JP3699104B2 - Ink jet recording medium and manufacturing method thereof - Google Patents

Description

  The present invention relates to an ink jet recording medium suitably used for ink jet recording and a method for producing the same, and more particularly to an ink jet recording medium suitable for ink jet recording using either a dye ink or a pigment ink and a method for producing the same.

  In general, the ink jet recording method uses a variety of mechanisms to eject ink droplets and deposit them on the recording paper to form dots and perform recording. However, compared with the dot impact type recording method, noise is generated. In addition, there is an advantage that full color is easy and high-speed printing is possible.

  Conventionally, water-based dye ink has been mainly used in the ink jet recording system. Although this water-based dye ink uses a low molecular weight dye as a colorant, it has good color developability, but it easily bleeds due to adhesion of water or the like, or is exposed to light or gas for a long time due to the structure of the colorant. Discoloration, discoloration, and there are problems with the storability of recorded images and image fastness.

  Therefore, in order to improve the problem of dye ink and improve water resistance and light resistance, ink using a pigment as a colorant has been put into practical use (see, for example, Patent Documents 1 to 3). However, the pigment ink has problems such as a lower printing density than the dye ink and inferior uniformity of the solid printing portion. In addition, if a large amount of pigment ink is ejected to enhance color development, the colorant accumulates on the surface of the recording medium, resulting in a decrease in friction resistance, print stains, or the absorption of the solvent in the ink due to the accumulation of the colorant. Sometimes.

  As described above, in recent years, both dyes and pigments have been used as inks for ink jet recording, and in order to cope with this, recording media suitable for both dye inks and pigment inks are required. Therefore, a technique is disclosed in which an ink receiving layer includes an adhesive composed of inorganic fine particles and a vinyl chloride-vinyl acetate copolymer, and both recording properties of dye ink and pigment ink are imparted (for example, Patent Document 4). reference).

  On the other hand, recently, high-definition digital video (camera), scanners and personal computers have become popular, and the image data has also been refined. However, the performance of inkjet printers has made these image data as high as silver halide photographs. Opportunities for output (hard copy) are increasing. Along with this, in addition to the glossiness of silver salt photographs, ink-jet recording media have a high ink drying speed, high print density, no ink overflow or bleeding, and paper does not wavy due to ink absorption. Such characteristics are required.

  In order to satisfy these characteristics, a technique for manufacturing a recording medium by a cast coating method has been proposed (for example, see Patent Document 5). In the cast coating method, an ink-receiving layer composed of a pigment mainly composed of synthetic silica and a binder is applied, and while the coating layer is in an undried wet state, the heated mirror-finished surface is applied. The layer is pressure-bonded to copy the mirror surface and simultaneously dried to obtain a high-gloss cast-coated paper.

  Further, a technique has been proposed in which a gloss layer containing pearl necklace-like colloidal silica is provided on an ink receiving layer without using a cast coating method (see Patent Document 6).

JP-A-11-20306 JP 2000-79752 A JP 2003-145916 A JP 2001-270238 A Japanese Patent Laid-Open No. 2-27487 JP 2000-108505 A

However, in the case of the technique described in Patent Document 4, both the print recording characteristics such as the print density and the ink absorbability cannot be satisfied, and it is difficult to obtain a high gloss recording medium. In the case of the technique described in Patent Document 5, the glossiness of the ink receiving layer is not yet sufficient, and the glossiness equivalent to that of a silver salt photograph has not been obtained. Furthermore, although the technique described in Patent Document 6 is suitable for dye inks, printing with pigment ink has drawbacks such as missing an image or contaminating a blank paper portion when the print portion is touched by hand. It was.
Accordingly, an object of the present invention is to provide an ink jet recording medium having good ink jet recording quality regardless of whether dye ink or pigment ink is used, and having glossiness equivalent to that of a silver salt photograph.

When the present invention contains a γ-type alumina and a specific colloidal silica as a pigment in the ink receiving layer, an ink jet recording medium having a good ink jet recording quality and a high glossiness can be obtained using either a dye ink or a pigment ink. I found out that I could get it.
The inventors have also found that when the ink jet recording medium is produced by a so-called cast coating method, a recording medium having the above characteristics can be obtained with high productivity.

