JP2006326867A - Inkjet recording medium and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording medium, which is excellent in ink absorbency and with which a recorded matter with high coloring density is obtained, and its manufacturing method. <P>SOLUTION: In this inkjet recording medium, a base material side porous layer including calcium carbonate-zinc carbonate-silica composite particles under the condition that the molar ratio of CaCO<SB>3</SB>/ZnCO<SB>3</SB>lies in 5-150 and the molar ratio of CaCO<SB>3</SB>/SiO<SB>2</SB>lies in 0.5-9 is provided on a base material and further a surface porous layer including inorganic particles selected from the group consisting of alumina hydrate, silica and a silica-alumina composite and having an average particle diameter of not more than 1 μm is laminated on the base material side porous layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording medium that is excellent in ink absorbability and provides a recorded matter having a high color density and a method for producing the same.

  In recent years, ink-jet recording systems have been required to have quality and performance close to silver halide photography in terms of color reproducibility, image density, glossiness, weather resistance, and the like. In order to cope with higher definition and higher speed of the recorded image, an ink jet recording medium comprising a porous layer using various inorganic pigments such as silica has been studied. As part of this study, it has been reported that an ink jet recording medium excellent in ink absorption and gloss can be obtained by forming a porous layer using calcium carbonate composite silica particles as an inorganic pigment (patent) Reference 1). However, when the calcium carbonate composite silica particles are used, there is a problem that the ink absorbability of the obtained porous layer is inferior to that when silica powder particles that are usually used are used. Furthermore, the resulting porous layer is likely to become cloudy and needs to be cast-coated in order to give glossiness, and there is a problem that the manufacturing process of the ink jet recording medium becomes large and the cost increases.

JP-A-5-59694 (Claims)

  The present invention provides an ink jet recording medium that is excellent in ink absorptivity and that provides a recorded matter with a high color density. Further, the present invention provides a method for producing an ink jet recording medium that can use a high concentration coating solution and has a short tact time.

In the present invention, a calcium carbonate-zinc carbonate-silica composite particle (hereinafter referred to as a CaCO ₃ / ZnCO ₃ molar ratio of 5 to 150 and a CaCO ₃ / SiO ₂ molar ratio of 0.5 to 9 is formed on a substrate. And an inorganic particle having an average particle size of 1 μm or less selected from the group consisting of alumina hydrate, silica, and silica-alumina composite. Provided is an ink jet recording medium in which a surface porous layer containing (hereinafter referred to as the present inorganic particles) is laminated. In the present specification, the average particle diameter is based on mass.

  Further, the present invention forms a substrate-side porous layer by applying a coating solution containing the present composite particles and a binder and having a solid content concentration of 20 to 55% by mass on a substrate. Furthermore, the present invention also provides a method for producing an ink jet recording medium in which a surface porous layer is formed by coating a coating liquid containing the present inorganic particles and a binder on the upper layer.

  According to the present invention, an ink jet recording medium that is excellent in ink absorbability and capable of obtaining a recorded matter having a high color density can be obtained. In addition, according to the present invention, it is possible to provide a method for producing an inkjet recording medium that can use a high-concentration coating liquid and has a short tact time.

  The ink jet recording medium of the present invention has a substrate-side porous layer containing the present composite particles on a substrate.

The substrate is not particularly limited, and examples thereof include paper, plastic, ceramic, metal, and the like, but a paper substrate mainly composed of pulp is preferable. As a paper base material, what contains 70 mass% or more of a pulp is preferable, and what contains 80 mass% or more is especially preferable. As the pulp constituting the paper substrate, natural pulp mainly composed of mixed pulp of softwood, hardwood, softwood and hardwood is preferred. These can be used in the state of bleached pulp such as kraft pulp, sulfide pulp, and soda pulp. In addition to natural pulp, a paper base material containing synthetic fiber or synthetic pulp can also be used. In addition, acid paper, neutral paper, coated paper and the like used in the coated paper field can be used as the paper base material. These paper base is preferably a basis weight 60~250g / ^{m 2,} and particularly preferably a basis weight 100~230g / ^{m 2.} Moreover, it is preferable that the paper base material is appropriately subjected to a smoothing process such as a calendar process as necessary.

