JP2011207173A - Inkjet recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recording medium which is excellent in a thin line drawing nature and glossiness.SOLUTION: The inkjet recording medium has a support, a first ink receiving layer which is provided on the support and includes first inorganic fine particles and a second ink receiving layer which is provided on the first ink receiving layer in contact therewith and includes second inorganic fine particles. A peak diameter in a fine pore diameter distribution of the second ink receiving layer is smaller than that of the first ink receiving layer. Further a ruggedness index of the boundary line between the first ink receiving layer and the second ink receiving layer in a cross-section in a direction perpendicular to a surface, where the first ink receiving layer and the second ink receiving layer of the support are provided, is made to be 1.5 to 15.0.

Description

  The present invention relates to an inkjet recording medium.

2. Description of the Related Art In recent years, inkjet recording methods have been widely used because they can be recorded on various recording materials, the hardware (device) is relatively inexpensive, compact, and quiet.
Accompanying this, the resolution of ink jet printers has been increased, and in recent years, so-called photographic-like high-quality images have been obtained. Properties required for inkjet recording media to obtain high-quality images include quick drying (ink absorption speed), dot uniformity (bleed resistance), granularity, color density, saturation, moisture resistance, and various other characteristics. It is necessary to meet the performance of.

  In relation to the above, a cast comprising an undercoat layer and amorphous silica having an average primary particle size of 3 to 40 nm and an average secondary particle size of 10 to 400 nm on a substrate. An ink jet recording sheet provided with a layer is disclosed, and is excellent in gloss (see, for example, Patent Document 1). Inkjet recording is provided with an ink receiving layer comprising two layers, an upper layer and a lower layer, and the specific surface area of the inorganic fine particles contained in the upper ink receiving layer is smaller than the specific surface area of the inorganic fine particles contained in the lower ink receiving layer. A medium is disclosed, and ink absorption is excellent (for example, see Patent Document 2).

JP 2004-306616 A JP 2007-98644 A

However, in the invention described in Patent Document 1 or Patent Document 2, it may be difficult to say that fine line drawing properties and glossiness are sufficient.
An object of the present invention is to provide an ink jet recording medium excellent in fine line drawing property and glossiness.

Specific means for solving the above problems are as follows.
<1> A support, a first ink receiving layer that is provided on the support and includes first inorganic fine particles, and a second ink that is provided on and in contact with the first ink receiving layer. An ink jet recording medium comprising: a second ink receiving layer including a second ink receiving layer having a peak diameter in the pore diameter distribution of the second ink receiving layer that is greater than a peak diameter in the pore diameter distribution of the first ink receiving layer. The first ink receiving layer in a cross section of the inkjet recording medium, which is smaller and is perpendicular to the surface of the support on which the first ink receiving layer and the second ink receiving layer are provided. An inkjet recording medium having an unevenness index of a boundary line with the second ink receiving layer of 1.5 to 15.0.
<2> The ink jet recording medium according to <1>, wherein the unevenness index of the boundary line is 3.0 to 10.0.

<3> The second ink receiving layer uses a liquid in which diethylene glycol, triethylene glycol monobutyl ether and water are mixed so that the mass ratio is 15/15/70 (diethylene glycol / triethylene glycol monobutyl ether / water). J. et al. TAPPI paper pulp test method no. The ratio (A) of the penetration amount A (ml / m ² ) measured at a contact time of 0.05 seconds by the Bristow method according to 51-87 to the average film thickness B (μm) of the second ink receiving layer. The ink jet recording medium according to <1> or <2>, wherein / B) is 3.0 to 10.0.

<4> The second inorganic fine particles are amorphous silica having an average primary particle size of 5 nm to 30 nm and a secondary particle volume average particle size of 0.05 μm to 0.20 μm, <1> to <3>, wherein the first inorganic fine particles are at least one selected from amorphous silica having a volume average particle diameter of secondary particles of 0.30 μm to 8.0 μm and colloidal silica. The inkjet recording medium of any one of Claims.
<5> The inkjet recording medium according to any one of <1> to <4>, wherein each of the first ink receiving layer and the second ink receiving layer further contains a water-soluble resin.

<6> A first ink-receiving layer-forming coating liquid containing first inorganic fine particles and a second ink-receiving layer-forming coating liquid containing second inorganic fine particles are formed on the support. <1> to <5>, including the steps of forming a first ink receiving layer and a second ink receiving layer by simultaneously applying multiple layers so as to be laminated in this order from the side to form a coating layer The method for producing an inkjet recording medium according to any one of the above.
<7> A basic compound containing a basic compound in the coating layer (1) simultaneously with the simultaneous multilayer coating or (2) during the drying of the coating layer and before the coating layer exhibits reduced-rate drying. The method for producing an inkjet recording medium according to <7>, further comprising a step of applying a solution.

  According to the present invention, it is possible to provide an ink jet recording medium excellent in fine line drawing property and glossiness.

It is a schematic diagram which shows the measuring method of the length of the boundary line of the 1st ink receiving layer and the 2nd ink receiving layer in the inkjet recording medium concerning a present Example. It is a schematic diagram which shows the approximate straight line of the boundary line of the 1st ink receiving layer and the 2nd ink receiving layer in the inkjet recording medium concerning a present Example. It is a figure which shows typically an example of the boundary line of the 1st ink receiving layer and the 2nd ink receiving layer in the inkjet recording medium concerning a present Example.

  The ink jet recording medium of the present invention is provided on a support, a first ink receiving layer which is provided on the support and includes first inorganic fine particles, and is provided on and in contact with the first ink receiving layer. And a second ink receiving layer containing two inorganic fine particles, wherein the pore diameter of the second ink receiving layer is larger than the peak diameter in the pore size distribution of the first ink receiving layer. The first peak in the cross section of the inkjet recording medium having a smaller peak diameter in the distribution and perpendicular to the surface of the support on which the first ink receiving layer and the second ink receiving layer are provided. The unevenness index of the boundary line between the ink receiving layer and the second ink receiving layer is 1.5 to 15.0.

  The ink receiving layer includes two adjacent ink receiving layers, the peak diameter in the pore size distribution of the upper layer of the adjacent ink receiving layer is smaller than the peak diameter in the pore size distribution of the lower layer, and two adjacent two Since the interface structure of the ink receiving layer is uneven and complicated, it is excellent in fine line drawing properties and glossiness. This can be attributed to, for example, an improvement in ink absorption speed in the ink receiving layer having the above-described configuration.

In the present invention, the peak diameter in the pore diameter distribution of the first ink receiving layer and the second ink receiving layer constituting the ink receiving layer is smaller in the second ink receiving layer. Here, the “peak diameter in the pore diameter distribution” means the pore diameter corresponding to the peak of the pore diameter distribution curve obtained by measuring the pore diameter distribution of the ink receiving layer.
In the present invention, the pore size distribution is measured using a mercury intrusion method. Specifically, it is measured using an auto pore manufactured by Shimadzu Corporation.

In the present invention, the pore size distributions of the first ink receiving layer and the second ink receiving layer are measured as follows.
When the second ink receiving layer is the outermost layer, the ink jet recording medium is used as it is, and when another layer is formed on the second ink receiving layer, the other layer is used. The pore size distribution (A) is measured by mercury porosimetry using the material from which the second ink-receiving layer is exposed.

