EP0246987B1 - Ink jet recording sheet and process for its manufacture - Google Patents

Abstract

Treated base material for recording. The recording sheet for ink-jet printing according to the invention includes, in its coating, a polyhydroxylic polymeric binder with the hydroxyl groups in the cis position, which has been gelled or coagulated with boric acid and/or its derivatives during coating, and a filler with a high absorption capacity. Application to recording paper for ink-jet printing.

Description

• une feuille d'enregistrement par jet d'encre,
• les procédés utilisables pour la préparation de ladite feuille.

The present invention relates to:

• an inkjet recording sheet,
• the methods which can be used for the preparation of said sheet.

The inkjet printing technique has been a definite success. However, the detailed study of the characters obtained by this technique shows the existence of a certain number of defects due to the non-adaptation of the sheet on which the recording is made, to the particularities of the inkjet technique.

There are already known a number of publications and, in particular, patents or patent applications, proposing means of obtaining sheets for printing by ink jet of good quality. Some, in particular, claim the coating of a support with a composition comprising absorbent fillers of defined nature or physical properties, intended to absorb the ink, or else paper-making supports having particular characteristics, or even the combination of of them.

Thus, for example, US Patents 4,269,891, US 4,461,174 recommend the use of absorbent fillers comprising, in particular, silica, diatoms, zeolite, synthetic or natural silicates.

Later, Japanese patent J 56 148 582 and the following claims the use of coating fillers of the same kind and, in particular, an amorphous silica micropowder with different synthetic binders.

US Patent 4,440,827 claims the coating of such absorbent compositions in at least two identical coating operations in order to obtain a high resolution, without harming the solidity of the layer.

US Patent 4,460,637 claims a particular distribution of pore diameters in the layers of paper for inkjet printing, consisting of absorbent fillers.

US Patent 4,478,910 or EP 0 121,916 claims the combination of a slightly bonded and very absorbent support for aqueous solutions and a layer comprising a synthetic binder and a fine silica powder with BET specific surface greater than 200 m² / g.

Mention may also be made of US Pat. No. 4,496,629 recommending a layer based on absorbent fillers such as silica, this layer being divided into a multitude of lamellae separated by microcrevasses giving rise, according to the inventor, to a higher quality.

According to the experience of the Applicant, the methods described make it possible to obtain inkjet prints, which are, unfortunately, often affected by qualitative defects the removal of which is difficult and expensive. In addition, the quality of these prints is very dependent on that of the support used for coating. In addition, although the US Pat . No. 4,460,637 evokes a relationship between the resolution, the thickness of the layer and the level of binder thereof, no publication clearly describes a means of varying the size of the dots obtained with a defined drop of ink, sent by a given inkjet system.

• a) Si les points sont gros, ils sont dentelés et de densité très hétérogène. Le résultat est un aspect flou de l'impression.
• b) Si les points sont petits, ils sont de forme extrêmement irrégulière, en raison surtout de microcraquelures de la couche analoques à celles qui sont prônées par le brevet US 4 496 629. En fait, ces crevasses s'opposent latéralement à la migration horizontale de l'encre et, au contraire, la canalisent dans le sens de leur longueur, donnant à ces points des formes très irrégulières et inacceptables.

If by acting on certain parameters of the layer (specific surface, nature and rate of binders, thickness of the layer, humidity) the size of the printing dots obtained from drops of ink of given size is varied, defects in form and uniformity of these points:

• a) If the points are large, they are serrated and of very heterogeneous density. The result is a blurry aspect of the print.
• b) If the dots are small, they are extremely irregular in shape, mainly due to micro cracks in the analoque layer to those advocated by US Patent 4,496,629 . In fact, these crevices laterally oppose the horizontal migration of the ink and, on the contrary, channel it in the direction of their length, giving these points very irregular and unacceptable shapes.

To remove these defects, one can act on the support by modifying its absorbency, its structure, the shape of its constituent elements, its smoothness, etc., which requires a precise definition of the quality of the support for each particular case.

