JP2005271444A - Inkjet recording medium - Google Patents

Abstract

An object of the present invention is to provide an ink jet recording medium having high gloss, high absorbency, and excellent color reproducibility.
According to the present invention, an undercoat layer containing an alkaline earth metal salt as a pigment is provided on at least one surface of a support, and an ink receiving layer containing inorganic ultrafine particles is provided on the undercoat layer. In the ink jet recording medium, 90-60% by mass of the pigment of the undercoat layer is an alkaline earth metal salt, and 10-40% by mass is kaolin or / and amorphous synthetic silica by a wet method. An ink jet recording medium is characterized. The alkaline earth metal salt is preferably calcium carbonate or magnesium carbonate. The inorganic ultrafine particles are preferably amorphous synthetic silica or alumina compound obtained by a vapor phase method.
[Selection figure] None

Description

  The present invention relates to an ink jet recording medium used in a printer using an ink jet recording method, and more particularly to an ink jet recording medium having high gloss, high absorbency and excellent color reproducibility. .

  Inkjet recording is a method for recording images, characters, etc. by ejecting micro droplets of ink by various operating principles and attaching them to a recording medium such as paper. However, it has features such as easy recording, high flexibility of recording patterns, no need for development and fixing, and has rapidly spread as a recording apparatus for various figures and color images including kanji. Furthermore, an image formed by the multi-color ink jet method can obtain a recording that is comparable to multi-color printing by an offset printing method or printing by a color photographic method. In applications where the number of copies to be produced is small, a plate making process is not required as compared with the offset printing method, so that it is widely applied to the field of full-color image recording.

  Recently, inkjet printers and the like that can output high-definition images comparable to images of silver salt photographs are commercially available at low cost. Inkjet recording media are very inexpensive compared to the silver halide photography method, but are very inexpensive, so for users who frequently change the displayed image in advertisements or product samples that require large-area images. There are economic benefits. Moreover, it has been impossible to create an image on a personal computer, which has become popular recently, and correct the color scheme and layout while looking at the printout. There is also an advantage that such an operation can be easily performed. From such a background, there is a growing demand for glossy inkjet recording media.

  Therefore, as an inkjet recording medium having high gloss, for example, those using a cast coating method have been proposed in JP-A Nos. 11-48604 and 2000-85242. However, the recording medium obtained by the cast coating method has many cracks on the surface of the coating layer, and in particular, the color reproducibility is inferior due to the colorant pigments of recent non-aqueous and aqueous pigment inks falling into the cracks. It was.

On the other hand, as a method for imparting high gloss without using the above-described casting treatment, an undercoat layer containing an alkaline earth metal salt and an adhesive and an ink receiving layer containing inorganic ultrafine particles are provided on a paper support. An ink jet recording medium provided with the above has been proposed. (Patent Document 1). However, high glossiness, high absorbency, and color reproducibility of the pigment ink were not fully satisfied at the same time.
JP 2003-170652 A

  An object of the present invention is to provide an ink jet recording medium having high gloss, high absorbency, and an excellent color reproduction range.

  The present invention relates to an ink jet recording medium in which an undercoat layer containing an alkaline earth metal salt as a pigment is provided on at least one surface of a support, and an ink receiving layer containing inorganic ultrafine particles on the undercoat layer. 90 to 60% by mass of the pigment of the undercoat layer is a salt of an alkaline earth metal, and 10 to 40% by mass is kaolin or / and amorphous synthetic silica obtained by a wet method. Inkjet recording medium.

  The alkaline earth metal salt is preferably calcium carbonate or magnesium carbonate.

  More preferably, the calcium carbonate is light calcium carbonate having an average primary particle size of 0.1 to 3 μm.

  The inorganic ultrafine particles are preferably amorphous synthetic silica or alumina compound obtained by a vapor phase method.

  Ink containing inorganic ultrafine particles on an undercoat layer in which 90 to 60% by mass of the pigment is an alkaline earth metal salt and 10 to 40% by mass is kaolin or / and amorphous synthetic silica by a wet method By providing the receiving layer, it is possible to obtain an excellently balanced white paper gloss, ink absorbability, and color reproducibility.

Hereinafter, the inkjet recording medium of the present invention will be described in detail.
The inkjet recording medium of the present invention comprises an undercoat layer on a support and an ink receiving layer containing inorganic ultrafine particles.

  90-60 mass% of the pigment in the undercoat layer of the present invention is an alkaline earth metal salt. The alkaline earth metal referred to in the present invention is a general term for beryllium, calcium, magnesium, strontium, barium, and radium. Examples of alkaline earth metal salts include carbonates, silicates, borates, hydrochlorides, sulfates, organic acid salts, etc., but since the coating solution for the undercoat layer is often aqueous, the solubility is low. Weak acid salts are preferred. Particularly preferred is calcium carbonate or magnesium carbonate.

