FR2862668A1 - Unlayered paper for high-quality ink jet printing e.g. of photographs, comprises silica-filled paper treated inside the paper machine with a formulation containing a hydrophilic binder and predispersed silica - Google Patents

Abstract

Unlayered paper suitable for high-quality ink jet printing comprises a fibrous support uniformly filled with ink-absorbent filler e.g. silica, and coated or impregnated with a formulation containing a hydrophilic binder (polyvinylpyrrolidone or polyvinyl alcohol) and predispersed silica, from an applicator inside the paper machine. Unlayered paper suitable for high-quality ink jet printing, comprising (a) a fibrous support with ink-absorbent filler over the entire thickness of the paper, comprising silica, silicate, aluminosilicate or aluminium pigment and (b) a treatment formulation applied by a coating or impregnation process to at least one side of the paper from an applicator mounted inside the paper machine and consisting of (b1) hydrophilic binder(s) selected from polyvinylpyrrolidones and polyvinyl alcohols (PVAL) and (b2) silica predispersed in an aqueous phase. An independent claim is also included for a method for the production of this paper by (i) making a fibrous web on a paper machine, containing at least 7 (preferably 10-20) wt% ink-absorbent filler as above and (ii) coating or impregnating the resulting paper on at least one side with a formulation (b) as above, preferably containing cationised PVAL as binder and a silica dispersion delivered ready-for-use from the manufacturers with a dry substance content of more than 15 wt%, with the aid of an applicator inside the paper machine. The formulation (b) penetrates to at least 20 (preferably to more than 50) % of the thickness of the fibrous mesh.

Description

to say that the ink of the impression does not come into contact with the fibers

cellulose.

  Also, since the inkjet printing technique exists, most of the research efforts have focused on the improvement of coating formulations, as described for example in FR 2795366 or WO 0145956. .

  However, the system for obtaining inkjet paper by coating has several disadvantages: The touch of the finished paper is very unpleasant, usually referred to as a mineral, compared, for example, with papers with very soft cotton linters, and this all the more so that the layer thickness is greater.

  Coating is usually done in a more expensive off-paper machine operation, since being done offline, and often even in factories other than those producing the paper used as supports, this is particularly essential in the case of textured papers or filigree objects of the invention.

  Coating of very rough papers is extremely difficult or even impossible satisfactorily on some highly textured papers because the processes lead to a clogging of the texture which is both unfavorable for the product from the point of view of print quality and from the point of view of aesthetics (heterogeneity of the surface state).

  In fact, when a relief is requested to the paper, one skilled in the art is generally required to carry out a paper processing operation called embossing to produce the texture after the coating operation which has the double disadvantage of introduce an extra off-machine operation and generally degrade the applied layer.

  In the field of inkjet papers, the coating is generally applied on one side of the paper, to limit the extra cost and because the printing is done only on one side, however for the end user there is always a risk of using the wrong side when printing and mistakes are common.

  In order to solve these various problems, it has been described, in particular in patent EP 747 235, treatment compositions for improving the ink-jet capability of papers, however these compositions applicable on all types of media are always present the unacceptable defect found on uncoated paper which is the heterogeneity of solid areas, moreover the formulation containing exclusively binders does not allow rapid fixing of the ink.

  Extensive laboratory studies have shown that the production of a support using absorbent fillers of the type used in the coating compositions but introduced into the mass of paper, as might be thought by those skilled in the art, does not allow to obtain a satisfactory inkjet quality because the charge has the particularity of absorbing the ink by lowering the optical densities of the prints, so the higher the amount of charge, the faint the printing and it has A linear decay between the amount of feed introduced and the optical densities of the prints has been found, which goes against the desired effect.

  The invention therefore aims to solve the problems posed by the known prior art as regards the surface treatments of uncoated papers and the disadvantages presented by coated papers, in particular with regard to the price of the final paper and the problems related to the texturing or marking of papers.

  According to the invention, the uncoated paper suitable for an inkjet printing of enhanced quality is characterized by the combination of a fibrous support comprising in all its thickness at least one absorbent filler of the inks selected from the family of silicas, silicates , silico-aluminates or aluminum pigments, and a treatment formulation, incorporated by a coating or impregnation system on at least one of the faces of the paper by an applicator device placed inside the machine paper, and comprising at least one hydrophilic binder selected from the family of polyvinyl pyrrolidones or polyvinyl alcohols, and at least one pre-dispersed silica in aqueous phase.