Next, the second ink-receiving layer (including other layers if there are other layers thereon) is scraped off to expose the first ink-receiving layer, and then the mercury intrusion method is used. The pore size distribution (B) is measured.
Further, the pore diameter distribution (C) is measured by mercury porosimetry using a material obtained by scraping from the outermost layer to the first ink receiving layer.
The pore size distribution obtained by subtracting the pore size distribution (B) from the pore size distribution (A) thus obtained is defined as the pore size distribution of the second ink receiving layer. The pore size distribution obtained by subtracting the pore size distribution (C) from the pore size distribution (B) is defined as the pore size distribution of the first ink receiving layer.
Incidentally, the layer constituting the ink receiving layer is scraped off from the ink jet recording medium using a razor or the like. Specifically, based on the thickness of the second ink receiving layer measured in advance, it was confirmed that the predetermined film thickness was removed while measuring the film thickness, and the first ink receiving layer was exposed. .

  In the present invention, in two adjacent ink receiving layers constituting the ink receiving layer, the peak diameter in the pore size distribution is a second value compared to the first ink receiving layer (hereinafter sometimes referred to as “lower layer”). The ink receiving layer (hereinafter sometimes referred to as the “upper layer”) is smaller.

  The difference in peak diameter in the pore size distribution between the upper layer and the lower layer is not particularly limited as long as the upper layer has a smaller peak diameter than the lower layer, but from the viewpoint of ink absorbability, the difference in peak diameter is 0.015 μm or more. Preferably, it is 0.015 μm or more and 4.5 μm or less, and more preferably 0.05 μm or more and 4.0 μm or less.

The peak diameter in the pore size distribution of the upper layer and the lower layer is preferably 0.010 to 5.0 [mu] m, more preferably 0.010 to 4.0 [mu] m. Moreover, it is preferable that an upper layer is 0.005-0.20 micrometer, and it is more preferable that it is 0.010-0.15 micrometer.
Furthermore, the peak diameter in the pore size distribution of the upper layer and the lower layer is that the lower layer is 0.010 to 5.0 μm, the upper layer is 0.005 to 0.20 μm, and the difference is 0.015 μm or more. The lower layer is preferably 0.010 to 4.0 μm, the upper layer is 0.010 to 0.15 μm, and the difference is more preferably 0.05 μm or more and 4.0 μm or less.

As for the pore size distribution in the ink receiving layer, the volume average particle diameter of the inorganic fine particles constituting the ink receiving layer, the content ratio of the inorganic fine particles relative to the water-soluble resin contained as necessary, and the ink receiving layer forming method are appropriately selected. Can be controlled.
For example, the peak diameter of the pore diameter distribution can be increased by increasing the volume average particle diameter of the inorganic fine particles and by increasing the content ratio of the inorganic fine particles to the water-soluble resin.

The ink receiving layer in the present invention includes a first ink receiving layer and a second ink receiving layer provided adjacently on the first ink receiving layer, and the first ink receiving layer of the support and The unevenness index of the boundary line between the first ink receiving layer and the second ink receiving layer in a cross section perpendicular to the surface on which the second ink receiving layer is provided is 1.5 to 15.0. .
That is, the interface structure between the first ink receiving layer and the second ink receiving layer that appears when the ink receiving layer of the ink jet recording medium is cleaved in the normal direction is not flat, but has complicated irregularities. It is in the shape. FIG. 3 shows an example of a boundary line extracted from the interface structure of the first ink receiving layer and the second ink receiving layer in the ink jet recording medium of the present invention.

  Specifically, the unevenness index in the present invention is calculated as follows. The inkjet recording medium is cut along a plane perpendicular to the surface on which the ink receiving layer is provided, and a cross-sectional sample in which the interface between the first ink receiving layer and the second ink receiving layer can be observed is produced. The obtained cross-sectional sample is observed using a scanning electron microscope (SEM) to obtain a cross-sectional image having a resolution of 0.01 μm / pixel. A boundary line between the first ink receiving layer and the second ink receiving layer is extracted from the obtained cross-sectional image using image analysis software. The unevenness index is calculated as the ratio of G to F (G / F) from the length G of the boundary line and the length F of the straight line when the boundary line is linearly approximated. The unevenness index is calculated in a section where the length of the straight line when the boundary line is approximated by a straight line is 13.0 μm.

The length of the boundary line is calculated as follows. As schematically shown in FIG. 1, the boundary line is displayed as a bitmap, and the center 2 of the pixel of the boundary line and the center 2 of the pixel of the adjacent boundary line are connected by a line segment 3, Let this be the length of the boundary between them. The same operation is performed on all pixels adjacent to the boundary line, and the total length of the obtained line segments is defined as the boundary line length G.
The length of the straight line 4 when the boundary line is approximated by a straight line is calculated as follows. As shown in the schematic diagram of FIG. 2, the centers of the pixels of the boundary line are all applied to the XY coordinates, and the length of the approximate straight line obtained by the least square method is used.

As a method of forming the interface structure between the first ink receiving layer and the second ink receiving layer so that the unevenness index is 1.5 to 15.0, for example, the first ink receiving layer is formed on a support. The coating solution for forming and the coating solution for forming the second ink-receiving layer are simultaneously applied in layers so as to be laminated in this order from the support side to form a coating layer, which is then dried to obtain the first A method for forming the ink receiving layer and the second ink receiving layer may be mentioned.
This can be considered, for example, because fine irregularities on the surface of the support are reflected in the interface structure of the first ink receiving layer and the second ink receiving layer before drying.

In the second ink receiving layer in the ink jet recording medium of the present invention, diethylene glycol, triethylene glycol monobutyl ether and water were mixed so that the mass ratio was 15/15/70 (diethylene glycol / triethylene glycol monobutyl ether / water). Using the liquid, the JAPAN TAPPI paper pulp test method no. The ratio (A) of the penetration amount A (ml / m ² ) measured at a contact time of 0.05 seconds by the Bristow method according to 51-87 to the average film thickness B (μm) of the second ink receiving layer. / B) is preferably 3.0 to 10.0, and more preferably 3.0 to 8.0.
When the permeation amount with respect to the specific solvent per average film thickness in the second ink receiving layer is within the above range, the fine line drawing property and the glossiness are more effectively improved.

In the present invention, the penetration amount A in the second ink receiving layer is measured in a state where the second ink receiving layer is on the outermost surface. That is, when the second ink receiving layer is the outermost surface layer, measurement is performed as it is, and when another layer is formed on the second ink receiving layer, the second ink receiving layer is removed and the second ink receiving layer is removed. It is measured in a state where the two ink-receiving layers are exposed or in a state before the layers are formed.
The method for removing the other layers is as described above.

  The average film thickness of the second ink receiving layer is measured by observing a cross section perpendicular to the surface of the support on which the ink receiving layer is provided with an electron microscope (SEM). Specifically, using the electron microscope image of the cross section, the thickness of the second ink receiving layer is measured at 10 points and calculated as the arithmetic average thereof.

(Inorganic fine particles)
Each of the first ink receiving layer and the second ink receiving layer contains at least one kind of inorganic fine particles. The inorganic fine particles form a porous structure when the ink receiving layer is formed, and have a role of improving the ink absorption performance.

  Examples of the inorganic fine particles include amorphous silica (also referred to as amorphous silica), colloidal silica, titanium dioxide, barium sulfate, calcium silicate, zeolite, kaolinite, halloysite, mica, talc, calcium carbonate, magnesium carbonate, calcium sulfate. Boehmite, pseudo boehmite and the like. These may be used alone or in combination of two or more.

  Amorphous silica is generally roughly classified into wet method particles and dry method (gas phase method) particles according to the production method. In the wet method, active silica is produced by acid decomposition of silicate, and the method is mainly polymerized and agglomerated and precipitated to obtain hydrous silica. On the other hand, in the vapor phase method, the high temperature of silicon halide is obtained. The mainstream method is to obtain anhydrous silica by a method using gas phase hydrolysis (flame hydrolysis method) and a method in which silica sand and coke are heated and reduced and vaporized by arc in an electric furnace and oxidized with air (arc method). It is. The vapor phase silica preferably used in the present invention is anhydrous silica fine particles obtained by the vapor phase method.

