JP2009083335A - Recording medium for inkjet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording medium for inkjet excellent in a printing aptitude (printing density and printing inconsistency) when pigment ink is used. <P>SOLUTION: The recording medium for ink jet is provided with an ink receiving layer containing a pigment and a binding agent on at least one face of a base paper containing calcium carbonate to be a filler and pulp by a cast coating method. An ash content of calcium carbonate in the base paper is 15 to 30 mass%, and also the ink receiving layer contains colloidal silica having a primary particle size of 30 to 70 nm and a ratio of a secondary particle size to the primary particle size of 1.5 to 3.0 as the pigment. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inkjet recording medium having high gloss.

  An ink jet recording medium has a structure in which an ink receiving layer containing a porous pigment such as silica or alumina and a binder is provided on the surface of a support such as paper. The droplets are fixed. With the remarkable progress of ink jet printers in recent years and the remarkable spread of digital cameras, the quality required for ink jet recording media is increasing year by year. In particular, in an inkjet recording medium having a gloss comparable to that of a conventional silver salt photograph, quality requirements are strict and technological development is actively being carried out.

  Such an inkjet recording medium having high gloss is generally produced by a cast coating method using a cast coater from the viewpoint of production cost. The cast coating method is a method in which a coating liquid mainly composed of a pigment and a binder is applied on a base paper to provide a coating layer, and the coating layer is gloss-finished using a cast drum, This gloss coating layer becomes the ink receiving layer. The cast coating method includes (1) a wet casting method (direct method) in which a coating layer is pressed onto a mirror-finished heating drum while the coating layer is wet, and (2) a wet coating layer is once dried. Alternatively, a semi-dried, rewetting method that is swollen and plasticized with a re-wetting solution, and is pressed onto a mirror-finished heating drum and dried. (3) A heated coating drum that is mirror-finished after the wet coating layer is gelled by coagulation There are generally known three types of gelation cast methods (coagulation methods) in which pressure is bonded to the substrate and dried. The principle of each method is the same in that the wet coating layer is pressed against the mirror-finished surface to give gloss to the coating layer surface.

The quality characteristics required for such a glossy inkjet recording medium include high gloss on the surface of the recording medium, high print density, no ink overflow or bleeding, and uneven printing (light / dark unevenness). In order to improve these characteristics, the ink receiving layer has been improved. For example, a technique has been reported in which the ink receiving layer has a layer structure of one or more layers, and at least one layer contains colloidal particles having an average particle diameter of 300 nm or less and a cationic resin (for example, see Patent Document 1).
In addition, since the cast coating layer contains colloidal silica having a primary particle diameter of 30 to 100 nm and a ratio of the secondary particle diameter to the primary particle diameter of 1.5 to 2.5, printing unevenness is prevented. A technique for preventing this has been reported (see, for example, Patent Document 2).
Furthermore, an ink jet recording paper having a cast coating layer on a paper substrate having an ash content of 13.5% and having high gloss and little printing unevenness has been reported (for example, see Patent Document 3).

JP 2004-209965 A JP 2004-270104 A JP-A-4-19595 (Table 1, paragraph 0118)

However, Patent Documents 2 and 3 describe improvement in printing unevenness when dye ink is used (the ink jet printers PM950C and PM970C described in the examples of these documents are for dye ink). There is no description of a technique for improving printability (print density and print unevenness) when pigment ink is used.
Accordingly, an object of the present invention is to provide an inkjet recording medium that is excellent in glossiness and excellent in printability (print density and print unevenness) when a pigment ink is used.

The present inventors have already described in Patent Document 2 that the cause of printing unevenness is caused by fine cracks on the surface of the coating layer provided by the cast coating method, and by using a predetermined colloidal silica, the dye ink It is disclosed that uneven printing can be prevented. Furthermore, as a particular problem when the pigment ink is used, the present inventors, when the ink absorbency is small, the colored pigment aggregates due to surface tension while the solvent of the pigment ink stays in the ink receiving layer, After all, it was found that uneven printing occurred.
Accordingly, as a result of various studies by the present inventors, colloidal silica having a predetermined primary particle size and secondary particle size is used as a pigment, and calcium carbonate having an ash content of 15 to 30% is contained as an internal filler of the base paper. It has been found that the above problems can be solved.

