JP2008087301A - Inkjet recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording medium which gives high glossy feeling in the case of using silica as a pigment, and has an excellent ink absorption, and high productivity/yield. <P>SOLUTION: The inkjet recording medium has a silica-containing under layer composed mainly of a pigment and a binder, formed on at least one surface of a support, and an ink receptive layer formed on the surface of the under layer by a cast coating process. The under layer is formed by first applying a coating liquid containing 0.1 to 20 pts.mass of quaternary ammonium hydroxide for 100 pts.mass of pigment and by drying the coating liquid. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording medium having an ink receiving layer formed by a cast coating method.

In general, the inkjet recording method is to form and record dots by attaching ink droplets ejected by various mechanisms onto the recording paper, and there is no noise compared to the dot impact type recording method, In addition, there are advantages such as easy full color and high-speed printing. On the other hand, inks used for ink jet recording are usually water-based inks using direct dyes, acid dyes, etc., and thus have a drawback of poor drying properties.
In particular, recently, with the widespread use of high-resolution digital video, digital cameras, scanners, and personal computers, there are many opportunities to handle high-definition images, and these hard copies are often output by inkjet printers. Along with this, the required characteristics for ink jet recording media have been diversified, and in particular, there has been a growing demand for recording media having glossiness comparable to silver salt photographs.

Properties required for ink jet recording paper include high ink drying speed, high print density, no ink overflow or bleeding, and no paper wavy due to ink absorption. . A method of manufacturing a high-quality inkjet recording paper satisfying these characteristics by a cast coating method has already been proposed (see Patent Document 1 and Patent Document 2).
Further, as a method for imparting sufficient ink absorbability to the ink jet recording paper, generally, the coating amount of the ink receiving layer is increased. However, when the ink receiving layer is provided by the casting method, the drying load is limited because the coating layer needs to be dried on the cast drum, and it is difficult to set a large coating amount. Therefore, it has been studied to provide an under layer having ink absorptivity under the ink receiving layer (cast layer).

JP-A-62-95285 JP-A-5-59694

By the way, in order to improve ink absorptivity, it is conceivable to use silica having a large oil absorption amount as a pigment contained in the coating layer. Moreover, since the solid content concentration of a coating liquid can be made high if the pigment density | concentration of a coating liquid becomes high, the drying load after coating can be reduced and a production rate can be improved. However, silica has poor dispersibility in the coating liquid, and it is difficult to increase the concentration of the paint. In addition, when the concentration of the coating solution is forcibly increased using silica, the pigment dispersibility at the time of dispensing deteriorates and the physical properties of the coating deteriorate, resulting in problems such as the occurrence of streaks during coating. . In addition, there is a problem of reducing glossiness.
Accordingly, an object of the present invention is to provide an ink jet recording medium having high glossiness when using silica as a pigment, excellent ink absorbability, and high productivity and yield.

As a result of studies to solve the above problems, the inventors have found that the above problems can be solved by increasing the pigment concentration in the coating liquid by adding a specific cationic dispersant to the coating liquid. It was.
That is, the ink jet recording medium of the present invention is provided with an under layer mainly composed of a pigment containing silica and a binder on at least one surface of a support, and is formed on the surface of the under layer by a cast coating method. An ink jet recording medium provided with an ink receiving layer, wherein the under layer is coated with a coating liquid containing 0.1 to 20 parts by mass of a quaternary ammonium hydroxide as a dispersant with respect to 100 parts by mass of the pigment. It is characterized by being dried after work.

  In the ink jet recording medium of the present invention, an under layer containing an under layer pigment is provided on at least one surface of a support, and an ink receiving layer formed by a cast coating method is provided on the surface of the under layer. Ink jet recording medium, wherein the ink receiving layer is composed mainly of a pigment for an ink receiving layer containing silica and a binder, and is 0.1 to 20 parts by weight with respect to 100 parts by weight of the pigment for the ink receiving layer. It is characterized by being casted after coating a coating liquid containing quaternary ammonium hydroxide as a dispersant.

  The pigment concentration in the coating solution is preferably 30 to 60% by mass.

  According to the present invention, when silica is used as a pigment, an inkjet recording medium having high glossiness, excellent ink absorbability, and high productivity and yield can be obtained.

  The present invention is an ink jet recording medium in which an under layer is provided on at least one surface of a support, and an ink receiving layer formed by a cast coating method is provided on the surface of the under layer. At least one of the under layer and the ink receiving layer is formed by applying a coating liquid containing a pigment containing silica and the following dispersant.

