JP2005103892A - Inkjet recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording medium which shows successful inkjet recording characteristics in a dye ink and a pigment ink and further, a feel of gloss equivalent to a silver salt photograph. <P>SOLUTION: In the inkjet recording medium with an ink acceptance layer formed on a gas-permeable support and an ink color developing layer formed by a cast coating process on the ink acceptance layer, the ink color developing layer contains not less than 90 %, in terms of a solid content, of a colloidal silica and a water-soluble resin and the colloidal silica has a ratio of a primary particle diameter to a secondary particle diameter of 1.5 to 2.5. In addition, the ink color developing layer is preferably formed by a gelation cast coating process and more preferably, the colloidal silica has the primary particle diameter of 10 to 40 nm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ink jet recording medium, and more particularly to an ink jet recording medium characterized in that both dye ink and pigment ink have high printability and have a glossiness equivalent to that of a silver salt photograph.

  For coated paper type inkjet recording media, the ink is absorbed by the porous pigment in the coating layer (so-called absorption type) and the resin in the coating layer is swollen by the solvent to fix the ink. It is roughly divided into types (so-called swelling types). Among these, the high-quality medium for ink-jet used for the purpose of reproducing an image comparable to a silver salt photograph has a mainstream use of an absorption type because the amount of ink discharged increases for reproducing the image quality. The absorption-type 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. 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.

The inkjet recording medium having gloss described above is generally manufactured by a cast coating method using a cast coater from the viewpoint of manufacturing cost (for example, Patent Documents 1 to 3). The cast coating method is a method in which a coating liquid mainly composed of a pigment and a binder is applied onto a base paper to provide a coating layer, and the coating layer is gloss-finished using a cast drum. The 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, after semi-drying, it is swollen and plasticized with a re-wetting liquid, pressed onto a mirror-finished heating drum and dried, and then (3) a wet coating layer is made into a gel state by coagulation. 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. 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. (For example, see Non-Patent Document 1)
Moreover, in order to give high glossiness to a coating layer, the method with a small particle size of the pigment in a coating layer is advantageous. For this reason, an inkjet recording medium containing colloidal silica having a small particle size as a pigment in a layer exhibiting gloss is disclosed. (For example, Patent Document 4 and Patent Document 5)
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 recent years, inkjet printers using pigment inks that are clearer in color than water-based inks and have excellent image storability have been released and are considered to become the mainstream of future inkjet systems. 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. In view of this, there is also disclosed a technique 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 6). reference).

JP-A-6-305237 JP 9-156210 A Japanese Patent Laid-Open No. 11-48604 JP 2000-108506 A JP 2000-62314 A Japanese Patent Laid-Open No. 2001-270238 Paper Pulp Technology Association, "Paper Pulp Manufacturing Technology Series (8) Coating" Chapter 9 "Cast Coated Paper" August 17, 1993 Issued

  However, in the case of the techniques described in Patent Documents 1 to 3, the recording suitability using the dye ink is improved, but the recording suitability using the pigment ink is insufficient. In addition, the ink jet recording sheets described in Patent Document 4 and Patent Document 5 have good color developability and ink absorbability in an ink jet printer using a dye ink, but a color material having a particle diameter of 50 nm to 150 nm in the ink. When printing with an ink jet printer using pigment ink containing particles, the ink particles are poorly cast on the ink coloring layer, so if the image area is touched by hand, the image may be lost or the blank area may be stained. There were drawbacks. In the case of the technique described in Patent Document 6, the print characteristics, particularly the print density and ink absorbency, are not yet compatible.

  Accordingly, an object of the present invention is to provide an ink jet recording medium having good ink jet recording characteristics for both dye inks and pigment inks, and having glossiness similar to that of a silver salt photograph.

  The present inventors use dye and pigment ink by providing an ink-receiving layer on a base paper and then providing an ink coloring layer mainly composed of specific colloidal silica and a water-soluble resin by a cast coating method. It was found that an ink jet recording medium having good gloss recording characteristics and glossiness equivalent to that of a silver salt photograph can be obtained.

Therefore, the above object has been achieved by the following invention.
The present invention provides an ink jet recording medium in which an ink-receiving layer is provided on a gas-permeable support and an ink-coloring layer is provided by a cast coating method. The ink-coloring layer comprises colloidal silica and a water-soluble resin. 90% or more in terms of solid content, and the colloidal silica is an ink jet recording medium having a ratio of secondary particle diameter to primary particle diameter of 1.5 to 2.5.

In the present invention, the ink coloring layer is preferably provided by a gelled cast coating method. The primary particle size of the colloidal silica is preferably 10 to 40 nm.
Further, the solid content weight ratio of the colloidal silica and the water-soluble resin of the ink coloring layer is preferably colloidal silica / water-soluble resin = 100/3 to 100/50, and the water-soluble resin of the ink coloring layer is preferably polyvinyl. It is preferable to use alcohol.

  The ink jet recording medium of the present invention can obtain excellent image quality regardless of whether dye ink or pigment ink is used, and has particularly high color developability and ink absorption performance, and has a glossiness similar to that of a silver salt photograph. doing.

(Support)
As the support used in the present invention, any support can be used as long as it has air permeability, but paper (coated paper, uncoated paper, etc.) is preferably 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. Further, 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.

(Ink receiving layer)
In the present invention, the ink color absorption layer alone is poor in ink absorbability, and ink absorption necessary for an ink jet recording medium cannot be obtained. Therefore, an ink receiving layer having a large absorption capacity is essential. The ink receiving layer is a layer intended to absorb ink or an ink solvent, and is a layer mainly composed of a pigment and a binder. As the pigment of the ink receiving layer, known pigments used in the ink receiving layer such as silica, alumina, calcium carbonate and calcined clay can be used alone or in combination. As the binder, known water-soluble resins such as polyvinyl alcohol and starch, and emulsion resins such as EVA / SBR can be used as binders used in the ink receiving layer. In addition, a known auxiliary agent such as a sizing agent, an ink fixing agent, a surfactant, or a dye may be appropriately added to the ink receiving layer as necessary. In the present invention, the ink coloring layer is highly transparent, and in order to increase the coating speed and increase the productivity, it is necessary to reduce the coating amount of the ink coloring layer. Desirably, the ink jet is suitable (specifically, the ink drying speed is high, the printing density is high, and the ink does not overflow or bleed).
In the present invention, the average oil absorption amount of the entire pigment in the ink receiving layer is preferably 100 ml / 100 g or more from the viewpoint of obtaining ink absorption. Moreover, it is preferable that the solid content weight ratio of pigment / binder is 100/3 to 100/50. When the solid content weight ratio of the pigment / binder is within this range, the ink receiving layer can satisfy both ink absorbency and coating strength. The ink receiving layer may be a multilayer or a single layer.

(Ink coloring layer)
In the present invention, it is necessary to increase the transparency of the ink coloring layer in order to improve the color developing property of the ink. For this reason, the ink coloring layer is mainly composed of colloidal silica and a water-soluble resin. In the present invention, the sum of the colloidal silica and the water-soluble resin in the ink coloring layer is required to be 90% or more, and preferably 95% or more in terms of solid content. Further, the ink coloring layer may be composed only of colloidal silica and a water-soluble resin.

  If the ink coloring layer contains silica particles, alumina, calcium carbonate, baked clay, etc., which are generally powder particles with a relatively large particle size (average particle size is about several μm), the transparency of the ink coloring layer is impaired and recording is performed. The sharpness of the image is impaired. For these reasons, in the present invention, the ink coloring layer contains colloidal silica having a relatively small particle size (average particle size of several tens to several hundreds nm) as a pigment. By using colloidal silica, the ink coloring layer can have high transparency, and the ink coloring layer can have high gloss.

(Colloidal silica of ink coloring layer)
Moreover, in this invention, ratio of the secondary particle diameter with respect to the primary particle diameter of the said colloidal silica shall be 1.5-2.5. This is because if the ratio is less than 1.5, the transparency of the ink coloring layer is enhanced, but the ink absorbability deteriorates because there are few voids, and if it exceeds 2.5, the ink absorbability is good due to the increase in voids. This is because the opacity increases and the color developability deteriorates. The primary particle size and secondary particle size of colloidal silica can be measured by the BET method, 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 is a chain (also referred to as a pearl necklace) colloidal silica (when observed with a microscope, at least 5 spherical single colloidal silicas, usually 10 or more continuous, the above ratio is also 5 This is not included. The term “excluded” as used herein does not mean that no chain colloidal silica is observed when observed under a microscope, but is a value obtained by measuring the ratio of the secondary particle diameter to the primary particle diameter, which is a macroscopic property. Is not more than 2.5 (usually 5 or more).

The colloidal silica used in the present invention 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. It is preferable to make it. As such colloidal silica, trade name Quatron manufactured by Fuso Chemical Industry Co., Ltd. can be mentioned.
In addition, as the colloidal silica of the present invention, an aggregate in which primary particles are aggregated is subdivided into secondary particles having an average particle diameter of about several tens to several hundreds of nanometers by mechanical means (excluding dry pulverization). It does not contain colloidal particles.

  In the present invention, when the average primary particle diameter of colloidal silica is smaller than 13 nm, the transparency is high, but the voids between the particles are impaired and the ink absorbability tends to be lowered. On the other hand, when the average primary particle size of the colloidal silica is larger than 40 nm, the voids between the particles are good, but since the opacity increases, the color developability at the time of ink jet recording tends to decrease, In particular, when printing is performed with an ink jet printer using a pigment ink containing particles having a particle diameter of 50 nm to 150 nm in the ink, the ink coloring property is greatly reduced.

  Further, colloidal silica not included in the above-mentioned range as a pigment of the ink coloring layer, and silica, alumina, calcium carbonate, as long as the transparency of the ink coloring layer, the ink coloring property and glossiness at the time of ink jet recording are not impaired. It is also possible to mix powdery particles such as baked clay. In order to maintain high transparency of the ink coloring layer, these auxiliary pigments are preferably 10% or less, more preferably 5% or less in terms of solid content in the pigment of the ink coloring layer.

(Binder for ink coloring layer)
In order to obtain high transparency, the ink coloring layer of the present invention mainly uses a water-soluble resin as a binder and contains at least one kind thereof. As the water-soluble resin, known resins can be used as long as they are soluble in water. For example, polyvinyl alcohol and modified products thereof, polyvinylpyrrolidone and modified products thereof, starch such as oxidized starch and esterified starch And cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, casein, gelatin, and soy protein are not particularly limited. Of these, partially saponified or fully saponified polyvinyl alcohols are preferably used because of their good transparency. In the present invention, it is possible to further mix other aqueous binders within a range not impairing ink absorbability, color developability and glossiness upon ink jet recording. Examples of aqueous binders other than water-soluble resins include urethane resins derived from urethane resin emulsions, styrene-acrylic resins and derivatives thereof, styrene-butadiene resin latex, acrylic resin emulsions, vinyl acetate resin emulsions, vinyl chloride resin emulsions, Examples include urea resin emulsions, alkyd resin emulsions, and derivatives thereof.

In the present invention, the addition amount of the water-soluble resin in the ink coloring layer (in the case of containing a binder other than the water-soluble resin, the total of the water-soluble resin and the binder other than the water-soluble resin) The amount is preferably 3 to 50 parts, more preferably 5 to 30 parts, based on 100 parts of the pigment of the ink coloring layer. When the amount of the binder to the pigment is large, the glossiness is enhanced, but the ink absorbability tends to be deteriorated. When the amount is small, the glossiness is difficult to obtain, and the strength is difficult to be obtained, so the productivity tends to be deteriorated. . In order to maintain high transparency in the ink coloring layer, it is desirable that the content of the binder other than the water-soluble resin is as small as possible. For this reason, the binder other than the water-soluble resin is not bound to the ink coloring layer. In the agent, the solid content is preferably 10% by weight or less, and more preferably 5% by weight or less.

(Coagulating liquid)
In the present invention, the ink coloring layer is formed by a casting method. As described above, the cast coating method includes a wet method, a rewet method, and a gelation method. Of these, the rewetting method is a method of moistening a once dried coating layer with a re-wetting liquid, but the degree of plasticization of the coating layer at the time when it is pressure-bonded to the mirror drum compared to the other two methods. Because it is small and it is difficult to copy the surface of the mirror drum, the surface has many fine irregularities, making it difficult to obtain the same glossiness as a silver salt photograph. In addition, the wet cast coating method has a high moisture content in the coating layer at the time when it is pressure-bonded to the mirror drum, and this imposes a load on drying. For this reason, the gelled cast coating method is most desirable in order to impart high gloss to the coating layer, that is, the ink coloring layer. The gelled cast coating method uses a coagulation liquid before pressure-bonding to a mirror drum, and gels (solidifies) the water-soluble resin of the ink coloring layer, so it is good with a small amount of coating without reducing productivity. You can copy the surface.

  For example, when polyvinyl alcohol is used as the water-soluble resin of the ink coloring layer, any aqueous solution containing a compound having a function of coagulating polyvinyl alcohol can be used. A treatment liquid containing borate is preferable. By mixing and using, it becomes easy to solidify the ink coloring layer to an appropriate hardness. Other coagulation combinations include a method in which a protein such as casein is used as a water-soluble resin and coagulated by salting out with calcium formate or the like, and known combinations can be appropriately selected and used. The ink coloring layer can be formed by using such a combination of solidifications alone, or the ink coloring layer can be formed by simultaneously using a plurality of combinations of solidification.

(Release agent / auxiliary)
A release agent can be added to the ink coloring layer or the coagulating liquid as necessary. The melting point of the release agent to be added 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 metal surface temperature of the mirror finish, the ability as a release agent is maximized. The release agent is not particularly limited as long as it has the above characteristics. A particularly preferred release agent is a polyethylene wax emulsion.

  In the present invention, a pigment dispersant, a water retention agent, a thickening agent, an antifoaming agent, a preservative, a colorant, water resistance is optionally added to the ink coloring layer or the treatment liquid (rewetting liquid, coagulating liquid, etc.). An agent, a wetting agent, a fluorescent dye, an ultraviolet absorber, a cationic polymer electrolyte, and the like can be appropriately added. However, in order to maintain high transparency, it is desirable that the water-insoluble resin and the water-insoluble component are as few as possible.

  In the present invention, the ink receiving layer and the ink coloring layer can be provided by applying a coating solution for each layer with a known coater and then drying. As a coating method, among coating methods using a known coating machine such as a blade coater, an air knife coater, a roll coater, a brush coater, a kiss coater, a squeeze coater, a curtain coater, a die coater, a bar coater, and a gravure coater. Can be appropriately selected and used. Examples of the method for applying the rewetting liquid or the coagulating liquid include, but are not limited to, a roll, a spray, and a curtain system. A back coat layer having various functions such as ink absorptivity, writing property, printer printability and the like can be further provided on the opposite side of the surface provided with the ink receiving layer.

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 absorbency is obtained, but from the viewpoint of achieving both recording density and ink absorbency, It is preferable that it is 3-30 g / m < ² > in conversion of solid content. A more preferred range is ^{10g / m 2 ~25g / m 2} . If it exceeds 30 g / m ² , the peelability from the mirror drum is lowered, and problems such as adhesion of the coating layer to the mirror drum occur. In the present invention, when a large coating amount of the ink receiving layer is required, it is possible to apply the ink receiving layer coating liquid a plurality of times to make the ink receiving layer multilayer. When the ink receiving layer has a multilayer structure, the total sum of the layers is desirably ³ to 30 g / m ^{2 in} terms of solid content per side on the support.

The coating amount of the ink coloring layer can be arbitrarily adjusted as long as the surface of the ink receiving layer is covered and sufficient gloss is obtained, but from the viewpoint of achieving both gloss and ink absorbency, It is preferable that it is 3-20 g / m < ² > in conversion of solid content. Furthermore preferably ^{5g / m 2 ~15g / m 2} . If it exceeds 20 g / m ² , drying on the mirror drum is insufficient, causing problems such as adhesion of the coating layer to the drum surface, and the ink absorbing ability of the ink receiving layer cannot be utilized.

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 weight” and “% by weight”, respectively.

Example 1
Pulp slurry consisting of 100 parts hardwood bleached kraft pulp (L-BKP) with a beating degree of 285 ml 10 parts by weight of talc, 1.0 part by weight of aluminum sulfate, 0.1 part by weight of synthetic sizing agent, 0.02 part by weight of yield improver When paper was added to the support to which the part was added with a paper machine, starch was coated on both sides so that the solid content per side was 2.5 g / m ² to obtain a base paper having a basis weight of 170 g / m ² . The base paper was coated with coating solution A with a blade coater so that the coating amount was 12 g / m ² on one side, and dried by blowing at 140 ° C. Next, 8 g / m ^{2 of} coating liquid B was applied on the surface coated with coating liquid A with a roll coater, and solidified with coagulating liquid C while the coating layer was wet, The mirror surface was pressed onto a mirror-finished surface heated via a press roll, and the mirror surface was copied to obtain a 170 g / m ² cast-coated paper for inkjet recording.

Coating liquid A: As a pigment, 100 parts of synthetic silica (Fine Seal X-37: trade name manufactured by Tokuyama Co., Ltd.), 5 parts of latex (LX438C: trade name manufactured by Sumitomo Chemical Co., Ltd.) and polyvinyl alcohol (PVA117) : 24 parts of Kuraray Co., Ltd. trade name) and 5 parts of sizing agent (Polymaron 360: trade name of Arakawa Chemical Co., Ltd.) to prepare an aqueous coating solution having a concentration of 20%.

Coating liquid B: 100 parts of colloidal silica (PL2: product name manufactured by Fuso Chemical Industry Co., Ltd.) having an average primary particle size of 23 nm as a pigment, and polyvinyl alcohol having a polymerization degree of 2400 as a binder (Kuraray 224: product manufactured by Kuraray Co., Ltd.) No.) was mixed with 10 parts to prepare a coating solution having a concentration of 18%.

Coagulating liquid C: The ratio of borax / boric acid is 1: 4, the concentration is 4% in terms of Na ₂ B ₄ O ₇ and H ₃ BO ₃ , and the release agent (FL-48C: manufactured by Toho Chemical Industry Co., Ltd.) (Trade name) 0.2% was blended to prepare a coagulation liquid.

Example 2
A cast coated paper for ink jet recording was obtained in the same manner as in Example 1 except that colloidal silica was replaced with colloidal silica (PL1: trade name manufactured by Fuso Chemical Co., Ltd.) having an average primary particle size of 14 nm.

Example 3
A cast-coated paper for inkjet recording was obtained in the same manner as in Example 1 except that colloidal silica in Example 1 was changed to colloidal silica having an average primary particle size of 30 nm (PL3: a trade name manufactured by Fuso Chemical Industries).

Example 4
A cast coated paper for inkjet recording was obtained in the same manner as in Example 1 except that the colloidal silica in Example 1 was changed to 100 parts of colloidal silica (PL7: trade name manufactured by Fuso Chemical Industries) having an average primary particle size of 70 nm. .

Example 5
A cast coated paper for ink jet recording was obtained in exactly the same manner as in Example 1 except that the coating liquid A was applied as an ink receiving layer so as to be 18 g / m ² .

Example 6
A cast coated paper for ink jet recording was obtained in exactly the same manner as in Example 1 except that the coating liquid F was used as the ink coloring layer.
Coating liquid D: 100 parts of colloidal silica (PL2) having an average primary particle diameter of 20 nm as a pigment and 30 parts of polyvinyl alcohol (Kuraray 224) having a polymerization degree of 2400 as a binder are prepared to prepare a coating liquid having a concentration of 18%. did.

Example 7
A cast coated paper for ink jet recording was obtained in the same manner as in Example 1 except that the coating liquid I was used as the ink coloring layer.
Coating liquid E: A coating liquid having a concentration of 18% was prepared by blending 100 parts of colloidal silica (PL2) having an average particle diameter of 20 m as a pigment and 60 parts of polyvinyl alcohol (Kuraray 224) having a polymerization degree of 2400 as a binder.

Example 8
A cast coated paper for ink jet recording was obtained in the same manner as in Example 1 except that the coating liquid G was used as the ink coloring layer and the coagulating liquid H was used as the coagulating liquid.
Coating liquid G: A coating liquid having a concentration of 18% was prepared by blending 100 parts of colloidal silica (PL2) having an average primary particle diameter of 23 nm as a pigment and 10 parts of casein as a binder.
Coagulating liquid H: A coagulating liquid was prepared by adding ammonium formate to a concentration of 10% and adding a release agent (FL-48C) 0.2%.

Comparative Example 1
A cast coated paper for ink jet recording was obtained in exactly the same manner as in Example 1 except that the ink receiving layer was not provided.

Comparative Example 2
A cast coated paper for ink jet recording was obtained in exactly the same manner as in Example 1, except that the coating liquid J was used as the ink coloring layer.
Coating liquid J: 100 parts of synthetic silica (Fine Seal X-37) as a pigment and 10 parts of polyvinyl alcohol (Kuraray 224) having a polymerization degree of 2400 as a binder were blended to prepare a coating liquid having a concentration of 18%.

Comparative Example 3
A cast coated paper for ink jet recording was obtained in the same manner as in Example 1 except that the coating liquid M was used as the ink coloring layer.
Coating liquid M: 100 parts of colloidal silica (PL2) having an average particle diameter of 20 m as a pigment, 10 parts of polyvinyl alcohol (Kuraray 224) having a polymerization degree of 2400 as a binder, a water-insoluble urethane emulsion (UD100N: manufactured by Mitsui Chemicals, Inc.) 30 parts of (trade name) was blended to prepare a coating solution having a concentration of 18%.

Comparative Example 4
For ink jet recording in the same manner as in Example 1 except that the colloidal silica of the coating liquid B in Example 1 was changed to a chain colloidal silica having a primary particle diameter of 12 nm (ST-UP: trade name manufactured by Nissan Chemical Industries). A cast coated paper was obtained.

Comparative Example 5
For ink jet recording as in Example 1, except that the colloidal silica of the coating liquid B in Example 1 was changed to a chain colloidal silica having a primary particle diameter of 22 nm (PS-M: a trade name manufactured by Nissan Chemical Industries, Ltd.). A cast coated paper was obtained.

Comparative Example 6
Inkjet recording was carried out in the same manner as in Example 1 except that the colloidal silica of the coating liquid B in Example 1 was changed to tufted colloidal silica (HS-M-20: trade name manufactured by Nissan Chemical Industries, Ltd.) having a primary particle size of 23 nm. A cast coated paper for recording was obtained.

Comparative Example 7
For ink jet recording in the same manner as in Example 1, except that the colloidal silica of the coating liquid B in Example 1 was changed to tuft-like colloidal silica (HS-ZL: trade name manufactured by Nissan Chemical Industries, Ltd.) having a primary particle diameter of 78 nm. A cast coated paper was obtained.