  Therefore, the ink jet recording medium of the present invention is provided with an ink receiving layer containing a pigment and a binder on the support surface, and the pigment contains γ-type alumina and colloidal silica, and the primary particles of the colloidal silica. The diameter is 10 to 50 nm, and the ratio of the secondary particle diameter to the primary particle diameter is 1.5 to 2.5. It is preferable that 5-50 mass% of the colloidal silica is contained with respect to the total amount of the pigment.

  In the method for producing an inkjet recording medium of the present invention, a coating liquid containing a binder and a pigment is applied to a support surface to provide a coating layer, and the binder is applied to the surface of the coating layer. Applying a treatment liquid having a solidifying action, while the coating layer coated with the treatment liquid is in a wet state, the coating layer is pressure-bonded and dried on a heated mirror surface, and an ink receiving layer is provided. The pigment is characterized by containing γ-type alumina and colloidal silica having a primary particle diameter of 10 to 50 nm and a ratio of the secondary particle diameter to the primary particle diameter of 1.5 to 2.5.

  According to the present invention, a high-quality recorded image can be obtained by using either dye-type ink or pigment-type ink, and glossiness equivalent to that of a silver salt photograph can be obtained. Moreover, it is excellent in productivity.

(Support)
Any material can be used as the support used in the present invention as long as it has air permeability. For example, paper such as coated paper or uncoated paper is used. 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 any of acidic, neutral and alkaline. Further, in order to improve opacity, it is preferable to contain a filler in the paper, but this filler is a hydrated silicic acid, white carbon, talc, kaolin, clay, calcium carbonate, titanium oxide, synthetic resin filler, etc. It can be used by appropriately selecting from known fillers. From the viewpoint of operability, the air permeability of the paper is preferably 1000 seconds or less, and from the viewpoint of coatability, the paper sizing degree is preferably 5 seconds or more.

(Pigment of ink receiving layer)
As the pigment of the ink receiving layer, a pigment containing γ-type crystal alumina (γ-type alumina) and colloidal silica is used.

  γ-type alumina is obtained by heating and baking pseudoboehmite or boehmite produced by a known method at a temperature of 400 ° C. to 900 ° C. The γ-type crystalline alumina thus produced is adjusted to a desired particle size and particle size distribution range by pulverization and classification. In addition, when performing the cast coating described later, it is necessary to copy the mirror surface of the heated mirror drum surface to the ink receiving layer, and therefore the average particle diameter of the γ-type alumina is preferably 1.0 to 3.5 μm.

When colloidal silica is observed with a microscope, the colloidal silica has a shape in which a plurality of spherical primary particles are combined, which is referred to as “peanut shape” for convenience. When single spherical colloidal silica with no primary particles is used, ink absorbency is inferior, but peanut-shaped colloidal silica satisfies both glossiness, ink color development (image sharpness), and ink absorbency. Can be made.
The peanut-like 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) can be controlled according to the synthesis conditions. preferable. An example of such colloidal silica is Quartron manufactured by Fuso Chemical Industries. In addition, the colloidal silica of the present invention does not include colloidal particles obtained by subdividing an aggregate in which primary particles are aggregated by mechanical means.

In the peanut-like colloidal silica, the ratio of the secondary particle diameter to the primary particle diameter of the colloidal silica (secondary particle diameter / primary particle diameter) is 1.5 to 2.5. When colloidal silica having a (secondary particle diameter / primary particle diameter) within the above range is used, it is possible to obtain high image quality both when a dye ink is used and when a pigment ink is used.
Furthermore, the primary particle diameter of peanut-like colloidal silica is 10 to 50 nm, and the particularly preferable primary particle diameter is 13 to 40 nm. When the primary particle size is smaller than 10 nm, the transparency is high, but the voids between the particles are impaired and the ink absorbability is lowered. On the other hand, if it is larger than 50 nm, the voids between the particles are good, but the opacity increases, so the color developability at the time of ink jet recording decreases. In particular, when printing is performed with an ink jet printer using a pigment ink containing colored particles having a particle diameter of 50 to 150 nm in the ink, the ink coloring property is greatly reduced.
In addition, in the said peanut-shaped colloidal silica, 1.8-2.5 are mentioned as an example of the average value of the connection number of a primary particle. This value is the same value as the above ratio.

