JP2004262232A - Ink-jet recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink-jet medium which is suitable for an ink-jet record using an aqueous pigment ink, excellent in coloring performance and rubbing resistance, non-bleeding and enables the formation of a high-quality image and capable of storing for a long time, while the color tone, gloss and feel of which being similar to the ones of common coated sheets of printing paper such as a sheet of art paper and coated sheet of paper and which can be applied for the preparation of commercial leaflets and pamphlets as well as for various printing matters used for publication/advertisement. <P>SOLUTION: The ink-jet recording medium is formed by laminating an undercoat layer with main components consisting of a pigment and binder and a finishing layer with main components consisting of a cationic polymer, one by one, at least on one side of the base material. The portion of 40 wt.% or higher of the total pigment in the undercoat layer is to be a Satin White and/or calcium sulfate. The cationic polymer is to be a quaternary ammonium salt cationic polymer having a SO<SB>2</SB>group or a quaternary ammonium salt cationic polymer having the repeating unit represented in the following chemical formula (1). <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to an ink jet recording medium, and more particularly, to an ink jet recording medium which can be suitably used for ink jet recording using an aqueous pigment ink, and has similar color tone, gloss and feel to general coated printing paper.

  The ink jet recording method is a printing method in which ink droplets are ejected from nozzles of a recording head, and the ink is attached to a recording medium such as paper to record an image. Ink jet recording inks are generally aqueous inks in which a dye-based or pigment-based coloring material is dissolved or dispersed in an aqueous medium, and are broadly classified into dye inks and pigment inks. Until now, dye inks with excellent color reproducibility and the like have been frequently used, but the long-term storability of recorded images has become more important due to the expanded use of inkjet recording technology in digital photography services and commercial printing. As a result, pigment inks that are more excellent in water resistance and light resistance than dye inks and have excellent image fastness have been used.

  In addition, as a recording medium for inkjet recording, uncoated paper typified by PPC paper can be used. However, uncoated paper has insufficient ink absorption amount and ink absorption speed. It is not possible to cope with printing using a large amount of ink as described above, and if color ink jet recording is performed on uncoated paper, there is a possibility that so-called bleed occurs where colors are blurred or mixed unevenly at the boundary of different colors. is there. Examples of the coated paper include coated paper having a coating layer mainly composed of various pigments and binders such as calcium carbonate, satin white, kaolin, and plastic pigment, which are referred to as art paper and coated paper. (See Patent Documents 1 to 5), such a coated printing paper is basically a recording medium for offset printing using an oil-based ink. Bleeding is inevitable.

  Therefore, many recording media for inkjet recording (inkjet recording media) that have good ink absorbency and high image density and can obtain images without bleeding have been proposed. A representative example thereof is a recording medium having a porous layer (ink receiving layer) mainly composed of inorganic particles such as alumina hydrate on a base material (see Patent Document 6). Further, there is known an ink jet recording paper having at least one kind of pigment such as satin white, calcium carbonate, and plastic pigment, and having a coating layer containing cationized pullulan as a pigment binder (see Patent Document 7).

  Further, as an ink jet recording medium using an ink containing an anionic compound such as a water-soluble dye having an anionic group, a recording medium containing a cationic compound in an ink receiving layer or a base material is known ( Patent Document 8). When ink-jet recording is performed on this ink-jet recording medium using a dye ink, the anionic compound in the ink and the cationic compound in the recording medium cause association on the surface of the recording medium by ionic interaction, and It is said that as a result of significantly improving the fixability to a recording medium, an image having good color developability and water resistance can be obtained.

Further, in particular, in the case of an ink jet recording medium having a porous layer (ink receiving layer) as disclosed in Patent Document 6, there is a problem that a recorded image deteriorates with time due to the influence of water, light, ozone, or the like. As a means of solving this problem and improving the storability of the recorded image, a latex layer is further provided on the ink receiving layer, and after the inkjet recording, the latex layer is heated to form a transparent film, whereby the water resistance of the recorded image is improved. A method for improving weather resistance is known (see Patent Document 9).
JP-A-9-256295 JP-A-7-238495 JP-A-8-92894 JP-A-9-67794 JP-A-6-158591 JP-A-2-276670 JP-A-6-328836 JP-A-11-78221 (paragraph numbers [0004] to [0006]) JP-A-7-237348

  Many of the conventional inkjet recording media disclosed in Patent Documents 6 to 9 are basically designed on the assumption that a dye ink which is currently mainstream is used as an inkjet recording ink. Therefore, it was not effective for inkjet recording using a pigment ink. Image formation using dye ink is to form an image by dyeing the recording medium itself by injecting the dye into the inside of the recording medium, and the dye is not remaining on the surface of the recording medium. Since a pigment particle much larger than a dye is retained on the surface of a recording medium and an image is formed by the color development of the pigment particle itself on the surface, an image formed by the pigment ink is compared with an image formed by the dye ink. In addition, differences in color appearance and a decrease in coloration due to irregular reflection of incident light are likely to occur, and pigment particles are easily peeled off, resulting in poor abrasion resistance of a printed portion. As described above, the principle of image formation is different between the dye ink and the pigment ink, and the dye ink is used as a recording ink by using a pigment ink having a difficulty in coloring properties or abrasion resistance of a recorded image. Even if inkjet recording is performed on a conventional recording medium designed on the premise that a recording image is formed, the image quality (coloring properties, prevention of bleeding, etc.) and the preservability (scratch resistance, etc.) are balanced. I can't.