  That is, the ink jet recording medium of the present invention is provided with an ink receiving layer containing a pigment and a binder on at least one surface of a base paper containing calcium carbonate and pulp as a filler by the cast coating method. The ash content of the calcium carbonate in the paper is 15 to 30% by mass, and the ink receiving layer has a primary particle size of 30 to 70 nm as the pigment and a ratio of the secondary particle size to the primary particle size of 1.5 to 1.5. Contains colloidal silica which is 3.0.

  The content ratio of the colloidal silica with respect to all the pigments in the ink receiving layer is preferably 20 to 80% by mass.

  According to the present invention, it is possible to obtain an inkjet recording medium that is excellent in glossiness and excellent in printability (print density and print unevenness) when a pigment ink is used.

  Embodiments of the present invention will be described below. In the ink jet recording medium of the present invention, an ink receiving layer containing a pigment and a binder is provided on at least one surface of a base paper by a cast coating method.

(Base paper)
As the base paper used in the present invention, paper such as coated paper and uncoated paper having air permeability is used. The raw material pulp of the paper includes chemical pulp (conifer 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, it is preferable that softwood pulp is contained as the raw material pulp. When softwood pulp is blended in the base paper, the strength of the base paper is improved and the glossiness of the ink receiving layer tends to be improved. However, since the surface property of the base paper tends to decrease when the content of softwood pulp increases, the content of softwood pulp is preferably 30% by mass or less in the total pulp. The pH of the paper may be acidic, neutral or alkaline.
From the viewpoint of production efficiency of the inkjet recording medium, the air permeability of the paper is preferably 1000 seconds or less, and from the viewpoint of coating properties, the Steecht size of the base paper is 5 seconds or more. desirable.

(Filler)
In the base paper, calcium carbonate is contained as a filler at a ratio of ash content of 15 to 30% by mass. By containing calcium carbonate with a high ash content, printing unevenness when printing with pigment ink can be suppressed. The reason for this is not clear, but is thought to be as follows.
First, by including colloidal silica specified as follows in the ink receiving layer, large cracks on the surface of the ink receiving layer formed by the cast coating method can be suppressed. And, when the ash content of calcium carbonate in the base paper is 15 to 25% by mass, when the ink receiving layer coating liquid is applied to the base paper, the binder component in the ink receiving layer coating liquid is reduced. It penetrates uniformly into the base paper, and as a result, minute cracks (small cracks) on the surface of the ink receiving layer can be suppressed. As a result, there are almost no cracks on the surface of the ink receiving layer, and printing unevenness particularly when printing pigment ink is greatly reduced. In addition, since there is no surface crack, the pigment is uniformly present in the ink receiving layer, so that high ink absorbability can be maintained, and printing unevenness due to aggregation of colored pigment due to surface tension can be suppressed. It becomes possible.
When the ash content of calcium carbonate in the base paper is less than 15% by mass, the above-described fine surface cracks are generated, and printing unevenness is remarkably generated when pigment ink is printed. On the other hand, the higher the ash content of calcium carbonate in the base paper is, the higher the effect of suppressing printing unevenness at the time of pigment ink printing is. However, if the ash content exceeds 30% by mass, powder falling occurs or the strength of the base paper decreases. In consideration of the balance between production costs and effects, the ash content is preferably 25% by mass or less.
The ash content can be measured by the method described in JIS-P8251.

The calcium carbonate is a fine particle having an average particle size of 0.1 to 5 μm, and is synthesized by a method of reacting heavy calcium carbonate obtained by mechanically pulverizing limestone, calcium chloride, and soda ash. There are light calcium carbonates to be obtained, and any of them may be used. However, in the present invention, it is preferable to use light calcium carbonate because fine particles having a uniform particle diameter and particle shape are easily obtained.
Further, as long as the effects of the present invention are not impaired, hydrated silicic acid, white carbon, talc, kaolin, clay, calcium carbonate, titanium oxide, synthetic resin fine particles and the like are appropriately selected from known fillers and used in combination with calcium carbonate. can do. In order to obtain a base paper with high whiteness at low cost, the filler other than calcium carbonate is preferably 30% by mass or less of the total filler, and more preferably no filler other than calcium carbonate is contained.

