JP2005280035A - Inkjet recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording medium capable of obtaining high recording quality in ink jet recording using an aqueous pigment ink and having an appearance similar to coated printing paper such as coated paper or art paper.
In an inkjet recording medium having an ink receiving layer on at least one side of a substrate, the ink receiving layer is formed on an undercoat layer containing two types of calcium carbonate of aragonite type and calcite type and a binder. A two-layer structure is formed by laminating an overcoat layer containing a cationic polymer.
[Selection figure] None

Description

  The present invention relates to an ink jet recording medium, and more particularly to an ink jet recording medium suitable for ink jet recording using an aqueous pigment ink and having an appearance similar to a coated printing paper such as coated paper or art paper.

  The ink jet recording method is a printing method in which an image is recorded by ejecting ink droplets from a recording head and attaching the ink to a recording medium such as paper. As recording media for ink-jet recording, it is possible to use plain paper such as general office paper or coated paper that does not consider ink-jet characteristics, but full color such as photographs and high-definition illustrations that require high-definition printing. In applications and the like, it is necessary to use a recording medium having higher ink absorbability. As such a recording medium, there is a recording medium called an ink jet recording medium, in which an ink receiving layer mainly composed of inorganic fine particles such as silica is provided on a substrate. This ink jet recording medium exhibits high ink absorbency due to the gaps between adjacent pigments in the ink receiving layer and the pores of the pigment particles themselves, and the ink drying speed is high, the image density is high, and there is little blurring. It has ideal ink jet characteristics.

  Ink for ink jet recording is generally water-based ink in which a dye-based or pigment-based color material is dissolved or dispersed in an aqueous medium, and is roughly classified into dye ink and pigment ink. Up to now, dye inks with excellent color development and color reproducibility of recorded images have been used extensively. However, in recent years, preservation of recorded images has become more important due to the expansion of applications such as digital photography services for inkjet recording technology and commercial printing. Accordingly, attention has been focused on pigment inks that are superior in water resistance and light resistance of recorded images as compared with dye inks.

  Image formation with pigment ink is very different from image formation with dye ink. That is, a dye ink is an image formed by dyeing a dye into the recording medium to form an image. The dye does not stay on the surface of the recording medium. Much larger pigment particles remain on the surface of the recording medium and form an image by the color development of the pigment particles themselves. Therefore, the image formed with the pigment ink has a defect that the image density is generally lower than that of the image formed with the dye ink, and a difference in color due to irregular reflection of incident light tends to occur. Many conventional inkjet recording media are designed on the assumption that recording is performed with dye ink, which is currently the mainstream, and recording is performed using pigment ink whose principle of image formation is significantly different from that of dye ink. However, in many cases, the image density is insufficient and a satisfactory image quality cannot be obtained.

Therefore, Patent Document 1 discloses an ink-jet recording medium that can obtain a sufficient image density even when recording with an aqueous pigment ink and is excellent in water resistance and strength of an ink receiving layer. The receiving layer contains silica, aragonite calcium carbonate, silanol-modified polyvinyl alcohol and hydrated aluminum oxide, and the silica has a pore volume of 0.9 to 1.5 ml / g and an average particle diameter of 2 to 5 μm. An ink jet recording sheet using silica and containing 50% by weight or more of silica is disclosed.
JP 2003-251930 A

  Along with the expansion of applications of ink jet recording technology, the characteristics required of ink jet recording media are not limited to orthodox characteristics such as improvement in image quality and water resistance of recorded images, but also extend to their appearance. For example, in the small-lot printing and short-run printing markets, there has been a full-scale shift to printing that has been performed in the offset printing method and gravure printing method to the inkjet recording method, and inkjet recording used in such applications. In addition to high recording quality, the medium is a coated printing paper such as coated paper or art paper that is used for offset printing, etc. It is required to be similar in appearance. Also, in some commercial printing fields, etc., color proofing is performed using an ink jet printer to confirm the finished product in advance before the main printing, in which a rotary press is operated to print a large amount of printed matter. The color proofing inkjet recording medium is also required to have an appearance similar to that of coated paper or art paper.