  In addition, conventional inkjet recording media are recording media specialized in unique printing methods that are completely different from the gravure printing method and offset printing method, etc., which are the mainstream in the commercial printing field. It has completely different color tone, gloss, and feel from ordinary coated printing paper (art paper, coated paper) with the above, and is more expensive than other printing paper. With the development of a new business model using technology, the development of an ink jet recording medium having an appearance and texture similar to art paper and coated paper and being affordable is desired. For example, in the commercial printing field, before printing a printed material by operating a rotary press, work (color proofing) for confirming the finish of the printed material using an ink jet printer has been performed in advance. The ink jet recording medium is required to faithfully reproduce the appearance and texture of the printing paper (art paper, coated paper). In addition, the main use of the inkjet recording method is still home use and personal use, and in order to expand this to business use in the future, it is necessary to eliminate the peculiarity of the conventional ink jet recording medium, The development of ink-jet recording media like art paper and coated paper is indispensable. Being able to output ink jet images on such ink jet recording media, in addition to creating commercial leaflets and pamphlets, expanding the ink jet recording method to various printing operations such as publishing and advertising related Becomes possible.

  Therefore, an object of the present invention is suitable for ink jet recording using an aqueous pigment ink, is excellent in coloring properties, excellent abrasion resistance of a printed portion, is free of bleed, and can form an image that can be stored for a long time with high quality and high image quality. The color tone, gloss, and feel are similar to general coated printing paper such as art paper and coated paper, and can be used for commercial leaflets and brochures, and for various printing jobs such as publishing and advertising. Another object of the present invention is to provide a simple ink jet recording medium.

The present inventor has studied various ink jet recording media which are suitable for ink jet recording using an aqueous pigment ink and which have an appearance and texture similar to art paper and coated paper. As a result, (1) Satin white and / or calcium sulfate are main pigments (2) specific cationic compounds such as a quaternary ammonium salt type cationic polymer having an SO ₂ group among the cationic compounds. (3) an undercoat layer containing satin white and / or calcium sulfate and an overcoat layer containing the specific quaternary ammonium salt-type cationic polymer described above; By using a coating layer, the effect is dramatically improved as compared with a case where each layer is provided alone, and a recording medium having such a coating layer is used. The present invention is found to be similar to art paper or coated paper in terms of tone, gloss, and feel, and based on these findings (1) to (3), forms the present invention capable of forming a good pigment ink image. Reached. Sachin White is a pigment that has long been used as a raw material for paper coating. In the field of manufacturing art paper and coated white paperboard, 10-20% by weight of the total pigment is used to improve whiteness, gloss and water resistance. However, it has not been known that a coating layer containing 40% by weight or more of the total pigment of satin white is effective for printing with an aqueous pigment ink. In addition, calcium sulfate is a so-called gypsum, and is generally used as a food additive, a resin filler, a trace moisture remover, an additive for civil engineering and construction, but is not generally used as a paper coating material. In addition, there is no known knowledge that a coating layer containing a high content of calcium sulfate is effective for printing with an aqueous pigment ink.

That is, the present invention provides an ink jet recording medium comprising an undercoat layer containing a pigment and a binder as main components, and an overcoat layer containing a cationic polymer as a main component, which are sequentially laminated on at least one surface of a substrate. 40% by weight or more of all the pigments therein is satin white and / or calcium sulfate, and the cationic polymer is a quaternary ammonium salt type cationic polymer having an SO ₂ group or represented by the following chemical formula (1). An object of the present invention is to provide an ink jet recording medium characterized by being a quaternary ammonium salt type cationic polymer having a repeating unit.

  The ink jet recording medium of the present invention can be suitably used for ink jet recording using an aqueous pigment ink, and has excellent coloring properties, excellent abrasion resistance of a printed portion, no bleeding, and high quality images that can be stored for a long period of time. Can be provided. In addition, this ink jet recording medium is similar in color tone, gloss, and feel to general coated printing paper such as art paper and coated paper, and furthermore, compared with the ink jet recording medium using a conventional porous pigment. Therefore, it can be suitably used for various purposes such as for printing proofreading, for producing commercial leaflets and pamphlets, and for various printing operations such as publishing and advertising.

  Hereinafter, the inkjet recording medium of the present invention will be described in detail.

  The inkjet recording medium of the present invention is a so-called coated paper having a configuration in which an undercoat layer and an overcoat layer are sequentially laminated on at least one surface of a substrate. Hereinafter, the substrate, the undercoat layer, and the overcoat layer will be described in this order.

<Base material>
As the substrate according to the present invention, paper containing cellulose pulp as a main component is preferably used. As such a paper, paper that is wet-processed in a known paper machine by appropriately mixing various pulp such as bleached kraft pulp (coniferous and hardwood), groundwood pulp, and deinked waste paper pulp can be used. In addition, fillers such as talc and calcium carbonate, sizing agents, retention aids, paper strength enhancers, dyes, sulfuric acid bands, pitch control agents, and other various kinds of auxiliary materials used in papermaking are used in this paper. It may contain a chemical agent, and may be manufactured by any papermaking method such as acidic papermaking, neutral papermaking, and alkaline papermaking. Further, the starch, polyvinyl alcohol, surface sizing agent and the like may be applied by various coaters such as a size press and a gate roll coater before final drying of the paper.