  Although the thickness of a base material is suitably selected as needed, it is preferable from surfaces, such as conveyance property, that thickness is 70-280 micrometers. The base material can contain various additives as necessary, for example, fillers, sizing agents, paper strength enhancers, pH adjusters, yield improvers and the like. Moreover, curling prevention and paper transportability can be improved by providing various back surface coating layers on the surface opposite to the surface having the porous layer.

The composite particles are required to have a CaCO ₃ / ZnCO ₃ molar ratio of 5 to 150. If the molar ratio of CaCO ₃ / ZnCO ₃ is less than 5, the particle size of the composite particles becomes too large, so that the dispersion stability of the resulting coating liquid is lowered, and the coatability may be lowered. Therefore, it is not preferable, and if the molar ratio is more than 150, the specific surface area of the obtained composite particles becomes small, so that the ink absorbability of the obtained ink receiving layer may be lowered, which is not preferable. The molar ratio of CaCO ₃ / ZnCO ₃ is particularly preferably 8 to 70.

Further, the present composite particles are required to have a CaCO ₃ / SiO ₂ molar ratio of 0.5 to 9. In this composite particle, if the molar ratio of CaCO ₃ / SiO ₂ is less than 0.5, the dispersibility of the resulting coating solution is lowered, the coating property is deteriorated, and the coating solution having a high solid content concentration Is not preferable, and if the molar ratio is more than 9, the surface area of the composite particles may be reduced, and the ink absorbability of the resulting substrate-side porous layer may be reduced. It is not preferable. When the molar ratio of CaCO ₃ / SiO ₂ is 1 to 5, it is particularly preferable because high coating stability and high absorbency are compatible.

  The composite particles can be obtained by coating the composite particles of calcium carbonate and zinc carbonate with silica. In order to manufacture the composite particles, first, composite particles of calcium carbonate and zinc carbonate are manufactured, and then this is coated with silica. As a method for producing composite particles of calcium carbonate and zinc carbonate, an aqueous solution containing zinc sulfate is added to an aqueous solution containing slaked lime as a raw material, and as shown in formula (1), calcium sulfate and zinc hydroxide are added. Is generated. Next, it is considered that carbon dioxide gas is blown into the reaction solution, whereby composite particles of calcium carbonate and zinc carbonate are generated in the presence of excess slaked lime as shown in Formula (2). At this time, the calcium carbonate is considered to contain a trace amount of calcium sulfate.

In the formula (1), the amount of zinc sulfate added to the slaked lime aqueous solution is preferably 1.5 to 35 parts by mass of zinc sulfate with respect to 100 parts by mass of slaked lime. Moreover, in Formula (2), it is preferable to introduce | transduce the carbon dioxide gas to blow in by the density | concentration of 15-35 volume%, and the flow volume of 1000-2000 m < ³ > / hr. This is preferable because a composite particle of calcium carbonate and zinc carbonate having a specific surface area of 50 to 130 m ² / g and a primary particle diameter of 10 to 15 nm can be obtained.

After the composite particles of calcium carbonate and zinc carbonate are formed, the calcium carbonate and zinc carbonate composite particles are then coated with silica by adding an equal amount of calcium chloride to sodium silicate, stirring and mixing. Since this composite particle is obtained, it is preferable. The obtained composite particles can be obtained by filtering, washing with water and drying, and then appropriately pulverizing and classifying as necessary. Incidentally, when manufacturing the present composite particles, as the sodium silicate to be added, at a concentration of 0.3 to 25 mass% in terms of SiO _2, relative to 100 parts by weight of calcium as CaO, is 2 to 80 parts by weight It is preferable.

  The composite particles preferably have an average particle size of 0.3 to 20 μm. When the composite particles have an average particle size of less than 0.3 μm, it is not preferable because the gap between the composite particles is reduced in the substrate-side porous layer to be obtained, and the ink absorbability may be lowered. If the diameter exceeds 20 μm, the smoothness of the surface of the obtained substrate-side porous layer is deteriorated, and the color density of the resulting recorded matter may be lowered, which is not preferable. The composite particles particularly preferably have an average particle size of 0.6 to 10 μm.