  The advantages of the uncoated paper according to the invention are multiple, in particular such a paper is produced more economically with a cost price lower than a coated paper with a neighboring image quality, especially when the configuration "photo" is selected on the inkjet printer.

  In the categories of paper mainly covered by the invention: printing and writing, texts and covers and fine arts the papers produced have an immediate industrial interest because they come in substitution of existing papers or allow the realization of papers that did not exist before Thus, in the application of printing and writing papers, especially those watermarked used as letterheads, the invention allows the production of papers of the same appearance in terms of smoothness, whiteness, touch, but having a jet quality of superior to commercially available papers that allow the printing of photos or images satisfactorily.

  In the application of textured papers it is possible to use the invention for the production of papers marked with markers, or any other means for printing a relief paper, before it is dry, to obtain papers with superior inkjet quality that allow the printing of photos or images satisfactorily, which is not the case at present for such uncoated papers.

  In the application of fine art papers, watercolor type or art edition, and one of whose goals may be to reproduce on large size inkjet printers works of artists on similar papers to existing ones, the invention allows the manufacture of these papers and their printing with a quality much higher than that of untreated papers but with characteristics of appearance that do not distinguish them from known equivalent art papers.

  More broadly than the aforementioned markets the invention applies to the manufacture of all uncoated paper, textured or not, which must have improved aptitude vis-à-vis the inkjet printing, especially for the printing photos or images.

  Other features and advantages of the invention will become apparent from the following description and examples provided.

  Making an uncoated paper of enhanced inkjet quality requires a completely new paper design since it is impossible, unlike all current embodiments, to immobilize the ink coming from the printer into the printer. a pigment layer on the surface of the paper.

  The ink-jet capability of the papers is here defined compared to "ordinary" papers or standard reprographic papers having an inkjet qualification for desktop printers, ie capable of reproducing text and images. graphics satisfactorily but not photographs or images with strongly contrasting colors.

  Within the meaning of the invention, inkjet-compatible paper with enhanced quality will be understood to mean a paper making it possible to obtain a color impression, with an inkjet printer set in photographic quality, characterized by a high colorimetric average rendering. As an indication, for printing with an EPSON STYLUS PHOTO 750 printer in the following print configuration: E paper option: photo quality inkjet paper, E option: color, E option quality settings: optimal.

  Depending on the operating systems other configurations are accessible, it is retained the basic automatic configuration available after selecting the paper quality.

  Will be considered as printable inkjet with enhanced quality, a paper whose printing obtained under the conditions defined above will be characterized by a colorimetric density measured with a densitometer GRETAG MACBETH 186, corresponding to the arithmetic average of 3 densities optical colors measured on a test pattern made with solid colors: 100% cyan, 100% magenta, 100% yellow, greater than or equal to 0.85 and preferably greater than or equal to 0.90.

  In order to manufacture the papers according to the above qualitative criteria, it is imperative to produce a fibrous network having particular characteristics and to synergistically treat this fibrous network with a treatment formulation penetrating, if possible, deep into the paper and allowing the fibers to be coated. This concept is the opposite of the known embodiment of a coated paper and all the treatments developed to try to prevent the penetration of inks.

  In a paper made according to the invention the printing ink penetrates the porous and rough support and is fixed directly onto the treated fibers.

  In order to maintain the appearance properties of the paper and in particular its feel and texture it is introduced into the support certain categories of absorbent fillers, these are coated with a treatment formulation introduced in a large proportion of the thickness of the paper. a fibrous network formed to impart an ability to rapidly fix inks from the printer, even in a very porous structure such as that formed by textured papers. Unlike coating, there is no physical separation between the ink and the fibrous network, the fibrous network is treated as much as possible in its entirety by a coating of the fibers themselves.

  The paper according to the invention is characterized in that a particular composition which combines cellulosic fibers and / or cotton linters with absorbent fillers is coated in a drying medium by a suitable application means. Which means may be a gluing press, a multiple roller device known as "gate roll" or "massey", an impregnator, a roller device having pre-dosages for the coating formulation such as for example that called "blade metering size press" or any other device comprising at least one roller in contact with the paper so as to facilitate the penetration of the treatment formulation in a significant proportion of the thickness of the fibrous network containing the absorbent or fillers.