Vapor phase method silica is different from hydrous silica in terms of the density of silanol groups on the surface, presence or absence of vacancies, and the like, and is suitable for forming a three-dimensional structure having a high porosity. The reason for this is not clear, but in the case of hydrous silica, the density of silanol groups on the fine particle surface is large at 5 to 8 / nm ² and the silica fine particles tend to aggregate (aggregate) easily. Has a low density of 2 to 3 silanol groups / nm ² on the surface of the fine particles, so that it is presumed that the structure becomes sparsely soft agglomerated (flocculate), resulting in a structure with a high porosity.

  Vapor phase silica has a particularly large specific surface area, so it has high ink absorption and retention efficiency, and low refractive index. Therefore, if it is dispersed to an appropriate particle size, it will provide transparency to the ink receiving layer. And high color density and good color developability can be obtained. The fact that the ink receiving layer is transparent can provide high color density, good color developability, and gloss even when applied to photo glossy paper as well as applications that require transparency such as OHP.

In the present invention, the first inorganic fine particles contained in the first ink receiving layer are preferably amorphous silica or colloidal silica from the viewpoint of ink absorbability, and the volume average particle diameter of the secondary particles is preferably 0.00. More preferably, it is amorphous silica or colloidal silica that is 30 μm to 8.0 μm, and it is further amorphous silica or colloidal silica that has a volume average particle diameter of secondary particles of 0.50 μm to 8.0 μm. preferable.
The second inorganic fine particles contained in the second ink receiving layer are preferably amorphous silica from the viewpoint of ink absorbability, and the primary particles have an average particle diameter of 5 nm to 30 nm, and secondary particles. Amorphous silica having a volume average particle diameter of 0.05 μm to 0.20 μm is more preferable, and the average particle diameter of primary particles is 5 nm to 20 nm, and the volume average particle diameter of secondary particles is 0.00. Amorphous silica having a thickness of 07 μm to 0.18 μm is more preferable.

Further, the second inorganic fine particles are amorphous silica having an average primary particle size of 5 nm to 30 nm and a secondary particle volume average particle size of 0.05 μm to 0.20 μm, and the first inorganic fine particles are The secondary particles are preferably amorphous silica or colloidal silica having a volume average particle size of 0.30 μm to 8.0 μm, and the second inorganic fine particles have an average primary particle size of 5 nm to 20 nm and 2 Amorphous silica having a volume average particle diameter of secondary particles of 0.07 μm to 0.18 μm, wherein the first inorganic fine particles have a volume average particle diameter of secondary particles of 0.50 μm to 8.0 μm. More preferably, it is regular silica or colloidal silica.
By being this mode, fine line drawing property and glossiness are more effectively improved.

  Further, for example, a first ink-receiving layer-forming coating solution containing amorphous silica or colloidal silica having a volume average particle diameter of secondary particles of 0.30 μm to 8.0 μm and an average particle diameter of primary particles of 5 nm. A second ink-receiving layer-forming coating solution containing amorphous silica having a volume average particle diameter of secondary particles of 0.05 μm to 0.20 μm, and By forming the second ink receiving layer, an ink receiving layer is formed in which the peak diameter in the pore diameter distribution of the second ink receiving layer is smaller than the peak diameter in the pore diameter distribution of the first ink receiving layer. be able to.

The content of the inorganic fine particles in the first and second ink receiving layers is preferably 50% by mass or more, and more preferably exceeds 60% by mass. When the amount of the inorganic fine particles is in the range of 50% by mass or more, and more than 60% by mass, it is possible to form a more favorable porous structure and to produce an ink jet recording medium excellent in ink absorbability. be able to.
The content of the inorganic fine particles in the ink receiving layer is an amount calculated based on solid components other than water in the composition forming the ink receiving layer. The content of the inorganic fine particles may be the same or different between the first ink receiving layer and the second ink receiving layer.

  In addition, the average particle diameter of the primary particles of amorphous silica is calculated as an arithmetic average of 100 primary particles measured using a transmission electron microscope. The volume average particle diameter of secondary particles of amorphous silica and the volume average particle diameter of colloidal silica are measured using a light scattering method.

(Water-soluble resin)
In the present invention, the first ink receiving layer and the second ink receiving layer each preferably contain at least one water-soluble resin.
Examples of water-soluble resins include polyvinyl alcohol (PVA), polyvinyl acetal, cellulose resins [methyl cellulose (MC), ethyl cellulose (EC), hydroxyethyl cellulose (HEC), carboxymethyl cellulose (CMC), etc.], chitins, and chitosans. , Starch; resins having ether bond, polypropylene oxide (PPO), polyethylene glycol (PEG), polyvinyl ether (PVE); polyacrylamide (PAAM), resin having amide group or amide bond, polyvinyl pyrrolidone (PVP) And polyacrylates, maleic resins, alginates, gelatins and the like having a carboxyl group as a dissociable group. These water-soluble resins may be used alone or in combination of two or more.

  Among these, polyvinyl alcohol is preferable. When polyvinyl alcohol and other water-soluble resin are used in combination, the content of polyvinyl alcohol in the total water-soluble resin is preferably 90% by mass or more, and more preferably 95% by mass or more.

  Examples of the polyvinyl alcohol include cation-modified polyvinyl alcohol, anion-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, and other polyvinyl alcohol derivatives in addition to polyvinyl alcohol (PVA).

  PVA has a hydroxyl group in its structural unit, and this hydroxyl group and a silanol group on the surface of the silica fine particle form a hydrogen bond, thereby making it easy to form a three-dimensional network structure in which the secondary particle of the silica fine particle is a chain unit. . By forming a three-dimensional network structure in this way, it is considered that an ink receiving layer having a porous structure with a high porosity is formed. The porous ink receiving layer formed in this manner can absorb ink rapidly by capillary action, and can suppress the occurrence of ink bleeding and form dots with good roundness.

  The content of the water-soluble resin in the ink receiving layer is to prevent the film strength from being reduced and cracking during drying due to the excessive content, and the excessive content causes the voids to be blocked by the resin. From the viewpoint of preventing the ink absorbency from being lowered by decreasing the porosity, the amount is preferably 9 to 40% by mass, more preferably 12 to 33% by mass with respect to the total solid content of the ink receiving layer. .

  The water-soluble resin preferably has a number average polymerization degree of 1800 or more, more preferably 2000 or more, from the viewpoint of preventing cracking of the ink receiving layer. Among them, from the viewpoint of glossiness and image density, PVA having a saponification degree of 88% or more is preferable, PVA having a saponification degree of 89 to 97.5% is more preferable, and PVA having a saponification degree of 91 to 96% is particularly preferable.

-Content ratio of inorganic fine particles and water-soluble resin-
The content ratio of inorganic fine particles (for example, amorphous silica; p) and water-soluble resin (for example, PVA; b) [PB ratio (p: b), the mass of inorganic fine particles relative to 1 part by mass of the water-soluble resin] The film structure of the receiving layer is also greatly affected. That is, as the PB ratio increases, the porosity, pore volume, and surface area (per unit mass) increase. Specifically, as the PB ratio (p: b), the film strength is reduced due to the PB ratio being too large, and cracking during drying is prevented. Further, the PB ratio is too small. The ratio of 1.5: 1 to 10: 1 is preferable from the viewpoint of preventing the void from being easily blocked by the water-soluble resin and preventing the ink absorbency from being lowered due to the decrease in the void ratio.