  Calcium carbonate is roughly classified into heavy calcium carbonate and light calcium carbonate (precipitated calcium carbonate). In the former, fine limestone is finely pulverized and supplied by dry or wet classification. The latter is supplied by dissolving quick lime in water, blowing carbon dioxide and filtering the precipitated calcium carbonate. Crystal types include calcite type and aragonite type, and the shape includes square, needle, columnar, spindle, and amorphous. The calcium carbonate used in the present invention may be either heavy calcium carbonate or light calcium, and any crystal type and shape can be used without any problem. However, from the viewpoint of ink absorbability, preferred shapes are needles, columns, and spindles. is there.

  When the calcium carbonate contained in the undercoat layer of the present invention is spherical, the average primary particle size is preferably 0.1 to 3 μm, and more preferably 0.1 to 2 μm. Here, the average primary particle diameter represents the diameter of a circle equal to the projected area of particles when calcium carbonate is observed with an electron microscope. In the case of acicular, columnar, or spindle-shaped calcium carbonate, both the “minor axis” and “major axis” are within the above range.

  In the undercoat layer of the present invention, the above-mentioned alkaline earth metal salt as a pigment and kaolin or / and amorphous synthetic silica by a wet method are used in combination. The content ratio of the alkaline earth metal salt is 90 to 60% by mass with respect to the total pigment in the undercoat layer, and the content ratio of kaolin and / or amorphous synthetic silica by a wet method (kaolin and wet method). When the amorphous synthetic silica is used in combination, the total amount thereof is 10 to 40% by mass with respect to the total pigment in the undercoat layer. With these content ratios, the object of the present invention, particularly high gloss and high absorbency can be sufficiently satisfied.

  Examples of other inorganic or organic pigments that can be contained in the undercoat layer include talc, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, and colloidal silica. And white inorganic pigments such as alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, and hydrous halloysite. Organic pigments include thermoplastic resins such as polystyrene resin, styrene-acrylic resin, acrylic resin, polyethylene resin, vinyl acetate copolymer polyolefin resin, polypropylene resin, polyacetal resin, chlorinated polyether resin, and polyvinyl chloride resin. Things can be mentioned. Of these, polystyrene resins, acrylic resins or styrene-acrylic resins which are organic pigments are particularly preferable.

  The undercoat layer preferably contains an adhesive together with the above-described pigment. Examples of such adhesives include cellulose-based adhesives such as methylcellulose, methylhydroxyethylcellulose, methylhydroxypropylcellulose, and hydroxyethylcellulose, starch and modified products thereof, gelatin and modified products thereof, casein, pullulan, gum arabic, and albumin. Natural polymer resins or derivatives thereof, polyvinyl alcohol and modified products thereof, styrene-butadiene copolymers, styrene-acrylic copolymers, methyl methacrylate-butadiene copolymers, latexes such as ethylene-vinyl acetate copolymers, Emulsions, polyacrylamides, vinyl polymers such as polyvinylpyrrolidone, polyethyleneimine, polypropylene glycol, polyethylene glycol, and maleic anhydride or copolymers thereof And the like. Preferably, it is a copolymer latex or emulsion.

  The undercoat layer contains 4% by mass or more and 80% by mass or less of an adhesive in terms of solid content with respect to all pigments. More preferably, it is the range of 5 mass% or more and 40 mass% or less.

  In addition, other additives include cationic dye fixing agents, pigment dispersants, thickeners, fluidity improvers, viscosity stabilizers, pH adjusters, surfactants, antifoaming agents, antifoaming agents, and release agents. , Foaming agent, penetrating agent, coloring dye, coloring pigment, fluorescent whitening agent, UV absorber, antioxidant, leveling agent, preservative, antibacterial agent, water resistance agent, wet paper strength enhancer, dry paper strength enhancer An agent or the like can be appropriately added within a range not impairing the object of the present invention.

  When providing the undercoat layer, a coating method is not particularly limited, and a known coating method can be used. For example, supports by various devices such as air knife coater, curtain coater, slide lip coater, die coater, blade coater, gate roll coater, bar coater, rod coater, roll coater, bill blade coater, short dwell blade coater, size press, etc. Can be coated on top.

  Further, the applied undercoat layer may be smoothed by a calendar process. Examples of the calendar processing device at that time include a gloss calendar, a super calendar, and a soft calendar. In particular, a thermal calendar process in which a smoothing process is performed while applying heat is preferable.

The coating amount (dry coating amount) of the undercoat layer is preferably 5 g / m ² or more and 30 g / m ² or less.