  However, the ink jet recording medium is basically premised on the use of water-based ink, and the composition of the coating layer is greatly different from the coating printing paper for offset printing method and gravure printing method using oil-based ink. Therefore, its appearance is also very different from coated printing paper. In addition, the inkjet recording medium is expensive and expensive compared to coated paper or the like. There has not yet been provided an ink jet recording medium that solves such problems relating to appearance and manufacturing cost, and that can provide good recording quality by recording with aqueous pigment ink.

  Accordingly, an object of the present invention is to provide an ink jet recording medium that has high recording quality in ink jet recording using an aqueous pigment ink and has an appearance similar to that of coated printing paper such as coated paper or art paper. .

  In order to achieve the above object, an ink jet recording medium of the present invention is an ink jet recording medium having an ink receiving layer on at least one side of a substrate, and the ink receiving layer comprises two types of calcium carbonate of aragonite type and calcite type. An overcoat layer containing a cationic polymer is laminated on an undercoat layer containing a binder and a binder.

  The ink jet recording medium of the present invention can provide a high-quality image having high image density and no bleeding in ink jet recording using an aqueous pigment ink. In addition, this inkjet recording medium is similar in appearance to coated printing paper, such as coated paper, in terms of its overall appearance based on color tone, glossiness, etc., so it can be used for printing proofing, commercial leaflets and brochures. It can be used for a wide range of applications including printing applications that have been performed by offset printing and gravure printing so far, such as for various printing business such as publishing and advertising.

  Hereinafter, the ink jet recording medium of the present invention will be described in detail. The ink jet recording medium of the present invention is a so-called coating type ink jet recording medium having an ink receiving layer on at least one surface of a substrate.

  The base material may be any material that can be coated with an ink receiving layer. For example, paper, resin-coated paper, resin film, plastic plate, non-woven fabric, cloth, metal film, metal plate, or a composite of these bonded together A base material etc. can be used. Among these, paper mainly composed of cellulose pulp is preferably used in the present invention. As raw materials for cellulose pulp, usually wood materials such as conifers and hardwoods are used, but besides these, grass fibers such as straw, esparto, bagasse and kenaf, and bast fibers such as hemp, cocoon, husk and trichome Or cotton can be used. In this invention, 1 type of these pulp raw materials may be used independently, and 2 or more types may be used together. The pulping method is not particularly limited, and a known pulping method such as kraft pulp, sulfite pulp, groundwood pulp, semi-chemical pulp, chemi-ground pulp, refiner ground pulp or the like can be used. Recycled pulp (deinked pulp) made from waste office paper, old newspapers, old magazines and the like is also preferably used in the present invention. In addition, inorganic fibers such as glass fibers, or synthetic fibers such as polyester fibers and aramid fibers can be appropriately used as necessary.

  The paper (paper base material) as the base material can be mixed with various auxiliaries usually used for paper making. For example, inorganic fillers such as clay, talc, light calcium carbonate, calcined kaolin, aluminum oxide, aluminum hydroxide, titanium oxide as fillers to improve paper flexibility, surface smoothness, opacity, printability, etc. Can be used. Further, a rosin sizing agent can be used as an internal sizing agent, and in this case, a sulfuric acid band can be used in combination as a fixing agent. When a neutral sizing agent such as an alkyl ketene dimer or alkenyl succinic acid is used, a cationic fixing aid such as cationic starch can be used in combination. Furthermore, if necessary, a polyacrylamide polymer, starch, or the like can be used as a paper strength enhancer.

  The base material may be subjected to a smoothing process such as super calendering, brushing, and cast finishing as necessary.

  The ink receiving layer formed on the substrate is a two-layer coating layer, and is formed by sequentially laminating an undercoat layer and an overcoat layer in order from the substrate side.