(mordant)
The first ink receiving layer and the second ink receiving layer in the present invention can each contain at least one mordant.
As the mordant, either an organic mordant or an inorganic mordant can be used. As the organic mordant, a polymer mordant containing a primary to tertiary amino group or a quaternary ammonium base as a cationic group is preferable. Cationic non-polymer mordants may also be used. Further, as the inorganic mordant, a water-soluble metal compound or the like is preferable.

  Examples of the polymer mordant include a homopolymer of a monomer having a primary to tertiary amino group and a salt thereof, or a quaternary ammonium base (mordant monomer), the mordant monomer and another monomer (non-mordant). Those obtained as copolymers or condensation polymers with monomers) are preferred. These polymer mordants can be used in any form such as a water-soluble polymer or water-dispersible latex particles.

  Specific examples of the mordant monomer include compounds described in paragraph numbers [0069] to [0075] of JP-A No. 2002-274024.

  Further, as a polymer mordant, polydiallyldimethylammonium chloride, polymethacryloyloxyethyl-β-hydroxyethyldimethylammonium chloride, polyallylamine hydrochloride, polyamide-polyamine resin, cationized starch, dicyandiamide formalin condensate, dimethyl-2-hydroxypropyl Ammonium salt polymers are also preferred.

  Among these, from the viewpoint of suppressing bleeding, cationic polyurethanes and cationic polyacrylates described in JP-A No. 2004-167784 are preferable, and cationic polyurethanes are more preferable. As the cationic polyurethane, for example, “Superflex 650”, “F-8564D”, “F-8570D” manufactured by Daiichi Kogyo Seiyaku Co., Ltd., “Neofix IJ” manufactured by Nikka Chemical Co., Ltd. are commercially available. -150 "and the like.

  The molecular weight of the polymer mordant is preferably 2000 to 300,000 in terms of weight average molecular weight. When the molecular weight is within the above range, water resistance and aging resistance are improved.

As the inorganic mordant, a water-soluble polyvalent metal compound is suitable.
Examples of the water-soluble polyvalent metal compound include water-soluble salts of metals selected from calcium, barium, manganese, copper, cobalt, nickel, aluminum, iron, zinc, zirconium, chromium, tungsten, and molybdenum. The “water-soluble” of the water-soluble metal compound means that 1% by mass or more dissolves in water at 20 ° C.

  Among the water-soluble metal compounds, trivalent or higher polyvalent metal compounds are preferable, aluminum compounds or compounds containing Group 4A metals of the periodic table (for example, zirconium, titanium) are preferable, aluminum compounds are more preferable, and water-soluble is particularly preferable. It is an aluminum compound.

Examples of the water-soluble aluminum compound include aluminum chloride or a hydrate thereof (eg, aluminum chloride hexahydrate), aluminum sulfate or a hydrate thereof, ammonium alum, aluminum sulfite, aluminum thiosulfate, aluminum nitrate nine water Japanese hydrates, aluminum acetate, aluminum lactate, basic aluminum thioglycolate and the like are known. Furthermore, basic polyaluminum hydroxide compounds (hereinafter also referred to as “basic polyaluminum chloride” and “polyaluminum chloride”), which are inorganic aluminum-containing cationic polymers, are known and preferably used. The basic polyaluminum hydroxide compound is represented by the following formula 1, formula 2 or formula 3, and for example, [Al ₆ (OH) ₁₅ ] ³⁺ , [Al ₈ (OH) ₂₀ ] ⁴⁺ , [Al ₁₃ (OH) ₃₄ ] ⁵⁺ , [Al ₂₁ (OH) ₆₀ ] ³⁺ , and the like, which are water-soluble polyaluminum hydroxides that stably contain basic and high-molecular polynuclear condensed ions.
[Al ₂ (OH) _n Cl _6-n ] _m Formula 1
[Al (OH) ₃ ] _n AlCl ₃ Formula 2
Al _n (OH) _m Cl _{(3 nm)} [0 <m <3n] Formula 3
These are water treatment agents under the name of polyaluminum chloride (PAC) from Taki Chemical Co., Ltd., polyaluminum hydroxide (Paho) from Asada Chemical Co., Ltd., and HAP from Riken Green Co., Ltd. The name is -25, from Daimei Chemical Co., Ltd., the name of Alpha-In 83, and also from other manufacturers for the same purpose, various grades can be easily obtained.

  The content of the mordant in the ink receiving layer is preferably 1 to 20% by mass and more preferably 3 to 15% by mass with respect to the total mass of the ink receiving layer. When the content of the mordant is within the above range, it is possible to effectively prevent the ink from being absorbed and transmitted. The ink image-receiving layer is either (1) simultaneously with the application of the coating liquid for forming the ink-receiving layer, or (2) during the drying of the coating layer formed by the coating, and before the coating layer exhibits reduced-rate drying, In any of the cases, when forming by a method (wet-on-wet method) of applying a basic solution containing a basic compound to the coating layer, it is contained in the coating solution for forming the ink receiving layer. The amount of the mordant preferably occupies 95% by mass or more of the total amount of the mordant contained in the finally obtained ink receiving layer. When the amount of the mordant contained in the coating liquid is within the above range, bronzing can be effectively prevented.

(Other ingredients)
In addition to the above components, the ink receiving layer in the invention may contain other components such as a crosslinking agent such as a boron compound, a surfactant, and an organic solvent.

  Examples of the crosslinking agent include those described in paragraph numbers [0125] to [0129] of JP-A-2006-321176, and preferred embodiments are also the same.

  Examples of the surfactant include those described in paragraph numbers [0149] to [0154] of JP-A-2006-321176, and preferred embodiments are also the same.

  Examples of the organic solvent include those described in paragraph No. [0155] of JP-A-2006-321176, and preferred embodiments are also the same.

  Furthermore, the ink receiving layer in the present invention may contain other additives such as various ultraviolet absorbers, antioxidants, and antifading agents such as singlet oxygen quenchers, if necessary. The details of these additives can be referred to the descriptions in paragraphs [0081] to [0090] of JP-A-2007-98657.

(Support)
The support in the ink jet recording medium of the present invention is not limited, but a water-permeable support is preferable in that a higher penetration amount can be obtained.

  Examples of the support that can be used in the present invention include the supports described in paragraphs [017] to [026] of JP-A-2009-73158.

-Inkjet recording medium manufacturing method-
The ink jet recording medium of the present invention may be produced by any method without particular limitation as long as it can form the above-described ink receiving layer on a support.

  In addition to the following wet-on-wet method, the receiving layer forming step for forming the ink receiving layer applies the first ink receiving layer forming coating liquid and the second ink receiving layer forming coating liquid on the support. Forming a coating layer, cooling the formed coating layer so as to decrease by 5 ° C. or more with respect to the temperature of the coating solution at the time of coating, and drying the cooled coating layer to form an ink The ink receiving layer can be formed by a form having a step of forming a receiving layer (set drying method).

  As a method of cooling the coating layer, a method of cooling the support on which the coating layer is formed in a cooling zone maintained at 0 to 10 ° C. for 5 to 30 seconds is preferable. In the process of cooling, it is preferable to cool so that it may fall 0-10 degreeC, and it is more preferable to cool so that it may fall 0-5 degreeC or more. The temperature of the coating layer is measured by measuring the temperature of the film surface.