<Support>
As the support used in the present invention, sheet-like materials such as paper, cloth, resin film, and resin-coated paper can be preferably used, but preferably paper (coated paper, uncoated paper, etc.) is used. Use. As the raw material pulp of the paper, chemical pulp (coniferous bleached or unbleached kraft pulp, hardwood bleached or unbleached kraft pulp, etc.), mechanical pulp (ground pulp, thermomechanical pulp, chemithermomechanical pulp, etc.), deinked pulp Etc. can be used alone or in admixture at any ratio. The pH of the paper may be acidic, neutral or alkaline. In addition, when a filler is included in the paper, the opacity of the paper tends to be improved. Therefore, it is preferable to include a filler. Examples of the filler include hydrated silicic acid, white carbon, talc, kaolin, clay, calcium carbonate. Well-known fillers such as titanium oxide and synthetic resin fillers can be used.

1. Embodiment of Inkjet Recording Medium Including Dispersant in Underlayer (First Embodiment)
<Under layer>
In this embodiment, the under layer is mainly composed of a pigment containing silica and a binder.
(Pigment)
Silica is used as the pigment. As the silica, synthetic amorphous silica can be preferably used, and the synthetic amorphous silica may be any method such as precipitated silica or gel silica.
The synthetic amorphous silica used for the under layer preferably has an oil absorption of 200 ml / 100 g or more, more preferably 300 ml / 100 g or more. If the amount of oil absorption is less than 200 ml / 100 g, the ink absorbability becomes insufficient, and the defect becomes particularly prominent in the mixed color portion where the ink adhesion amount is large on the recording surface of the obtained recording medium. In addition, the smaller the oil absorption amount, the more adsorption of the binder to the silica, and the ink absorbability decreases. Although any silica particle size can be used, the preferred particle size is 5 μm or less. The BET specific surface area of the synthetic amorphous silica is preferably 200 to 500 m ² / g.
The use of synthetic crystalline silica produced by the gel method improves the coating layer strength, and the use of synthetic crystalline silica produced by the precipitation method improves color developability. Is preferably used.

In particular, it is more preferable to use synthetic crystalline silica having a secondary particle diameter of 5 to 15 μm occupying 20% by mass or more. If it does in this way, the coating layer intensity | strength of an under layer will improve and the paper dust generation | occurrence | production at the time of cutting can be reduced. When the secondary particle diameter of the synthetic crystalline silica is less than 5 μm, the coating layer strength is lowered, and a large amount of paper powder tends to be generated during cutting. As the secondary particle size of the synthetic crystalline silica increases, the coating layer strength improves. However, if it exceeds 15 μm, the voids of the layer increase too much, and the ink receiving layer provided on the under layer tends to be difficult to form uniformly. At the same time, the coating property of the coating liquid is lowered, and the productivity tends to be lowered. The secondary particle diameter of the synthetic crystalline silica can be measured by a laser diffraction / scattering method. When the proportion of the synthetic crystalline silica having a secondary particle size of 5 to 15 μm is less than 20% by mass, the ink absorption of the under layer is good, but the coating layer strength tends to be lowered.
In addition, as described above, from the viewpoint of coating layer strength and paper dust generation, it is preferable to use synthetic crystalline silica having a secondary particle diameter of 5 to 15 μm occupying 20% by mass or more, but has secondary particles. Since synthetic crystalline silica has lower dispersibility than other silica (colloidal silica), the present invention using a dispersant is useful.

In addition to silica, pigments include alumina, alumina hydrates (alumina sol, colloidal alumina, pseudoboehmite, etc.), aluminum silicate, magnesium silicate, calcium silicate, magnesium carbonate, light calcium carbonate, heavy calcium carbonate, kaolin, talc. , Calcium sulfate, titanium dioxide, zinc oxide, zinc carbonate, aluminum hydroxide, calcined clay and the like, which are usually used as pigments for coated paper, can be used alone or in combination of two or more with silica.
The proportion of silica in the total pigment is preferably 30% by mass or more, more preferably 60% by mass or more, and the total pigment may be silica.

(binder)
The under layer is required to have ink absorptivity and transparency, and in order to secure the surface strength of the ink receiving layer thereon, a hydrophilic binder is usually used as a binder, but the effect of the present invention is impaired. As long as there is no binder, what kind of binder which has adhesiveness may be used.
It is preferable that the compounding quantity of a binder is 2-50 mass parts with respect to 100 mass parts of all the pigments, More preferably, it is 5-30 mass parts. When the under layer contains a large amount of binder, the ink absorbability becomes insufficient. Therefore, the amount of the binder is preferably an optimum amount that can ensure the surface strength necessary for the under layer.