<Undercoat layer>
The undercoat layer according to the present invention is a coating layer containing a pigment and a binder as main components, wherein 40% by weight or more, preferably 50% by weight or more of the total pigment is satin white and / or calcium sulfate. When both satin white and calcium sulfate are used, the ratio of the total amount of both to the total pigment in the undercoat layer may be within this range, and the mixing ratio of both is not particularly limited. If the content of satin white and / or calcium sulfate is less than 40% by weight of the total pigment, the undercoat layer becomes dense, the ink absorbency decreases, and bleeding may occur, which may cause a problem in image quality. is there. On the other hand, if the content of satin white and / or calcium sulfate is too large, the strength of the coating film is remarkably reduced, and there is a possibility that powder may fall off during paper transport inside the printer. The content is preferably about 90% by weight of the pigment. In consideration of the fact that a large amount of crystallization water is contained in satin white and calcium sulfate, the content of satin white and calcium sulfate in the present specification is as follows. Based on absolute dry weight measured later.

  As the satin white used in the present invention, those usually used as a raw material for paper coating can be used. Satin white is a fine needle-shaped crystal, industrially produced by adding aluminum sulfate to a lime mud or slaked lime solution with stirring.Chemically, it is calcium sulfoaluminate, but its molecular structure is The properties vary depending on the manufacturing conditions, and the properties also vary. Satin white that can be suitably used in the present invention includes SW-BL series manufactured by Shiraishi Industry Co., Ltd. In addition, from the viewpoint of imparting an appropriate gap to the undercoat layer to achieve a balance between the strength of the coating film and the ink absorbency, satin white has a needle-like crystal having a long side of 0.3 to 3 μm and a short side. Is preferably in the range of 0.05 to 0.3 μm.

The calcium sulfate used in the present invention may be any one that can be used as a coating layer, such as dihydrate (CaSO ₄ .2H ₂ O), hemihydrate (CaSO ₄ .1 / 2H ₂ O), Anhydrous salts (CaSO ₄ ) and the like can be mentioned. Dihydrate is commonly called gypsum, hemihydrate is called calcined gypsum, and anhydrous salt is called anhydrous gypsum or hard gypsum.

  As pigments other than satin white and calcium sulfate, known raw materials for coated paper can be used, for example, kaolin, calcium carbonate, clay, clay, zinc oxide, titanium dioxide, barium sulfate, aluminum hydroxide, magnesium carbonate , Talc, plastic pigment and the like, and one or more of these can be contained in the coating layer.

  In particular, while ensuring the required coating film strength and capable of outputting a good image, art paper, from the viewpoint of a coated paper-like recording medium, as a pigment other than satin white and calcium sulfate in the undercoat layer. It is preferable to use kaolin, calcium carbonate and plastic pigment in combination. In this case, the content of these three pigments is preferably adjusted to the following ranges with respect to all the pigments in the undercoat layer. Kaolin; 5-30% by weight. Calcium carbonate; 5-30% by weight. Plastic pigment; 3-20% by weight.

  As the above-mentioned kaolin and calcium carbonate, those usually used as paper coating raw materials can be used, respectively. Calcium carbonate may be heavy or light, and its crystal structure is not particularly limited, such as an aragonite crystal structure and a calcite crystal structure.

  Further, the above-mentioned plastic pigment is fine particles composed of a polymer compound, and examples thereof include polystyrene-based plastic pigment, styrene-butadiene-based plastic pigment, acrylic-based plastic pigment, and styrene-acryl-based plastic pigment. Two or more types can be used in combination. These are generally commercially available. Plastic pigments having various shapes and properties such as spherical, flat, hollow, fine particle aggregates, and binder pigments can be used.

  The binder (adhesive) contained in the undercoat layer together with the pigment is not particularly limited, and binders used in a general coated paper manufacturing field, for example, various starches, casein, Proteins such as soy protein and gelatin, cellulose-modified resins such as hydroxyethyl cellulose (HEC) and carboxymethyl cellulose (CMC), styrene-butadiene copolymer (SBR), methyl methacrylate-butadiene copolymer (MBR), and acrylic resins Latexes such as those described above, and synthetic polymers such as polyvinyl alcohol can be used as appropriate. Among them, SBR is relatively low cost, but is effective in terms of coating film strength and image quality. Therefore, in the present invention, SBR is used as a main binder (meaning a binder occupying 50% by weight or more of all binders in the ink receiving layer). It can be used preferably.

  The SBR is a copolymer containing butadiene and styrene as main monomers. In addition to these monomers, methacrylic acid, itaconic acid, maleic acid, fumaric acid, methacrylamide, N-methylol methacrylamide, hydroxyethyl methacrylate Those obtained by copolymerizing such a functional group-containing monomer can also be used in the present invention. When SBR is actually used as an ink receiving layer component, an emulsion containing SBR particles as a dispersoid can be used. The average particle diameter of the SBR particles in this emulsion is preferably in the range of 80 to 250 nm in that a coating liquid having good coatability is obtained.

  The content of the binder is preferably adjusted in the range of 5 to 40% by weight based on all the pigments in the undercoat layer, from the viewpoint of ensuring the strength of the coating film required for transporting the paper inside the printer. If the content is less than 5% by weight with respect to the total pigment, the strength of the undercoat layer will be insufficient, and if it is more than 40% by weight, coating suitability and ink absorbability will be reduced, which is not preferable in terms of production cost.