  The ink jet recording medium of the present invention comprises a first ink receiving layer forming coating solution containing first inorganic fine particles and a second ink receiving layer forming coating solution containing second inorganic fine particles on the support side. In this order, simultaneous multi-layer coating on the support, (1) simultaneously with the coating, or (2) in the middle of drying of the coating layer formed by the coating, before the coating layer exhibits reduced rate drying, In any of the above, a basic solution containing a basic compound is applied to the coating layer (wet-on-wet method, hereinafter referred to as “WOW method”), It is preferably produced by a method in which at least one of the coating solution and the basic solution contains a crosslinking agent, and a receiving layer forming step for forming a crosslinked and cured ink receiving layer is provided.

Details of the components contained in the ink-receiving layer-forming coating solution, specifically, the inorganic fine particles, the water-soluble resin, the mordant, and, if necessary, other components such as a crosslinking agent are as described above.
The ink-receiving layer-forming coating liquid contains, for example, gas phase method silica (inorganic fine particles), PVA (water-soluble resin), mordant, boric acid (crosslinking agent), nonionic or amphoteric surfactant, and high-boiling organic solvent. In this case, the preparation method is shown as an example. That is,
First, vapor phase silica is added to water, and a mordant is further added, followed by dispersion with a high-pressure homogenizer, a sand mill, or the like. Thereafter, boric acid is added to this, an aqueous PVA solution (for example, PVA having a mass of about 1/3 of that of vapor phase method silica) is added, and a nonionic or amphoteric surfactant and a high boiling point organic solvent are further added. And can be prepared by stirring. The obtained coating solution is a uniform sol, and a porous layer having a three-dimensional network structure can be formed by coating this on a support by the following coating method.

  Moreover, partial gelatinization of PVA can be prevented by adding PVA after thinning boric acid as described above. A crosslinking agent such as boric acid may be added in addition to or added to the basic solution described later, in addition to or in addition to the ink receiving layer forming coating solution.

In dispersing the inorganic fine particles, a form in which a cationic resin is added together with the inorganic fine particles and the inorganic fine particles are dispersed in the cationic resin is preferable.
Although there is no restriction | limiting in particular in cationic resin, A water-soluble or aqueous emulsion type etc. can be used conveniently. Examples of the cationic resin include a dicyan cationic resin represented by a dicyandiamide-formalin polycondensate, a polyamine cationic resin represented by a dicyanamide-diethylenetriamine polycondensate, an epichlorohydrin-dimethylamine addition polymer, and dimethyldiallylammonium chloride. -SO ₂ copolymer, diallylamine salt -SO ₂ copolymer, dimethyl diallyl ammonium chloride polymer, polymer of allylamine salt, dialkylaminoethyl (meth) acrylate quaternary salt polymer, acrylamide - diallylamine salt copolymer Polycationic cationic resins such as dimethyldiallylammonium chloride, monomethyldiallylammonium chloride and polyamidine are preferred. Ammonium chloride, and monomethyl diallyl ammonium chloride are particularly preferred. A cationic resin may be used individually by 1 type, and may use 2 or more types together.

  The content of the cationic resin in the ink receiving layer is preferably 1 to 30 parts by mass, more preferably 3 to 20 parts by mass with respect to 100 parts by mass of the inorganic fine particles. As a mode of addition of the cationic resin, a small amount may be added before pulverization and dispersion, and after pulverization and dispersion until a desired particle size is obtained, it may be further added.

  The coating solution for forming the ink receiving layer is preferably an acidic solution, and its pH is preferably 5.0 or less, more preferably 4.5 or less, and even more preferably 4.0 or less. The pH can be adjusted by selecting the type and amount of mordant. Moreover, you may adjust by adding an organic or inorganic acid. When the pH is 5.0 or less, the crosslinking reaction of the water-soluble resin by a crosslinking agent such as a boron compound can be suppressed.

In the present invention, it is preferable that the first ink-receiving layer-forming coating solution and the second ink-receiving layer-forming coating solution are simultaneously applied in multiple layers.
The simultaneous multilayer coating can be performed, for example, by a coating method using an extrusion die coater or a curtain flow coater. After the simultaneous multilayer coating, the formed coating layer is dried. In this case, drying is generally performed by heating the coating layer at 40 ° C. to 150 ° C. for 0.5 minutes to 10 minutes, preferably 40 ° C. It is carried out by heating at -100 ° C for 0.5-5 minutes. When using a boron compound, it is preferable to heat at 60 to 100 ° C. for 5 to 20 minutes.

The coating amount of the first ink receiving layer coating solution and the second ink receiving layer coating solution is preferably from 10 to 200 g / ^{m 2,} respectively, and more preferably 15 to 180 g / ^{m 2.} The total coating weight of the first ink receiving layer coating solution and the second ink receiving layer coating solution is preferably from 10 to 200 g / ^{m 2,} and more preferably 15 to 180 g / ^{m 2.}

  The basic solution is preferably a solution having a pH of 7.1 or more, and more preferably a solution having a pH of 7.5 or more. When the pH is 7.1 or more, the dura mating reaction of the ink receiving layer becomes good and scratches are less likely to occur. The pH of the basic solution can be adjusted by adding a basic substance. Examples of the basic substance include amine compounds having a molecular weight of 700 or less. For example, ammonia, primary amine (ethylamine etc.), secondary amine (dimethylamine etc.), tertiary amine (N-ethyl- N-methylbutylamine, triethylamine, etc.), hydroxides of alkali metals and alkaline earth metals and / or salts thereof (preferably ammonium salts). In addition, other polyvalent amines such as ethylenediamine may be added.

  Among basic substances, at least one selected from ammonia and primary to tertiary amines having a molecular weight of 700 or less is preferable from the viewpoint of improving the performance of the ink receiving layer such as scratch resistance, wet heat bleeding, and storage stability. Furthermore, ammonia and an ammonium salt having a molecular weight of 700 or less are preferable.

  The basic solution may contain a crosslinking agent such as a boron compound with or without being contained in the ink receiving layer forming coating solution. In addition, the basic solution may contain a mordant component such as a cationic mordant in order to further improve the water resistance and aging resistance of the image. Details of the crosslinking agent and mordant component are as described above.

  “Before the coating layer shows reduced-rate drying” usually refers to several minutes immediately after coating of the coating solution, and during this time, the content of the solvent in the coated layer decreases in proportion to the time. The phenomenon is constant rate drying. About the time which shows this constant rate drying, it describes in chemical engineering handbook (pp.707-712, Maruzen Co., Ltd. issue, October 25, 1980).

  The coating layer formed by coating the coating liquid for forming the ink receiving layer is dried until it shows reduced rate drying. In this case, the drying is generally performed at 40 ° C. to 180 ° C. for 0.5 minutes to 10 minutes. (Preferably, 0.5 to 5 minutes). The drying time naturally varies depending on the coating amount, but the above range is appropriate.

  As a method for applying a basic solution before the coating layer formed by applying the first and second ink-receiving layer-forming coating solutions exhibits reduced drying, (i) a basic solution is used. A method of further coating on a coating layer formed with a coating solution for forming an ink receiving layer, (ii) a method of spraying a basic solution by a method such as spraying, (iii) for forming an ink receiving layer in a basic solution Examples include a method of immersing a support on which a coating solution is applied and a coating layer is formed. In addition, as a method to apply in the method (i), for example, known methods such as curtain flow coater, extrusion die coater, air doctor coater, blade coater, rod coater, knife coater, squeeze coater, reverse roll coater, bar coater, etc. Application methods may be mentioned. Among them, a method in which the coater does not contact an existing coating layer such as an extrusion die coater or a curtain flow coater is preferable.

As a provision amount of a basic solution, 0.1-40 g / m < ² > is preferable and 0.5-30 g / m < ² > is more preferable.