(Dispersant)
The under layer coating solution contains the above-described pigment, a binder, and a dispersant composed of a quaternary ammonium hydroxide compound. Among the quaternary ammonium hydroxide compounds, SN Dispersant 7347-C (trade name, manufactured by San Nopco) can be given as an industrially available compound. Quaternary ammonium hydroxide compounds are cationic.
The dispersant has a high effect of dispersing silica in the coating liquid, and can increase the silica (pigment) concentration in the coating liquid accordingly. That is, when a high-concentration silica slurry and a coating solution are prepared using the silica slurry, the fluidity of the coating solution is reduced, and it is difficult to feed the solution with a pump, thereby reducing workability. In addition, since the dispersibility of silica in the coating solution is poor, when coating is performed using a coating solution containing a high concentration of silica, the surface feel (coating amount profile) of the coated surface is reduced, and glossiness is felt. There is a problem that the streak drops or streaks occur. Streak refers to streaks that occur on the coating surface when the pigment in the coating solution aggregates and clogs the blade of the blade coater and scratches the coating surface, and indicates the degree of dispersibility of the coating solution. .
On the other hand, when the above dispersant is used, workability is good even if the silica slurry and coating solution are prepared at high concentrations, and the coating solution can be made high in concentration, so the drying load on the coater is reduced. This improves productivity. Furthermore, even when a coating liquid containing silica is applied, the surface feel and glossiness of the coated surface are not lowered, and streaks are reduced.
Furthermore, when a cationic ink fixing agent is contained in the under layer, a decrease in compatibility can be avoided. This is considered that the ink fixing agent is likely to be adsorbed on silica and hinders the dispersing action in the silica coating solution, but the addition of the dispersing agent is considered to reduce the adsorption of the ink fixing agent to silica.

  The dispersant is contained in an amount of 0.1 to 20 parts by weight, preferably 0.1 to 10 parts by weight, more preferably 0.5 to 100 parts by weight with respect to 100 parts by weight of the total pigment in the underlayer coating liquid. 10 parts by mass are included. When the content of the dispersant is less than 0.1 parts by mass, the effect of the dispersant cannot be obtained. The effect is not obtained.

The silica concentration in the silica slurry when the above dispersant is used (the maximum concentration at which no coating problem occurs) varies depending on the type of silica, the proportion of silica in the pigment, the type and amount of the dispersant, and the like. However, when the silica in the pigment is 100%, the silica concentration can usually be about 40 to 50% by mass.
The silica concentration in the coating solution obtained by adding a binder or additive to the silica slurry varies depending on the blending amount of the binder or additive. When the silica in the pigment is 100%, usually 30-60. It can be about mass%.
The silica concentration in the silica slurry tends to decrease as the silica oil absorption amount and specific surface area increase. However, the silica oil absorption amount is 300 ml / 100 g or more and the specific surface area is in the range of 200 to 500 m ² / g. In general, the above silica concentration can be secured.

(Other ingredients)
As long as the effect of the present invention is not impaired, in the coating liquid to be an under layer, an ink fixing agent, a viscosity modifier, a fluidity improver, an antifoaming agent, an antifoaming agent, a release agent, a penetrating agent, Coloring dyes, coloring pigments, fluorescent brighteners, ultraviolet absorbers, antioxidants, preservatives, antibacterial agents, water-proofing agents, and the like can be appropriately blended. In addition, vinyl acetate, etherified starch, casein, gelatin, soy protein, carboxymethyl cellulose, SB latex, NB latex, acrylic latex, ethylene vinyl acetate latex, polyurethane, unsaturated polyester resin, etc. Two or more types can be mixed and added to the coating solution.

<Under layer coating>
The coating amount of the under layer can be changed according to the purpose and is not particularly limited, but is preferably 4 to ²⁰ g / m ² per one side. When the coating amount is less than 4 g / m ² , the ink absorption capacity of the under layer tends to be insufficient. On the other hand, when the coating amount is more than 20 g / m ² , the ink absorbability is good, but the time for the binder to penetrate into the support becomes long, so the strength of the under layer is lowered, and the resulting ink jet recording paper There is a tendency for powder to fall off during cutting and to increase costs.

<Coating method>
Further, the method of coating the underlayer coating liquid on the support is not particularly limited, but various known blade coaters, air knife coaters, roll coaters, curtain coaters, kiss coaters, bar coaters, gate roll coaters, gravure coaters, and the like. A coating device can be used.