  The undercoat layer contains two types of calcium carbonate of aragonite type and calcite type, and a binder as essential components. By using two types of calcium carbonate having different crystal structures (aragonite type is orthorhombic and calcite type is hexagonal) in combination, ink necessary for ink jet recording is combined with the action of the overcoat layer described later. Absorbability can be ensured, and an appearance similar to coated printing paper such as coated paper or art paper can be imparted to the ink jet recording medium.

  From the viewpoint of ensuring the effect of the undercoat layer, the weight ratio of the two types of calcium carbonate of the aragonite type and the calcite type in the undercoat layer is aragonite type: calcite type = 1: 9 to 9: 1. It is preferable to be in the range.

  The content of calcium carbonate in the undercoat layer (total of aragonite type and calcite type) is preferably in the range of 60 to 95% by weight with respect to the total solid content of the undercoat layer. If the calcium carbonate content is less than 60% by weight, sufficient ink absorptivity cannot be obtained. If the calcium carbonate content exceeds 95% by weight, the coating film strength decreases, and the calcium carbonate falls off when the paper is conveyed inside the printer. There is a risk of powder falling.

  If necessary, a pigment other than calcium carbonate can be contained in the undercoat layer. Examples of pigments that can be used for the undercoat layer include inorganic pigments such as kaolin, satin white, calcium sulfate, clay, clay, zinc oxide, titanium dioxide, barium sulfate, aluminum hydroxide, magnesium carbonate, talc, and silica, or polystyrene. And organic pigments such as plastic pigments, styrene-butadiene plastic pigments, acrylic plastic pigments, and styrene-acrylic plastic pigments. In the undercoat layer, one of these pigments may be used alone or a plurality of types may be used in combination with the above two types of calcium carbonate.

  In addition, as the binder contained in the undercoat layer, one that functions as an adhesive for binding calcium carbonate onto the substrate can be used, for example, methyl cellulose, methyl hydroxyethyl cellulose, methyl hydroxypropyl cellulose, and Cellulose adhesives such as hydroxyethyl cellulose, starch and modified products thereof, gelatin and modified products thereof, natural polymer resins such as casein, pullulan, gum arabic, and albumin or derivatives thereof, polyvinyl alcohol and modified products thereof, styrene Latex and emulsions such as butadiene copolymer, styrene-acrylic copolymer, methyl methacrylate-butadiene copolymer, ethylene-vinyl acetate copolymer, vinyl polymers such as polyacrylamide and polyvinylpyrrolidone, Li ethyleneimine, polypropylene glycol, polyethylene glycol, and maleic acid or a copolymer thereof, and the like anhydride. In the present invention, one of these may be used alone, or a plurality of these may be used in combination.

  The content of the binder is preferably adjusted in the range of 5 to 40% by weight with respect to the total pigment in the undercoat layer. When the content of the binder is less than 5% by weight of the pigment, there is a risk of powder falling due to insufficient coating strength of the undercoat layer. On the other hand, if the binder content exceeds 40% by weight with respect to the pigment, the ink absorbability is lowered, and the image quality of the recorded image may be adversely affected.

  In the undercoat layer, in addition to the above calcium carbonate and binder, if necessary, a cationic dye fixing agent, a pigment dispersant, a thickener, a fluidity improver, a viscosity stabilizer, a pH adjuster, a surfactant, Antifoaming agent, antifoaming agent, mold release agent, foaming agent, penetrating agent, coloring dye, coloring pigment, fluorescent whitening agent, ultraviolet absorber, antioxidant, leveling agent, preservative, antibacterial agent, water resistance agent Various additives such as a wet paper strength enhancer and a dry paper strength enhancer can be appropriately contained.