We can also act on the composition of the layer and the coating method. Thus, the microcracks can be reduced by increasing the rate of binder, but we then come up against problems such as the difficulty of drying, the increase in the cost of the composition and the lowering of the color densities. It is also possible to reduce the microcracks by decreasing the temperature and the drying speed, but this leads to significant economic limitations. It is also possible to sleep in two or more passes, which is the subject of US Pat . No. 4,440,827 , but again the economic cost is considerable.

The object of the present invention is to eliminate the defects mentioned above without supporting the harmful consequences, the difficulties and the costs which result from the application of the methods described.

We have also described, for different types of paper, the use, in conjunction with the use of polyhydroxylated polymeric binders, of coagulating and gelling products.

Among the various coagulating or gelling products for polyhydroxylated binders, the best known and above all the most effective are boric acid and / or its derivatives.

The chemical reaction and the effect obtained by boric acid and its derivatives on polyhydroxylated binders are well known and have already been described in detail in various publications.

Boric acid and its derivatives have been frequently used for various industrial applications, among which it is possible to cite abrasives, antifreezes, cements and plasters, glues, enamels, fireproofing, metallurgy, products pharmaceutical and cosmetic, tanneries, glassware, stationery.

In these many applications, we use most time, either their gelling reaction with polyhydroxylated binders, their buffering capacity, or their antiseptic properties.

• en combinaison avec des liants polyhydroxylés pour la réalisation de colles et adhésifs pour le carton ondulé, cette application étant, notamment, décrite dans les brevets FR 2 469 439 et 2 331 591. Le collage de surface ainsi réalisé permet d'obtenir une barrière aux graisses, solvants, vernis, une imperméabilité du papier ou carton à l'air, ainsi qu'une meilleure résistance à l'abrasion,
• en combinaison avec l'alcool polyvinylique pour l'obtention d'un papier présentant un effet barrière, obtenu grâce à la gélification de l'alcool, permettant de fixer une goutte d'encre dès son arrivée sur la surface du papier non couché. Cette application a été décrite dans les brevets japonais J 52 088 406 et J 52 126 305 (TOPPAN PRINTING K. K.) : un papier est traité en surface par de l'acide borique ou un borate ou bien un produit minéral ou organique capable de coaguler l'alcool polyvinylique. Ce papier est ensuite destiné à être imprimé en héliographie, flexographie ou par jet d'encre avec une encre aqueuse contenant de l'alcool polyvinylique.

Boric acid and its derivatives have been used in stationery for various results:

• in combination with polyhydroxylated binders for the production of glues and adhesives for corrugated cardboard, this application being, in particular, described in patents FR 2 469 439 and 2 331 591 . The surface bonding thus produced makes it possible to obtain a barrier to grease, solvents, varnish, an impermeability of the paper or cardboard to the air, as well as a better resistance to abrasion,
• in combination with polyvinyl alcohol to obtain a paper having a barrier effect, obtained by gelling the alcohol, making it possible to fix a drop of ink as soon as it arrives on the surface of the uncoated paper. This application has been described in Japanese patents J 52 088 406 and J 52 126 305 (TOPPAN PRINTING KK) : a paper is surface treated with boric acid or a borate or a mineral or organic product capable of coagulating l polyvinyl alcohol. This paper is then intended to be printed in heliography, flexography or by ink jet with an aqueous ink containing polyvinyl alcohol.

It should be noted, however, that so far this gelling or coagulation reaction of polyhydroxylated binders, by boric acid and / or its derivatives, had never been used to produce a recording sheet for inkjet absorbing ink evenly and evenly and thus leading to an inkjet recording medium with remarkable properties.