  In the present invention, the peanut-shaped colloidal silica is preferably contained in an amount of 5 to 50% by mass, more preferably 10 to 40% by mass, based on the total pigment of the ink receiving layer. When the content is less than 5% by mass of the entire pigment, the effect of improving ink absorbability and color development when printed by an ink jet printer tends to be insufficient. When the content exceeds 50% by mass of the entire pigment, the ink absorbability when printing with an ink jet printer is good, but the effect of improving color developability is reduced and the operability during coating is reduced. Tend.

As the blending ratio of γ-type alumina and peanut-like colloidal silica, the value of (γ-type alumina) / (colloidal silica) is preferably in the range of 95/5 to 50/50, more preferably in the range of 90/10 to 60/40. It is.
In addition, other pigments such as aluminum hydroxide, alumina sol, pseudoboehmite and other aluminas (α-type crystal alumina, θ-type crystal alumina), synthetic silica, and the like, as long as ink absorbability, color developability and glossiness are not impaired. , Kaolin, talc, calcium carbonate, titanium dioxide, clay, zinc oxide and the like may be used in combination.

(Binder for ink receiving layer)
As the binder, one or more kinds of polymer compounds capable of forming a film can be used. For example, as a binder, polyvinyl alcohol, polyvinylpyrrolidone, starches such as oxidized starch and esterified starch, cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, water-soluble resins such as casein, gelatin, and soy protein, urethane resins, Styrene-acrylic resin, styrene-butadiene resin, acrylic resin, vinyl acetate resin, vinyl chloride resin, urea resin, alkyd resin, and derivatives thereof can be used alone or in combination.

  The amount of the binder is preferably 3 to 30 parts by mass with respect to 100 parts by mass of the total pigment in the ink receiving layer, but is not particularly limited as long as the required coating layer strength is obtained. . Note that the polymer compound used as the binder is preferably aqueous. “Aqueous” means that the resin is dissolved or dispersed and stabilized in water or a medium composed of water and a small amount of an organic solvent. These binders are dissolved or dispersed as particles in the coating solution, but after coating and drying, they become pigment binders and form an ink receiving layer. When an organic solvent is used for the medium, it is necessary that the mixing ratio is less than 50% by weight, preferably less than 10% by weight, and the flash point of the resin liquid is high.

  The binder preferably contains polyvinyl alcohol. When polyvinyl alcohol is used as a binder, ink absorbability and color developability are particularly improved, and when an ink receiving layer is provided by a cast coating method to be described later, an ink jet recording medium having high gloss is obtained. Can do. The polyvinyl alcohol is preferably contained in an amount of 50 to 100% by mass with respect to the total binder of 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.

(Formation of ink receiving layer)
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 that covers the surface of the support and sufficient ink absorbency 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 occur.

  In the present invention, when a large coating amount of the ink receiving layer is required, the ink receiving layer can be formed in multiple layers. Further, an undercoat layer having various functions such as ink absorptivity and adhesiveness may be provided between the support and the ink receiving layer. Furthermore, 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 provided with the ink receiving layer.

(Formation of ink receiving layer by cast coating method)
In the present invention, it is preferable to impart high gloss 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 pressed onto a heated finished surface and dried. 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, it is semi-dried and then swollen and plasticized with a rewetting liquid, and is pressed onto a mirror-finished heated drum and dried (rewetting method). (3) The wet coating layer is made into a gel state by coagulation treatment. There are generally known three types: a gelled cast method (coagulation method) in which a heated drum having a mirror finish is pressed and dried.

  As a method for heating the mirror surface (drum), the mirror surface (drum) can be heated to a predetermined temperature with steam, heating wire, induction heating coil or the like. A coating equipment having a coating device and a mirror drum for applying an ink receiving layer or the like on a support is usually referred to as a cast coater.