<Ink receiving layer>
The ink receiving layer is formed on the surface of the under layer by a cast coating method. In the first embodiment in which the under layer contains a dispersant, the pigment used in the ink receiving layer is not limited, and the ink receiving layer coating liquid may not contain the dispersant. The cast coating method will be described in the second embodiment below.

  As described above, in the case of the ink jet recording medium according to the first embodiment, since the glossiness of the under layer is high, the glossiness of the ink receiving layer formed thereon is also improved. Further, since the silica concentration in the under layer coating solution can be increased, productivity is improved. Furthermore, ink absorptivity is also improved by using silica stably as a pigment for the under layer.

2. Embodiment of Inkjet Recording Medium Containing Dispersant in Ink Receiving Layer (Second Embodiment)
<Under layer>
In this embodiment, the under layer is mainly composed of an under layer pigment and a binder, but the pigment used in the under layer is not limited, and the under coating liquid may not contain the dispersant.

<Ink receiving layer>
In this embodiment, the ink receiving layer is mainly composed of a pigment for an ink receiving layer containing silica and a binder.
(Pig for ink receiving layer)
Silica is used as the pigment. As the silica, it is preferable to use the synthetic amorphous silica exemplified as the pigment for the under layer of the first embodiment. Moreover, colloidal silica can be used as silica, and it is preferable to use colloidal silica and synthetic amorphous silica in combination.
Furthermore, as a pigment, in addition to silica, one of various known pigments such as alumina, calcium carbonate, magnesium carbonate, aluminum hydroxide, kaolin, calcined kaolin, talc, titanium dioxide, zinc oxide, and various plastic pigments, or Two or more can be selected and used with silica. Among these, porous pigments such as alumina form a porous layer with excellent ink absorbability like synthetic amorphous silica, and become relatively transparent in the coating layer, and ink color development during ink jet recording. Is preferable.
The proportion of silica in the total pigment is preferably 30% by mass or more, more preferably 60% by mass or more, and the total pigment may be silica.

(binder)
Examples of the binder include starches such as oxidized starch and esterified starch; cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose; proteins such as gelatin, casein and soybean protein; polyvinyl alcohol, polyvinyl pyrrolidone, acrylic resin, styrene-acrylic resin, Select one or more known binders such as vinyl acetate resin, vinyl chloride resin, urea resin, urethane resin, alkyd resin, polyester resin, polycarbonate resin, styrene-butadiene latex, and derivatives thereof. Can be used.
From the viewpoint of the strength and transparency of the ink receiving layer, it is preferable to include at least polyvinyl alcohol as a binder.
Although the compounding quantity of a binder is not specifically limited unless required quality, such as ink absorptivity, is impaired, For example, it is preferable that it is 5-30 mass parts with respect to 100 mass parts of all pigments.

(Dispersant)
The ink-receiving layer coating liquid contains the above-described pigment, binder, and dispersant composed of a quaternary ammonium hydroxide compound. As the dispersing agent, the same dispersing agent as that contained in the underlayer coating liquid of the first embodiment is used, and the action of the dispersing agent is also the same, so that the description thereof is omitted. The blending ratio of the dispersant to the pigment is the same as that in the first embodiment.

(Other ingredients)
As long as the effects of the present invention are not impaired, the ink-receiving layer coating solution contains an ink fixing agent, a pigment dispersant, a thickener, a fluidity improver, an antifoaming agent, an antifoaming agent, a lubricant, and a penetrating agent. An agent, a coloring dye, a coloring pigment, a fluorescent brightening agent, an ultraviolet absorber, an antioxidant, an antiseptic, a baitproofing agent, a water-proofing agent, and the like can be appropriately blended.
Further, when the ink receiving layer is provided by the cast coating method described later, a release agent can be contained in the ink receiving layer coating liquid for the purpose of improving the peelability from the cast drum. The melting point of the release agent is preferably 90 to 150 ° C, and particularly preferably 95 to 120 ° C. In the above range, since the melting point of the release agent is almost equal to the surface temperature of the mirror-finished metal (drum), the ability as a release agent is maximized. The release agent is not particularly limited as long as it has the above characteristics.

<Coating of ink receiving layer>
The coating amount of the ink receiving layer can be arbitrarily adjusted within the range that covers the surface of the under layer and sufficient ink absorbability is obtained, but from the viewpoint of achieving both ink jet recording density and ink absorbency, It is preferably 5 to 30 g / m ² in terms of solid content. Furthermore preferably ^{5g / m 2 ~20g / m 2} . If the coating amount exceeds 30 g / m ² , the drying load on the coating layer is large and inefficient, and the coating layer is prone to insufficient drying when applied by the cast coating method. May decrease, causing problems such as adhesion of the coating layer to the mirror drum.