  The inorganic ultrafine particles contained in the ink receiving layer of the present invention are inorganic fine particles having an average primary particle diameter of 100 nm or less and an average secondary particle diameter of 400 nm or less. For example, JP-A-1-97678 and 2- No. 275510, No. 3-281383, No. 3-285814, No. 3-285815, No. 4-92183, No. 4-267180, No. 4-275717, etc. Pseudo boehmite sol which is an alumina hydrate, JP-A-60-219083, JP-A-61-19389, JP-A-61-188183, JP-A-63-178074, JP-A-5-51470, etc. Colloidal silica as described in Japanese Patent Publication No. 4-19037, Japanese Patent Application Laid-Open No. 62-286787. Silica / alumina hybrid sol, silica sol in which amorphous synthetic silica by a vapor phase method is dispersed with a high-speed homogenizer, as described in JP-A-10-119423 and JP-A-10-217601, and others Typical examples include smectite clays such as hectite and montmorillonite (Japanese Patent Laid-Open No. 7-81210), zirconia sol, chromia sol, yttria sol, ceria sol, iron oxide sol, zircon sol, and antimony oxide sol.

  Among these inorganic ultrafine particles, amorphous synthetic silica and alumina compounds (alumina hydrate or aluminum oxide ultrafine particles) obtained by a gas phase method can be preferably used.

Silica fine particles are fine particles composed of SiO ₂ 93% or more, Al ₂ O ₃ about 5% or less, Na ₂ O about 5% or less on a dry basis. There is crystalline synthetic silica. As methods for producing amorphous synthetic silica fine particles, there are a liquid phase method, a pulverized solid phase method, a crystallization solid phase method and a gas phase method. The liquid phase method is a fine particle production method in which a silicate compound or the like existing in a so-called liquid is precipitated in a solid state by a chemical change or a physical change. The pulverized solid phase method is a method for mechanically pulverizing silica solids, and the crystallization solid phase method is a method for producing fine particles using melting, solid phase transition, or the like. The gas phase method is a method for producing fine particles by thermal decomposition of vapor of a volatile metal compound, heating and evaporation of raw materials, cooling of a generated gas phase species, and condensation.

  The silica ultrafine particles used in the present invention are preferably amorphous synthetic silica ultrafine particles synthesized by a gas phase method. Among these, ultrafine silica particles having an average primary particle diameter of 3 nm to 20 nm are preferable. A particularly preferable primary particle size is 4 nm to 10 nm. Moreover, it is preferable to set it as 10 nm-400 nm as an average secondary particle diameter which these connected. Aerosil (Tegusa Co., Ltd.) is a product commercially available as amorphous synthetic silica ultrafine particles synthesized by this vapor phase method.

  Amorphous synthetic silica by the vapor phase method used in the present invention is obtained by adding silica fine particles having the above primary particle diameter to water and dispersing with a high-speed homogenizer or the like, so that the average secondary particle diameter is 400 nm or less, preferably 200 nm or less. It is distributed to.

The alumina hydrate used in the present invention can be represented by the following general formula.
Al ₂ O ₃ · nH ₂ O
Alumina hydrates are classified into dipsite, vialite, norstrandite, boehmite, boehmite gel (pseudoboehmite), diaspore, amorphous amorphous, etc., depending on the composition and crystal form. In particular, in the above formula, when the value of n is 1, it represents an alumina hydrate having a boehmite structure, and when n is more than 1 and less than 3, it represents an alumina hydrate having a pseudo boehmite structure, where n is 3 or more represents an amorphous alumina hydrate. In particular, the preferred alumina hydrate for the present invention is an alumina hydrate having a pseudo boehmite structure in which at least n is more than 1 and less than 3.

  The shape of the alumina hydrate used in the present invention may be any of a flat plate shape, a fiber shape, a needle shape, a spherical shape, a rod shape, and the like, and a preferable shape is a flat shape from the viewpoint of ink absorbability. The plate-like alumina hydrate has an average aspect ratio of 3 to 8, and preferably an average aspect ratio of 3 to 6. The aspect ratio is expressed as the ratio of the “diameter” to the “thickness” of the particles. Here, the diameter of the particle represents the diameter of a circle equal to the projected area of the particle when the alumina hydrate is observed with an electron microscope.

  The alumina hydrate used in the present invention can be produced by a known method such as hydrolysis of aluminum alkoxide such as aluminum isopropoxide, neutralization of aluminum salt with alkali, hydrolysis of aluminate. The physical properties of alumina hydrate, such as particle size, pore size, pore volume, and specific surface area, should be controlled by conditions such as precipitation temperature, aging temperature, aging time, solution pH, solution concentration, and coexisting compounds. Can do.