• B. A. BEARWOOD et EP. CZERWIN - TAPPI volume 43, 11, pages 944-952 (1960),
• B. A. BEARWOOD et C. J. STAPS, papier, carton et cellulose, 13, 2, pages 83-90 (1964),

décrivent un procédé destiné, au contraire, à conférer à la surface du papier ou du carton d'impression des propriétés dites "barrières", c'est-à-dire à les rendre imperméables aux liquides comme les huiles, l'eau, les encres d'imprimerie, liquides qui, de ce fait, restent à la surface une fois déposés sur ce support.The publications of the prior art, mentioning the use of this reaction on papers intended to receive a printing of conventional type, such as those of:

• BA BEARWOOD and EP. CZERWIN - TAPPI volume 43, 11, pages 944-952 (1960),
• BA BEARWOOD and CJ STAPS , paper, cardboard and cellulose, 13, 2, pages 83-90 (1964),

describe a process intended, on the contrary, to confer on the surface of the printing paper or cardboard so-called "barrier" properties, that is to say to make them impermeable to liquids such as oils, water, printing inks, liquids which therefore remain on the surface once deposited on this support.

Finally, patent JP-A-87 089/85 is known which describes a sheet for ink jet recording comprising an oil absorption pigment, a coagulating agent for this pigment consisting of a magnesium compound, and a binder.

The sheet thus obtained has improved properties relating to the drying speed. The sheet thus obtained is however not likely to lead to an enlarged shape of the points, while retaining a good quality of shape and uniformity of said points.

The object of the present invention is to produce a coated printing sheet usable by the inkjet technique, which can be implemented by known papermaking techniques and which eliminate the defects noted in the results obtained by use of the inkjet technique on the printing sheets described to date.

The object of the invention will be better appreciated by comparison of the results obtained illustrated by the following figures.

Figs. 1 to 6 are representations of results obtained with certain known printers using, according to two examples of implementation, an ordinary inkjet printing paper sold, a specific paper and a paper according to the invention.

Figs. 7 to 9 show one of the advantages provided by a paper according to the invention.

The sheet according to the invention for inkjet printing, consisting of a support sheet, one face of which is surmounted by a layer, said layer being produced by coating of a sauce on this support, is characterized in that it comprises, in its layer, a polyhydroxylated polymeric binder comprising hydroxyl groups in the cis position, said binder having been gelled or coagulated with boric acid and / or its derivatives when lying down, and a filler having absorbing power.

The polyhydroxylated polymeric binder whose hydroxyl groups are in the cis position is preferably of the polyvinyl alcohol or polyvinyl alcohol copolymer type. The products which can be used are, for example, described in the book "Polyvinyl alcohol properties and applications" published by CA FINCH and published by J. WILEY and sons. We will preferably use a polyvinyl alcohol, the characteristics of which (degree of hydrolysis and degree of polymerization) may be suitably chosen as a function, in particular, of the process for preparing the sheet used.

In the sheet according to the invention, all or a substantial part of this polyhydroxylated polymeric binder has been gelled (or coagulated), thanks to the action of boric acid and / or its derivatives (borax, etc.), assuming a function of gelling or coagulating agent.

The amount of gelling agent (or coagulant) used can vary depending on the mode of use of this agent. When said agent is deposited on the support of the sheet, preferably 0.05 to 2 g / m² of boric acid and its derivatives will be used.

The gelation of the polymeric binder must take place during the coating operation, hence the development of various methods which will be explained later and which form part of the invention. It will be noted here that, in the finished product (sheet), a certain proportion of the gelling agent or of derivatives of this gelling agent is generally still present, either in the coating layer, or in the support or on the surface of the support. of the sheet.

The filler having a high absorbency, used in the invention, is a material known for its large specific surface and can be chosen from the following products: silica, various silicates, zeolites, calcined kaolins, diatoms, barium sulphate, d hydroxides. aluminum, melamine-formaldehyde or urea-formaldehyde pigments.

The proportions between the two main constituents of this coating layer, namely the binder and the filler, can vary within a wide range, but are very generally between 10 and 100% by weight of binder relative to the filler.

It is clear that the coating layer may contain additives, conventionally used in such layers, such as, for example, defoamers, surfactants, brighteners, etc. The layer weight is approximately 0.5 to 20 g. / m².

