it is provided with a size press or a film coater, surface sizing may be more appropriate. The addition of sizing agent in the mass, as well as on the surface, is usually in the region of 1%, based on the base paper weight.
• the base paper can be provided with a primer before the top coat is provided.
• primers are expediently applied to the base paper by means of on-line coating devices in the paper making machine. These can be film presses as well as doctor coating devices.
• Conventional formulations which have a mass of 5-12 g / m 2 and Side on paper. When speaking of conventional formulations, it is meant that these primers can in particular also be anionic. It has been shown that a cationic topcoat can easily be applied to an anionic primer and that even the holdout of the topcoat can be increased in order to improve the quality of the paper surface, since the different ionogenicity of the two coating slips means their mutual affinity and thus mutual penetration is also inhibited.
• the surface sizing agent used can also and should be anionic.
• the coating color to be applied to the base paper for the top coat generally has solids contents of between 30 and 65%, but is preferably adjusted to solids contents of more than 50%.
• the mass applied to the base paper can be between 2 and 15 g / m 2 , but is preferably in the range between about 7 and 10 g / m 2 .
• starch is added in bulk as a strengthening agent in high-speed paper machines, it is difficult to avoid using a highly cationic starch to improve the retention of this agent on the paper machine screen, so that the starch really remains largely in the paper on the one hand and does not remain in the paper machine on the other. Water cycle enriches with the resulting adverse consequences. It has been shown that even on high-speed paper machines with gap formers, up to about 2% cationic starch, based on the base paper input, can be added. If you choose a surface treatment with starch, for example in the size press of the paper machine, the starch input can be increased. When using such a surface treatment with starch, according to the invention, about 3%, based on the base paper input, is used. However, the quantities can vary. In contrast to the addition of starch to the paper pulp, an anionic starch can be used quite and even advantageously in the surface treatment. Such a surface treatment then has approximately the same effect as an anionic primer mentioned above.
• both an anionic and a cationic primer can be used according to the invention, depending on the objective.
• a base paper already equipped with an anionic surface treatment with starch, to which a certain amount of pigment can also be added, and should be applied to it Pre-coat only to reinforce the top coat and its effect, a cationic coating color can also be used for the pre-coat, for example the same that is subsequently used for the top coat.
• an anionic surface treatment with starch has been dispensed with, it is advantageous to apply an anionic formulation as a primer or prepigmentation before the cationic top coat, so that there is an ionogenicity change at least at an interface within the paper coating.
• wood-free base papers it is entirely possible to use wood-free base papers, but if other fiber materials are additionally used, the use of new cellulose can possibly be reduced to 10% of the total fiber material. Fibrous compositions with 10-40% cellulose, 5-60% wood pulp and 0-60% fibers made from processed, thin waste paper are possible. When wood pulp is mentioned here, this term is intended to include both wood pulp as well as the wood pulp TMP and CTMP and the like which are common in the paper industry.
• Tables 1, 2 and 3 show paper compositions and test results of inkjet papers according to the invention in comparison with conventional papers.
• cationic substances are marked with a plus sign in a circle and anionic substances with a minus sign in a circle.
• Table 1 contains raw paper entries, where it contains a typical entry for conventional inkjet paper in the first column Inkjet Standard and the entries of the test papers produced in the columns of Examples 1 to 3.
• the first two lines only indicate the raw paper weights that were produced for the production of a certain final weight after coating the raw or base paper.
• the difference between the base paper weight and the final weight in Example 3 is greater, since this paper was intended for a double line on each side.
• the standard base paper only contains cellulose as the pulp, in a ratio of 30 parts long fiber to 46 parts short fiber, eucalyptus pulp being often used as the short fiber.
• the base papers of Examples 1 to 3 contain wood pulp (Examples 1 and 2) or thermal wood pulp (Example 3).
• the base paper according to Example 2 was provided with a surface sizing and a surface strengthening (starch) to produce the base paper for the top coat.
• Example 1 contained strength agents (starch) and sizing agents in bulk.
• the standard base paper contained in Table 1 is in principle also suitable for a coating according to the invention, but it is more expensive, and the comparative experiments are intended to show that correspondingly good printing results can also be obtained with papers which contain waste paper fibers and wood pulp.
• Table 2 contains in the columns Example 1 to 3 the formulations of the top coats with which the respective base papers according to Examples 1 to 3 were coated.
• column 1 shows a range for standard top coat formulations for conventional inkjet papers.
• the papers of Examples 1 and 2 were provided with a top coat which Contained 100% calcium carbonate as a coating pigment, while the top coat for Example 3 contained 80% calcium carbonate and 20% kaolin as a coating pigment. All pigments were cationic.
• the binders of all test coating colors contained polyvinyl alcohol, in addition cationic plastic binders and cationic starch (example 3). The total amount of binder was between 8 and 10.4%, based on the coating pigment. This is in stark contrast to the 50 to 100% polyvinyl alcohol in the standard formulation.
• the zeta potentials of the test coating colors were clearly in the positive range.
• the base paper according to Example 3 was provided with a conventional primer before the top coat was applied. As can be seen from Tables 1 and 2 together, this had a mass of approximately 11 g / m 2 and side.
• the three base papers of the examples differed from the application of the topcoat, apart from the differences in their fiber composition, in that the paper according to example 1 had only one size and solidification in the mass, the paper according to example 2 had no size and solidification in the mass, on the other hand, sizing and consolidation in the surface and the paper according to Example 3 again sizing and consolidation in the mass, but only the primer as surface finish.
• the grammages of the top coat on each side can be seen in Table 2 below and the level was 8 g / m 2 in contrast to the higher coat weights for conventional paper.
• the papers according to Examples 1 and 2 were provided with the top coat in a film press, the paper according to Example 3 in a doctor coater.
• Table 3 shows the paper test results and the results of the printability assessment using the inkjet process. Since reference papers with a conventional top coat were not produced in-house, commercial reference papers were used, and for the test papers of Examples 1 and 2 accordingly a simple one coated comparison paper and for the test paper of example 3 also a double-coated comparison paper.
• the assessment of the print results in the lower part of Table 3 is essential.
• the assessments show without further ado that the test papers behaved at least as well as, if not partially better than, the comparison papers.
• inkjet paper can be obtained by using inexpensive base papers containing wood and waste paper and providing them with a cationic top coat, which can essentially contain calcium carbonate as a cheap coating pigment and relatively little binder.

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Cited By (14)

Citations (7)

• 1997
  • 1997-01-15 EP EP97100498A patent/EP0790135A3/fr not_active Withdrawn

Patent Citations (7)

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