  According to the invention, the uncoated paper suitable for inkjet printing of enhanced quality is characterized by the use of a high quantity of at least one absorbent filler of the inks included in the family of silicates, silico-aluminates , silicas, or aluminum pigments such as trihydroxides for example. More specifically, a pigment is introduced having a high internal porosity and a large oil uptake, which generally results in a high adsorption and absorption capacity of the inks. Said high amount of absorbent filler being for this type of pigment above 7% and more particularly above 10% relative to the weight of the fibers introduced.

  According to an advantageous variant of the invention, the porous filler is created within the fiber network itself at the time of preparation of the dough by a conventional system of precipitation of the pigment, such as that obtained by the combination of a silicate of sodium and a di or trivalent metal such as magnesium, calcium or aluminum .... so as to fix as much as possible the charges on the cellulosic fibers.

  In another favorable variant of the invention it is also possible to treat the absorbent filler during or after its formation, before or at the moment of its introduction into the paper pulp, with an additive used as dye fixator conventionally known in the art. ink jet such as for example the CARTAFIX LA or the LOCRONO L sold by the CLARIANT company or with a binder of the type of those used to carry out the treatment formulation described below.

  It is also quite conceivable to carry out a production of the charge by precipitation in situ in the medium, as mentioned above, by introducing into the charge formed, either in its network or on its surface, flocculant additives of the inks. or cationic binders leading to the same effect.

  The maximum allowable absorbent load rate is defined by several parameters including the inkjet print rendering, the type of paper considered and the mechanical characteristics required of the product and independent of the inkjet capability. Usually a load ratio greater than 20% relative to the fibers will be exceptional, the preferred rate in the context of the invention is between 10 and 20% and more particularly around 15%. Absorbent charge rates greater than 20% lead to decreases in optical densities, by trapping the inks, which are too large.

  The use of absorbent filler is known in the coating formulations, however, the introduction of a substantial amount of these fillers into the support is not favorable because a very poor result is obtained if the support without the adapted treatment formulation, especially in terms of optical densities of the inks. And this way all the more important that it is added more loads in the paper.

  Thus the fibrous network alone, drained on the table of the paper machine, obtained according to the invention and described above, is generally of an inkjet capacity lower than the average uncoated paper on the market, textured or not, which runs counter to the logical approach that would be followed by those skilled in the art in developing uncoated paper of enhanced inkjet quality as contemplated. The inkjet capability is always judged according to the test methodology described above.

  The treatment formulation applied by a means usable inside the paper machine is composed of at least one hydrophilic binder having, in the dry state, a very large water absorption capacity, mainly selected in the family of polyvinyl pyrrolidones and derivatives, or normal or modified polyvinyl alcohols. In the context of the invention, it has been found particularly advantageous to use a cationized PVA of which a typical example is the reference CM318 of KURARAY.

  Preferably said hydrophilic binder is incorporated at a level of at least 1% based on the weight of the finished paper and preferably more than 1.5% so as to avoid the powdering of the fillers introduced into the paper.

  Which binder is associated with at least one pre-dispersed silica in aqueous phase having a high solids content. The dispersion of the silica as recently carried out by the silica manufacturers is in fact particularly favorable for carrying out the invention for the following reasons: Silica can be directly used by factories that do not have equipment Specific implementation, E dry extract is higher and more homogeneous preparation than that which could possibly be obtained by a dispersion on the production site, the large amount of silica in the dispersion can increase the overall material In the case of the drying of the treatment formulation and depositing a larger amount of said formulation in the paper, a silica in aqueous phase does not pose the problems usually related to dust and the handling of silica powder. Which problems are crippling at many paper manufacturing sites.

  Such pre-dispersed silicas are, for example, TIXOSIL 365 SP from the company RHODIA, whose solids content is 22% or the grades SYLOJET 703A, 703C, 710A, 710C or 733C from the company GRACE, whose solids vary between 18% and 30% depending on the dispersions.

  It has been found advantageous to introduce into the treatment formulation a ready-to-use pre-dispersed silica, as supplied by the silica manufacturers, in excess of 15% solids.

  Favorably it can be added in the treatment formulation various additives such as flocculants inks, insolubilizers, anti-foams, dyes, compatible brighteners, antifungal agents or more generally all types of additives that usually occur in inkjet compositions, without departing from the scope of the invention. Similarly, the pH of the composition can be adjusted acidic or basic depending on the constituents of the formulation and the intended application.