The present invention also relates to methods for producing the sheets according to the invention.

Any support will be used on which a coating sauce will be deposited. The support used may or may not be of a cellulosic nature and may have been obtained by paper or not. We can use paper, cardboard, synthetic film, non-woven support ... The nature and physical properties of said support are not critical and depend mainly on the type of finished product sought.

In a first method, the gelling agent will be provided with said support, either by incorporating said agent into the support itself, or by depositing said agent on the surface to receive the coating sauce. In this case, the coating sauce comprising the polyhydroxylated polymeric binder will simply be deposited on the support comprising said gelling agent and the charge and gelling of said binder will occur during the coating operation.

In a second method, the gelling agent will be incorporated into the coating sauce, but it will be necessary, beforehand, to deactivate (temporarily) said gelling agent and to reactivate it at the time of coating. For example, the inactivated gelling agent can be boric acid which, if it causes an increase in the viscosity of the aqueous medium containing polyvinyl alcohol, does not cause total gelling of this alcohol. In this case, gelation occurs by contact between the coating preparation and the support, the pH of which should preferably be close to neutral.

The coating of the support is carried out by conventional coating methods with a roller (size-press, engraved roller, bar, reverse roll, etc.) or with a blade (air knife, trailing blade, etc.).

In all cases, a smooth and flawless layer is thus obtained, the thickness variations of which between distant points of less than 500 microns in the direction of the plane of the sheet, are insensitive and have no measurable effect. The layer is smoother, has no cracks and is better individualized with respect to the support, the interpenetration area being reduced.

• 1°) - Avec une feuille selon l'invention, la qualité des points obtenus par impression jet d'encre est supérieure à celle que l'on obtiendrait par les procédés déjà décrits, tant du point de vue de leur circularité que de leur uniformité interne, et ceci quel que soit leur diamètre.
• 2°) - De ce fait, il est possible d'élargir la gamme des diamètres de points que l'on peut obtenir en leur conservant cette qualité de forme et d'uniformité, du diamètre mini au diamètre maxi qui sont dans un rapport de 1 à 3 (ceci pour un même volume de goutte d'encre).
• 3°) - Le résultat obtenu ne dépend plus autant qu'avant de la qualité du support utilisé, qui peut être pratiquement quelconque, tant du point de vue composition, morphologie de ses constituants (fibres, charges ...), pouvoir absorbant (porosité, collage ...), structure interne, lissé de surface, etc. Il en résulte plus de facilité, plus de sécurité et un coût réduit de fabrication.
• 4°) - Ce résultat peut être obtenu en une seule opération de couchage, quelle que soit la taille des points désirée, sans avoir à recourir à de difficiles et onéreuses opérations de couchage en deux ou plus de deux opérations successives.
• 5°) - L'invention permet un accroissement de la solidité de la couche.
• 6°) - Elle permet une augmentation de la densité des impressions, à la fois par une modification de la formulation du couchage permise par l'accroissement de sa solidité et par la possibilité d'augmenter le diamètre des points dans de bonnes conditions.

The advantages of the invention can be summarized as follows.

• 1) - With a sheet according to the invention, the quality of the dots obtained by inkjet printing is higher than that which would be obtained by the methods already described, both from the point of view of their circularity and of their uniformity internal, regardless of their diameter.
• 2 °) - As a result, it is possible to widen the range of point diameters that can be obtained by retaining this quality of shape and uniformity, from the minimum diameter to the maximum diameter which are in a ratio of 1 to 3 (this for the same volume of ink drop).
• 3 °) - The result obtained no longer depends as much as before on the quality of the support used, which can be practically any, both from the point of view of composition, morphology of its constituents (fibers, fillers, etc.), absorbency ( porosity, bonding ...), internal structure, surface smoothness, etc. This results in more ease, more security and a reduced manufacturing cost.
• 4 °) - This result can be obtained in a single coating operation, whatever the desired stitch size, without having to resort to difficult and expensive coating operations in two or more of two successive operations.
• 5 °) - The invention allows an increase in the strength of the layer.
• 6 °) - It allows an increase in the density of the prints, both by a modification of the formulation of the coating allowed by the increase in its solidity and by the possibility of increasing the diameter of the points under good conditions.