  As methods for obtaining alumina hydrates from alkoxides, JP-A-57-88074, JP-A-62-256321, JP-A-4-275717, JP-A-6-64918, JP-A-7-10535, JP-A-7-267633, US Pat. No. 2,656,321 and the like disclose a method for hydrolyzing aluminum alkoxide. These aluminum alkoxides include isopropoxide, 2-butoxide and the like.

  JP-A Nos. 54-116398, 55-23034, 55-27824, and 56-120508 disclose a method using an inorganic salt of aluminum or a hydrate thereof as a raw material. It is disclosed. Examples of the raw material include inorganic salts such as aluminum chloride, aluminum nitrate, aluminum sulfate, polyaluminum chloride, ammonium alum, sodium aluminate, potassium aluminate, aluminum hydroxide, and hydrates thereof.

  Further, as another method, a method for growing crystals of alumina hydrate by alternately changing the pH from acidic side to basic side as described in JP-A-56-120508, JP-B-4-33728 There is also a method of rehydrating alumina by mixing alumina hydrate obtained from an inorganic salt of aluminum and alumina obtained by the Bayer method, as described in Japanese Patent Publication No. JP-A.

Commercially available alumina hydrate can also be suitably used for the inkjet recording medium of the present invention. One example is given below, but the present invention is not limited thereto.
For example, as alumina hydrate, Cataloid AS-1, Cataloid AS-2, Cataloid AS-3 (above, manufactured by Catalytic Chemical Industry Co., Ltd.), Alumina sol 100, Alumina sol 200, Alumina sol 520 (Established, manufactured by Nissan Chemical Industries, Ltd.) M-200 (manufactured by Mizusawa Chemical Co., Ltd.), aluminum sol 10, aluminum sol 20, aluminum sol 132, aluminum sol 132S, aluminum sol SH5, aluminum sol CSA55, aluminum sol SV102, aluminum sol SB52 (above, manufactured by Kawaken Fine Chemical Co., Ltd.), DIPERAL HP8, DIPERAL HP14, DIPERAL H14 Type2, and DIPERAL H18 (manufactured by Sasol Japan Co., Ltd.).

  The aluminum oxide (hereinafter referred to as alumina) ultrafine particles used in the present invention are preferably γ type alumina fine particles which are γ type crystals. If the γ-type crystal is classified crystallographically, it can be further divided into a γ group and a δ group. Fine particles having a δ group crystal form are preferred.

  The γ-type alumina fine particles can reduce the average particle diameter of the primary particles to about 10 nm, but generally the primary particles form a secondary aggregated form (hereinafter referred to as secondary particles). The particle diameter increases from several thousand to several tens of thousands nm. When such γ-type alumina fine particles having a large particle diameter are used, the ink receiving layer has good printability and absorbability, but lacks transparency and tends to cause coating film defects. The average particle diameter of the primary particles is preferably less than 80 nm. When secondary particles composed of primary particles of 80 nm or more are used, brittleness increases and coating film defects are very likely to occur.

  In order to obtain a γ-type alumina fine particle sol, the average particle size of the γ-type alumina crystals, which are usually secondary particles of several thousand to several tens of thousands nm, is obtained by pulverizing means such as a bead mill, an ultrasonic homogenizer, and a high-pressure homogenizer. Grind to ultrafine particles of 400 nm or less, preferably 200 nm or less. When the average particle diameter exceeds 400 nm, the ink absorbability increases, but the coating becomes brittle and the transparency is lowered. As the pulverization means, a method using an ultrasonic homogenizer or a high-pressure homogenizer is preferable, and in other pulverization methods such as a bead mill, the γ-type alumina crystal is a hard crystal, so that foreign matters are easily mixed from the pulverization container, and transparency. Cause deterioration and defects. The γ-type alumina fine particles have excellent ink absorbability, good print quality such as drying and ink fixing properties, and by forming ultrafine particles, even if they are included in the ink receiving layer at a high ratio, they are excellent in transparency. A recording medium can be obtained.

  The γ-type alumina fine particles are commercially available as aluminum oxide C belonging to the δ group (manufactured by Nippon Aerosil Co., Ltd.), AKP-G015 belonging to the γ group (manufactured by Sumitomo Chemical Co., Ltd.), and the like.

  The ink receiving layer of the present invention preferably contains an adhesive together with inorganic ultrafine particles. As such an adhesive, a water-soluble or water-insoluble polymer compound may be added. The polymer compound used in the present invention is a compound having an affinity for ink as a constituent component of the ink receiving layer. Examples of water-soluble polymer compounds include cellulose-based adhesives such as methylcellulose, methylhydroxyethylcellulose, methylhydroxypropylcellulose, and hydroxyethylcellulose, starch and modified products thereof, gelatin and modified products thereof, casein, pullulan, gum arabic, and Natural polymer resins such as albumin or derivatives thereof, polyvinyl alcohol and modified products thereof, styrene-butadiene copolymer, styrene-acrylic copolymer, methyl methacrylate-butadiene copolymer, ethylene-vinyl acetate copolymer, etc. Latex and emulsion, vinyl polymers such as polyacrylamide and polyvinylpyrrolidone, polyethyleneimine, polypropylene glycol, polyethylene glycol, and maleic anhydride or its co-polymer Like the body or the like. Polyvinyl alcohol is preferable.