  On the other hand, the overcoat layer laminated on the undercoat layer contains a cationic polymer as an essential component. Immediately after the aqueous pigment ink is applied on the topcoat layer by adding a cationic polymer to the topcoat layer that is the outermost layer of the ink jet recording medium, the anionic pigment or dispersant contained in the ink is overcoated. Aggregation reaction occurs instantaneously with the cationic polymer in the layer, and the aggregate of the pigment is fixed on the surface of the topcoat layer or on the surface layer, thereby improving the color development (image density) of the recorded image. In the recorded image, it is possible to effectively prevent a phenomenon in which colors are smeared or mixed non-uniformly at different color boundary portions, so-called bleeding. As a result, combined with the above-described action of the undercoat layer, a high-quality and high-quality image can be obtained.

Examples of the cationic polymer include a quaternary ammonium salt type cationic polymer having an SO ₂ group (hereinafter also referred to as “cationic polymer A”) and a fourth unit having a repeating unit represented by the following chemical formula (1). Preferred is a quaternary ammonium salt type cationic polymer [(N, N-dimethyl-N- (2-hydroxypropyl) ammonium chloride type cationic polymer; hereinafter also referred to as “cationic polymer B”].

  As the cationic polymer A, a diallyldimethylammonium chloride salt type cationic polymer having a repeating unit represented by the following chemical formula (2) is particularly preferable.

  Both the cationic polymers A and B have a weight average molecular weight of preferably 2000 or more, and more preferably 4000 or more. If the weight average molecular weight of the cationic polymer is less than 2000, the effect of improving the image density is poor, and bleeding may not be effectively prevented. On the other hand, if the weight average molecular weight of the cationic polymer is too large, the ink absorbability may be impaired. Therefore, it is preferable to use a cationic polymer having a weight average molecular weight of less 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-92 (weight) manufactured by Nitto Boseki. Average molecular weight 5000) and the like.

  Examples of the cationic polymer B that can be suitably used in the present invention include KHE104L (weight average molecular weight 20000) manufactured by SENKA.

  The more the above-mentioned cationic polymer is, the more preferable the topcoat layer is. Usually, the total solid content of the topcoat layer is a cationic polymer, but if necessary, the above-mentioned various additives that can be added to the undercoat layer are appropriately contained in the topcoat layer. Can be made.

  The inkjet recording medium of the present invention can be produced by the same method as for ordinary coated paper. The various components of the undercoat layer described above are usually prepared as water-based coating solutions, such as air knife coaters, curtain coaters, slide lip coaters, die coaters, blade coaters, gate roll coaters, bar coaters, rod coaters, roll coaters, It coats on the said base material using various coating apparatuses, such as a bill blade coater, a short dwell blade coater, and a size press. And an undercoat layer can be formed on a base material by drying after coating. Next, an overcoat layer can be formed by applying a coating liquid (aqueous emulsion) containing the cationic polymer on the undercoat layer in the same manner as the undercoat layer and drying.

  When it is desired to increase glossiness and surface strength, the top coat layer or the undercoat layer can be smoothed by a calendar device. As the calendar device, a gloss calendar, a super calendar, a soft calendar, or the like can be used. Further, the overcoating layer or the undercoating layer can be made highly glossy by a so-called casting method in which the coated surface is copied onto a mirror surface such as metal or film.

If the coating amount of the undercoat layer is too small, the ink absorbability decreases, and it becomes difficult to obtain a coated paper-like appearance. On the other hand, if the coating amount is too large, the effect of the undercoat layer is saturated and the economy is poor. From such a viewpoint, the coating amount of the undercoat layer is preferably in the range of 5 to 30 g / m ² by dry weight.

On the other hand, the coating amount of the topcoat layer is preferably 0.6 to 10 g / m ² in terms of dry weight. If the coating amount of the topcoat layer is less than 0.6 g / m ² , the effect of improving the image density and preventing bleeding is low, and if it exceeds 10 g / m ² , a coated paper-like appearance may not be obtained.