  It should be noted that the application of a treatment formulation as described above, even at large doses, does not lead alone to any unspecified support, to a satisfactory print quality, especially when large quantities of ink are applied, because the homogeneity of the solids is not satisfactory. It has therefore been concluded that this treatment formulation alone does not allow a significant improvement in the ability to print photos with sufficient quality.

  After tests of combinations between different fibrous supports and different treatment formulations, surprisingly and almost fortuitously, it was found that the combination of a mediocre support and a bath deemed unsatisfactory by him even leads to a printing result much higher than normal if the operating conditions of the invention are respected. This result, which was not predictable in the state of the art, corroborates the concept of coating the fibers themselves, this concept being radically different from that of coated paper.

  In the context of the invention, it has been found particularly advantageous to penetrate the treatment formulation into the fibrous network over a substantial part of its thickness, ie at least 20% and preferably more than 50%, which usually corresponds to a wet weight by weight of treatment formulation of at least 30% with respect to the dry fibrous network. Said penetration into the fibrous network is a necessity so that a correct homogeneity of the printing is obtained simultaneously with a high rendering of the colors. Therefore all the application systems are not equivalent to obtain an optimum printing result and those skilled in the art will prefer to use a sizing press or an impregnator even if other devices are possible.

  The invention also relates to the process for obtaining an uncoated paper suitable for enhanced quality ink jet printing comprising the following two steps: paper-making of a fibrous network comprising at least one load absorbent selected from the family of silicas, silicates, silico-aluminates or aluminum pigments, which absorbent filler is introduced in an amount of at least 7% relative to the amount of fibers introduced and preferably between 10 and 20% Coating or impregnating on at least one side of the paper by an applicator device placed inside the paper machine, a treatment formulation comprising: # at least one hydrophilic binder selected from the polyvinyl pyrolidone family or polyvinyl alcohols, and preferably that of the cationized polyvinyl alcohols, # and at least one pre-dispersed silica in aqueous phase, delivered to by ready-to-use silica manufacturers with more than 15% solids.

  Which treatment formulation penetrates at least 20% of the thickness of the fibrous network and preferably more than 50%.

  Preferably, according to the invention, the uncoated paper is characterized in that the treatment formulation is coated simultaneously on both sides of the paper by means of an applicator device comprising at least one roller in contact with one side of the paper .

  In the process claimed the fibers used to make the paper may be cellulosic and / or cotton linters, wholly or partly, in association or not with synthetic fibers or fibers of other kinds. All additives traditionally used in paper industry such as additional fillers (talc, kaolin, calcium carbonate, etc.), gluing agents, retention agents, dyes, brighteners, etc. may be used, in addition to the aforementioned products which characterize the product. , and this without departing from the scope of the invention, if they remain in low doses, less than 10% relative to the fibers, which do not significantly disturb the ink-jet capability of the paper.

  The texture of the product may be strong or non-existent, the paper may be watermarked or not, of high or low grammage, without departing from the scope of the invention which is to bring a reinforced inkjet ability to uncoated papers while retaining their usual appearance properties including roughness and touch.

  It is also possible, as has been pointed out above, to carry out a treatment of the mass or surface charge used in the paper by a dye flocculating agent, a cationic binder or any other product which would allow precipitation of the inks used, without departing from the scope of the invention.

  In addition to those already mentioned, one of the advantages of the invention is that it is possible to produce a textured paper differently on both sides, directly in the paper-making process, and thus to obtain finally a paper usable in inkjet on both sides, so having two textures per paper, which represents a strong commercial advantage. For example a paper marked with a marker pen on one side, and a smooth surface on the back, or more sophisticated two different textures on both sides by combinations of different marker pens and / or engraved presses.

  The examples below illustrate the invention but are not limiting in any way.

EXAMPLE 1

  According to an advantageous embodiment of the invention, an ink-coated, 100 g / m 2, watermarked uncoated paper is produced by the manufacture of a fibrous support containing a cellulosic composition with 70% short fibers of hardwood and 30% of long fibers of softwood in which is inserted, by weight relative to the fibers, 15% of Sipernat 820A sold by Degussa, 1% by weight of cationic starch, 4% of commercial product AQUAPEL 305 gluing agent from the company HERCULES.

  The preceding composition is drained on the table of the paper machine, pressed and dried in the usual manner to the sizing press.

  The sizing press treatment formulation consists of a solution comprising, by weight relative to the total weight of the formulation: 4% PVP K 90 from ISP (polyvinyl pyrrolidone), 20% pre-dispersed silica TIXOSIL 365 SP from RHODIA and 3% of LOCRON L sold by CLARIANT.