  In the undercoat layer, if necessary, various auxiliaries other than the above components, for example, a dispersant, a coating film reinforcing agent, a dye fixing agent, a preservative, a fungicide, a dusting inhibitor, a water retention agent, a fluid A modifying agent, a curing agent and the like can be contained.

  Above all, a dispersing agent is preferably contained in the undercoat layer from the viewpoint of enhancing the dispersibility of satin white and calcium sulfate and forming an undercoat layer more effective for printing using a pigment ink. Examples of the dispersant include sodium hexametaphosphate, sodium polyacrylate, polycarboxylic acid, sodium polycarboxylate, and sulfonic acid-modified polyvinyl alcohol. The content of the dispersant is preferably adjusted in the range of 0.1 to 4% by weight based on all the pigments in the undercoat layer. If the content is less than 0.1% by weight of the total pigment, the dispersing effect is poor, and if it exceeds 4% by weight, the image quality may be adversely affected.

  Examples of the coating film strengthening agent that can be used in the present invention include ammonium zirconium carbonate, urea formalin resin, urea resin, melamine resin, and glyoxal resin. The dry surface strength (dry lab) and wet surface strength (wet lab) of the undercoat layer can be improved by adding the coating film reinforcing agent to the undercoat layer. The content of the coating film reinforcing agent is preferably adjusted in the range of 1 to 10% by weight based on all the pigments in the undercoat layer. If the content is less than 1% by weight based on the total pigment, the effect of improving the strength of the coating film is poor, and if it exceeds 10% by weight, the ink absorbency is reduced, and the undercoat layer itself is hard and brittle.

In addition, examples of the dye fixing agent usable in the present invention include cationic organic substances, polyvalent metal ions, and cationic surfactants. Examples of the cationic organic substance include low-molecular compounds such as primary to tertiary amine compounds, primary to tertiary amine salts, and quaternary ammonium salts, and primary to tertiary amino groups and primary to tertiary amine bases. Or an oligomer having a quaternary ammonium base or a polymer having these groups. Specific examples thereof include diallyldimethylammonium chloride polymer, epihalohydrin-secondary amine copolymer, diallyldimethylammonium chloride-sulfur dioxide copolymer, diallyldimethylammonium Chloride-acrylamide copolymer, diallylmethyl ammonium salt polymer, diallylamine hydrochloride-sulfur dioxide copolymer, dimethylmethylamine hydrochloride copolymer, polyallylamine, polyethyleneimine, polyethyleneimine quaternary ammonium Compounds, (meth) acrylamide alkyl ammonium salt polymers, ionene like including a quaternary ammonium base. Examples of the polyvalent metal ion include Al ³⁺ , Ca ²⁺ , and Mg ²⁺ . Examples of the cationic surfactant include benzalkonium chloride and the like. The content of the dye fixing agent is preferably adjusted in the range of 0.1 to 10% by weight based on all the pigments in the undercoat layer. If the content is less than 0.1% by weight based on the total pigment, the effect of improving the water resistance and color developability of the recorded image is poor. May be caused.

The coating amount of the undercoat layer is preferably 7 to 50 g / m ² , more preferably 15 to 35 g / m ² in terms of dry weight, from the viewpoint of image quality and ink absorbability. If the coating amount is less than 7 g / m ² , the desired effect cannot be sufficiently obtained, and the base material cannot be sufficiently covered. On the other hand, if the coating amount is more than 50 g / m ² , there is a possibility that coating failure or cracking of the coating layer may occur.

  In addition, from the viewpoint of securing good ink absorbency, the undercoat layer preferably has a porosity of 9.5% or more determined by the following (measurement method).

(Measuring method)
A coating layer to be measured is coated on a polyethylene terephthalate (PET) film having a basis weight of 47.5 g / m ² so as to have a dry weight of 30 g / m ^2, and JIS P8140 of the coating layer is applied. Is measured by the Cobb method based on the water absorption. Specifically, a 130 mm square sample (a coating film provided on a PET film) was prepared, sandwiched by a circular clamp used in the Cobb method, and 50 ml of distilled water was poured. The weight of the sample at this time is obtained by discarding the distilled water therein, and the difference between this weight and the weight of the sample before water absorption (47.5 + 30 = 77.5 g / m ² ) is obtained. The porosity can be obtained by substituting the thus obtained “water absorption by the Cobb method based on JIS P8140” into the following (Equation 1).

<Overcoat layer>
The overcoat layer according to the present invention is a coating layer containing a cationic polymer as a main component. This cationic polymer causes association with the coloring material in the ink or the dispersant of the coloring material by ionic interaction, and causes the coloring material to be instantaneously aggregated. This is related to important functions and effects of the present invention.

In the present invention, as the cationic polymer, a quaternary ammonium salt type cationic polymer having an SO ₂ group (hereinafter, also referred to as “cationic polymer A”) or a repeating unit represented by the above chemical formula (1) is used. Quaternary ammonium salt type cationic polymer [(N, N-dimethyl-N- (2-hydroxypropyl) ammonium chloride salt type cationic polymer; hereinafter also referred to as "cationic polymer B") ".

  The cationic polymer A is particularly preferably a diallyldimethylammonium chloride salt-type cationic polymer having a repeating unit represented by the following chemical formula (2).

  Each of the cationic polymers A and B has a weight average molecular weight of preferably 2,000 or more, more preferably 4,000 or more. If the weight-average molecular weight of the cationic polymer is less than 2,000, the effect of improving the abrasion resistance of the recorded image is poor, and the above-described deterioration in image quality due to the occurrence of roller traces may not be prevented. On the other hand, if the weight average molecular weight of the cationic polymer is too large, the ink absorbability may be impaired, and it is preferable to use one having a weight average molecular weight smaller than 100,000.