<Coating method>
The method for coating the ink receiving layer coating liquid is not particularly limited, but various blade coaters, air knife coaters, roll coaters, brush coaters, kiss coaters, squeeze coaters, curtain coaters, die coaters, bar coaters, gravure coaters, etc. It can also be used by appropriately selecting from methods using a known coating machine.

<Cast coat method>
The ink receiving layer is formed by applying an ink receiving layer coating solution and then performing a cast treatment by a cast coating method. By performing the cast treatment, an inkjet recording medium having high gloss can be obtained.
In the cast coating method, a coating liquid mainly composed of a pigment and a binder is coated on a support (underlayer) to form a coating layer that serves as an ink receiving layer, and then wet or plasticized. In this method, the work layer is pressed against a cast drum (mirror-finished surface) to give a gloss finish. In general, the cast coating method includes (1) a wet casting method (direct method) in which a coating layer is pressed against a heated drum that has been mirror-finished while the coating layer is wet, and (2) a wet coating layer once. (Semi-) Rewetting cast method (rewetting method) in which it is swelled and plasticized with a rewetting liquid after drying, and pressed onto a mirror-finished heated drum (drying method). (3) The wet coating layer is made into a gel state by coagulation treatment. Then, it can be divided into three types, that is, a gelling cast method (coagulation method) in which pressure is applied to a heated mirror drum and dried.

  In the present invention, any of the direct method, the coagulation method, and the rewet method can be used, but the coagulation method is preferable from the viewpoint of obtaining high gloss, and the rewet method is used from the viewpoint of improving productivity. preferable.

  In the case of the solidification method, while the coating layer serving as the ink receiving layer is in a wet state, a treatment liquid that acts to solidify (or crosslink) the binder in the coating layer is applied and then applied to the heated mirror surface. Crimp and give gloss. For example, when polyvinyl alcohol is used as the binder, any aqueous solution containing a compound having a function of coagulating polyvinyl alcohol can be used as the treatment liquid. In particular, boric acid and boric acid can be used. A treatment liquid containing a salt is preferred. By mixing and using boric acid and borate, it becomes easy to obtain solidification with an appropriate hardness, and good glossiness can be imparted.

  In the case of the rewet method, a treatment liquid having an action of plasticizing the binder in the coating layer is applied to the coating layer in a dry state, and then pressed onto a heated mirror surface to give gloss. In the rewet method, since the ink-receiving layer is in a dry state when the treatment liquid is applied, it is difficult to copy the mirror drum surface, and the surface has many minute irregularities and the glossiness tends to be slightly reduced. Since it is possible to increase the work speed compared to other methods, productivity is improved.

  Examples of the method for applying the treatment liquid used in the above-described coagulation method and rewet method include a roll, a spray, and a curtain method, but are not particularly limited.

  As described above, in the case of the ink jet recording medium according to the second embodiment, since the glossiness at the time of coating the ink receiving layer is high, the gloss of the ink receiving layer is greatly improved by the subsequent casting process. Further, since the silica concentration in the ink receiving layer coating solution can be increased, productivity is improved. Furthermore, the ink absorptivity is improved by stably using silica as the pigment of the ink receiving layer.

The present invention is not limited to the first and second embodiments described above, and the under layer according to the first embodiment is provided on a support, and the ink receiving layer according to the second embodiment is provided on the under layer. May be provided.
In the present invention, if necessary, a back layer for providing writing property, antistatic property, antifouling property, slipperiness and the like is provided on the surface of the support opposite to the surface on which the ink receiving layer is provided. It is also possible.

<Example>
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples. Unless otherwise specified, “part” and “%” described below represent “part by mass” and “% by mass”, respectively.

  1. Experiments (Examples 1 to 4 and Comparative Examples 1 to 5) containing a dispersant in the under layer

(Manufacture of support)
A pulp slurry consisting of 100 parts of hardwood bleached kraft pulp (L-BKP) with a beating degree of 285 ml, 10 parts of talc, 1.0 part of aluminum sulfate, 0.1 part of a synthetic sizing agent, and 0.02 part of a yield improver. It was added and paper was made with a paper machine. At the time of papermaking, starch was applied on both sides so that the solid content per side was 2.5 g / m ² to obtain a support having a basis weight of 170 g / m ² .