(Pigment of ink receiving layer)
The pigment in the ink receiving layer contains colloidal silica having a primary particle diameter of 30 to 70 nm and a ratio of the secondary particle diameter to the primary particle diameter of 1.5 to 3.0. When the primary particle size of the colloidal silica is less than 30 nm, the ink receiving layer is highly transparent, but fine cracks are generated on the surface of the coating layer, and printing unevenness occurs during printing of pigment ink, resulting in a reduction in printing density. As the primary particle size is larger, cracks are reduced and printing unevenness when using pigment ink tends to be reduced.
In particular, when printing with an ink jet printer using a pigment ink containing colored particles having a particle size of about 30 to 150 nm in the ink, it is effective that the primary particle size of the colloidal silica is 30 nm or more.
On the other hand, when the primary particle diameter exceeds 70 nm, the transparency of the ink receiving layer is lowered, the printing density during printing of the dye ink is greatly lowered, and the suitability of the dye ink is deteriorated.

This is because if the ratio of the secondary particle diameter to the primary particle diameter of the colloidal silica is less than 1.5, the ink absorption of the ink receiving layer decreases, and if it exceeds 3.0, the glossiness of the ink receiving layer decreases. The primary particle diameter of colloidal silica can be measured by the BET method, and the secondary particle diameter can be measured by a dynamic light scattering method or the like.
In addition, when the colloidal silica in this invention is normally observed with a microscope, many things which two or three spherical single colloidal silica (primary particle) continued are observed. For convenience, this is expressed as a peanut shape. A value obtained by averaging the number of connected primary particles substantially corresponds to the above ratio. The colloidal silica in the present invention includes chain-like (or pearl necklace-like) colloidal silica and tuft-like colloidal silica (when microscopically observed, at least 5 spherical single colloidal silicas, usually 10 or more are connected. It does not include those that are mainly aggregated and the above ratio is also 5 or more. The term “excluded” as used herein does not mean that no tufted colloidal silica is observed at the time of microscopic observation, but some tufted colloidal silica may be observed. The value of the ratio of the secondary particle diameter to the primary particle diameter is more than 3 (usually 5 or more).

  The colloidal silica is synthesized by sol-gel method using alkoxysilane as a raw material, and the primary particle size (BET method particle size) and secondary particle size (dynamic light scattering method particle size) are controlled according to the synthesis conditions. Preferably, it is not preferable to use pulverized silica whose secondary particle diameter is adjusted by mechanically pulverizing synthetic silica that has become secondary particles. As a colloidal silica that can be preferably used in the present invention, a trade name Quartron series manufactured by Fuso Chemical Industry Co., Ltd. can be raised.

  The compounding amount of colloidal silica is preferably 20 to 80 parts by mass, and more preferably 30 to 70 parts by mass with respect to 100 parts by mass of the total pigment in the ink receiving layer. When the blending amount of colloidal silica is less than 20 parts by mass of the total pigment, not only the glossiness is lowered, but also the effect of improving ink absorbability and color development at the time of ink jet printing becomes insufficient, and uneven printing is also caused. May not be improved. Moreover, when a compounding quantity exceeds 80 mass parts, the operativity at the time of coating may fall.