  The composite particles preferably have an oil absorption of 130 to 300 ml / 100 g as defined in JIS K5101. If the oil absorption amount of the composite particles is less than 130 ml / 100 g, the ink absorbability of the resulting substrate-side porous layer may be reduced, which is not preferable. If the oil absorption amount exceeds 300 ml / 100 g, the composite particles Since the particles are bulky and the reflected light is scattered, the transparency of the substrate-side porous layer obtained may be lowered, which is not preferable. The oil absorption is particularly preferably 130 to 200 ml / 100 g.

  The substrate-side porous layer preferably contains 1 to 50 parts by mass of a binder with respect to 100 parts by mass of the present composite particles. If the binder content is less than 1 part by mass, the strength of the resulting substrate-side porous layer may be reduced, which is not preferable. If the content exceeds 50 parts by mass, the resulting substrate-side porous This is not preferable because the ink absorbability of the quality layer may be reduced. The content of the binder is particularly preferably 3 to 30 parts by mass.

  Examples of the binder include gelatin, starch or a modified product thereof, polyvinyl alcohol or a modified product thereof, polyvinylpyrrolidone, styrene / butadiene rubber latex, nitrile / butadiene rubber latex, methyl cellulose, carboxymethyl cellulose, hydroxy cellulose, hydroxymethyl cellulose, and polyacrylic acid. Water-soluble polymers such as polyacrylamide, alcohol-soluble polymers, emulsions containing polyacrylate particles or polyurethane particles are preferred. Among these, an emulsion containing polyacrylic acid ester particles or polyurethane particles is particularly preferable because the concentration of the coating liquid can be further increased and the strength of the obtained coating film is high. The average particle size of these emulsions is preferably 10 to 300 nm. If the average particle size is less than 10 nm, the dispersion of the coating liquid may be lowered due to a decrease in the stability of the emulsion. This is not preferable because the strength of the layer may be insufficient.

  Moreover, in this invention, 1 or more types of other inorganic pigments or organic pigments can be used for a base material side porous layer suitably other than this composite particle as needed. Examples of inorganic pigments include alumina hydrates such as alumina and boehmite, silica such as colloidal silica, synthetic fine particle silica and gas phase synthetic silica, silica alumina composite, synthetic fine particle aluminosilicate, zeolite, montmorillonite group mineral, and beidellite. Group mineral, saponite group mineral, hectorite group mineral, stevensite group mineral, hydrotalcite group mineral, smectite group mineral, bentonite group mineral, calcium carbonate, magnesium carbonate, calcium sulfate, barium sulfate, titanium oxide, zinc oxide, carbonic acid Examples include zinc, aluminum silicate, calcium silicate, magnesium silicate, kaolin, and talc. Examples of the organic pigment include urea resin particles, cellulose particles, and starch particles.

The substrate-side porous layer preferably has an average pore radius of ^{3 to} 40 nm and a pore volume of 0.05 to 10 cm ³ / g. This is preferable because the resulting substrate-side porous layer has good ink absorbability. The substrate-side porous layer particularly preferably has an average pore radius of 5 to 25 nm and a pore volume of 0.1 to ² cm ³ / g. In addition, it is preferable to measure the pore diameter characteristic in the present invention by a nitrogen adsorption / desorption method.

  The thickness of the substrate-side porous layer is preferably 1 to 60 μm. If the thickness is less than 1 μm, the ink absorbability may be lowered, which is not preferable. If the thickness is more than 60 μm, the strength of the obtained substrate-side porous layer may be reduced, which is not preferable. The thickness of the substrate-side porous layer is particularly preferably 5 to 30 μm.

  The ink jet recording medium of the present invention has a surface porous layer containing the present inorganic particles as an upper layer of the substrate-side porous layer. As a result, the ink jet recording medium of the present invention can be obtained with excellent color density. The present inorganic particles are any inorganic particles selected from the group consisting of alumina hydrate, silica, and silica-alumina composite. The alumina hydrate is preferably boehmite, and the silica is preferably colloidal silica, synthetic fine particle silica, or gas phase synthetic silica. As the silica-alumina composite, conventionally known ones can be used as appropriate, but as the present inorganic particles, an aluminum salt that is acidic when dissolved in water is gradually added to a silica sol containing silica particles. Aggregated particles made of silica and alumina obtained by addition are preferred. The inorganic particles are particularly preferably boehmite or vapor-phase synthetic silica from the viewpoint of excellent transparency of the resulting surface porous layer. Further, the inorganic particles are required to have an average particle size of 1 μm or less. Thereby, the smoothness of the resulting surface porous layer is improved, scattering of reflected light is suppressed, and the color density is improved, which is preferable. The inorganic particles particularly preferably have an average particle size of 50 to 500 nm.