(Under layer)
On one side of this support, coating solution A was applied with a blade coater so that the coating amount was 15 g / m ^2, and air-dried at 140 ° C. to form an under layer.
Coating liquid A: As a pigment, 50 parts of precipitated silica (Fine Seal X-12: manufactured by Tokuyama Co., Ltd.) and 50 parts of gel method silica (Mizukasil P-50: manufactured by Mizusawa Chemical Co., Ltd.) are blended, and water is appropriately added. The pigment dispersion was adjusted to a solid content of 48% (maximum dispersible pigment dispersion concentration). To this pigment dispersion, 5 parts of completely saponified polyvinyl alcohol (PVA-117, polymerization degree 1700, saponification degree 98%, manufactured by Kuraray Co., Ltd.) and an ethylene / vinyl acetate copolymer emulsion (AM-3150) were further added as a binder. 30 parts of Showa Polymer, abbreviated as “EVA”), 0.5 parts of quaternary ammonium hydroxide (SN Dispersant 7347C: manufactured by San Nopco Co., Ltd.) as a dispersant, and cation 5 parts of a basic ink fixing agent (T-DK129, manufactured by Seiko PMC Co., Ltd.) and 5 parts of a cationic sizing agent (SE-2250, manufactured by Seiko PMC Co., Ltd.) were blended to prepare a coating liquid having a solid content of 37%. . The pigment dispersion concentration is a concentration at the time of dispersing only the pigment, and is different from the concentration of the final coating solution.

(Ink receiving layer)
On the surface of the under layer, the coating liquid B is applied with a blade coater so that the coating amount is 15 g / m ^2, and the coagulation liquid C is applied while the coating layer is in a wet state, and then 120 The ink-receiving layer was formed by applying pressure to a mirror surface heated to 0 ° C. to give gloss, and an ink jet recording medium was obtained.
Coating liquid B: 50 parts by weight of colloidal silica (Quarton PL-1: Fuso Chemical Industry Co., Ltd.) and 50 parts of precipitation method silica (Fine Seal X-37: precipitation method silica manufactured by Tokuyama Corporation) 20 parts of partially saponified polyvinyl alcohol (PVA-617: trade name of Kuraray Co., Ltd.) is blended as a binder, and 2 parts of a mold release agent (Maycatex HP50: manufactured by Meisei Chemical Co., Ltd.) is blended to a concentration of 27%. A coating solution was prepared.
Coagulation liquid C: The blending ratio represented by (borax / boric acid) is 2, the concentration when borax is converted to Na ₂ B ₄ O ₇ and boric acid is converted to H ₃ BO ₃ is 6 %, Further mold release agent (Maycatex HP50: manufactured by Meisei Chemical Co., Ltd.) 0.25%, penetrant (Pionin D-3120-W: trade name manufactured by Takemoto Yushi Co., Ltd.) 0.5%, and pH adjustment A coagulation liquid was prepared by adding 0.25% citric acid as an agent.

  An ink jet recording medium was obtained in exactly the same manner as in Example 1 except that the amount of the dispersant for coating liquid A (SN Dispersant 7347C: manufactured by San Nopco Co., Ltd.) was changed to 1.0 part.

  An ink jet recording medium was obtained in exactly the same manner as in Example 1 except that the amount of the dispersant for coating liquid A (SN Dispersant 7347C: manufactured by San Nopco Co., Ltd.) was changed to 5.0 parts.

An inkjet recording medium was prepared in the same manner as in Example 1 except that the amount of the dispersant for coating liquid A for the ink receiving layer (SN Dispersant 7347C: manufactured by San Nopco Co., Ltd.) was changed to 10.0 parts. Obtained.
<Comparative Example 1>

An ink jet recording medium was obtained in the same manner as in Example 1 except that the dispersant (SN Dispersant 7347C: manufactured by San Nopco Co., Ltd.) was not blended in the coating liquid A.
<Comparative Example 2>

In the coating liquid A, the example (except that the dispersant (SN Dispersant 7347C: manufactured by San Nopco Co., Ltd.) was not blended and 1.5 parts of the acrylic dispersant (Disperbyk-180: Big Chemie) was blended instead) In the same manner as in Example 1, an ink jet recording medium was obtained.
<Comparative Example 3>

In the coating liquid A, the example (except that the dispersant (SN Dispersant 7347C: manufactured by San Nopco Co., Ltd.) was not blended and 2.5 parts of the acrylic dispersant (Disperbyk-183: Big Chemie) was blended instead. In the same manner as in Example 1, an ink jet recording medium was obtained.
<Comparative Example 4>

In coating solution A, Example 1 was used except that 5 parts of an acrylic dispersant (Disperbyk-194: Big Chemie) was blended instead of blending a dispersant (SN Dispersant 7347C: manufactured by San Nopco). An ink jet recording medium was obtained in exactly the same manner.
<Comparative Example 5>

  In coating liquid A, a dispersant (SN Dispersant 7347C: manufactured by San Nopco Co., Ltd.) was not blended, and instead of a dispersant containing a polycarboxylic acid sodium salt (Nopcos Perth 44-C: manufactured by San Nopco Co., Ltd.) An ink jet recording medium was obtained in the same manner as in Example 1 except that it was blended.

<Evaluation>
The ink jet recording media of each Example and Comparative Example were evaluated by the following method. However, those that cannot be measured due to the inability to create a recording medium are indicated as-.
(1) Dispersibility of the pigment dispersion The state of the pigment dispersion of the coating liquid A was visually evaluated, and the dispersibility was evaluated according to the criteria shown below. If the evaluation is ○, there is no practical problem.
○: Dispersibility is not a problem. △: Dispersibility is inferior, but coating liquid can be prepared. ×: Dispersibility is extremely inferior, and preparation of coating liquid cannot be continued.

(2) Maximum concentration of pigment dispersion The maximum concentration of stirrable solid content at the time of pigment dispersion in water was measured. The result is expressed in%.
The stirrable concentration was determined by visualizing and evaluating the pigment dispersion by dispersing the silica with a mixer. If the pigment dispersion had fluidity, it could be stirred. If stirring is not possible, the pigment dispersion loses fluidity and the mixer stops, so silica is added until the mixer stops.
The higher the concentration of the pigment dispersion, the better. However, since the productivity is determined by the concentration of the final paint (coating liquid), it cannot be determined only by the concentration of the pigment dispersion. However, in the present invention, the concentration of the pigment dispersion may be 40% or more, and more preferably 45% or more.
(3) Paint stability The concentration of the coating liquid A was adjusted to 30%, the B-type viscosity was measured, and the paint stability was evaluated according to the following criteria. If the evaluation is ○, there is no practical problem. The B-type viscosity was measured using a B-type viscometer (BM type VISCOMETER: manufactured by TOKIMEC INC.) According to JIS Z8803.
○: Paint viscosity after blending is 1500 cps or less Δ: Paint viscosity after blending is 1500 cps or more and 3000 cps or less ×: Paint viscosity after blending is 3000 cps or more

(4) Productivity improvement evaluation (drying time)
In order to evaluate the drying time required for production, hand coating evaluation using the coating liquid A was performed. If the evaluation is ○, there is no practical problem. The coating amount was 15 g / m ² and the drying temperature was 115 ° C.
○: A sufficient support can be secured within 1 minute of drying time.
Δ: A sufficient support can be secured in a drying time of 1 minute to 2 minutes. X: A sufficient support can be secured in a drying time of 2 minutes or more.

(1) Glossiness The glossiness and image clarity of the ink receiving layer surface after the cast treatment of the inkjet recording medium were measured, and the glossiness was evaluated according to the following criteria. If the evaluation is ○, there is no practical problem. In addition, the glossiness measured 75 degree | times specular glossiness using the glossiness meter (Murakami Color Research Laboratory make, True GLOSS GM-26PRO). The image clarity was measured in the MD direction of the paper using a image clarity measuring device (model number: ICM-1DP, manufactured by Suga Test Instruments Co., Ltd.) under the conditions of a measurement angle of 60 degrees and a comb width of 2 mm.
○: 75 degree specular gloss of 75% or more and image sharpness of 60% or more Δ: 75 degree specular gloss of 60% to less than 75% and image sharpness of 40% or more ×: 75 With a specular gloss of less than 60% or image clarity of less than 40%

(2) Print quality A predetermined pattern on the surface of the ink receiving layer is recorded using an ink jet printer (PM-950C: a product name manufactured by Epson Corporation), and the recorded image portion is visually observed to evaluate the print quality based on the following criteria. did.
○: No blurring and vivid Δ: Slight blurring or slightly inferior in color ×: Blemishing or invisible

  The obtained results are shown in Table 1.

  As is apparent from Table 1, in the case of the ink jet recording medium of each example, the dispersibility of the underlayer coating liquid and the paint stability were excellent, and the glossiness and print quality of the obtained ink jet recording medium were improved.

  On the other hand, in the case of Comparative Example 1 in which the underlayer coating liquid did not contain a dispersant, the silica dispersion effect did not occur, and the dispersibility and stability of the paint (coating liquid A) deteriorated. The glossiness of the ink jet recording medium was lowered. This is presumably because coating unevenness was caused by the deterioration of the physical properties of the paint. This is because the concentration was forcibly increased without using a dispersant.