  In addition, when the application of the basic solution is performed simultaneously with the application of the ink-receiving layer-forming coating solution, the ink-receiving layer-forming coating solution and the basic solution are stacked in the order in which the ink-receiving layer-forming coating solution contacts the support. Thus, simultaneous multilayer coating can be performed on the support and dried and cured.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “part” and “%” are based on mass.

<Example 1>
-Production of support-
Wood pulp composed of 100 parts of LBKP is beaten to 300 ml Canadian freeness with a double disc refiner, 0.5 parts of epoxidized behenamide, 1.0 part of anionic polyacrylamide, 0.1 part of polyamide polyamine epichlorohydrin, 0.5 part of cationic polyacrylamide All the parts were added at an absolutely dry mass ratio to the pulp, and weighed with a long net paper machine to make a base paper of 170 g / m ² .

In order to adjust the surface size of the base paper, 0.04% of a fluorescent whitening agent (“Whiteex BB” manufactured by Sumitomo Chemical Co., Ltd.) was added to a 4% aqueous solution of polyvinyl alcohol, and this was converted to 0 in terms of absolute dry weight. After impregnating the base paper so as to have a density of 0.5 g / m ² and drying, a base paper adjusted to a density of 1.05 g / cm ³ by further calendering was obtained. did.

-Formation of ink receiving layer-
(Preparation of coating liquid A-1 for forming an ink receiving layer)
358.3 kg of colloidal silica (secondary particle size 0.4 μm, SiO ₂ concentration 24%) is mixed with 127.7 kg of ion-exchanged water having the following composition, and 7.0 kg of Charol DC-902P is mixed with this, and ultrasonic waves are mixed. It was dispersed using a disperser (manufactured by SMT Co., Ltd.). The resulting silica dispersion had a volume average particle size of 0.4 μm.
Thereafter, stirring was performed for 60 minutes, and an aqueous boric acid solution (5%) was added with stirring. In addition, a 5% aqueous solution of polyvinyl alcohol having the following composition was added with stirring, an aqueous polyoxyethylene lauryl ether solution (2%) and diethylene glycol monobutyl ether were added, and ion-exchanged water was further added to make a total amount of 1000.0 kg. In this way, a coating liquid A-1 for forming an ink receiving layer was prepared. The mass ratio of the inorganic fine particles to the water-soluble resin (inorganic fine particles: water-soluble resin) was 4.9: 1.

<Composition of coating liquid A-1 for forming ink receiving layer>
・ Ion-exchanged water ... 127.7kg
・ Colloidal silica ・ ・ ・ 358.3kg
(Inorganic fine particles, SiO ₂ concentration 24%)
(PL-20, manufactured by Fuso Chemical Industry Co., Ltd.)
・ Charol DC-902P (51.5% aqueous solution) 7.0 kg
(Cationic resin, mordant, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
・ ZA-30 ... 5.0kg
(Mordant, zirconyl acetate, manufactured by Daiichi Rare Element Chemical Co., Ltd.)
・ Boric acid aqueous solution (5% aqueous solution) ... 63.0 kg
・ Polyvinyl alcohol 5% aqueous solution ・ ・ ・ 353.0kg
(JM-33, degree of saponification 94.3 mol%, degree of polymerization 3300, manufactured by Nihon Azuma Bi-Poval)
・ Polyoxyethylene lauryl ether ... 52.0kg
(Emulgen 109P 2% aqueous solution, manufactured by Kao Corporation; nonionic surfactant)
・ Diethylene glycol monobutyl ether ... 3.0kg
(DEGmBE; high boiling point organic solvent)
・ Ion-exchanged water: Remaining amount of 1000.0 kg

(Preparation of coating liquid B-1 for forming an ink receiving layer)
86.0 kg of gas phase method silica fine particles (average particle diameter of primary particles 7 nm) are mixed with 400 kg of ion-exchanged water having the following composition, and 7.0 kg of Charol DC-902P is mixed with this, and Nanomizer LA31 (Nanomizer Co., Ltd.) is mixed. ), And the treatment was performed twice at a pressure of 500 kg / m ² . The volume average particle diameter of secondary particles of the obtained silica dispersion was 0.12 μm.

  Thereafter, stirring was performed for 60 minutes, and an aqueous boric acid solution (5%) was added with stirring. In addition, a 5% aqueous solution of polyvinyl alcohol having the following composition was added with stirring, an aqueous polyoxyethylene lauryl ether solution (2%) and diethylene glycol monobutyl ether were added, and ion-exchanged water was further added to make a total amount of 1000.0 kg. In this way, a coating liquid B-1 for forming an ink receiving layer was prepared. The mass ratio of the inorganic fine particles to the water-soluble resin (inorganic fine particles: water-soluble resin) was 4.9: 1.

<Composition of coating liquid B-1 for forming ink receiving layer>
・ Ion-exchanged water ... 400.0kg
・ Vapor phase silica fine particles (inorganic fine particles) 86.0 kg
(AEROSIL300SF75, manufactured by Nippon Aerosil Co., Ltd.)
・ Charol DC-902P (51.5% aqueous solution) 7.0 kg
(Cationic resin, mordant, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
・ ZA-30 ... 5.0kg
(Mordant, zirconyl acetate, manufactured by Daiichi Rare Element Chemical Co., Ltd.)
・ Boric acid aqueous solution (5% aqueous solution) ... 63.0 kg
・ Polyvinyl alcohol 5% aqueous solution ・ ・ ・ 353.0kg
(JM-33, degree of saponification 94.3 mol%, degree of polymerization 3300, manufactured by Nihon Azuma Bi-Poval)
・ Polyoxyethylene lauryl ether ... 52.0kg
(Emulgen 109P 2% aqueous solution, manufactured by Kao Corporation; nonionic surfactant)
・ Diethylene glycol monobutyl ether ... 3.0kg
(DEGmBE; high boiling point organic solvent)
・ Ion-exchanged water: Remaining amount of 1000.0 kg

(Formation of ink receiving layer)
The front surface of the support obtained above is subjected to corona discharge treatment, and the ink receiving layer forming coating liquid A-1 (lower layer coating liquid) 120 g / m ² and the ink receiving surface are applied to the corona discharge treated surface. The layer forming coating solution B-1 (upper layer coating solution) 40 g / m ² was applied simultaneously by an extrusion die coater so that the upper layer coating solution was laminated on the lower layer coating solution, and the coating was formed. The applied layer was dried with a hot air dryer at 80 ° C. (wind speed 3 to 8 m / sec) until the solid content concentration of the layer became 20% by mass. During this time, the coating layer formed with the coating liquid A-1 for forming the ink receiving layer and the coating liquid B-1 for forming the ink receiving layer showed constant rate drying. Immediately thereafter, this coating layer was immersed in a basic solution having the following composition for 30 seconds, and the basic solution was deposited on the coating layer at a wet coating amount of 15 g / m ² (application of basic solution before rate-decreasing drying, WOW method). Then, it was further dried at 80 ° C. for 10 minutes to form an ink receiving layer, whereby an inkjet recording medium 1 was produced.

<Composition of basic solution>
・ Ion exchange water: 70.0 kg
・ Boric acid: 0.65 kg
・ Polyoxyethylene lauryl ether ・ ・ ・ 5.0kg
(Nonionic surfactant: 10% aqueous solution of Emulgen 109P, manufactured by Kao Corporation)
-Ammonium carbonate ... Amount added to pH 7.3-Ion-exchanged water ... Remaining amount of 100.0 kg in total

<Example 2>
In the production of the inkjet recording medium 1 of Example 1, the ion-exchanged water 127.7 kg used in the ink-receiving layer-forming coating liquid A-1 was changed to 400.0 kg, and colloidal silica (inorganic fine particles, SiO ₂ concentration 24%). , PL-20, manufactured by Fuso Chemical Industry Co., Ltd.) In place of 358.3 kg, the ink receiving layer was changed to 86.0 kg of amorphous silica (inorganic fine particles, manufactured by Mizusawa Chemical Co., Ltd.) having a secondary particle size of 4 μm. An inkjet recording medium 2 was produced in the same manner as in Example 1 except that the forming coating liquid A-2 was used.