  In particular, in the present invention, it is preferable to use the methods (2) and (3). In this case, after applying a coating liquid to be an ink receiving layer on a support, a treatment liquid having an action of coagulating a binder (particularly an aqueous binder) in the coating liquid is applied to the coating layer, 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 when applying the treatment liquid may be in a wet state or in a dry state. The former corresponds to the method (3), and the latter corresponds to the method (2). In particular, the method (3) is easy to copy the mirror-finished surface on the surface of the ink receiving layer and can reduce the fine irregularities on the surface of the coating layer. It becomes easy to give glossiness. Examples of the method for applying the treatment liquid include, but are not limited to, a roll, a spray, and a curtain method.

When the gelling cast method (method (3)) is used, when polyvinyl alcohol is used as the aqueous binder, it is preferable to use a liquid containing boric acid and borate as the coagulation treatment 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 give a good gloss to the ink receiving layer.
When casein is used as the aqueous adhesive, an aqueous solution containing various salts such as calcium, zinc, magnesium, etc. such as formic acid, acetic acid, citric acid, tartaric acid, lactic acid, hydrochloric acid, sulfuric acid, etc. is used as the treatment liquid. .

  Moreover, a release agent can be added to the coating liquid and / or the coagulating liquid for the ink receiving layer, if 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 almost equal to the temperature of the mirror-finished 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.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in full detail, this invention is not limited by this. Unless otherwise specified, “part” and “%” described below represent “part by mass” and “% by mass”, respectively.

(Manufacture of support)
To a pulp slurry consisting of 100 parts 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 by weight of a yield improver. Added. Using this slurry, a support was made with a paper machine. In addition, starch was applied on both sides of the support during paper making so that the solid content per side was 1.5 g / m ² to obtain a base paper having a basis weight of 170 g / m ² .

(Formation of under layer)
The following coating solution A was applied to one side of the base paper using a blade coater so that the coating amount was 8 g / m ^2, and air-dried at 140 ° C.
Coating liquid A: As a pigment, 100 parts of synthetic silica (Fine Seal X-37: manufactured by Tokuyama Corporation), 5 parts of latex (LX438C: trade name manufactured by Sumitomo Chemical Co., Ltd.), polyvinyl alcohol (PVA117: stock) 24 parts of Kuraray Co., Ltd. (trade name) and 5 parts of a sizing agent (Polymaron 360: trade name of Arakawa Chemical Co., Ltd.) were mixed to prepare an aqueous coating solution having a concentration of 20%.

(Formation of ink receiving layer)
Next, the following coating liquid B is applied to the coating surface of the coating liquid A using a roll coater so that the coating amount becomes 23 g / m ^2, and the following solidification is performed while the coating layer is in a wet state. Liquid C is solidified, and then the coated layer is pressure-bonded to the heated mirror-finished surface via a press roll, and the mirror surface is copied to obtain a cast coated paper for inkjet recording having a basis weight of 200 g / m ^2. It was.

Coating liquid B: 70 parts of γ-alumina (AKP-G015: trade name, manufactured by Sumitomo Chemical Co., Ltd.) having a particle size of 2.4 μm as a pigment, colloidal silica having an average primary particle size of 14 nm (PL1: Fuso Chemical Industries, Ltd.) 30 parts, polyvinyl alcohol A with a polymerization degree of 2400 as a binder (Kuraray 224: trade name made by Kuraray Co., Ltd.) and polyvinyl alcohol B with a polymerization degree of 2600 (MA26GP: trade name made by Shin-Etsu Chemical Co., Ltd.) ) 10 parts in total (mixing mass ratio is 1: 1), 5 parts of cationic polyurethane (F8570 D2: trade name of Daiichi Kogyo Seiyaku Co., Ltd.), ink fixing agent (Saftomer ST3300: manufactured by Mitsubishi Chemical Industries) 3 Part and 0.2 part of antifoaming agent were blended to prepare a coating solution having a concentration of 28%.
Coagulating liquid C: A coagulating liquid was prepared by blending a total concentration of borax and boric acid of 4% and a release agent (FL-48C: manufactured by Toho Chemical Co., Ltd.) 0.2%. The blending mass ratio of borax and boric acid was 1, and the above total concentration was a value for borax converted to Na ₂ B ₄ O ₇ and boric acid converted to H ₃ BO ₃ .

In addition, the particle size of the colloidal silica in the dispersed state of the coating liquid B was measured by the following method. The primary particle size was obtained by calculating from the following formula (1) by obtaining the specific surface area by the nitrogen adsorption method.
Specific surface area = 4πr ² / ((4πr ³ /3)*2.2) (1)
(Wherein the value 2.2 is the true specific gravity of silica and r is the primary particle diameter (nm))
The secondary particle size was measured using ZETASIZER 3000HSA manufactured by MALVERN INSTRUMENTS.

  Ink for ink jet recording was carried out in the same manner as in Example 1 except that in the coating liquid B, colloidal silica having an average primary particle size of 23 nm (PL2: trade name manufactured by Fuso Chemical Co., Ltd.) was blended instead of the colloidal silica. Coated paper was obtained.

  Ink coating for ink jet recording was carried out in the same manner as in Example 1 except that in the coating liquid B, colloidal silica having an average primary particle size of 35 nm (PL3: trade name manufactured by Fuso Chemical Co., Ltd.) was blended in place of the colloidal silica. Coated paper was obtained.

  A cast-coated paper for inkjet recording was obtained in exactly the same manner as in Example 2 except that in the coating liquid B, the blending amount of γ-alumina was 95 parts and the blending amount of colloidal silica was 5 parts.

  A cast-coated paper for inkjet recording was obtained in exactly the same manner as in Example 2 except that the coating amount of γ-alumina in coating solution B was 85 parts and the amount of colloidal silica was 15 parts.

  A cast-coated paper for inkjet recording was obtained in exactly the same manner as in Example 2 except that the coating amount of γ-alumina was 50 parts and the amount of colloidal silica was 50 parts.

A cast coated paper for ink jet recording was obtained in the same manner as in Example 2 except that the coating liquid A was not applied and the coating amount of the coating liquid B was 30 g / m ² .

  A cast-coated paper for ink jet recording was obtained in the same manner as in Example 2 except that the coating amount of γ-alumina in coating solution B was 97 parts and the amount of colloidal silica was 3 parts.

  A cast coated paper for ink jet recording was obtained in the same manner as in Example 2 except that the coating amount of γ-alumina was 40 parts and the amount of colloidal silica was 60 parts.

<Comparative Example 1>
In coating solution B, cast-coated paper for inkjet recording was obtained in exactly the same manner as in Example 1 except that the amount of γ-alumina was 100 parts and no colloidal silica was added.

<Comparative Example 2>
Ink coating for ink jet recording was carried out in the same manner as in Example 1, except that in the coating liquid B, colloidal silica having an average primary particle size of 52 nm (PL5: trade name manufactured by Fuso Chemical Co., Ltd.) was blended instead of the colloidal silica. Coated paper was obtained.

<Comparative Example 3>
Ink coating for ink jet recording was carried out in the same manner as in Example 1 except that in the coating liquid B, colloidal silica having an average primary particle diameter of 70 nm (PL7: trade name manufactured by Fuso Chemical Co., Ltd.) was blended instead of the colloidal silica. Coated paper was obtained.

<Comparative Example 4>
Cast coating paper for ink-jet recording was obtained in exactly the same manner as in Example 2 except that in the coating liquid B, γ-alumina was not blended and the amount of colloidal silica was 100 parts.

<Comparative Example 5>
The coating liquid B was replaced with the colloidal silica, except that it was blended with a chain colloidal silica (ST-OUP: product name manufactured by Nissan Chemical Industries) having an average primary particle size of 12.5 nm and a length of 170 nm. A cast coated paper for ink jet recording was obtained in exactly the same manner as in Example 1.

<Comparative Example 6>
Example in which coating liquid B was replaced with spherical colloidal silica having a mean primary particle diameter of 15 nm (Snowtex AK: trade name, non-agglomerated silica manufactured by Nissan Chemical Industries, Ltd.) instead of colloidal silica. In the same manner as in No. 1, a cast coated paper for ink jet recording was obtained.

  About the cast coated paper for inkjet recording obtained in each Example and the comparative example, the operativity at the time of cast coating, glossiness, and inkjet recording quality were evaluated with the following method.