Further, in Comparative Examples 2 to 3 using an acrylic dispersant as the dispersant for the under layer coating liquid, the effect of dispersing the silica as a pigment does not occur, and the dispersibility and stability of the paint (coating liquid A). As in Comparative Example 1, the glossiness of the inkjet recording medium was lowered. Furthermore, the drying property was also inferior.
In the case of Comparative Example 4 in which another acrylic dispersant is used as the dispersant for the underlayer coating liquid, and in the case of Comparative Example 5 in which a dispersant containing sodium polycarboxylic acid is used, the concentration of the pigment dispersion liquid Even if it was about 35%, the dispersibility of the pigment was remarkably lowered, and it became impossible to prepare, so the subsequent evaluation was stopped.

  2. Experiments in which a dispersant was contained in the ink receiving layer (Examples 5 and 6, Comparative Examples 6 and 7)

(Support)
The same support as in Example 1 was produced.

(Under layer)
In coating liquid A, an under layer was formed on the support in the same manner as in Example 1, except that the dispersant (SN Dispersant 7347C: manufactured by San Nopco Co., Ltd.) was not blended.

(Ink receiving layer)
Except that 0.5 part of a dispersant (SN Dispersant 7347C: manufactured by San Nopco Co., Ltd.) was further added to the coating liquid B (this is referred to as “coating liquid B2”), exactly the same as Example 1. Then, an ink receiving layer was formed on the under layer and cast to obtain an ink jet recording medium.

An inkjet recording medium was obtained in exactly the same manner as in Example 5 except that the amount of the dispersant for coating liquid B2 (SN Dispersant 7347C: manufactured by San Nopco) was changed to 1.0 part.
<Comparative Example 6>

Example 5 is the same as Example 5 except that in the coating liquid B2, a dispersant (SN Dispersant 7347C: manufactured by San Nopco Co., Ltd.) is not blended, and 5 parts of an acrylic dispersant (Disperbyk-194: Big Chemie) is blended instead. An ink jet recording medium was obtained in exactly the same manner.
<Comparative Example 7>

  In the coating liquid B2, a dispersant (SN Dispersant 7347C: manufactured by San Nopco Co., Ltd.) was not blended, and instead of a dispersant containing a polycarboxylic acid sodium salt (Nopcos Perth 44-C: manufactured by San Nopco Co., Ltd.) An ink jet recording medium was obtained in the same manner as in Example 5 except that it was blended.

<Evaluation>
Evaluation of the inkjet recording media of each Example and Comparative Example was performed in the same manner as Example 1.

  The obtained results are shown in Table 2.

  As is apparent from Table 2, in the case of the ink jet recording medium of each example, the dispersibility of the ink receiving layer coating liquid and the paint stability were excellent, and the glossiness and print quality of the obtained ink jet recording medium were improved. .

  On the other hand, in the case of Comparative Example 6 using an acrylic dispersant as the dispersant for the ink receiving layer coating liquid and in the case of Comparative Example 7 using a dispersant containing polycarboxylic acid sodium salt, silica as a pigment is used. Thus, the dispersibility and stability of the paint (coating liquid B2) deteriorated, and the glossiness of the ink jet recording medium decreased. This is presumably because coating unevenness was caused by the deterioration of the physical properties of the paint. Further, in the case of Comparative Example 7, the print quality was also deteriorated.

Claims (3)

  An ink jet recording medium in which an under layer mainly composed of a pigment containing silica and a binder is provided on at least one surface of a support, and an ink receiving layer formed by a cast coating method is provided on the surface of the under layer. The under layer is formed by applying a coating liquid containing 0.1 to 20 parts by mass of a quaternary ammonium hydroxide as a dispersant with respect to 100 parts by mass of the pigment, and then drying. An inkjet recording medium.   An ink jet recording medium in which an under layer containing an under layer pigment is provided on at least one surface of a support, and an ink receiving layer formed by a cast coating method is provided on the surface of the under layer. The receiving layer is mainly composed of a pigment for an ink receiving layer containing silica and a binder, and 0.1 to 20 parts by weight of a quaternary ammonium hydroxide is used as a dispersant with respect to 100 parts by weight of the pigment for an ink receiving layer. An ink jet recording medium, wherein the ink jet recording medium is cast after the coating liquid containing the coating liquid is applied.   The inkjet recording medium according to claim 1 or 2, wherein the pigment concentration in the coating liquid is 30 to 60% by mass.