  Further, as the water-insoluble polymer compound, a water-insoluble adhesive that dissolves in alcohols such as ethanol and 2-propanol or a mixed solvent of these alcohols and water stabilizes the dispersion of aluminum oxide. Therefore, it is particularly preferable. Examples of such water-insoluble adhesives include acetal resins such as vinyl pyrrolidone / vinyl acetate copolymer, polyvinyl butyral, and polyvinyl formal, and in particular, the degree of acetalization is in the range of 5 mol% to 20 mol%. This acetal resin is particularly preferable because it can contain some water and can easily disperse the inorganic ultrafine particles.

  These polymer compounds may be used alone or in combination, and 2% by mass or more and 50% by mass or less are added to the inorganic ultrafine particles. Preferably, 5 mass% or more and 30 mass% or less are added.

The coating amount of the ink receiving layer of the present invention (dry coating amount) is preferably in the range of 3 to 30 g / ^{m 2,} in particular in the range of 5 to 30 g / ^{m 2} is preferred. More preferably, it is 5-20 g / m < ² >. Although it depends on the amount of voids, the thickness is particularly preferably from 5 μm to 20 μm.

  The method of applying the ink receiving layer coating liquid in the present invention employs various coating methods such as slide bead coating, curtain coating, straddle hopper coating, extrusion coating, roll coating, air knife coating, gravure coating, rod bar coating, etc. Can do.

  In the present invention, the layer structure of the ink jet receiving layer may be a single layer or a laminated layer, but the uppermost layer is an ink receiving layer containing inorganic ultrafine particles, and the layer in contact with the ink receiving layer is an undercoat layer. For example, a multilayer structure in which different layers are provided between the undercoat layer and the support may be used.

  As a means for drying after coating, a generally known method can be used and is not limited. For example, there are a method of conveying heated air generated by a heat source into a heated air heater, a method of passing the vicinity of a heat source such as a heater, and the like.

  The applied ink receiving layer may be smoothed by calendaring. Examples of the calendar processing device at that time include a gloss calendar, a super calendar, and a soft calendar. In particular, a thermal calendar process in which a smoothing process is performed while applying heat is preferably used.

  Furthermore, the coating liquid for forming the ink-receiving layer of the present invention may contain a surfactant, an inorganic pigment, a coloring dye, a coloring pigment, an ink dye fixing agent (cationic resin), an ultraviolet absorber, and an antioxidant as necessary. Various known additives such as an agent, a pigment dispersant, an antifoaming agent, a leveling agent, an antiseptic, a fluorescent brightening agent, a viscosity stabilizer, a pH adjuster, and a hardening agent can be added.

  The support used in the present invention is not limited, but preferably a paper support can be used. As the pulp constituting the paper support, natural pulp, recycled pulp, synthetic pulp or the like is used alone or in combination. As the natural pulp, pulps usually used for papermaking, that is, bleached chemical pulp such as softwood kraft pulp, hardwood kraft pulp, softwood sulfite pulp, hardwood sulfite pulp, and the like can be used. Moreover, mechanical pulp with high whiteness may be sufficient. Further, non-wood pulp made from grass fibers such as straw, esparto, bagasse and kenaf, bast fibers such as hemp, straw, scabbard and scabbard, cotton and the like may be used. Of these, bleached chemical pulp such as softwood kraft pulp, hardwood kraft pulp, softwood sulfite pulp, and hardwood sulfite pulp, which are most commonly used industrially, is particularly preferable.

  Examples of the present invention will be described below, but the present invention is not limited to these examples. “Parts” and “%” indicate solid parts by mass and solids mass%.

<Creation of support>
Pigment having a light calcium carbonate / heavy calcium carbonate / talc mass ratio of 10/10/10 to 100 parts of wood pulp comprising 80 parts of LBKP (freeness 400 mlcsf) and 20 parts NBKP (freeness 450 mlcsf) After adjusting 1% pulp slurry containing 25 parts, 0.10 parts of commercially available alkyl ketene dimer, 0.03 parts of commercially available cationic polyacrylamide, 0.80 parts of commercially available cationized starch, and 0.40 parts of sulfuric acid band in water Then, the paper was made at a basis weight of 90 g / m ² using a long net paper machine to prepare a “support”.

<Undercoat layer coating solutions 1a to 1e>
100/0 each of light calcium carbonate (Tama Pearl TP123: manufactured by Okutama Kogyo Co., Ltd.) and kaolin (caoblite: manufactured by Shiraishi Calcium Co., Ltd.) having an average primary particle length of 0.2 × 1.5 μm as the alkaline earth metal salt. , 90/10, 70/30, 60/40, 50/50 parts added to an appropriate amount of ion-exchanged water, dispersed with a homomixer, and then heat-gelatinized urea phosphated starch (MS4600: Japan) 3 parts of Food Processing Co., Ltd.) and 10 parts of styrene-butadiene copolymer latex (E-1585: manufactured by Asahi Kasei Co., Ltd.) were mixed to prepare 45% undercoat layer coating solutions 1a to 1e, respectively.

<Undercoat layer coating solutions 2a to 2d>
Light calcium carbonate having an average primary particle size of 0.3 to 0.5 μm as an alkaline earth metal salt (Tama Pearl TP222H: manufactured by Okutama Kogyo Co., Ltd.) and amorphous synthetic silica by a wet method (Fine Seal X37B: manufactured by Tokuyama Co., Ltd.) 90/10, 70/30, 60/40, and 50/50 parts of each were added to appropriate amounts of ion-exchanged water, dispersed with a homomixer, and then heated and gelatinized as an adhesive (MS4600: Japan) 3 parts of Food Processing Co., Ltd.) and 10 parts of styrene-butadiene copolymer latex (E-1585: manufactured by Asahi Kasei Co., Ltd.) were mixed to prepare 25% undercoat layer coating solutions 2a to 2d, respectively.

<Undercoat layer coating liquids 3a to 3d>
Light calcium carbonate (Tama Pearl TP121: manufactured by Okutama Kogyo Co., Ltd.), kaolin (DB Prime: manufactured by Sumitomo Corporation), and a wet method with an average primary particle size of 0.5 × min. 90/5/5, 70/15/15, 60/20/20, and 50/25/25 parts of amorphous synthetic silica (Fine Seal X37B, manufactured by Tokuyama Corporation) were added to appropriate amounts of ion-exchanged water, respectively. After dispersing with a mixer, 3 parts of urea phosphate esterified starch (MS4600: manufactured by Nippon Food Processing Co., Ltd.) and 10 parts of styrene-butadiene copolymer latex (E-1585: manufactured by Asahi Kasei Co., Ltd.) were mixed as an adhesive. 25% of the undercoat layer coating solutions 3a to 3d were respectively adjusted.

<Undercoat layer coating solution 4>
Add 70/30 parts each of magnesium carbonate (Venus: manufactured by Kamishima Chemical Co., Ltd.) and kaolin (caoblite: manufactured by Shiraishi Calcium Co., Ltd.) as alkaline earth metal salts to a suitable amount of ion-exchanged water, and then disperse them with a homomixer, followed by bonding. 3 parts of urea phosphate esterified starch (MS4600: manufactured by Nippon Food Processing Co., Ltd.) and 10 parts of styrene-butadiene copolymer latex (E-1585: manufactured by Asahi Kasei Co., Ltd.) were mixed as an agent, and 35% undercoat layer Coating solution 4 was prepared.

<Undercoat layer coating solution 5>
Add 70/30 parts each of heavy calcium carbonate (FMT90: manufactured by Phimatech) and kaolin (caoblite: manufactured by Shiraishi Calcium) as an alkaline earth metal salt to an appropriate amount of ion-exchanged water, and then disperse with a homomixer. 3 parts of urea phosphate esterified starch (MS4600: manufactured by Nippon Food Processing Co., Ltd.) and 10 parts of styrene-butadiene copolymer latex (E-1585: manufactured by Asahi Kasei Co., Ltd.) and an appropriate amount of ion-exchanged water as adhesives A 45% undercoat layer coating solution 5 was prepared by mixing.

<Undercoat layer coating liquid 6>
70/30 parts of calcium sulfate (CoCoat P80HB: manufactured by KEMIRA) and kaolin (Caobrite: manufactured by Shiraishi Calcium) as alkaline earth metal salts are added to an appropriate amount of ion-exchanged water, and dispersed with a homomixer. 3 parts of urea-phosphate esterified starch (MS4600: manufactured by Nippon Food Processing Co., Ltd.) and 10 parts of styrene-butadiene copolymer latex (E-1585: manufactured by Asahi Kasei Co., Ltd.) and an appropriate amount of ion-exchanged water were mixed as A 25% undercoat layer coating solution 6 was prepared.