  Examples of the cationic polymer A that can be suitably used in the present invention include PAS-A-1 (weight average molecular weight 2000), PAS-A-5 (weight average molecular weight 4000), and PAS-A manufactured by Nitto Boseki Co., Ltd. 92 (weight average molecular weight 5000).

  Examples of the cationic polymer B that can be suitably used in the present invention include KHE104L (weight average molecular weight 20,000) manufactured by SENKA CORPORATION.

  By the way, since the above-mentioned overcoat layer is a resin layer containing a polymer as a main component, there is a slight difficulty in drying the ink, which may cause the following problem. That is, as shown in FIG. 1, the paper transport mechanism of the inkjet printer transports the recording medium M on which printing has been completed by the recording head 10 in the paper discharging direction with the paper discharging rollers 12 while pressing the printing surface P with the rollers 11. In general, the ink is applied to the overcoat layer having poor ink drying properties, and when the ink is brought into contact with the rollers 11 in an insufficiently dried state, the rollers have passed through the surface of the overcoat layer. Traces (called "roll traces") are formed, and the image quality is significantly reduced.

  Therefore, as a result of various studies by the present inventors, it has been found that the occurrence of traces of rollers can be prevented by including a specific surfactant in the overcoat layer. That is, by including one or more surfactants selected from the group consisting of a fluorine-based surfactant and a silicone-based surfactant in the overcoat layer, the cations can be formed without causing a decrease in image quality due to traces of rollers. The effect (improvement of the coloring property and the abrasion resistance of the recorded image) by the conductive polymer can be enjoyed.

The above-mentioned fluorine-based surfactant is a general surfactant having a hydrophilic group and a hydrophobic group, and a part or all of a hydrogen atom (H) bonded to a carbon atom (C) in the hydrophobic group is a fluorine atom (F ). The hydrophilic group may be either ionic or nonionic, and is not particularly limited. Examples of the fluorine surfactants, for example, cationic fluorochemical surfactant represented by such general formula Rf-NR'R "HX; formula Rf-OH, general formula _{Rf-BNR '(CH 2)} nOH _{, Rf-BN (C 2 H} 4 O) a non-ionic fluorine-based surface active agents represented by like nH and the like. here, Rf is selected from the group consisting of some or all of the H in the alkyl group substituted with F X represents a silver halide, R ′ and R ″ each represent H or a lower alkyl group, and B represents CO or SO ₂ .

The above-mentioned silicone-based surfactant is an ordinary surfactant having a hydrophilic group and a hydrophobic group, which contains a silicon atom (Si) in the main chain of the hydrophobic group. Typical examples of the silicone surfactant include a polyether-modified silicone oil represented by the general formula (CH ₃ ) ₃ Si [OSi (CH ₃ ) ₂ ] x (C ₂ H ₄ O) yCH _3. As Here, x and y each represent an integer of 1 to 15.

  The content of the surfactant is preferably adjusted in the range of 0.2 to 15% by weight based on the cationic polymer in the overcoat layer. When the content of the surfactant is less than 0.2% by weight, there is no effect in preventing the deterioration of the image quality due to the trace of the roller, and conversely, even if the content is more than 15% by weight, no significant improvement is observed.

It is preferable that the above-mentioned overcoat layer contains colloidal silica from the viewpoint of increasing the abrasion resistance (the difficulty of the coating layer surface being damaged). Colloidal silica is silica particles (SiO ₂ ) in which primary particles are colloidally dispersed without aggregation in water or an organic solvent that mixes well with water. The average particle size of the primary particles of the colloidal silica is preferably in the range of 30 to 100 nm from the viewpoint of ink absorption and surface gloss. The shape of the colloidal silica may be spherical, or may be particles in which beads are connected in a bead shape or branched and connected by a special treatment (chain shape, pearl necklace shape, etc.). Further, those whose surfaces are modified with ions or compounds such as ammonia, calcium, and alumina can also be used.

  Examples of the colloidal silica suitably used in the present invention include, for example, Snowtex S, Snowtex N, ST-XS, ST-O, ST-OL, ST-C, ST-20 (all manufactured by Nissan Chemical Industries), Cataroid SI-350, Cataloid SI-30, SN, SA, S-20L, S-20H, S-30L, S-30H (manufactured by Catalyst Kasei Kogyo), Aerosil 200, 200V, 200CF, 300 (manufactured in Japan) Aerosil).

  The content of colloidal silica is preferably in the range of 10 to 90% by weight based on the cationic polymer in the overcoat layer. When the content of the colloidal silica is less than 10% by weight based on the cationic polymer, the effect of improving the scratch resistance is poor. On the other hand, when the content is more than 90% by weight, the ink absorbency may be reduced.

  In the overcoat layer, if necessary, various auxiliaries other than the above components, for example, ultraviolet absorbers, light stabilizers, quenchers, antioxidants, fungicides, preservatives, thickeners, wetting agents , A flow improver, a pH adjuster, an antifoaming agent, a foam inhibitor, a leveling agent, an antistatic agent and the like.