  The previous solution is impregnated in the sheet at a rate of at least 40 L of treatment formulation per 100 kg of paper, ie about 80% of the treated thickness and a level of hydrophilic binder corresponding to 1. 6% by dry weight compared to the paper, then dried post drying.

  In addition to its usual printing and writing skills, the watermarked paper thus formed has a very good printout when an image or photo is printed with a standard desktop inkjet printer, for example an EPSON STYLUS PHOTO 750 with a paper selection in the "photo quality coated paper" configuration.

  Such paper can be used for letter head paper and allow, for example, joint printing of text and photos in a work report or printing of a company logo with fine detail and a image rendering superior to other uncoated watermark papers available on the market.

EXAMPLE 2

  A textured paper of 250 g / m 2 is produced by the manufacture of a base containing a fibrous composition of 100% cotton linters, in which is inserted, by weight relative to the fibers 15% of TIXOLEX 28 of the RHODIA company, 1% by weight of cationic starch, 3% of commercial product of AQUAPEL 305 gluing agent from HERCULES and 3% of calcium carbonate used as an additional filler. The previous composition is deposited on the canvas of a round shape of a paper machine, pressed with a markers felt device to give the texture of a watercolor paper and then dried in the usual way until the end of pre-drying where is coated a sizing press treatment formulation.

  The treatment formulation comprises, by weight, commercial products with respect to the total weight of the solution: 6% cationic PVA CM 318 from KURARAY, 20% TIXOSIL 365SP, 22% dry matter from RHODIA.

  The previous solution is applied to the sheet at a rate of at least 30 L of treatment formulation per 100 kg of paper, which considering this paper represents about 30% of the treated thickness and a quantity of hydrophilic binder of 1.8 % based on the weight of paper.

  The paper thus coated is dried post-drying and the finished product is wound without calendering so as to maintain the texture formed with marker pens. The product has the usual appearance of watercolor paper and a high aptitude for inkjet printing.

  Such paper can be used for art reproduction on large format inkjet printers or as a support for photo prints in desktop printers.

EXAMPLE 3

  A textured paper of 90 g / m 2 is produced by the manufacture of a support containing a fibrous composition of 30% of cotton linters and 70% of eucalyptus fibers in which is inserted, by weight relative to the fibers 15% of TIXOLEXO 28 sold by RHODIA, 1% by weight of cationic starch, 3% of commercial product AQUAPELO 305 gluing agent from the company HERCULES.

  The preceding composition is injected onto the table of the Fourdrinier-type paper machine on which an embossing roll is applied to give the paper a substantial texture and then dried in the usual manner up to the end of the pre-drying stage where the sizing press is coated with treatment formulation consisting of a solution comprising, by weight relative to the total weight of solution: 4% of PVA CM 318 from KURARAY, 10% of SYLOJET8733C, pre-dispersed silica containing 30% of dry matter from the company GRACE, and 5% of LOCRONO L sold by CLARIANT.

  The preceding solution is impregnated into the sheet at a rate of at least 50 L of treatment formulation per 100 kg of paper, ie over its entire thickness and this represents a quantity of hydrophilic binder of 2% relative to the weight of paper. .

  The paper thus treated is dried post-drying and wound without calendering so as to maintain the texture formed with the idler roll. It has all its usual properties plus enhanced quality for inkjet printing, especially for printing photos on desktop printers such as EPSON or HP.

  Such a paper can be used, for example, to make personalized impressions of invitations or event cards, menus, etc.

  This paper has a marked texture on both sides and a touch comparable to that of untreated paper, it can be used on both sides in inkjet and is therefore of undeniable interest for the user who does not have to to be concerned about the face to use.

  The cost of production of this product is much lower than that of a paper that would be laid and then put out of the machine.

EXAMPLE 4

  A textured paper of 640 g / m 2 is produced by manufacturing a support containing a fibrous composition of 100% cotton linters, in which is inserted, by weight relative to the fibers 15% of Sipernat 820A sold by the company Degussa, 1% by weight of cationic starch, 4% by commercial product of AQUAPEL 305 gluing agent from the company HERCULES and 2% of FISSATORE L sold by LAMBERTI, the latter product being introduced into the pulper together with the filler absorbent and fibers, before refining. The previous composition is deposited on the canvas of a round shape of a paper machine, pressed with a markers felt device to give the texture of a watercolor paper on one side and a press system etched on the other face to give a line texture; the fibrous support thus formed is dried in the usual manner until the pre-drying stage where the treatment formulation is coated by means of an impregnator.