  In the present invention, the surface porous layer is also preferably a porous layer having a structure in which the present inorganic particles are bonded with a binder, like the substrate-side porous layer. As the binder, the same binder as that used for the substrate-side porous layer described above can be used, and polyvinyl alcohol or a modified product thereof is particularly preferable because a highly porous surface porous layer can be obtained.

  It is preferable that a surface porous layer is 1-50 mass parts of binders with respect to 100 mass parts of this inorganic particle. If the binder is less than 1 part by mass, the strength of the resulting surface porous layer may be reduced, which is not preferable. If the binder exceeds 50 parts by mass, the ink absorbability may be reduced. It is not preferable. The binder is particularly preferably 3 to 20 parts by mass.

The surface porous layer preferably has an average pore radius of ^{3 to} 25 nm and a pore volume of 0.3 to ² cm ³ / g. Thereby, since the transparency of the surface porous layer to be obtained becomes high, a recorded matter having a high color density can be obtained, and the ink absorption rate is also high, which is preferable. It is particularly preferable that the average pore radius is 5 to 15 nm and the pore volume is 0.5 to 1.5 cm ³ / g.

  The thickness of the surface porous layer is preferably 3 to 30 μm. When the thickness of the surface porous layer is less than 3 μm, it is not preferable because the color density of the obtained recorded matter may be insufficient. Is not preferable because it does not improve and there is no economic advantage. The thickness of the surface porous layer is particularly preferably 5 to 15 μm.

  The inkjet recording medium of the present invention comprises a substrate-side porous layer formed by applying a coating liquid containing the present composite particles and a binder and having a solid content of 20 to 55% by mass on a substrate. Further, it is preferable to form a surface porous layer by coating a coating liquid containing the present inorganic particles and a binder on the upper layer.

  The coating liquid for forming the substrate-side porous layer preferably has a solid content concentration of 20 to 55% by mass. Thereby, when forming the base material side porous layer with thick coating thickness, the frequency | count of coating can be decreased and tact time can be reduced significantly, and it is preferable. If the solid content concentration of the coating liquid is less than 20% by mass, the number of times of coating increases, which is not preferable. If the solid content concentration exceeds 55% by mass, the viscosity of the coating liquid increases and the coating property is improved. This is not preferable because it may decrease. The solid content concentration of the coating liquid for forming the substrate-side porous layer is particularly preferably 30 to 50% by mass.

  Moreover, it is preferable that solid content concentration is 10-25 mass% of the coating liquid for forming a surface porous layer. If the solid content concentration of the coating liquid is less than 10% by mass, the number of times of coating increases, which is not preferable. This is not preferable because it may decrease. The solid content concentration of the coating solution for forming the surface porous layer is particularly preferably 13 to 20% by mass.

  As means for forming the substrate-side porous layer and the surface porous layer, both can be performed by a conventionally known method. In the case of the substrate-side porous layer, for example, a binder is added to this composite particle to form a slurry, which is a roll coater, air knife coater, blade coater, rod coater, bar coater, comma coater, gravure coater, die coater, curtain coater, sprayer. The method of apply | coating using a coater, a slide die coater, etc., and drying is mentioned. Similarly, in the case of the surface porous layer, it can be formed, for example, by adding a binder to the inorganic particles to form a slurry, and applying and drying the slurry.

  The ink jet recording medium obtained according to the present invention can be preferably used for both dye ink and pigment ink.

  Examples 1 to 3 (Examples) and Examples 4 to 6 (Comparative Examples) are shown below. In the examples, unless otherwise indicated, parts indicate parts by mass, and% indicates mass%.

[Example 1]
Beating hardwood bleached kraft pulp 85 parts (solid content) and softwood bleached kraft pulp 15 parts (solid content) to a beating degree of 320 CSF (Canadian Standard Freeness), 15 parts light calcium carbonate, A stock slurry was prepared by adding 1 part of cationic starch and 0.1 part of an alkenyl succinic anhydride neutral sizing agent and mixing well.