The coating amount of the above-mentioned overcoat layer is preferably adjusted in the range of 0.6 to 10 g / m ² in terms of dry weight. If the coating amount of the overcoat layer is less than 0.6 g / m ² , a problem may occur in ink absorption. If it exceeds 10 g / m ² , an appearance similar to art paper or coated paper cannot be obtained, and There is a possibility that the deterrent to the occurrence of roller traces is inferior.

<Manufacturing method>
The ink jet recording medium of the present invention having the configuration described above can be manufactured in the same manner as a known coated paper. For example, a so-called wet-on-dry method in which an undercoat layer is applied first, followed by a drying step, and then an overcoat layer may be used, or the overcoat layer is applied immediately after the undercoat layer is applied A so-called wet-on-wet method of drying after drying may be used. The overcoat layer has excellent drying properties after coating, and as described below, the coating amount of the overcoat layer may be smaller than that of the undercoat layer. You can also.

  The method of applying the coating liquid for the overcoat layer or the undercoat layer is not particularly limited, and includes an air knife coater, a roll coater, a bar coater, a blade coater, a slide hopper coater, a gravure coater, a flexographic gravure coater, a curtain coater, and an extrusion coater. The coating can be performed in a usual manner using a known coating device such as a floating knife coater, a comma coater, a die coater, a gate roll coater, and a size press.

  When it is desired to further increase the glossiness or surface strength, a calendar treatment can be applied to the overcoat layer or the undercoat layer. The calendering treatment is a treatment method in which a coated paper or the like is passed between pressurized and heated rolls to smooth the surface thereof using a known calender such as a super calender or a gloss calender. In addition, a coated surface having a higher glossiness can be obtained by a so-called casting method in which the coated surface is transferred to a mirror surface such as a metal or a film.

  As described above, the ink jet recording medium of the present invention is most suitable for ink jet recording using an ink containing a pigment-based color material (pigment ink), and is used for color ink jet recording which requires a high ink absorption capacity. Can provide an image having good image quality and storage stability. Examples of the pigment-based coloring materials include titanium oxide and iron oxide, inorganic pigments such as carbon black produced by a known method such as a contact method, a furnace method, and a thermal method; azo pigments (azo lakes, insoluble azo pigments, condensed azo pigments); , Chelate azo pigments, etc.), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinoflurone pigments, etc.), dye chelates (for example, Organic dyes such as nitro pigments, nitroso pigments, and aniline black.

  Generally, a pigment ink for ink jet recording is an aqueous pigment ink in which the above pigment-based coloring material is contained in an aqueous medium comprising water, various organic solvents, a surfactant and the like. The content of the pigment-based coloring material in the ink is appropriately adjusted in consideration of characteristics required for the ink and the like, and is usually about 0.5 to 30% by weight based on the total weight of the ink. In the case of performing color ink jet recording, four or more colors of inks of three primary colors of subtractive mixture of yellow (Y), magenta (M) and cyan (C) or black (K) and other colors are added thereto. Use ink.

  Further, the ink jet recording medium of the present invention can be used for a recording method other than the ink jet recording method, for example, a sheet-fed offset printing method, a rotary offset printing method, and the like. Since the offset printing method uses an ink (oil-based pigment ink) containing a pigment-based color material, the inkjet recording medium of the present invention can be sufficiently used.

  Hereinafter, the present invention will be described more specifically with reference to examples of the present invention and test examples showing the effects of the present invention. However, the present invention is not limited to the examples. In the examples, “parts” and “%” are based on weight unless otherwise specified.

(Preparation of undercoat liquid)
Undercoat liquids 1 to 4 shown in the following [Table 1] to [Table 4] were prepared.

  In the above undercoating liquids 1 and 2, an attempt was made to prepare coating liquids having the same composition as the undercoating liquids 1 and 2 except that no dispersant was added. Could not be prepared. From this, it can be said that a dispersant is indispensable in the preparation of a coating liquid containing satin white or calcium sulfate.

(Preparation of overcoat liquid)
The following overcoat solutions 1 to 6 (all having a solid content of 15% by weight) were prepared.

(Overcoat liquid 1)
15 parts of cationic polymer A (manufactured by Nitto Boseki, PAS-A-5, Mw = 4,000), 0.3 part of a fluorinated surfactant (manufactured by Dainippon Ink and Chemicals, F-144D, nonionic) and water 85 parts were prepared by mixing.

(Overcoat liquid 2)
15 parts of cationic polymer B (manufactured by Senka, KHE104L, Mw = 20,000), 0.3 part of a fluorinated surfactant (manufactured by Dainippon Ink and Chemicals, F-144D, nonionic) and 85 parts of water were mixed. Prepared.

(Overcoat liquid 3)
15 parts of cationic polymer A (PAS-A-5, manufactured by Nitto Boseki, Mw = 4,000), 0.3 part of silicone surfactant (BYK348, nonionic, manufactured by BYK Japan) and 85 parts of water are mixed. Prepared.

(Overcoat liquid 4)
It prepared by mixing 15 parts of cationic polymers A (Nitto Boseki, PAS-A-5, Mw = 4,000) and 85 parts of water.

(Overcoat liquid 5)
15 parts of a quaternary ammonium salt type cationic polymer having no SO ₂ group [PAS-J-81 (diallyldimethylammonium chloride-acrylamide copolymer), manufactured by Nitto Boseki Co., Ltd., Mw = 200,000], fluorine-based interface It was prepared by mixing 0.3 parts of an activator (F-144D, nonionic, manufactured by Dainippon Ink and Chemicals) and 85 parts of water.