<Undercoat layer coating solution 7>
100 parts of amorphous synthetic silica (Fine Seal X37B: manufactured by Tokuyama Corporation) with an average secondary particle diameter of 3.7 μm by a wet method is added to an appropriate amount of ion-exchanged water, and dispersed with a homomixer. 30 parts of polyvinyl alcohol (PVA105: manufactured by Kuraray Co., Ltd.) was mixed to prepare an undercoat layer coating solution 7 of 15%.

<Ink-receiving layer coating solution A>
Add 100 parts of ultrafine alumina (HP14: manufactured by Sasol Japan) and 2 parts of a dispersant (nitric acid) into an appropriate amount of ion-exchanged water, and use a homomixer to make the secondary particle diameter 250 nm or less. Thus, a 20% alumina dispersion was prepared. Further, 15 parts of 10% polyvinyl alcohol (PVA624: manufactured by Kuraray Co., Ltd.) was mixed, and then ion-exchanged water was added to obtain a 15% ink receiving layer coating solution A.

<Ink-receiving layer coating solution B>
100 parts of amorphous synthetic silica fine particles (AEROSIL300: manufactured by Nippon Aerosil Co., Ltd.) by a gas phase method having a primary particle diameter of 7 nm and 3 parts of a dispersant (Charol DC902P: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) are added to an appropriate amount of ion-exchanged water. Then, using a homomixer, the mixture was dispersed so as to have a secondary particle diameter of 200 nm or less to obtain a 20% dispersion. Further, 15 parts of 10% polyvinyl alcohol (manufactured by PVA235 Kuraray Co., Ltd.) was mixed, and then ion-exchanged water was added to obtain an ink receiving layer coating liquid B having a solid content of 15%.

<Ink-receiving layer coating solution C>
100 parts of amorphous synthetic silica (Fine Seal X37B: manufactured by Tokuyama) with a secondary particle size of 3.7 μm was added to an appropriate amount of ion-exchanged water, and a 20% dispersion was obtained using a homomixer. . Furthermore, after adding 15 parts of 10% polyvinyl alcohol (PVA105: manufactured by Kuraray Co., Ltd.), ion exchange water was added to obtain 15% ink-receiving layer coating solution C.

On the support prepared above, the undercoat layer coating solution 1b was applied and dried with a wire bar so as to have a dry solid content of 15 g / m ² . Next, the ink receiving layer A was coated and dried on the undercoat layer with a curtain coater so as to have a dry solid content of 10 g / m ² to obtain a recording medium of Example 1.

  A recording medium of Example 2 was obtained in the same manner as in Example 1 except that the undercoat layer coating solution 1b was replaced with the undercoat layer coating solution 1c in Example 1.

  A recording medium of Example 3 was obtained in the same manner as in Example 1 except that the undercoat layer coating solution 1b was replaced with the undercoat layer coating solution 1d in Example 1.

  In Example 1, except that the undercoat layer coating solution 1b was replaced with the undercoat layer coating solution 2a, and the ink receiving layer coating solution A was replaced with the ink receiving layer coating solution B, the same as in Example 1, The recording medium of Example 4 was obtained.

  In Example 1, except that the undercoat layer coating solution 1b was replaced with the undercoat layer coating solution 2b and the ink receiving layer coating solution A was replaced with the ink receiving layer coating solution B, the same as in Example 1, The recording medium of Example 5 was obtained.

  In Example 1, except that the undercoat layer coating liquid 1b was replaced with the undercoat layer coating liquid 2c and the ink receiving layer coating liquid A was replaced with the ink receiving layer coating liquid B, the same as in Example 1, The recording medium of Example 6 was obtained.

  A recording medium of Example 7 was obtained in the same manner as in Example 1 except that the undercoat layer coating solution 1b was replaced with the undercoat layer coating solution 3a in Example 1.

  A recording medium of Example 8 was obtained in the same manner as in Example 1 except that the undercoat layer coating solution 1b was replaced with the undercoat layer coating solution 3b in Example 1.

  A recording medium of Example 9 was obtained in the same manner as in Example 1 except that the undercoat layer coating solution 1b was replaced with the undercoat layer coating solution 3c in Example 1.

  In Example 1, except that the undercoat layer coating liquid 1b was replaced with the undercoat layer coating liquid 4 and the ink receiving layer coating liquid A was replaced with the ink receiving layer coating liquid B, the same as in Example 1, The recording medium of Example 10 was obtained.

  In Example 1, except that the undercoat layer coating solution 1b was replaced with the undercoat layer coating solution 5 and the ink receiving layer coating solution A was replaced with the ink receiving layer coating solution B, the same as in Example 1, The recording medium of Example 11 was obtained.

  In Example 1, except that the undercoat layer coating solution 1b was replaced with the undercoat layer coating solution 6 and the ink receiving layer coating solution A was replaced with the ink receiving layer coating solution B, the same as in Example 1, The recording medium of Example 12 was obtained.