Comparative Example 8
Example 1 except that the colloidal silica of the coating liquid B was changed to colloidal silica having an average primary particle size of 15 nm and not connected (Snowtex ST-30: trade name manufactured by Nissan Chemical Industries, Ltd.) in Example 1. In the same manner, a cast coated paper for ink jet recording was obtained.

  The cast coating operability, glossiness, and inkjet recording test of the inkjet recording paper obtained in Examples 1 to 6 and Comparative Examples 1 to 8 were performed by the following methods. The results are summarized in Table 1.

(1) Glossiness The glossiness of the cast coated paper surface was visually evaluated.
○ Highly transparent glossy △ Cloudy glossy × Low glossiness or uneven coating

(2) Inkjet recording test The recording test was performed using an inkjet printer using a dye ink (PM-970C: trade name manufactured by Epson Corporation) and an inkjet printer using a pigment ink (PM-4000PX: trade name manufactured by Epson Corporation). A predetermined pattern was recorded using and evaluated according to the following criteria.
a. Ink absorption (bleeding)
Bleeding was visually evaluated at the boundary between the red and green mixed colors.
○ The color boundary is clearly separated △ The color boundary is slightly blurred x The color boundary is heavily blurred b, vividness The vividness of the recorded image area was visually evaluated. .
○ Vivid △ Somewhat inferior in vividness × Not vivid

(3) Particle size measurement of colloidal silica The primary particle size was determined from the following formula by calculating the specific surface area by the nitrogen adsorption method.
Specific surface area = 4πr ² / ((4πr ³ /3)*2.2
2.2: True specific gravity of silica
r: particle diameter nm
The secondary particle size was measured with a Coulter N4 meter (trade name, manufactured by Coulter), and the number average value was used as the particle size.

As is apparent from Table 1, the inkjet recording papers of the present invention of Examples 1 to 5 were highly evaluated in terms of glossiness and printability. In Example 4 using colloidal silica having a large primary particle size, the vividness of the dye ink was slightly inferior. Further, in Examples 6 and 7 in which the amount of PVA was increased as the binder, the ink absorbability tended to deteriorate. In Example 8 in which casein was used in place of PVA as the binder, the color developability of the ink was slightly lowered.
On the other hand, in Comparative Example 1 in which no under layer was provided, ink absorbability was difficult, and ink jet printing suitability was not obtained. In Comparative Example 2 in which ordinary silica was used as the pigment of the ink coloring layer, although the absorbency was excellent, a vivid ink jet recording was not obtained, and the glossiness was not as good as that of the example. It was. In Comparative Example 3 in which a water-insoluble resin was used, the ink absorbability and the ink coloring property were greatly reduced. In Comparative Examples 4 and 5 in which linear colloidal silica was used, and in Comparative Examples 6 and 7 in which tufted colloidal silica was used, the ink colorability was reduced, although the absorbency was excellent. In Comparative Example 8 using non-associated spherical colloidal silica, the ink absorbability was lowered.

Claims (5)

In an ink jet recording medium in which an ink receiving layer and an ink coloring layer provided by a cast coating method are sequentially provided on a gas-permeable support, the ink coloring layer contains 90 colloidal silica and water-soluble resin in terms of solid content. An ink jet recording medium comprising: at least wt%, wherein the colloidal silica has a ratio of secondary particle diameter to primary particle diameter of 1.5 to 2.5. 2. The ink jet recording medium according to claim 1, wherein the ink coloring layer is provided by a gelled cast coating method. The ink jet recording medium according to claim 1 or 2, wherein the colloidal silica has a primary particle diameter of 10 to 40 nm. 4. The ink jet recording medium according to claim 1, wherein a solid content weight ratio of the colloidal silica and the water-soluble resin of the ink coloring layer is colloidal silica / water-soluble resin = 100/3 to 100/50. The inkjet recording medium according to claim 1, wherein polyvinyl alcohol is used as the water-soluble resin.