The invention therefore allows, more easily and cheaply, the optimal adaptation of the quality of the recording sheet to the type of printer for which it is intended.

The nonlimiting examples below illustrate the invention with respect to the prior art.

EXAMPLE 1 :

• a) Un papier absorbant, relativement poreux et peu lissé, caractérisé par les tests suivants :
  • porosité à l'air AFNOR 2,1
  • collage COBB (1 min) 300
  • lissé BEKK 40
• b) Le même papier support a été enduit d'une solution de borax à 5 i de concentration, résultant en un dépôt de borax de 0,4 g/m² en matières sèches.

We used two different media.

• a) An absorbent paper, relatively porous and not very smooth, characterized by the following tests:
  • air porosity AFNOR 2.1
  • COBB collage (1 min) 300
  • smoothed BEKK 40
• b) The same support paper was coated with a borax solution at 5 i concentration, resulting in a borax deposit of 0.4 g / m² in dry matter.

• 70 parts en poids de silice synthétique, en poudre fine, caractérisée par une prise d'huile de 250 g par gramme de poudre <mesuré suivant T 30.022 ou ISO R 787),
• 30 parts en poids d'un silicate d'alumine en poudre, d'un diamètre moyen de particules de 2,5 microns et comportant plus de 95 96 de particules de diamètre inférieur à 10 microns,
• 30 parts en poids d'un alcool polyvinylique de viscosité moyenne <environ 7 à 11 cps en solution à 4 et de degré d'hydrolyse 98,
• quantité d'eau suffisante pour aboutir à une préparation à 10 % de teneur en matières sèches.

In a second stage, these two supports were coated under identical conditions with the following coating sauce:

• 70 parts by weight of synthetic silica, in fine powder, characterized by an oil intake of 250 g per gram of powder <measured according to T 30.022 or ISO R 787),
• 30 parts by weight of a powdered alumina silicate, with an average particle diameter of 2.5 microns and comprising more than 95% of particles with a diameter of less than 10 microns,
• 30 parts by weight of a polyvinyl alcohol of average viscosity <approximately 7 to 11 cps in solution at 4 and of degree of hydrolysis 98,
• sufficient water to produce a preparation with 10% dry matter content.

The solidity of the layer and its bond to the support were measured by the speed at which the layer begins to tear off by printing a Lorilleux 3802 ink on an IGT Ait 2 device. The tearing speeds and the layer weights are the following :

These two coated papers were printed by ink jet on a SIEMENS PT 88 printer, as well as a commercial paper c) sold under the name of Neujet 1/7 as being suitable for this printer among others. These three papers were printed with the same black SIEMENS ink.

Examination of the prints made on these various papers and illustrated by figs. 1 to 3 , shows that the points obtained on paper coated on a support with the use of borax (b) are much more regular than those obtained on other papers. The representations of fig. 1 to 3 correspond to photographs taken with the same POLAROID SX70 camera with the same magnification, under the same lighting conditions and within the same deadlines after printing.

EXAMPLE 2 :

• a) Un papier assez imperméable à l'eau et à l'air et relativement lisse, caractérisé par les tests ci-dessous :
  • porosité à l'air AFNOR ............ 0,6
  • collage COBB (1 min) .............. 15
  • lissé BEKK ...................... 200
• b) Le même papier a été enduit d'une solution de borax à 10 % de concentration, ce qui a donné un dépôt de borax sec de 0,7 g/m².

Similarly, two supports were made from the same base.