<Example 3>
~ Formation of ink receiving layer ~
The front surface of the support obtained above is subjected to corona discharge treatment, and on this corona discharge treatment surface, an ink-receiving layer-forming coating solution A-3 (underlayer coating solution) 100 g / m ² having the following composition: The ink receiving layer forming coating solution B-3 (upper layer coating solution) 34 g / m ² was applied simultaneously with an extrusion die coater so that the upper layer coating solution was laminated on the lower layer coating solution. After cooling at 5 ° C. for 20 seconds, it was dried under conditions of 40 ° C. and 10% RH. By such a set drying method, an inkjet recording medium 3 having an ink receiving layer formed on a support was produced.

<Composition of coating liquid A-3 for forming ink receiving layer>
・ Ion-exchanged water ... 127.7kg
・ Colloidal silica ・ ・ ・ 358.3kg
(Inorganic fine particles, SiO ₂ concentration 24%, PL-20, manufactured by Fuso Chemical Industry Co., Ltd.)
・ Charol DC-902P (51.5% aqueous solution) 7.0 kg
(Cationic resin, mordant, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
・ Aqueous borax solution (6% solution) 80.0 kg
・ 7% aqueous solution of polyvinyl alcohol ・ ・ ・ 252.0kg
(JM-33, degree of saponification 94.3 mol%, degree of polymerization 3300, manufactured by Nihon Azuma Bi-Poval)
・ Polyoxyethylene lauryl ether ・ ・ ・ 5.0kg
(10% aqueous solution of Emulgen 109P, manufactured by Kao Corporation; nonionic surfactant)
・ Diethylene glycol monobutyl ether ... 3.0kg
(DEGmBE; high boiling point organic solvent)
・ Ion-exchanged water: Amount that makes the total amount 852.0 kg

<Composition of coating liquid B-3 for forming ink receiving layer>
・ Ion exchange water: 400.0kg
-Vapor phase silica fine particles (inorganic fine particles) 86.0 kg
(AEROSIL300SF75, manufactured by Nippon Aerosil Co., Ltd.)
・ Charol DC-902P (51.5% aqueous solution) 7.0 kg
(Cationic resin, mordant, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
・ Aqueous borax solution (6% solution) 80.0 kg
・ 7% aqueous solution of polyvinyl alcohol ・ ・ ・ 252.0kg
(JM-33, degree of saponification 94.3 mol%, degree of polymerization 3300, manufactured by Nihon Azuma Bi-Poval)
・ Polyoxyethylene lauryl ether ・ ・ ・ 5.0kg
(10% aqueous solution of Emulgen 109P, manufactured by Kao Corporation; nonionic surfactant)
・ Diethylene glycol monobutyl ether ... 3.0kg
(DEGmBE; high boiling point organic solvent)
・ Ion-exchanged water: Amount that makes the total amount 852.0 kg

<Example 4>
In the production of the inkjet recording medium 1 of Example 1, the ion-exchanged water 127.7 kg used in the ink-receiving layer-forming coating liquid A-1 was changed to 400.0 kg, and colloidal silica (inorganic fine particles, SiO ₂ concentration 24%). ) Instead of 358.3 kg (PL-20, manufactured by Fuso Chemical Industry Co., Ltd.), the ink was changed to amorphous silica (inorganic fine particles) 86.0 kg (manufactured by Mizusawa Chemical Industry Co., Ltd.) having a secondary particle size of 8 μm. An inkjet recording medium 4 was produced in the same manner as in Example 1 except that the receiving layer forming coating solution A-4 was used.

<Example 5>
In the production of the inkjet recording medium 1 of Example 1, 180 g / m ² instead of 120 g / m ² of the ink receiving layer forming coating liquid A-1 (lower layer coating liquid), the ink receiving layer forming coating liquid B-1 was used. (Upper layer coating solution) An ink jet recording medium 5 was produced in the same manner as in Example 1 except that 30 g / m ² was laminated instead of 40 g / m ² .

<Example 6>
In the production of the inkjet recording medium 1 of Example 1, the ion-exchanged water 127.7 kg used in the ink-receiving layer-forming coating liquid A-1 was changed to 400.0 kg, and colloidal silica (inorganic fine particles, SiO ₂ concentration 24%). ) Instead of 358.3 kg (PL-20, manufactured by Fuso Chemical Industry Co., Ltd.), the ink receiving layer was changed to amorphous silica (inorganic fine particles) 86.0 kg (AEROSIL 90G, manufactured by Nippon Aerosil Co., Ltd.) An inkjet recording medium 6 was produced in the same manner as in Example 1 except that the coating liquid A-6 was used.

<Example 7>
In the production of the inkjet recording medium 1 of Example 1, the ion-exchanged water 127.7 kg used in the receiving layer forming coating liquid A-1 was changed to 400.0 kg, and colloidal silica (inorganic fine particles, SiO ₂ concentration 24%). Instead of 358.3 kg (PL-20, manufactured by Fuso Chemical Industry Co., Ltd.), the ink acceptance was changed to amorphous silica (inorganic fine particles) 86.0 kg (manufactured by Mizusawa Chemical Industry Co., Ltd.) having a secondary particle size of 12 μm. An inkjet recording medium 7 was produced in the same manner as in Example 1 except that the layer forming coating solution A-7 was used.

<Comparative Example 1>
In forming the ink receiving layer in Example 2, the front surface of the support obtained above was subjected to corona discharge treatment, and the ink receiving layer forming coating liquid A-2 was applied to the corona discharge treated surface at 40 g / m ² . Apply with an extrusion die coater at a coating amount,
Then, the coating layer formed by coating was dried with a hot air dryer at 80 ° C. (wind speed 3 to 8 m / sec) until the solid content concentration of the layer became 20% by mass. During this time, the coating layer formed with the ink-receiving layer-forming coating liquid A-2 exhibited constant rate drying. Immediately thereafter, this coating layer was immersed in the basic solution of Example 1 for 30 seconds, and the basic solution was deposited on the coating layer at a wet coating amount of 15 g / m ² (application of basic solution before rate-decreasing drying) , WOW method). Then, after further drying at 80 ° C. for 10 minutes to form the first ink receiving layer, 120 g / in of the ink receiving layer forming coating liquid B-1 is formed on the formed first ink receiving layer. Applying with an extrusion die coater at a coating amount of m ² , and coating the formed coating layer with a hot air dryer at 80 ° C. (wind speed 3-8 m / sec) until the solid content concentration of the layer reaches 20% by mass Dried. During this time, the coating layer formed with the ink-receiving layer-forming coating solution B-1 exhibited constant rate drying. Immediately thereafter, this coating layer was immersed in a basic solution having the above composition for 30 seconds, and the basic solution was deposited on the coating layer at a wet coating amount of 15 g / m ² (application of basic solution before rate-decreasing drying, WOW method). Then, it was further dried at 80 ° C. for 10 minutes to form an ink receiving layer, thereby producing an inkjet recording medium C1.

<Comparative example 2>
In Example 2, the stacking order of the ink receiving layer forming coating liquid A-2 and the ink receiving layer forming coating liquid B-1 was reversed, that is, the ink receiving layer forming coating liquid A was used as the upper layer coating liquid. -2 was used, and an ink jet recording medium C2 was prepared in the same manner as in Example 1 except that the ink receiving layer forming coating solution B-1 was used as the lower layer coating solution.