(Comparative Example 1)
A recording medium of Comparative Example 1 was obtained in the same manner as in Example 2 except that the ink receiving layer coating liquid A was replaced with the ink receiving layer coating liquid C in Example 2.

(Comparative Example 2)
A recording medium of Comparative Example 2 was obtained in the same manner as in Example 1 except that the undercoat layer coating solution 1b was replaced with the undercoat layer coating solution 1a in Example 1.

(Comparative Example 3)
A recording medium of Comparative Example 3 was obtained in the same manner as in Example 1 except that the undercoat layer coating solution 1b was replaced with the undercoat layer coating solution 1e in Example 1.

(Comparative Example 4)
A recording medium of Comparative Example 4 was obtained in the same manner as in Example 1 except that the undercoat layer coating solution 1b was replaced with the undercoat layer coating solution 2d in Example 1.

(Comparative Example 5)
A recording medium of Comparative Example 5 was obtained in the same manner as in Example 1 except that the undercoat layer coating solution 1b was replaced with the undercoat layer coating solution 3d in Example 1.

(Comparative Example 6)
A recording medium of Comparative Example 6 was obtained in the same manner as in Example 1 except that the undercoat layer coating solution 1b was replaced with the undercoat layer coating solution 7 in Example 1.

  For the ink jet recording media of the above Examples and Comparative Examples, the following quality evaluation was performed. The results are shown in Table 1.

<Evaluation of white paper gloss>
Example 1 was defined as a standard (◯), and visually higher than Example 1 was visually evaluated as ◎, inferior to Example 1, but at a level that had no practical problem, Δ, and extremely glossy as ×.

<Evaluation of ink absorbency>
By using PM4000PX (setting: MC mat, clean) manufactured by Epson Corporation, which is an ink jet recording apparatus, on the manufactured recording medium, black, cyan, magenta, yellow, blue, red, and green 100% solid printing portions and their An image with white letters inside was printed. “Ink absorbability” was evaluated by visually observing the uniformity in a solid print portion, the boundary between adjacent solid print portions, the sharpness of white characters, and the like. "◎" indicates good, "○" indicates slightly good, and "△" indicates slightly non-uniformity in the solid print part due to poor ink absorption performance, or slightly more than "○" due to collapsed white characters. Although it is inferior, there is no problem in practical use, and “x” indicates that there is a problem in practical use.

<Evaluation of color reproducibility>
Using the PM4000PX (setting: MC mat, fine) manufactured by Epson Corporation, which is an inkjet recording apparatus, 100% solid printing of each color of black, cyan, magenta, yellow, blue, red, and green is performed on the recording medium thus manufactured. The color reproducibility was visually evaluated. “◎” has a good color and the image can be seen. “○” looks good in color. “△” indicates that the color looks somewhat dull, but there is no practical problem. “X” indicates that the color is dull and there is a problem in practical use.

  From Table 1, 90-60% by mass of the pigment is an alkaline earth metal salt, and 10-40% by mass of kaolin or / and an amorphous synthetic silica by a wet method, inorganic ultrafine particles In Examples 1 to 12 in which the ink receiving layer containing the above was provided, excellent visual balance of gloss of white paper, ink absorbability, and color reproducibility was obtained. However, when the pigment of the ink receiving layer is not inorganic ultrafine particles (Comparative Example 1) and the pigment of the undercoat layer does not contain an alkaline earth metal salt (Comparative Example 6), the visual blank paper gloss and color reproducibility are poor. Further, when the pigment of the undercoat layer contains more than 40% by mass of kaolin or / and amorphous synthetic silica by a wet method (Comparative Examples 3, 4, and 5), the visual white paper gloss or ink absorbability is inferior. If the pigment of the undercoat layer contains an alkaline earth metal salt and does not contain kaolin or / and an amorphous synthetic silica obtained by a wet process (Comparative Example 2), the gloss of the white paper is slightly inferior.

Claims (4)

  An inkjet recording medium comprising an undercoat layer containing an alkaline earth metal salt as a pigment on at least one surface of a support, and an ink receiving layer containing inorganic ultrafine particles on the undercoat layer. 90 to 60% by mass of the pigment in the undercoat layer is an alkaline earth metal salt, and 10 to 40% by mass is kaolin or / and amorphous synthetic silica obtained by a wet method. recoding media.   2. The ink jet recording medium according to claim 1, wherein the alkaline earth metal salt is calcium carbonate or magnesium carbonate.   The inkjet recording medium according to claim 2, wherein the calcium carbonate is light calcium carbonate having an average primary particle size of 0.1 to 3 μm.   The inkjet recording medium according to claim 1, wherein the inorganic ultrafine particles are amorphous synthetic silica or alumina compound obtained by a vapor phase method.