(1) Glossiness The glossiness of the cast coated paper surface (ink receiving layer surface) was visually observed and evaluated according to the following criteria.
○: Highly transparent glossy △: Cloudy glossy ×: Low glossiness or uneven coating

(2) Inkjet recording quality Each of dye ink and pigment ink was evaluated. When dye ink was used, a predetermined pattern was recorded by an ink jet printer (PM-950C: trade name, manufactured by Epson Corporation) and evaluated according to the following criteria. In the case of pigment ink, the same evaluation was performed using an inkjet printer (PM-4000PX: trade name of Epson Corporation).
3-1. Ink absorption (bleeding)
The blur at the boundary of the solid print of red and green was visually evaluated.
○: Color boundary portion clearly separated Δ: Color boundary portion with slight blurring ×: Color boundary portion with large blurring 3-2. Vividness The vividness of a predetermined recorded image was visually evaluated.
○: Vivid △: Slightly inferior x: Invisible

(3) Operability at the time of cast coating The stain | pollution | contamination of the cast drum surface at the time of coating the coating liquid B and forming an ink receiving layer was observed visually, and the following references | standards evaluated.
○: Cast drum surface is not dirty △: Cast drum surface is slightly cloudy ×: Part of the coating layer adheres to the cast drum surface

The obtained results are shown in Table 1.
(4) Particle size measurement of colloidal silica-Primary particle size The specific surface area was determined by the nitrogen adsorption method and was calculated from the following formula (1).

Specific surface area = 4πr ² / ((4πr ³ /3)*2.2) (1)
2.2: True specific gravity of silica (unit: g / cm ³ )
r: primary particle diameter (nm)
The secondary particle size was measured using ZETASIZER 3000HSA manufactured by MALVERN INSTRUMENTS.

  The obtained results are shown in Table 1.

  As is apparent from Table 1, in each of the examples, the ink jet recording quality was good and glossiness equivalent to that of a silver salt photograph was obtained regardless of whether dye ink or pigment ink was used. Moreover, the operability at the time of cast coating was also excellent. In the case of Example 9 where the blending amount of colloidal silica is less than 5% by mass, the vividness is slightly lowered, and in the case of Example 10 where the blending amount of colloidal silica exceeds 50% by mass, glossiness, cast coating Although the operability at the time of construction slightly decreased, there was no practical problem. This shows that it is preferable to contain 5-50 mass% of colloidal silica with respect to the total amount of pigment.

On the other hand, in the case of Comparative Example 1 in which no colloidal silica was blended and in the case of Comparative Examples 2 and 3 in which the primary particle diameter of the colloidal silica exceeded 50 nm, the vividness when recorded by inkjet was reduced. In the case of Comparative Example 4 in which γ-type alumina was not blended, the ink absorbability was lowered. Further, in the case of Comparative Example 5 using chain colloidal silica in which the ratio of the secondary particle diameter to the primary particle diameter exceeds 2.5, the vividness is inferior and the above ratio is less than 1.5 spherical colloidal silica (aggregation). In the case of Comparative Example 6 in which the primary particle size was set to the secondary particle size for the sake of convenience, both the ink absorptivity and the vividness were reduced.

Claims (3)

An ink jet recording medium having an ink receiving layer containing a pigment and a binder on a support surface, wherein the pigment contains γ-type alumina and colloidal silica, and the primary particle diameter of the colloidal silica is 10 An inkjet recording medium having a secondary particle diameter ratio of 1.5 to 2.5 and a primary particle diameter of ˜50 nm. The inkjet recording medium according to claim 1, wherein the colloidal silica is contained in an amount of 5 to 50% by mass with respect to the total amount of the pigment. On the surface of the support, a coating liquid containing a binder and a pigment is applied to provide a coating layer, and a coating liquid is applied to the surface of the coating layer, which has a function of solidifying the binder. While the coating layer to which the treatment liquid is applied is in a wet state, the coating layer is pressure-bonded to a heated mirror surface and dried to provide an ink receiving layer, wherein the pigment comprises: An ink jet recording medium comprising: γ-type alumina; and colloidal silica having a primary particle diameter of 10 to 50 nm and a ratio of the secondary particle diameter to the primary particle diameter of 1.5 to 2.5. Production method.