(Overcoat liquid 6)
15 parts of a cationic polymer A (manufactured by Nitto Boseki, PAS-A-5, Mw = 4,000), 15 parts of colloidal silica (manufactured by Nissan Chemical Industries, Snowtex ST-OL, average primary particle diameter of 40 to 50 nm) And 0.3 part of a fluorine-based surfactant (F-144D, nonionic) manufactured by Dainippon Ink and Chemicals, and 70 parts of water.

[Example 1]
Using a wire bar, apply the undercoat liquid 1 on a whole surface of one side of a base material (trade name “Marshmallow” <110>, basis weight 128 g / m ² , manufactured by Oji Paper) so that the dry weight becomes 25 g / m ^2. After uniformly coating and drying, using a Yuri Roll desktop calendar PSG180, the temperature was 50 ° C., the linear pressure was 30 kg / cm, and the speed was 2 m / min. And a super-calender treatment was performed by reciprocating once to form an undercoat layer. Next, overcoating liquid 1 was uniformly applied to the entire surface of the undercoat layer using a wire bar so that the dry weight was 2 g / m ² , thereby forming an overcoat layer. The ink jet recording medium thus obtained was used as a sample of Example 1.

[Examples 2 to 12 and Comparative Examples 1 to 6]
In Example 1, an ink jet recording medium was produced in the same manner as in Example 1 except that the types and amounts of the undercoat liquid and the overcoat liquid were appropriately changed, and Examples 2 to 12 and Comparative Examples 1 to 4, respectively. Samples were used.
A commercially available general coated printing paper (trade name “OK Topcoat N” <135>, basis weight 135 g / m ² , manufactured by Oji Paper) was used as a sample of Comparative Example 5.
Further, a commercially available coated paper for ink jet recording (trade name “MC mat paper” manufactured by Seiko Epson) was used as a sample of Comparative Example 6.

(Test example)
For each of the above-mentioned ink jet recording media, color development, bleeding, rubbing resistance of a printed portion, coating film strength, similarity in appearance, glossiness of white paper, anti-rolling property, rubbing resistance and offset printing suitability were evaluated by the following methods. The results are shown in Table 5 below.

(Evaluation method of coloring property)
Using a pigment ink jet printer ("PM4000PX" manufactured by Seiko Epson), 100% color patches of KCMY are printed on the surface of the coating layer of the ink jet recording medium. , The reflection optical density (OD value) was measured under the conditions of a viewing angle of 2 degrees, a light source of D50, and no filter, and if the sum of the OD values of the four colors of KCMY exceeded 7.5, the result was A (good color developability). B having the total OD value of four colors of 6.0 or more and 7.5 or less is B (no problem in practical use), and the total OD value of four colors is less than 6.0 (the average OD value is less than 1.5) ) Was designated C (impractical).

(Bleed evaluation method)
Using the above-mentioned PM4000PX, 100% color patches of yellow and black are printed on the surface of the coating layer of the ink jet recording medium, and adjacent portions of the two color patches (regions where image quality deterioration is most easily discriminated) are visually observed, respectively. Samples with no color mixing were rated A, those with slight color mixing were rated B (no practical problem), and those with color mixing such that the color boundaries were not clear were rated C (impractical).

(Evaluation method of abrasion resistance of printed portion)
A 100% color patch of KCMY was printed on the surface of the coating layer of the inkjet recording medium using the PM4000PX to prepare a printed material. Then, the printed matter is fixed so that the inclination angle of the printing surface becomes 60 degrees, and the color patch printing portion is rubbed 10 times reciprocally while applying a load of 1 kg using an eraser having a width of 20 mm. Observed by visual inspection, the color patch where no scratch or peeling was seen was A (good rub resistance of printed portion), the color patch was slightly scratched but there was no practical problem B and the color patch was peeling. Is C (impractical).

(Method of evaluating coating film strength)
A Nichiban adhesive tape was adhered to the surface of the coating layer of the ink jet recording medium, and a roll having a weight of 5 kg was reciprocated two times on the tape. Then, the tape was manually peeled off at a constant peeling speed. A (peeling of the coating film strength) causes peeling between materials (paper), B (partially no problem in practical use) when the coating layer partially peels off, and C (practical) when the coating layer peels off almost completely. No).

(Method of evaluating appearance similarity)
Using a Gretag Macbeth X-Rite938, the CIELAB value (L ^* / a ^* / b ^* ) of the coating layer surface of the inkjet recording medium was measured under the conditions of a viewing angle of 2 degrees, a light source of D50, and Black Backing. JIS Z8730 from these measured values and the CIELAB value (91/0 / -2) of ISO standard paper type 1 (art paper) or type 3 (coated paper) used for “Japan Color color reproduction printing 2001”. The specified color difference (ΔE ^* ) is calculated, and ΔE ^* of 4.0 or less is A (similar in appearance to art paper and coated paper), and ΔE ^* of more than 4.0 and less than 7.0 is B ( The appearance similarity limit) and ΔE ^* of 7.0 or more were C (the appearance was not similar to art paper and coated paper).

(Evaluation method for glossiness of blank paper)
According to TAPPI T480 om-90, the glossiness at 75 degrees of the coating layer surface of the above-mentioned ink jet recording medium was measured, and 50% or more of the measured value was A (a glossiness equal to or higher than that of art paper or coated paper), 40 % Or more and less than 50% was B (practical limit), and less than 40% was C (unsuitable for practical use). The measured value of the 75 degree glossiness of the ISO standard paper type 1 (art paper) or type 3 (A2 gloss white coated paper) is about 60 ± 10%.