Next, the stock slurry is made using a long paper machine, and 5 g / m ² of 5% aqueous solution of oxidized starch is applied to both sides with a size press machine, and then dried until the water content becomes 7%. As a result, high-quality paper having a basis weight of 157 g / m ² was produced.

  On the obtained fine paper, the following substrate-side porous layer formulation 1 was applied using a bar coater so that the coating thickness after drying was 10 μm, and dried at 120 ° C. for 2 minutes to form the substrate side After forming the porous layer, the following surface porous layer formulation 1 is further applied to the upper layer so that the coating thickness after drying is 10 μm, and dried at 120 ° C. for 2 minutes to form the surface porous layer. Formed. Thereafter, the surface of the surface porous layer is calendered (line speed: 5 m / min, roll temperature: 20 ° C., nip pressure: 50 kN / m) with a mini super calender (manufactured by Yuri Roll Machinery Co., Ltd.), and ink jet recording paper Got.

Base material side porous layer formulation 1 (total solid content concentration: 44%):
Dispersion liquid containing calcium carbonate-zinc carbonate-silica composite particles (Made by Yonesho Lime Industry Co., Ltd., molar ratio of CaCO ₃ / ZnCO ₃ : 20, molar ratio of CaCO ₃ / SiO ₂ : 2.3, solid content concentration: 44.5%, average particle diameter: 3.2 μm, specific surface area of calcium carbonate-zinc carbonate-silica composite particles obtained by drying the dispersion liquid: 146 m ² / g, oil absorption: 175 ml / 100 g): 100 parts Styrene / acrylic acid copolymer emulsion (manufactured by Meisei Chemical Industry Co., Ltd., trade name: Pascoal JK-710, solid content concentration: 40%, average particle size: 150 nm, the same applies hereinafter): 13 parts Surface porous layer formulation 1: ( (Total solid content concentration: 17.9%)
Alumina sol (solid content concentration: 21%): 100 parts polyvinyl alcohol aqueous solution (manufactured by Kuraray, trade name: PVA-124, solid content concentration: 7%): 28.6 parts.

The alumina sol was produced by the following method.
Polyaluminum chloride aqueous solution (23.5% in terms of aluminum concentration converted to Al ₂ O ₃ , Cl concentration: 8.1%, basicity: 84%, manufactured by Taki Chemical Co., Ltd.) , Trade name: Takibaine # 1500) 327 g and 1548 g of water were charged, and the temperature was raised to 95 ° C. Next, 125 g of a commercially available sodium aluminate solution (Al ₂ O ₃ : 20%, Na ₂ O: 19%) was added, and the mixture was aged for 24 hours while maintaining the liquid temperature at 95 ° C. with stirring to obtain a slurry. The pH of the solution immediately after the addition of the sodium aluminate solution was 8.7 at 95 ° C. After washing the mature slurry using an ultrafiltration device, the temperature is raised again to 95 ° C., and amide sulfuric acid is added in an amount that is 2% of the total solid content of the washed slurry, and the total solid content concentration The solution was concentrated under reduced pressure until it reached 21%, and then ultrasonically dispersed to obtain an alumina sol composed of boehmite crystal particles having a pH of 4.5. In the alumina sol, boehmite crystal particles are agglomerated particles, and an average particle diameter of 190 nm is measured by a dynamic light scattering method using a particle size measuring device (manufactured by Otsuka Electronics Co., Ltd., model: LPA-30100). Met.

  The following evaluation was performed about the obtained inkjet recording paper. The evaluation results are shown in Table 1. Hereinafter, evaluation is similarly performed for Examples 2 to 6, and the results are summarized in Table 1 together with Example 1.

[Glossiness]
Using a handy gloss meter (Nippon Denshoku Industries Co., Ltd., model: PG-1M), the 60 ° gloss was measured.

[Dye ink absorbency]
Using an ink-jet printer equipped with a dye ink (Seiko Epson Corporation, model: PM950C, the same applies hereinafter), heavy solid printing was performed, and the ink absorptivity of the printing portion was visually evaluated. In addition, the case where there was no ink overflow was evaluated as ○, and the case where ink overflow was scattered was evaluated as ×.