  The ink jet recording medium of the present invention is compatible with various inks, and is particularly effective for a recording system using an ink containing at least a pigment (pigment ink) as a coloring material. In particular, the ink jet recording medium of the present invention is most suitable for an ink jet recording system using an aqueous pigment ink.

  An aqueous pigment ink for ink jet recording is usually prepared by containing a pigment-based color material in an aqueous medium composed of water, various organic solvents, a surfactant and the like. Examples of pigment-based color materials include titanium oxide and iron oxide, inorganic pigments such as carbon black produced by known methods such as contact method, furnace method, thermal method; azo pigments (azo lakes, insoluble azo pigments, condensed azo pigments) , Chelate azo pigments, etc.), polycyclic pigments (eg, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, etc.), dye chelates (eg, Organic dyes such as nitro pigments, nitroso pigments, aniline black, and the like. The content of the pigment-based color material is usually about 0.5 to 30% by weight with respect to the total weight of the ink. When color ink jet recording is performed, three or more subtractive primary inks of yellow (Y), magenta (M), and cyan (C), or black (K) and other colors are added to four or more colors. Ink is 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. The “parts” and “%” shown in this example are based on weight unless otherwise specified.

<Preparation of undercoat liquid>
Undercoat liquids 1 to 3 were prepared by the following procedure. In all cases, the solid content concentration was 15%.
Undercoat liquid 1: Aragonite-type calcium carbonate (Callite SA, manufactured by Shiroishi Central Research Laboratories) 70 parts, calcite-type calcium carbonate (light calcium carbonate made by Maruo calcium), and polyvinyl alcohol (PVA105, manufactured by Kuraray) as a binder Prepared by mixing 25 parts in water.
Undercoat liquid 2: 90 parts of aragonite type calcium carbonate (Callite SA, manufactured by Shiroishi Central Research Laboratories), 10 parts of calcite type calcium carbonate (light calcium carbonate made of Maruo calcium),
And 25 parts of polyvinyl alcohol (PVA105, manufactured by Kuraray) were mixed in water.
Undercoat liquid 3: prepared by mixing 100 parts of aragonite-type calcium carbonate (Callite SA, manufactured by Shiroishi Central Research Laboratory) and 25 parts of polyvinyl alcohol (PVA105, manufactured by Kuraray) in water.

<Preparation of topcoat liquid>
The topcoat liquids 1-2 were prepared by the following procedure. In all cases, the solid content concentration was 15%.
Topcoat liquid 1: 15 parts of cationic polymer A (PAS-A-5, Mw = 4,000), 0.3 part of fluorosurfactant (F-144D, nonionic, manufactured by Dainippon Ink and Chemicals, Inc.) Prepared by mixing 85 parts of water.
Topcoat liquid 2: prepared by mixing 15 parts of cationic polymer B (KHE104L, Mw = 2,0000), 0.3 part of a fluorosurfactant (F-144D) and 85 parts of water.

[Example 1]
The undercoat liquid 1 is uniformly applied with a bar coater to a dry weight of 15 g / m ² on the entire surface of one side of a paper base (gold rhombus, basis weight 128 g / m ² , manufactured by Mitsubishi Paper Industries), and dried. To form an undercoat layer. Subsequently, the above-mentioned overcoat liquid 1 was uniformly coated on the entire surface of this undercoat layer with a bar coater so that the dry weight was 2 g / m ² , thereby forming an overcoat layer. The ink jet recording medium thus produced was used as a sample of Example 1.

[Example 2]
In Example 1, an ink jet recording medium was produced in the same manner as in Example 1 except that the undercoat liquid 2 was used instead of the undercoat liquid 1, and this was used as a sample of Example 2.

Example 3
In Example 1, an inkjet recording medium was produced in the same manner as in Example 1 except that the overcoating liquid 2 was used instead of the overcoating liquid 1, and this was used as a sample of Example 3.

[Comparative Example 1]
In Example 1, an ink jet recording medium was produced in the same manner as in Example 1 except that the overcoat layer was not formed, and this was used as a sample of Comparative Example 1.

[Comparative Example 2]
An ink jet recording medium was produced in the same manner as in Example 1 except that the undercoat liquid 3 was used in place of the undercoat liquid 1 in Example 1, and this was used as a sample of Comparative Example 2.

[Test example]
About each said sample (inkjet recording medium), the white background gloss and appearance similarity were evaluated by the following method. Further, using an inkjet printer (PM-4000PX, manufactured by Seiko Epson), four colors of cyan (C), magenta (M), yellow (Y), and black (K) are formed on the recording surface of each sample. Using water-based pigment ink (ink standardly installed in PM-4000PX), color patches with a duty of 100% for each color are recorded to obtain recorded materials. The bleed and color developability of these recorded materials are evaluated by the following methods. did. The evaluation results are shown in [Table 1] below.

(Evaluation method for white paper gloss)
According to TAPPI T480 om-90, the 75-degree glossiness of the surface of the coating layer of each of the above samples was measured, and when the measured value was 50% or more, A (glossiness equivalent to or better than art paper or coated paper), 40% or more and less than 50% was designated as B (practical limit), and less than 40% was designated as C (unusable). The measured value of 75 degree gloss of the ISO standard paper type 1 (art paper) or type 3 (A2 gloss white coated paper) is about 60 ± 10%.

(Appearance similarity evaluation method)
Measure the CIELAB value (L ^* / a ^* / b ^* ) of the coating layer surface of each sample under the conditions of viewing angle 2 degrees, light source D50, Black Backing using X-Rite938 manufactured by Gretag Macbeth Co., Ltd. Specified in JIS Z8730 from these measured values and CIELAB values (91/0 / -2) of ISO standard paper type 1 (art paper) or type 3 (coated paper) used for “Japan Color Color Reproduction Printing 2001” Color difference (ΔE ^* ) is calculated, ΔE ^* is 4.0 or less A (appearance is similar to art paper and coated paper), and ΔE ^* is more than 4.0 and less than 7.0 B (appearance) (Similarity limit), ΔE ^* of 7.0 or higher was defined as C (art paper and coated paper are not similar in appearance).

(Bleed evaluation method)
Immediately after printing, a portion where the Y and C color patches of the recorded matter are adjacent to each other (a portion where image quality deterioration is most easily discerned) is visually observed. A portion where no color mixture is observed is A (no bleed). Although it was slightly seen, B was used as a practical problem, and C was used as a color mixture where the color boundary was not clear.

(Evaluation method of color development)
For each color patch of the recorded matter, the reflection optical density (OD value) was measured under the conditions of a viewing angle of 2 degrees, a light source D50, and no filter using a Spectrolino SPM-50 manufactured by Gretag Macbeth Co. evaluated.
Evaluation criteria A: The sum of the OD values of the four colors of CMYK exceeds 7.5. High image density and good color development.
B: The total of the OD values of the four colors is 7.5 to 6.0. There is no practical problem.
C: The sum of the OD values of the four colors is less than 6.0 (an average OD value of less than 1.5). Not practical.

Claims (4)

In an inkjet recording medium having an ink receiving layer on at least one side of a substrate,
The ink-receiving layer is formed by laminating an overcoat layer containing a cationic polymer on an undercoat layer containing two types of calcium carbonate of aragonite type and calcite type and a binder. Medium. The cationic polymer is a quaternary ammonium salt type cationic polymer having an SO ₂ group or a quaternary ammonium salt type cationic polymer having a repeating unit represented by the following chemical formula (1). The ink jet recording medium according to claim 1.

The quaternary ammonium salt type cationic polymer having the SO ₂ group is a diallyldimethylammonium chloride type cationic polymer having a repeating unit represented by the following chemical formula (2). Inkjet recording medium.

The inkjet recording medium according to any one of claims 1 to 3, wherein the inkjet recording medium is for aqueous ink containing at least a pigment as a coloring material.