(Evaluation method of roller trace prevention)
After printing a 100% color patch of KCMY on the surface of the coating layer of the ink jet recording medium using the PM4000PX, visually observe the surface of the coating layer (printed surface) without any trace of rollers. Was rated as A (good roller mark prevention), B was a case where roller traces were slightly observed but there was no practical problem, and C was one where the roller traces were conspicuous and were not practical.

(Evaluation method for scratch resistance)
The two unprinted ink jet recording media are superposed on each other so that the coating layer surfaces face each other, and a weight of 40 g / m ² is applied to the entirety of these recording media, and the lower portion is placed under the weight. The recording medium was removed by hand, and the state of the surface of the coating layer was visually observed. A where no scratch was seen, B was seen where some scratches were found but there was no practical problem, and scratches were clearly seen. C that was not practically usable.

(Evaluation method for offset printing suitability)
Using an RI printing suitability tester (manufactured by Ishikawajima-Harima Sangyo Kikai), offset printing was performed on the above-mentioned ink jet recording medium, and color development and surface strength were evaluated by the following methods.

<Offset color development>
Using the above-mentioned RI printing suitability tester, using three color inks of C, M, and Y (TK Hi-Echo SOY, manufactured by Toyo Ink), under the printing conditions of a printing cylinder of 8000 m / h and an ink filling amount of 0.5 cc / one time, Solid printing of each color was performed on the surface of the coating layer of the inkjet recording medium. The reflection optical density (OD value) of each printed portion was measured using Spectrolino SPM-50 manufactured by Gretag Macbeth under the conditions of a viewing angle of 2 degrees, a light source D50, and no filter, and evaluated according to the following evaluation criteria.
Evaluation Criteria A: C color print portion 1.7 or more, M color print portion 1.6 or more, and Y color print portion 1.5 or more. All colors have high image density and good offset coloring.
B: 1.4 or more C color print parts, 1.3 or more M color print parts, and 1.2 or more Y color print parts. Practical limit.
C: Less than 1.4 of C color print portion, less than 1.3 of M color print portion, or less than 1.2 of Y color print portion. Not practical.

<Offset surface strength>
Using the RI printing suitability tester, solid printing was performed on the surface of the coating layer of the inkjet recording medium with K ink (Ink Tack 15, manufactured by Toyo Ink) under the same printing conditions as above, and the printed paper surface was printed. The state of paper peeling was visually observed and evaluated according to the following evaluation criteria.
Evaluation Criteria A: No paper peeling, and little paper dust adhered to the printing cylinder. Good surface strength.
B: No paper peeling, but paper dust adheres to some parts of the printing cylinder. Practical limit.
C: Paper peeling has occurred. Not practical.

FIG. 2 is an explanatory diagram of a paper transport mechanism of the inkjet printer.

Explanation of reference numerals

10 Recording head 11 Roller 12 Discharge roller M Recording medium P Printing surface

Claims (10)

In at least one surface of the substrate, an undercoat layer containing a pigment and a binder as main components, and an ink jet recording medium obtained by sequentially laminating an overcoat layer containing a cationic polymer as a main component,
40% by weight or more of the total pigment in the undercoat layer is satin white and / or calcium sulfate, and the cationic polymer is a quaternary ammonium salt type cationic polymer having an SO ₂ group or represented by the following chemical formula (1). An ink jet recording medium comprising a quaternary ammonium salt type cationic polymer having a repeating unit represented by the formula:

  2. The ink jet recording medium according to claim 1, wherein 50% by weight or more of the total binder in the undercoat layer is a styrene-butadiene copolymer.   The undercoat layer contains one or more dispersants selected from the group consisting of sodium hexametaphosphate, sodium polyacrylate, polycarboxylic acid, sodium polycarboxylate, and sulfonic acid-modified polyvinyl alcohol. 3. The ink jet recording medium according to 1 or 2. The inkjet recording medium according to any one of claims 1 to 3, wherein the porosity of the undercoat layer determined by the following (measurement method) is 9.5% or more.
(Measuring method)
A coating layer to be measured is applied on a polyethylene terephthalate film having a basis weight of 47.5 g / m ² so that the dry weight becomes 30 g / m ^2, and the Cobb method based on JIS P8140 of the coating layer is applied. And the porosity of the coating layer is determined by the following (Equation 1).

The quaternary ammonium salt type cationic polymer having an SO ₂ group is a diallyl dimethyl ammonium chloride salt type cationic polymer having a repeating unit represented by the following chemical formula (2). 5. The ink jet recording medium according to any one of 4.

  The inkjet recording according to any one of claims 1 to 5, wherein the overcoat layer contains at least one surfactant selected from the group consisting of a fluorine-based surfactant and a silicone-based surfactant. Medium.   The ink jet recording medium according to any one of claims 1 to 6, wherein the overcoat layer contains colloidal silica. And wherein the coating amount of the undercoat layer is in the range of 15 to 35 g / m ² by dry weight, and the coating amount of the overcoat layer is in the range of 0.6~10g / m ² by dry weight The ink jet recording medium according to claim 1.   The ink jet recording medium according to any one of claims 1 to 8, wherein the base material is a paper containing cellulose pulp as a main component. The inkjet recording medium according to any one of claims 1 to 9, wherein the inkjet recording medium is used in a recording method using an ink containing a pigment-based coloring material.

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