  The treatment formulation comprises the following commercial products expressed in% relative to the total weight of the formulation: 5% cationic PVA CM 318 from KURARAY, 25% TIXOSIL 25 365SP, 22% dry matter from RHODIA and 2 % of LOCRON L sold by CLARIANT.

  The previous solution is applied to the sheet at a rate of at least 40 L of treatment formulation per 100 kg of paper, which considering this paper represents about 25% of the treated thickness; this represents a quantity of hydrophilic binder of 2% relative to the weight of paper.

  The paper thus coated is dried post-drying and the finished product is coiled without calendering so as to maintain the texture formed with marker pens and the engraved press. The product has the usual appearance of watercolor paper on one side, a textured texture on the other side and a high aptitude for inkjet printing, especially with an EPSON STYLUS PHOTO 750 printer.

  Such paper can be used for the reproduction of works of art or the manufacture of posters on large format inkjet printers or as a support for photo prints in office printers.

  Of course, the invention is not limited to the embodiments described and shown by way of example, but it also includes all technical equivalents as well as their combinations.

Claims (10)

  1-uncoated paper suitable for an inkjet printing of enhanced quality, characterized by the combination of: a) a fibrous support comprising throughout its thickness at least one absorbent charge of the inks selected from the family of silicas, silicates , silico-aluminates or aluminum pigments, b) a treatment formulation, incorporated by a coating or impregnation system on at least one of the faces of the paper by an applicator device placed inside the paper machine, and comprising: # at least one hydrophilic binder selected from the family of polyvinyl pyrrolidones or polyvinyl alcohols, # and at least one pre-dispersed silica in aqueous phase.   2- uncoated paper suitable for a high quality inkjet printing according to claim 1 characterized in that the absorbent load contained in the fibrous support is in an amount of at least 7%, relative to the amount of fiber introduced, and preferably between 10% and 20%.   3- uncoated paper suitable for enhanced quality inkjet printing according to claim 1 characterized in that at least one hydrophilic binder in the treatment composition is selected from the family of cationized polyvinyl alcohols.   4- uncoated paper suitable for enhanced quality inkjet printing according to claim 3 characterized in that the cationized polyvinyl alcohol is incorporated at a rate of at least 1% based on the weight of the finished paper and preferably more than 1.5%.   5-uncoated paper suitable for a high quality inkjet printing according to claim 1 characterized in that the pre-dispersed silica of the treatment formulation is a ready-to-use solution delivered by the silica manufacturers to more than 15% dry matter.   6- uncoated paper suitable for a high quality inkjet printing according to claim 1 characterized in that it can be textured, watermarked, laid, marked with markers, engraved presses or any other device known to give a relief or heterogeneity to the paper by any method within the paper machine, before the treatment formulation is applied to its surface.   7- uncoated paper suitable for enhanced quality inkjet printing according to claim 1 characterized in that the treatment formulation is coated simultaneously on both sides of the paper by means of an applicator device comprising at least one roller in contact with one side of the paper.   8- uncoated paper suitable for enhanced quality inkjet printing according to claim 7, characterized in that the treatment formulation penetrates inside the fibrous support, by at least one of its faces, in at least 20 % of its thickness and preferably more than 50%.   9- uncoated paper suitable for enhanced quality inkjet printing according to claim 1 characterized in that the absorbent load included in the fibrous network is manufactured in-situ inside the dough by a precipitation process .   10- A process for preparing uncoated paper suitable for enhanced quality inkjet printing, comprising the following two steps: paper-making of a fibrous network comprising at least one absorbent filler selected from the family of silicas, silicates, silico-aluminates or aluminum pigments, which absorbent filler is introduced in an amount at least equal to 7% relative to the amount of fibers introduced and preferably between 10 and 20%, coating or impregnation on at least one of the faces of the paper by an applicator device placed inside the paper machine, of a treatment formulation comprising: at least one hydrophilic binder selected from the family of polyvinyl pyrrolidones or polyvinyl alcohols, and preferably that of the cationized polyvinyl alcohols, # and at least one pre-dispersed silica in aqueous phase, delivered by the silica manufacturers ready e use at more than 15% dry matter.   Which treatment formulation penetrates at least 20% of the thickness of the fibrous network and preferably more than 50%.