Synthetic amorphous silica can be used as a pigment other than the colloidal silica in the ink receiving layer. Synthetic amorphous silica can be roughly classified into wet process silica and gas phase process silica depending on the production method. Synthetic amorphous silica produced by a wet process is inferior to gas phase process silica in pigment transparency, but is excellent in paint stability when used in combination with polyvinyl alcohol. Furthermore, wet process silica has better dispersibility than gas phase process silica without internal voids, and can increase the coating concentration. Therefore, the ratio of the pigment (to the binder) in the ink receiving layer can be increased, and the absorbability of the ink receiving layer can be increased, so that the ink absorbability can be improved and the color developability of the dye ink can be improved. From the viewpoint of obtaining a high gloss feeling, the preferred secondary particle diameter of the synthetic amorphous silica (synthetic silica other than colloidal silica) is preferably 1 to 5 μm. Moreover, it is preferable that a BET specific surface area is 150-500 m < ² > / g.

Increasing the blending ratio of synthetic amorphous silica with respect to all pigments in the ink receiving layer improves ink absorbency, but coloring pigments are more likely to enter the ink receiving layer, improving color development during pigment ink printing. Tend to be insufficient. Further, when the blending ratio of the synthetic amorphous silica is small, the ink absorptivity decreases, and as a result, the printing unevenness tends to increase.
As the pigment in the ink receiving layer, it is best to use a mixture of the colloidal silica and the synthetic amorphous silica.

  As a pigment other than the colloidal silica in the ink receiving layer, other pigments such as aluminum hydroxide, alumina sol, colloidal alumina, pseudo boehmite, etc. are used as long as the ink absorbability, color developability and glossiness upon ink jet recording are not impaired. Alumina (α-type crystal alumina, θ-type crystal alumina, γ-type crystal alumina, etc.) or alumina hydrate, synthetic silica, kaolin, talc, calcium carbonate, titanium dioxide, clay, zinc oxide, etc. good.

(Binder for ink receiving layer)
As the binder in the ink receiving layer, a polymer compound capable of forming a film can be used. For example, as a binder, starches such as starch, oxidized starch, and esterified starch; cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose; polyvinyl alcohol; polyvinylpyrrolidone; casein; gelatin; soy protein; styrene-acrylic resin and derivatives thereof Styrene-butadiene resin, acrylic resin, vinyl acetate resin, vinyl chloride resin, urethane resin, urea resin, alkyd resin, and derivatives thereof can be used alone or in combination. The amount of the binder is preferably 5 to 30 parts by mass with respect to 100 parts by mass of the total pigment in the ink receiving layer, but is particularly limited as long as the required coating layer strength is obtained. It is not something.

The polymer compound used as the binder is preferably aqueous. “Aqueous” means that the resin is dissolved or dispersed and stabilized (water-soluble or / and water-dispersible resin emulsion) in water or a medium composed of water and a small amount of an organic solvent. These binders are dissolved or dispersed in the coating liquid to be applied to the support, but after coating and drying, they become pigment binders to form an ink receiving layer.
In particular, it is preferable to use partially saponified polyvinyl alcohol as the water-based polymer compound. The addition amount of polyvinyl alcohol is preferably 3 to 30 parts by mass with respect to 100 parts by mass of the total pigment in the ink receiving layer.

  The ink receiving layer contains the above-described pigment and binder, but other components such as a thickener, an antifoaming agent, an antifoaming agent, a pigment dispersant, a release agent, a foaming agent, a pH adjusting agent, and a surface. Sizing agent, coloring dye, coloring pigment, fluorescent dye, ultraviolet absorber, antioxidant, light stabilizer, preservative, water resistance agent, dye fixing agent, surfactant, wet paper strength enhancer, water retention agent, cation A functional polymer electrolyte or the like can be appropriately added within a range not impairing the effects of the present invention.

  As a method of applying a coating liquid to be an ink receiving layer on a support, blade coater, air knife coater, roll coater, brush coater, kiss coater, squeeze coater, curtain coater, die coater, bar coater, gravure coater, gate roll A known coating machine such as a coater or a short dwell coater can be appropriately selected from on-machine or off-machine coating methods.

The coating amount of the ink receiving layer can be arbitrarily adjusted within the range where the surface of the base paper is covered and sufficient ink absorbability is obtained, but from the viewpoint of achieving both recording density and ink absorbency, is preferably 5 to 30 g / ^{m 2} in terms of solid content, in particular, when considering also the productivity is preferably 10 to 25 g / ^{m 2.} If it exceeds 30 g / m ² , the peelability from the mirror-finished surface of the cast drum is lowered, and problems such as adhesion of the coating layer to the mirror-finished surface may occur.