[Dye ink color density]
Black solid printing was performed using an ink-jet printer equipped with a dye ink, and the color density of the printed portion was measured using a colorimeter (GRETAG-MACBETH, model: SPM100-II, the same applies hereinafter).

[Pigment ink absorbency]
Using an ink-jet printer equipped with pigment ink (Seiko Epson Corp., model: PM4000PX, the same applies below), heavy solid printing was performed, and the ink absorbency of the printing portion was visually evaluated. In addition, the case where there was no ink overflow was evaluated as ○, and the case where ink overflow was scattered was evaluated as ×.

[Pigment ink color density]
Black solid printing was performed using an ink jet printer equipped with pigment ink, and the color density of the printed portion was measured using a colorimeter.

[Example 2]
An ink jet recording paper was obtained in the same manner as in Example 1 except that the surface porous layer formulation 2 was used instead of the surface porous layer formulation 1.
Surface porous layer formulation 2: (total solid content concentration: 11.7%)
Silica dispersion (solid content concentration: 14%): 100 parts polyvinyl alcohol aqueous solution (Kuraray Co., Ltd., trade name: PVA-420, solid content concentration: 7%): 50 parts.

  The silica dispersion was prepared by mixing a mixture of gas phase synthetic silica fine particles (manufactured by Nippon Aerosil Co., Ltd., trade name: Aerosil 300, average particle size 7 μm) and water with a high-speed rotating colloid mill (manufactured by M Technique Co., Ltd., (Trade name: Clear Mix), and dispersion treatment was performed at 10,000 rpm for 30 minutes.

[Example 3]
An ink jet recording paper was obtained in the same manner as in Example 1 except that the surface porous layer formulation 3 was used instead of the surface porous layer formulation 1.
Surface porous layer formulation 3: (total solid content concentration: 21.5%)
Alumina sol (solid content concentration: 21%): 100 parts Acrylate ester copolymer emulsion (manufactured by Meisei Chemical Industry Co., Ltd., trade name: Pascoal JK-734, solid content concentration: 28%, average particle size: 30 nm): 7 parts .

[Example 4]
In Example 1, the same operation was performed except that the thickness of the substrate-side porous layer was 20 μm and the surface porous layer was not provided, and an ink jet recording paper was obtained.

[Example 5]
An ink jet recording paper was obtained in the same manner as in Example 1 except that the substrate-side porous layer was not provided and the thickness of the surface porous layer was changed to 20 μm.

The ink jet recording medium of the present invention is most suitable for either a pigment ink jet printer or a dye ink jet printer.

Claims (4)

A group containing calcium carbonate-zinc carbonate-silica composite particles having a CaCO ₃ / ZnCO ₃ molar ratio of 5 to 150 and a CaCO ₃ / SiO ₂ molar ratio of 0.5 to 9 on the substrate. A material-side porous layer is provided, and a surface porous layer containing inorganic particles having an average particle size of 1 μm or less selected from the group consisting of alumina hydrate, silica, and silica-alumina composite is laminated thereon. Inkjet recording medium.   2. The inkjet recording medium according to claim 1, wherein the calcium carbonate-zinc carbonate-silica composite particles are particles having an average particle size of 0.3 to 20 μm obtained by coating composite particles of calcium carbonate and zinc carbonate with silica. .   The inkjet recording medium according to claim 1 or 2, wherein the calcium carbonate-zinc carbonate-silica composite particles have an oil absorption of 130 to 300 ml / 100 g as defined in JIS K5101. On the substrate, calcium carbonate-zinc carbonate-silica composite particles having a CaCO ₃ / ZnCO ₃ molar ratio of 5 to 150 and a CaCO ₃ / SiO ₂ molar ratio of 0.5 to 9 and a binder are contained, And the coating liquid whose solid content density | concentration is 20-55 mass% is applied, the base material side porous layer is formed, and also it consists of an alumina hydrate, a silica, and a silica alumina composite in the upper layer. A method for producing an ink jet recording medium, wherein a surface porous layer is formed by applying a coating liquid containing inorganic particles having an average particle size of 1 μm or less selected from the group and a binder.