<Comparative Example 3>
Ink jet recording medium C3 was produced in the same manner as in Example 1 except that the ink receiving layer forming coating liquid A-1 was used as the upper layer coating liquid and the lower layer coating liquid.

-Evaluation-
The following evaluation was performed about the obtained inkjet recording medium. The evaluation results are shown in Table 1 below.
In Table 1, “primary particle size” means the average particle size of primary particles, and “secondary particle size” means the volume average particle size of secondary particles. “WOW” means that the ink receiving layer was formed by the WOW method, and “set drying” means that the ink receiving layer was formed by the set drying method.

(Pore size distribution)
The obtained ink jet recording medium was used as it was, and the pore size distribution (C) was measured by mercury porosimetry. Next, the pore size distribution (D) was measured by a mercury intrusion method using the second ink receiving layer that had been scraped off with a razor to expose the first ink receiving layer. Further, the pore size distribution (E) was measured by mercury porosimetry using the support used for the production of the ink jet recording medium.

  By subtracting the pore diameter distribution (D) from the obtained pore diameter distribution (C), the pore diameter distribution of the second ink receiving layer is obtained, and the second pore diameter corresponding to the peak of the pore diameter distribution curve is obtained as the second pore diameter distribution curve. The peak diameter in the pore diameter distribution of the ink receiving layer was determined.

Also, the pore size distribution (E) is subtracted from the pore size distribution (D) to obtain the pore size distribution of the first ink receiving layer, and the first ink is used as the pore diameter corresponding to the peak of the pore size distribution curve. The peak diameter in the pore size distribution of the receiving layer was determined.
The measurement of the pore size distribution by the mercury intrusion method was performed under normal conditions using an auto pore manufactured by Shimadzu Corporation.

(Penetration amount per average film thickness)
About the obtained inkjet recording medium, using a liquid in which diethylene glycol, triethylene glycol monobutyl ether and water were mixed so that the mass ratio was 15/15/70 (diethylene glycol / triethylene glycol monobutyl ether / water), JAPAN TAPPI paper Pulp test method no. The permeation amount A (ml / m ² ) measured at a contact time of 0.05 seconds was measured by the Bristow method according to 51-87.

  In addition, using the electron microscopic image of the cross section, the thickness of the second ink receiving layer was measured at 10 points, and the average film thickness B (μm) of the second ink receiving layer was obtained as the arithmetic average. The permeation amount (A / B, permeation amount / average film thickness) was calculated.

(Roughness index)
A cross section of the obtained ink jet recording medium was cut out by a microtome to obtain a measurement sample. The obtained measurement sample was observed using a scanning electron microscope (SEM) to obtain image data with a resolution of 0.01 μm / pixel. The vicinity of the boundary between the first ink receiving layer and the second ink receiving layer was subjected to image processing to extract the boundary line, and the unevenness index was calculated by the above method.
FIG. 3 schematically shows an example of the extracted boundary line in the inkjet recording medium 1 of the first embodiment.

(Thin line drawing 1)
Using a commercially available inkjet printer (EP-801A, manufactured by Seiko Epson Corporation) on an inkjet recording medium, red, green, and blue thin lines (line width 0.5 mm) were printed, and then with a magnifying glass of 25 times. Observed and evaluated according to the following evaluation criteria.
~Evaluation criteria~
(Double-circle): There was no blur in a thin wire | line.
○: Slight bleeding was observed on the thin line.
Δ: Bleeding was observed on the fine line.
X: Fine lines were significantly blurred.

(Thin line drawing 2)
After printing red, green, and blue thin lines (line width: 1.0 mm) sandwiched between yellow solids using a commercially available inkjet printer (EP-801A, manufactured by Seiko Epson Corporation) on an inkjet recording medium This was visually observed and evaluated according to the following evaluation criteria.
~Evaluation criteria~
(Double-circle): There was no blur in a thin wire | line.
○: Slight bleeding was observed on the thin line.
Δ: Bleeding was observed on the fine line.
X: Fine lines were significantly blurred.

(Glossiness)
A black solid image was recorded on an inkjet recording medium in an environment of 23 ° C. and 50% RH using an inkjet printer EP-801A (manufactured by Seiko Epson Corporation). The 60 ° glossiness at the outermost surface of the ink image-receiving layer was measured with a digital variable glossiness meter (UGV-50DP, manufactured by Suga Test Instruments Co., Ltd.) and evaluated according to the following criteria.
~Evaluation criteria~
A: Glossiness is 30% or more B: Glossiness is 20% or more and less than 30% B: Glossiness is 10% or more and less than 20% X: Glossiness is less than 10%

  From Table 1, it can be seen that the ink jet recording medium of the present invention is excellent in fine line drawing property and glossiness.

1: Pixel of boundary line 2: Pixel center of boundary line 3: Line connecting respective centers of pixels of adjacent boundary line 4: Approximate straight line 5 obtained by least square method: First extracted from SEM image of cross section Boundary line 6 of the ink receiving layer and the second ink receiving layer 6: approximate straight line of the boundary line

Claims (7)

A support, a first ink-receiving layer provided on the support and containing first inorganic fine particles, and a second ink provided on and in contact with the first ink-receiving layer and containing second inorganic fine particles An ink receiving layer, and an ink jet recording medium comprising:
The peak diameter in the pore diameter distribution of the second ink receiving layer is smaller than the peak diameter in the pore diameter distribution of the first ink receiving layer, and
The first ink receiving layer and the second ink receiving layer in a cross section of the ink jet recording medium that is perpendicular to the surface of the support on which the first ink receiving layer and the second ink receiving layer are provided. An ink jet recording medium having a boundary line irregularity index of 1.5 to 15.0.   The inkjet recording medium according to claim 1, wherein the unevenness index of the boundary line is 3.0 to 10.0. The second ink receiving layer uses a liquid obtained by mixing diethylene glycol, triethylene glycol monobutyl ether and water so that the mass ratio is 15/15/70 (diethylene glycol / triethylene glycol monobutyl ether / water). TAPPI paper pulp test method no. The ratio (A) of the penetration amount A (ml / m ² ) measured at a contact time of 0.05 seconds by the Bristow method according to 51-87 to the average film thickness B (μm) of the second ink receiving layer. The ink jet recording medium according to claim 1 or 2, wherein / B) is 3.0 to 10.0. The second inorganic fine particles are amorphous silica whose primary particles have an average particle diameter of 5 nm to 30 nm and whose secondary particles have a volume average particle diameter of 0.05 μm to 0.20 μm,
The first inorganic fine particle is at least one selected from amorphous silica and colloidal silica in which the volume average particle diameter of the secondary particles is 0.30 μm to 8.0 μm. 4. 2. An ink jet recording medium according to item 1.   The inkjet recording medium according to claim 1, wherein each of the first ink receiving layer and the second ink receiving layer further contains a water-soluble resin.   A first ink-receiving layer-forming coating solution containing first inorganic fine particles and a second ink-receiving layer-forming coating solution containing second inorganic fine particles are placed on the support in this order from the support side. 6. The method according to claim 1, further comprising the step of forming a first ink-receiving layer and a second ink-receiving layer by simultaneously applying multiple layers so as to be laminated with each other to form a coating layer. The manufacturing method of the inkjet recording medium of description.   A basic solution containing a basic compound is applied to the coating layer (1) at the same time as the simultaneous multilayer coating, or (2) while the coating layer is being dried and before the coating layer exhibits reduced-rate drying. The method for producing an ink jet recording medium according to claim 6, further comprising a step of: