JP2008230077A - Inkjet recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording medium which has excellent printing quality at the time of inkjet printing and has a sufficient surface strength for offset printing. <P>SOLUTION: This inkjet recording medium has an ink receptive layer formed on at least, one of the surfaces of a support, and the ink receptive layer contains a binding agent and a powder cellulose manufactured by dry grinding. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ink jet recording medium, and more particularly, to an ink jet recording medium excellent in surface strength as well as color developability and ink absorbability.

  The ink jet recording system has been developed rapidly in recent years, and has features such as easy full color and high speed, low print noise, etc. It has become popular as a color printer in offices. The ink jet recording method is a non-impact printing method in which an ink droplet is ejected from a nozzle toward a recording medium such as paper to form an image, so that the recording medium and the printer are not in direct contact. In addition, since the ink contains a large amount of solvent in order to form stable droplets, the recording medium needs to quickly absorb the ink droplets ejected from the nozzles in order to print with good image quality. . For this purpose, the recording medium is provided with an ink receiving layer.

  In general, the ink receiving layer includes a pigment for absorbing a large amount of ink instantaneously, a binder for binding the pigment to the support, an ink fixing agent for fixing the ink to the ink receiving layer, and various auxiliary agents. Formed from. As the pigment, synthetic amorphous silica is most commonly used from the viewpoint of ink absorbability and color developability. Silica is a highly absorptive pigment, but it is bulky and has large voids, so it can be applied with the same binder amount compared to pigments such as kaolin and calcium carbonate, which are used for general printing coated paper. Since the surface strength of the layer is significantly low, it is not suitable for use on general printing paper. However, as described above, since the inkjet recording method is non-impact printing, the surface strength at the time of printing has not been a big problem in the past, and the ink absorption and color development characteristics are utilized to accept the inkjet recording medium. Has been widely used for layers.

  In recent years, with the rapid spread of inkjet recording methods, for example, it is assumed that inkjet printing is performed after partially performing general offset printing, and inkjet printing paper excellent in both offset printing aptitude and inkjet recording aptitude Development is desired. However, the coating layer composed of a pigment having a high ink absorbability such as silica described above generally has a low surface strength. Also, if a large amount of binder is added to increase the surface strength, the viscosity of the coating solution will increase, making it difficult to apply, resulting in coating unevenness. Since the portion remains adsorbed to the pigment particles, there arises a problem that the print density and ink absorbability of ink jet recording are insufficient. In general, when preparing the coating liquid, the binder is first mixed into an aqueous solution. In this case, since the concentration of the aqueous binder solution is low, increasing the amount of binder added reduces the concentration of the coating solution, which may make it difficult to maintain the designed coating amount. May decrease.

In order to increase the surface strength, as described above, by using a pigment having a low absorbency compared to silica used for general printing coated paper, such as kaolin, talc, calcium carbonate, etc. Although the surface strength can be increased, since these pigments are inferior in ink absorbability, it is difficult to achieve both surface strength and ink jet printing quality. For example, when a light calcium carbonate having a specific surface area of 50 to 130 m ² / g as a pigment component is blended in an amount of 50% by mass or more and silica is less than 50% by mass, the specific surface area of the light calcium carbonate is too large. The effect of improving the surface strength is small (Patent Document 1). In addition, an inkjet recording medium for non-aqueous ink containing 30% by mass or more of heavy calcium carbonate with respect to all pigments in the receiving layer is disclosed (Patent Document 2). In addition, the coloring property is inferior, and there is a disadvantage that it is not suitable for a water-based full-color ink jet printer that is usually used.

Japanese Patent Laid-Open No. 2001-146071 JP-A-2001-260524

  Accordingly, an object of the present invention is to provide an ink jet recording medium that has not only good print quality at the time of ink jet printing but also sufficient surface strength for offset printing.

As a result of intensive studies to solve the above problems, the present inventors have used powdered cellulose produced by dry pulverization instead of the pigment of the ink receiving layer, without deteriorating the inkjet print quality, The inventors have found that the surface strength of the ink receiving layer is improved more than usual, and have reached the present invention.
That is, the present invention is an ink jet recording medium having an ink receiving layer provided on at least one surface of a support, wherein the ink receiving layer contains a binder and powdered cellulose produced by dry pulverization. An inkjet recording medium.

The ink jet recording medium of the present invention is suitable not only for excellent ink jet recording performance but also for offset printing suitability, and therefore suitable for applications in which both offset printing and ink jet recording are performed.

  Hereinafter, the present invention will be described in detail. The support used in the present invention is not particularly limited, and may be transparent or opaque. For example, plastic films such as cellophane, polyethylene, polypropylene, soft polyvinyl chloride, hard polyvinyl chloride, polyester, fine paper, postcard, photographic paper base paper, drawing paper, art paper, art paper, coated paper, cast coated paper, Kraft paper, impregnated paper, synthetic paper, resin-coated paper and the like can be mentioned, and can be used according to the intended use. A support having ink absorbability is particularly preferable.

  As the support having ink absorptivity, for example, paper (coated paper, non-coated paper, etc.) mainly composed of pulp and filler is preferably used. The raw material pulp of the paper includes chemical pulp (coniferous bleached or unbleached kraft pulp, hardwood bleached or unbleached kraft pulp, etc.), mechanical pulp (ground pulp, thermomechanical pulp, chemisermomechanical pulp, etc.), deinking Pulp or the like can be used alone or mixed at an arbitrary ratio.

  In the present invention, the ink receiving layer provided on the support contains powdered cellulose produced by dry pulverization, and does not deteriorate the ink jet printing quality. So guessed. The powdered cellulose used in the present invention (for example, see FIG. 1) is manufactured through the steps of acid hydrolysis of wood pulp and non-wood pulp, followed by filtration / washing, dehydration / drying, pulverization / sieving. It is characterized by being pulverized after drying (so-called dry pulverization). This dry pulverization is a method in which dried pulp is treated under high pressure and pulverized by frictional force generated when the pulps collide with each other. This frictional force is generally smaller than the impact force generated between the pulp and the beads when the beads and the pulp are processed (that is, wet pulverized) in water. For this reason, it is considered that the powdered cellulose obtained by the dry pulverization is one in which the pulp is pulverized and the pulp surface becomes fluffy in the state where the internal voids of the conduit-derived pulp are present.

  For this reason, the powdered cellulose absorbs and fixes the ink in the voids of the powdered cellulose itself like the inorganic pigment, and absorbs the ink by a capillary phenomenon between the cellulose fibers constituting the powdered cellulose. As a result, powdered cellulose has a faster ink absorption rate than the conventional porous inorganic pigments (synthetic silica, etc.). In particular, powdered cellulose made from wood pulp is derived from the raw material conduit. Since it has a large gap, it can hold an excessive amount of ink, so that it is considered that excellent ink absorbability is exhibited.

  Moreover, this powdery cellulose has fine fibers extending outward from the center fibers of the cellulose and fluffing on the surface thereof due to the above-mentioned production characteristics. In this case, sufficient coating layer strength can be obtained, and good general printability can be obtained. Furthermore, since the layer containing powdered cellulose has low frictional resistance, it is considered that good scratching properties can be obtained when powdered cellulose is contained in the outermost layer.

  As the powdered cellulose produced by dry pulverization used in the present invention, powdered cellulose products (manufactured by Nippon Paper Chemical Co., Ltd.) with NP fiber or KC flock, specifically, NP fiber W-10MG2, KC floc W -50, KC flock W-100G, KC flock W-200G, KC flock W-300G, KC flock W-400G (manufactured by Nippon Paper Chemical Co., Ltd.) and the like. Moreover, you may use the equivalent goods of these powdered cellulose manufactured by the dry-type grinding | pulverization like these as mentioned above.

  As the binder used in the ink receiving layer of the present invention, a known resin (natural resin, synthetic resin, etc.) used in conventional coated paper can be used. Specifically, polyvinyl alcohol, starches such as oxidized starch and esterified starch, cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, polyvinyl pyrrolidone, casein, gelatin, soybean protein, styrene-acrylic resin and its derivatives, styrene-butadiene Latex, acrylic emulsion, vinyl acetate emulsion, vinyl chloride emulsion, urethane emulsion, urea emulsion, alkyd emulsion and derivatives thereof can be used alone or in combination as required. In particular, from the viewpoint of ink coloring property, it is preferable to use polyvinyl alcohol.

  The amount of the resin component in the ink-receiving layer is preferably 5 to 50 parts by mass with respect to 100 parts by mass of powdered cellulose, but is particularly limited as long as the required coating layer strength is obtained. Is not to be done.

  The ink receiving layer formed by the present invention includes an ink fixing agent, a pigment dispersant, a thickener, an antifoaming agent, a defoaming agent, a release agent, a foaming agent, a coloring dye, which are usually used in an inkjet receiving layer. Auxiliary agents such as coloring pigments, fluorescent brighteners, ultraviolet absorbers, antioxidants, preservatives, water-resistant agents, surfactants, wet paper strength enhancers, surface sizing agents, and the like that do not impair the effects of the present invention Can be added as appropriate.

Further, in the ink receiving layer used in the present invention, the powdered cellulose used by the dry pulverization method described above and an inorganic or organic pigment can be used in combination as long as the effects of the present invention are not impaired. Examples of the pigment include synthetic amorphous silica, colloidal silica, light calcium carbonate-silica composite particles, kaolin, clay, calcium carbonate, talc, alumina, hydrated alumina (alumina sol, colloidal alumina, pseudoboehmite, etc.), hydroxylation Pigments such as aluminum, magnesium carbonate, satin white, titanium dioxide, montmorillonite, and plastic pigment can be used alone or in combination of two or more.
In the present invention, it is preferable to use compatible amorphous silica or alumina, which has high transparency and improves color developability when ink jet recording is performed.

In the present invention, in order to provide an ink receiving layer on a support, various blade coaters, roll coaters, air knife coaters, bar coaters, gate roll coaters, curtain coaters, short dwell coaters, gravure, which are general coating apparatuses. Each device such as coater, flexographic gravure coater, size press, etc. can be used on-machine or off-machine.
In the present invention, a support such as a base paper can be surface-treated with a calendar device such as a machine calendar, a super calendar, or a soft calendar before and after the application of the ink receiving layer.

  In the present invention, the total number and configuration of the ink receiving layers provided on the support are not particularly limited. That is, two or more ink receiving layers may be provided on one side or both sides of the support. In the present invention, when the ink receiving layer is provided on one side of the support, a coating layer may be provided on the surface of the support opposite to the ink receiving layer for the purpose of curling correction or improving transportability. Is possible.

The coating amount of the ink receiving layer is preferably determined based on the ink absorption capacity of the ink receiving layer and the adhesive strength between the ink receiving layer and the support that can withstand practical use. In the present invention, the dry coating amount is preferably in the range of 3 to 30 g / m ² , more preferably 5 to 20 g / m ² . If the dry coating amount is less than 3 g / m ² , it is difficult for the coating layer, which is an ink receiving layer, to completely cover the support surface, and the ink absorption by the coating layer is not sufficient. Occurs and adversely affects the ink jet printing performance. Moreover, when the dry coating amount exceeds 30 g / m ² , the adhesive strength between the ink receiving layer and the support becomes a level that cannot be practically used, and the peeling of the coating layer from the support, which is called powdering off, occurs. Serious problems arise.

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. Further, “parts” and “%” shown in the examples represent parts by mass and mass% unless otherwise specified.
<Example 1>
15 parts of calcium carbonate as filler and 100 parts of internal sizing agent (size pine NT-87: manufactured by Arakawa Chemical Co., Ltd.) to 100 parts of pulp slurry consisting of hardwood bleached kraft pulp (freezing degree 350 ml csf) % Cationized starch (0.8 parts) was added, and the externally added sizing agent (a solution of 5% phosphorylated starch and 0.5% polyvinyl alcohol) was dried to 3.6 g / m ² by a size press. The base paper (support) having a basis weight of 175 g / m ² was produced by coating with a machine calender.

On one side of the support X, 80 parts of powdered cellulose NP fiber W-06MG (manufactured by Nippon Paper Chemical Co., Ltd.), 20 parts of synthetic amorphous silica fine seal X-37 (manufactured by Tokuyama Corporation), polyvinyl alcohol (PVA103: Kuraray Co., Ltd.) Coating) 50 parts, cationic resin (polyamine ammonia epichlorohydrin, anion requirement: 6 meq / g, molecular weight 100,000) 20 parts, cationic sizing agent (SS335: manufactured by Seiko PMC) 10 parts The liquid (solid content: 21%) was applied using the bar blade coater so that the dry coating amount was 7.5 g / m ² to obtain an ink jet recording medium.

<Example 2>
Powdered cellulose NP fiber W-06MG (manufactured by Nippon Paper Chemicals Co., Ltd.) Instead of using 80 parts of powdered cellulose NP fiber W-10MG2 (manufactured by Nippon Paper Chemicals Co., Ltd.) (Solid content: 21%) was prepared, and this coating solution was applied to the support X in the same manner as in Example 1 so that the dry coating amount was 7.5 g / m ^2. A recording medium was obtained.

<Example 3>
Except for 20 parts of synthetic amorphous silica fine seal X-37 (manufactured by Tokuyama), coating was performed in the same manner as in Example 1 except that 100 parts of powdered cellulose NP fiber W-06MG (manufactured by Nippon Paper Chemicals) was used. A working solution (solid content: 21%) was prepared, and this coating solution was applied to the support X in the same manner as in Example 1 so that the dry coating amount was 7.5 g / m ^2. As a result, an ink jet recording medium was obtained.

<Comparative Example 1>
A coating liquid (solid content: 30%) was prepared in the same manner as in Example 1 except that 80 parts of Tosoh Silica Co., Ltd. nip gel AY-601 was used instead of powdered cellulose NP fiber W-06MG. The coating liquid was applied to the support X in the same manner as in Example 1 so that the dry coating amount was 7.5 g / m ² to obtain an ink jet recording medium.

<Comparative example 2>
Powdered cellulose NP fiber A coating liquid (solid content: 28%) was prepared in the same manner as in Example 1 except that 80 parts of Tokuyama Fine Seal X-12 was used instead of W-06MG. The coating liquid was applied to the support X in the same manner as in Example 1 so that the dry coating amount was 7.5 g / m ² to obtain an ink jet recording medium.

<Evaluation method>
The ink jet recording media obtained in Examples and Comparative Examples were evaluated by the following methods. In each item, if it is evaluated as ◯ or Δ, it can be put into practical use. In addition, regarding the evaluation of inkjet recording, a commercially available inkjet printer PM-G820 (an inkjet printer manufactured by Seiko Epson Corporation) was used. The results are summarized in Table 1.

・ Ink absorbability:
Each solid image of red and green was printed side by side, and the degree of bleeding at the boundary was evaluated.
◎: No border blur at the print part ○: Little border blur at the print part △: There is a border blur at the print part, but the degree is light ×: The border blur at the print part is severe

・ Feathering:
A line of 0.5 Pt was printed on a sample with PM-G820 manufactured by Seiko Epson Corporation, and evaluation was performed by magnifying observation after 3 hours.
○: Feathering is hardly recognized. △: Feathering is slightly recognized, but there is no problem in actual use.

·water resistant:
PM-G820 manufactured by Seiko Epson Co., Ltd. printed “Electric” on the sample in black, and after 3 hours, 20 μl of water was dropped onto the printed portion for evaluation.
○: Bleeding of the printed part is hardly seen Δ: Bleeding of the printed part is seen, but the character can be distinguished ×: The printed part is blurred, and the character can hardly be distinguished.

・ Surface strength:
An adhesive tape (18 mm manufactured by Nichiban Co., Ltd.) was attached to the sample by reciprocating 20 times with a roller, and the amount of the coating layer attached to the adhesive tape was visually evaluated when the adhesive tape was peeled 180 °.
○: There is almost no peeling of the coating layer. Δ: There is peeling of the coating layer, but the degree is light. ×: The coating layer is peeled off and the entire surface of the adhesive tape becomes white.

  As can be seen from Table 1, in Examples 1 to 3 containing dry pulverized cellulose in the ink receiving layer, an ink jet recording medium having good ink absorbability, feathering and surface strength could be obtained. On the other hand, Comparative Example 1 containing synthetic silica having a small particle size instead of pulverized cellulose had insufficient surface strength. In Comparative Example 2 containing synthetic silica having a large particle size, the feathering and surface strength were poor.

Claims (1)

  An ink jet recording medium comprising an ink receiving layer provided on at least one surface of a support, wherein the ink receiving layer contains a binder and powdered cellulose produced by dry pulverization.