  In the present invention, when a large coating amount of the ink receiving layer is required, the ink receiving layer can be multi-layered. Further, an undercoat layer having various functions such as ink absorptivity, adhesiveness and the like may be provided between the base paper and the ink receiving layer. Further, a back coat layer having various functions such as ink absorbability, writing property, printer printability and the like may be further provided on the side opposite to the surface on which the ink receiving layer is provided.

(Formation of ink receiving layer)
In the present invention, gloss is imparted by forming the outermost ink receiving layer by a cast coating method. Here, the cast coating method is a method in which a coated surface in a wet state after coating is pressure-bonded to a heated finished surface and dried. Preferably, the ink receiving layer is preferably formed using a gelled cast coating method (coagulation method) in terms of providing a surface feeling and gloss comparable to silver salt photography.

  The cast coating method is performed as follows, for example. First, a coating liquid to be an ink receiving layer is applied to the base paper. Next, a treatment liquid having an action of coagulating a binder (particularly an aqueous binder) in the coating liquid is applied to the coating layer, and the coating layer is wetted. Then, the wet coating layer is pressure-bonded to a heated mirror-finished surface and dried to form an ink receiving layer, and gloss is imparted to the surface. The coating layer at the time of applying the treatment liquid may be in a wet state or a dry state, but in particular when it is in a wet state, it is easy to copy the mirror-finished surface, and the coating layer surface has a minute amount. Since the unevenness can be reduced, it is easy to give the obtained ink-receiving layer glossiness equivalent to that of a silver salt photograph. Examples of the method for applying the treatment liquid include, but are not limited to, a roll, a spray, and a curtain method.

Next, the case where the gelation cast method is used will be described. In this method, in the cast coating method, after applying the coating layer, the undried coating layer is gelled with a coagulating liquid, and then pressed and dried on a heated mirror-finished surface. If the coating layer is in a dry state when applying the coagulation liquid, it is difficult to copy the mirror drum surface, and the resulting ink-receiving layer surface has many minute irregularities, making it difficult to obtain a glossiness similar to that of a silver salt photograph. Therefore, the coagulating liquid is applied to the undried coating layer.
The coagulation liquid has the action of coagulating the aqueous binder in the wet coating layer, for example, formic acid, acetic acid, citric acid, tartaric acid, lactic acid, hydrochloric acid, sulfuric acid and other calcium, zinc and magnesium Salt is used. In particular, when polyvinyl alcohol is used as the aqueous binder, it is preferable to use a liquid containing boric acid and borate as the coagulating liquid. By mixing and using boric acid and borate, it becomes easy to make the hardness at the time of solidification moderate, and it is possible to impart a good gloss to the ink receiving layer.
The method for applying the coagulating liquid is not particularly limited as long as it can be applied to the coating layer, and can be appropriately selected from known methods (for example, roll method, spray method, curtain method, etc.).

  Moreover, a release agent can be added to the coating layer and / or the coagulating liquid as necessary. The melting point of the release agent is preferably 90 to 150 ° C, and particularly preferably 95 to 120 ° C. In the above temperature range, since the melting point of the release agent is substantially equal to the temperature of the mirror finish surface, the ability as a release agent is maximized. The release agent is not particularly limited as long as it has the above characteristics, but it is preferable to use a polyethylene wax emulsion.

<Example 1>
The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples. “Part” and “%” represent “part by mass” and “% by mass”, respectively, unless otherwise specified.
Further, the primary particle size of the colloidal silica and the ratio of the secondary particle size to the primary particle size (particle size ratio) are manufacturer's measured values (catalog values are almost the same).

Composed of 90 parts of hardwood bleached kraft pulp (L-BKP) and 10 parts of softwood bleached kraft pulp (N-BKP), a light calcium carbonate (TP-121: manufactured by Okutama Kogyo Co., Ltd.) Name) was added so as to have an ash content of 20%, and 1.0 part of aluminum sulfate, 0.15 part of AKD, and 0.05 part of a yield improver were added.
The slurry was made with a paper machine, and 5% starch and 0.2% surface sizing agent (AKD) were applied to both sides of the base paper so that the solid content was 1.5 g / m ² . A base paper of 180 g / m ² was obtained.
On one side of the obtained base paper, the coating liquid A is applied at 15 g / m ² with a roll coater, and while the coating layer is in a wet state, the coagulating liquid B is applied to solidify the coating layer, Next, the coating layer was pressure-bonded to the mirror-finished surface heated via a press roll, and the mirror surface was copied to obtain a recording medium for inkjet of 195 g / m ² .

Coating liquid A: 60 parts of colloidal silica (Quarton PL-5: trade name, manufactured by Fuso Chemical Industry Co., Ltd., primary particle diameter of 50 nm and the ratio of secondary particle diameter to primary particle diameter is 2.2) as pigment. 20 parts of synthetic silica (Aerosil 200V: manufactured by Nippon Aerosil Co., Ltd.) and 20 parts of wet synthetic amorphous silica (Fine Seal X-37B: manufactured by Tokuyama Co., Ltd.) were added as a binder. 12 parts of polyvinyl alcohol (PVA224: trade name manufactured by Kuraray Co., Ltd.) was added, and 1.5 parts of fluorescent dye (BLANKOPHORPliquid01: trade name manufactured by LANXESS) 1.5 parts release agent (Mecatex HP68: Meisei Chemical Industries) 0.5 parts of a product name (trade name made by the company) and 0.1 part of an antifoaming agent (SN deformer 480: trade name made by San Nopco) were mixed to prepare a coating solution having a concentration of 25%.
Coagulating liquid B: Borax 2%, boric acid 4% (mass ratio of borax / boric acid = 1/2, calculated in terms of Na ₂ B ₄ O ₇ and H ₃ BO ₃ ), malic acid 0.2%, mold release A coagulating liquid was prepared by blending 0.5 parts of an agent (Mecatex HP68: trade name manufactured by Meisei Chemical Co., Ltd.) and 0.01% of an antifoaming agent (SN deformer 480: product name manufactured by San Nopco).

  In Example 1, colloidal silica (Quatron PL-5: trade name manufactured by Fuso Chemical Industries) in the coating liquid A was changed to colloidal silica (Quatron PL-3: trade name manufactured by Fuso Chemical Industries, Ltd., primary particle diameter 30 nm). In the same manner as in Example 1, except that the ratio of the secondary particle diameter to the primary particle diameter was changed to 2.3) and the coating liquid was adjusted, an inkjet recording medium was obtained.

  In Example 1, colloidal silica (Quortron PL-5: trade name manufactured by Fuso Chemical Industry Co., Ltd.) in the coating liquid A was changed to colloidal silica (Quartron PL-7: trade name manufactured by Fuso Chemical Industry Co., Ltd., primary particle diameter 70 nm). In the same manner as in Example 1, except that the ratio of the secondary particle diameter to the primary particle diameter was changed to 1.7) and the coating liquid was adjusted, an ink jet recording medium was obtained.

In Example 1, the amount of colloidal silica (Quortron PL-5: trade name manufactured by Fuso Chemical Industry Co., Ltd.) in the coating liquid A was changed to 30 parts, and another colloidal silica (Quortron PL-3: Fuso) was added. The same as in Example 1 except that 30 parts of a trade name, a primary particle size of 30 nm, and a ratio of the secondary particle size to the primary particle size of 2.3) were mixed to adjust the coating solution. An ink jet recording medium was obtained.
In addition, although colloidal silica in Example 4 is a mixture of two types, even if mixed, the dispersion state of each colloidal silica particle does not change, so the average value obtained by weighting the blending ratio of the mixture is expressed as the primary particle diameter (two Secondary particle size) and particle size ratio.

  In Example 1, the compounding amount of colloidal silica (Quarton PL-5: trade name manufactured by Fuso Chemical Industry Co., Ltd.) in the coating liquid A was changed to 40 parts, and a vapor-phase synthetic amorphous silica (Aerosil 200V: The blending amount of Nippon Aerosil Co., Ltd. was changed to 10 parts, and the blending amount of wet method synthetic amorphous silica (Fine Seal X-37B: Tokuyama Co., Ltd.) was changed to 50 parts. An ink jet recording medium was obtained in the same manner as in Example 1 except for the adjustment.

  In Example 1, the compounding amount of colloidal silica (Quarton PL-5: trade name manufactured by Fuso Chemical Industry Co., Ltd.) in the coating liquid A was changed to 80 parts, and a vapor-phase synthetic amorphous silica (Aerosil 200V: (Nippon Aerosil Co., Ltd.) was changed to 10 parts, and wet method synthetic amorphous silica (Fine Seal X-37B: manufactured by Tokuyama Corporation) was changed to 10 parts. An ink jet recording medium was obtained in the same manner as in Example 1 except for the adjustment.

  In Example 1, the amount of colloidal silica (Quarton PL-5: trade name manufactured by Fuso Chemical Industry Co., Ltd.) in the coating liquid A was changed to 20 parts, and a vapor-phase synthetic amorphous silica (Aerosil 200V: The blending amount of Nippon Aerosil Co., Ltd.) was changed to 10 parts, and the blending amount of wet method synthetic amorphous silica (Fine Seal X-37B: Tokuyama Co., Ltd.) was changed to 70 parts. An ink jet recording medium was obtained in the same manner as in Example 1 except for the adjustment.

  Inkjet ink as in Example 1, except that the blending amount of light calcium carbonate (TP-121: trade name manufactured by Okutama Kogyo Co., Ltd.) in the base paper in Example 1 was changed to 15% ash content. A recording medium was obtained.

<Comparative Example 1>
Instead of using colloidal silica (Quortron PL-5: trade name manufactured by Fuso Chemical Industry Co., Ltd.) in the coating liquid A in Example 1, instead of colloidal silica (Quortron PL-2: product manufactured by Fuso Chemical Industries Co., Ltd.) The recording medium for ink jet recording was obtained in the same manner as in Example 1 except that 60 parts of No., primary particle diameter of 20 nm and the ratio of the secondary particle diameter to the primary particle diameter of 2.5) were blended and the coating liquid was adjusted. It was.

<Comparative Example 2>
In Example 1, colloidal silica (Quatron PL-10: product made by Fuso Chemical Industry Co., Ltd.) was used instead of the colloidal silica (Quatron PL-5: product name made by Fuso Chemical Industry Co., Ltd.) in the coating liquid A. The recording medium for ink jet was obtained in the same manner as in Example 1 except that 60 parts of the primary particle diameter of 100 nm and the ratio of the secondary particle diameter to the primary particle diameter of 2.1) were blended and the coating liquid was adjusted. It was.

<Comparative Example 3>
Inkjet ink as in Example 1, except that the blending amount of light calcium carbonate (TP-121: trade name manufactured by Okutama Kogyo Co., Ltd.) in the base paper in Example 1 was changed to 13% ash content. A recording medium was obtained.

<Comparative Example 4>
In Example 1, without using light calcium carbonate (TP-121: trade name manufactured by Okutama Kogyo Co., Ltd.) in the base paper, instead of talc (IRK-085: trade name manufactured by Iriki Kaolin Co., Ltd.) as a filler. An ink jet recording medium was obtained in the same manner as in Example 1 except that was added so as to have an ash content of 15%.

<Evaluation>
1. Pigment ink printability
A predetermined pattern was recorded on the obtained inkjet recording medium using a pigment inkjet printer (PX-G900: trade name, manufactured by Epson Corporation), and evaluated according to the following criteria.
1-1. Vividness when printing pigment ink (print density)
The vividness of the recorded image portion of the predetermined pattern was visually evaluated. If the overall evaluation is greater than or equal to ○, there is no practical problem.
◎: Very vivid ○: Vivid △: Slightly inferior in vividness X: Not vivid 1-2. Unevenness of pigment ink printing portion The degree of unevenness of the solid printing portion was visually evaluated by a four-step evaluation. The visual evaluation A was the best (no unevenness), and the visual evaluation x was the worst (conspicuous unevenness). If the evaluation is Δ or more, there is no practical problem.
◎: No unevenness ○: Some unevenness △: There is unevenness ×: There is significant unevenness

2. Dye ink printing suitability
A predetermined pattern is recorded on the obtained ink jet recording medium using a dye ink jet printer (PM-970C: trade name manufactured by Epson Corporation), and the vividness (print density) of the recorded image portion is visually evaluated. did. If the overall evaluation is greater than or equal to ○, there is no practical problem.
◎: Very vivid ○: Vivid △: Slightly inferior in vividness ×: Invisible vivid 3. 20 ° glossiness
The 20 ° glossiness of the unprinted portion on the surface of the ink receiving layer of the obtained inkjet recording medium was measured according to JIS-Z8741. It measured using the glossiness meter (Murakami Color Research Laboratory make, True GLOSS GM-26PRO). As an evaluation, there is no practical problem if the 20 degree gloss is 20% or more, but it is preferably 30% or more.

  The obtained results are shown in Table 1.

As is apparent from Table 1, in each of the examples, the printability (print density and print unevenness) when using pigment ink was excellent, and the print density when using dye ink was also excellent.
In the case of Example 8, the amount of calcium carbonate in the base paper was less than that in the other examples, so that the ink unevenness when using the pigment ink was slightly increased. However, in the case of Example 8, there was no practical problem.
Further, when Example 5 and Example 6 using the same pigment are compared, Example 5 has less ink unevenness when using pigment ink. This is presumably because when the blending amount of the synthetic amorphous silica having excellent ink absorbability increases, ink unevenness due to aggregation of the color material of the pigment ink on the surface of the ink receiving layer is eliminated.
However, in Example 7 in which the blending amount of the synthetic amorphous silica was further increased and the blending amount of the colloidal silica was further decreased, the glossiness decreased and the ink unevenness increased. This is thought to be because the unevenness of the ink receiving layer surface increased due to the small amount of colloidal silica, resulting in ink unevenness and a decrease in print density. However, in the case of Example 7, there was no practical problem.
From the above, it can be seen that the blending amount of colloidal silica in the ink receiving layer is preferably 30 to 70 parts.

On the other hand, in the case of Comparative Example 1 where the primary particle size of the colloidal silica in the ink receiving layer was less than 30 nm, the pigment ink printability was greatly deteriorated. This is presumably because fine cracks occurred on the surface of the coating layer, and the colored pigment in the pigment ink fell into (flowed into) the cracks.
In the case of Comparative Example 2 in which the primary particle size of the colloidal silica in the ink receiving layer exceeded 70 nm, the print density when using the dye ink was greatly deteriorated. This is presumably because the transparency of the ink receiving layer was lowered.
In the case of Comparative Example 3 in which the ash content of calcium carbonate in the base paper was less than 15% by mass, and in Comparative Example 4 in which calcium carbonate was not embedded in the base paper, the pigment ink printability deteriorated. This is presumably because the amount of calcium carbonate in the base paper is small (or does not contain), so that the binding of the binder from the ink receiving layer coating liquid is nonuniform, and the surface of the ink receiving layer is cracked.

Claims (2)

  An ink jet recording medium in which an ink receiving layer containing a pigment and a binder is provided on at least one surface of a base paper containing calcium carbonate and pulp as a filler by a cast coating method, The ash content of the calcium carbonate is 15 to 30% by mass, and the ink receiving layer has a primary particle size of 30 to 70 nm as the pigment and a ratio of the secondary particle size to the primary particle size of 1.5 to 3.0. An ink jet recording medium containing colloidal silica.   The inkjet recording medium according to claim 1, wherein a content ratio of the colloidal silica to all the pigments in the ink receiving layer is 20 to 80% by mass.