• a) A paper that is fairly impermeable to water and air and relatively smooth, characterized by the tests below:
  • AFNOR air porosity ............ 0.6
  • COBB collage (1 min) .............. 15
  • smoothed BEKK ...................... 200
• b) The same paper was coated with a 10% concentration borax solution, which gave a dry borax deposit of 0.7 g / m².

• 100 parts en poids de silice synthétique, de qualité identique à celle de l'exemple 1,
• 20 parts en poids d'un alcool polyvinylique complètement hydrolysé et de viscosité à 4 % comprise entre 26 et 32 cps,
• quantité d'eau suffisante pour obtenir une préparation à 18 % de teneur en matières sèches.

These two supports were coated and dried under identical conditions with the following coating sauce:

• 100 parts by weight of synthetic silica, of quality identical to that of Example 1 ,
• 20 parts by weight of a completely hydrolyzed polyvinyl alcohol with a viscosity at 4% of between 26 and 32 cps,
• sufficient water to obtain a preparation with 18% dry matter content.

Layer deposits and tear resistance are shown in the table below.

The two papers were printed with a Diablo inkjet printer (SHARP I0.0700 technology), as well as a commercial paper c) presented as a reference for such a printer. These three papers were printed with the same black SCHARP ink.

Here again, the examination of the ink spots obtained clearly shows, by comparison of FIGS. 4 to 6 , that on the paper according to the invention said spots are more precise and have a sharper outline.

Operating conditions identical to those above were used to make the basic photographs of the representations according to FIGS. 4 to 6 .

Figs. 7 to 9 correspond to photographs produced according to the same operating conditions as above, from papers treated in accordance with the invention and printed by a SIEMENS PT 88 printer with black SIEMENS ink. Examination of these figures shows that it is possible to widen the range of point diameters that can be obtained, while retaining the qualities of shape and uniformity highlighted above. Examination of these figures shows that it is possible to obtain points of very good quality whose diameters are in a ratio of 1 to 3 for the same volume of ink, by acting on certain parameters of the layer. paper processing, such as specific surface, nature and rate of binders, thickness, humidity.

Claims (5)

1. Sheet for ink-jet printing constituted by a base sheet of which at least one face is topped by a layer produced by coating of a slip, said layer including a gel or a coagulate,
      characterized in that the layer comprises :

   - a gel or a coagulate constituted by reacting boric acid salt and/or its derivatives with a polyhydroxylic polymeric binder comprising hydroxyl groups in the cis position,

   - a filler with an absorption capacity.
2. Sheet according to claim 1, characterized in that the polyhydroxylic polymeric binder is polyvinyl alcohol or a polyvinyl alcohol copolymer.
3. Sheet according to claim 1 or 2, characterized in that the filler is selected from the group comprising silica, silicated, zeolites, calcined kaolins, diatomaceous earths, barium sulfate, aluminium hydroxides and melamine/formaldehyde or urea/formaldehyde pigments.
4. Process for the preparation of a sheet for ink-jet printing from a base sheet, for obtaining a sheet according to one of claims 1 to 3, in which a gellying or coagulating reaction is caused in the layer topping at least one face of the base sheet,
      characterized in that :

   - boric acid and/or its derivatives are applied to the base sheet by incorporation or surface deposition,

   - a coating slip containing a filler with an absorption capacity and a polyhydroxylic polymeric binder with the hydroxyl groups in the cis position is coated then onto said base sheet, said binder being gelled or coagulated with boric acid and/or its derivatives.
5. Process for the preparation of a sheet for jet-ink printing from a base sheet, for obtaining a sheet according to one of claims 1 to 3, in which a gellying or coagulating reaction is caused in the layer topping at least one face of the base sheet,
      characterized in that :

   - a coating slip is produced which contains :

   . a polyhydroxylic polymeric binder with the hydroxyl groups in the cis position,

   . a filler with an absorption capacity and boric acid and/or its derivatives,

   - said slip is applied onto the base sheet whose pH is close to neutrality in order to cause gellyfication or coagulation of the polyhydroxylic polymeric binder by boric acid and/or its derivatives.

Images