JP4305404B2 - Inkjet recording paper - Google Patents

Description

  The present invention relates to a coated paper type ink jet recording paper containing an ink receiving layer.

  The ink jet recording method is a recording method in which fine droplets of ink ejected by various methods are attached to a recording medium such as paper to form images and characters. This recording system is easy to achieve high speed and full color, and has low noise during recording and a low price of the apparatus, so that it is remarkably widespread for household users. In the field of commercial use, non-impact (NIP) printing has conventionally been used for printing variable information (such as utility bills and credit bills, receipts, delivery slips, and advertisements). It is beginning to replace printing with high-speed inkjet printers.

  Recording media used in the ink jet recording method are roughly classified into a plain paper type not provided with an ink receiving layer containing a pigment and a coated paper type provided with an ink receiving layer containing a pigment. In general, inexpensive plain paper types are mainly used for homepage printing and business reports, and coated paper types that can reproduce high-definition images are mainly used for image output from digital cameras. With the recent expansion of the use of inkjet recording methods, the quality and price of recording paper is increasing, and it is inexpensive and can be used to reproduce high-definition images on both sides. A medium is sought.

  Generally, a large amount of expensive material such as silica is blended in the ink receiving layer, and as a means for reducing the cost, the ink receiving layer can be thinned. However, in the conventional ink jet recording paper, an ink absorbing layer is provided in an ink receiving layer containing a large amount of silica having a large specific surface area. When the ink receiving layer is simply made thin, the ink cannot be absorbed by the ink receiving layer alone, and reaches the base paper, causing a problem called so-called back-through, in which the printed image can be seen through from the back surface of the recording paper. In recent ink jet printers, a printing method in which a large amount of low-density ink is dropped in order to obtain further high-definition images has been adopted. In the future, ink jet recording paper has further anti-through-through prevention and ink absorption. Required. That is, it is difficult to simply make the ink receiving layer thin for cost reduction.

  In addition, printers using pigment inks have been put on the market in combination with conventional dye inks, but when conventional ink jet recording media are printed with pigment inks, the print density tends to be greatly reduced compared to dye inks. It is in. That is, there is a demand for an ink jet recording medium with good coloring with both dye ink and pigment ink.

Conventionally, as a technique relating to an ink jet recording medium having good ink absorbability, light carbonic acid composed of calcite having an oil absorption of 30 to 80 g / 100 g and containing 80% or more of a filler having a particle size of 0.5 to 1.5 μm is used. An ink jet recording paper in which an ink receiving layer is provided on a base paper using calcium in an amount of 1 to 10 g / m ² has been proposed (see Patent Document 1).

Japanese Patent Application Laid-Open No. 64-30780

  However, when the ink jet recording paper described in Patent Document 1 is used to print with a dye-type or pigment-type ink jet printer that drops a large amount, the light calcium carbonate filler has a small particle size and a low oil absorption. The opacity of the base paper is low, and the effect of preventing show-through is insufficient when printed.

  Accordingly, an object of the present invention is to provide an ink jet recording paper that has high print density and ink absorbency and does not show through even when printing is performed using any dye type or pigment type ink jet printer.

  As a result of diligent research, the present inventors have solved the above-mentioned problems in ink-jet recording and provided a cheaper ink-jet recording paper by using a base paper that defines the average particle diameter and ash content of rosetta-type calcium carbonate used as a filler. I found out that I can do it.

  That is, the plain paper type ink jet recording paper of the present invention is mainly composed of a filler mainly containing rosetta type light calcium carbonate having an average particle diameter of 1.6 μm or more and an oil absorption of 90 to 200 ml / 100 g. It is an inkjet recording paper having at least one ink receiving layer containing a pigment and a binder on at least one side of the base paper, and the ash content of the base paper defined in JIS-P8251 is 15 to 40%. It is essential.

In particular, a great effect can be obtained in an inkjet recording paper in which the coating amount of the ink receiving layer is ² to 7 g / m ² . In addition, it is essential to use 10 to 100% by weight of synthetic silica in the pigment in the ink receiving layer. Further, synthetic silica has an oil absorption of 90 to 200 ml / 100 g, a BET specific surface area of 45 to ²⁰⁰ m ² / g, and an average particle diameter. It is essential that the silica is 1.0 to 3.0 μm.

  Moreover, it is preferable that the synthetic silica is obtained by wet pulverizing a synthetic silica slurry obtained by neutralizing a sodium silicate aqueous solution with a mineral acid and / or an acidic metal salt aqueous solution, and the synthetic silica further comprises a sodium silicate aqueous solution. Synthetic silica obtained by neutralization with an aqueous aluminum sulfate solution is preferred.

  According to the present invention, when ink jet recording is performed on a coated paper type ink jet recording paper, it is possible to obtain an excellent ink absorbability and a back-through prevention effect while maintaining an excellent print density. In particular, even when the ink receiving layer has a low coating amount, it is possible to obtain excellent ink absorptivity and a back-through prevention effect, and hence it is possible to obtain an inexpensive and high quality inkjet recording paper.

Hereinafter, embodiments of the present invention will be described.
The ink jet recording paper of the present invention is a coated paper type paper in which an ink receiving layer containing a pigment is provided on a base paper mainly composed of the following filler and pulp.

<Pulp>
The base paper is a non-coated paper composed of wood pulp and fillers, auxiliaries, and the like, and those that can be used as wood pulp include known chemical pulp, mechanical pulp, and deinked pulp. It is done. Moreover, these various pulps are used individually or in combination as needed. As the pulp, those conventionally used for papermaking can be used, for example, hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood bleached sulfite pulp (LBSP), softwood bleached sulfite pulp. Examples thereof include wood pulp such as chemical pulp such as (NBSP), mechanical pulp such as groundwood pulp (GP), and thermomechanical pulp (TMP), and waste paper pulp (DIP). Further, non-wood pulp such as cotton pulp, hemp, bagasse, kenaf, esparto, cocoon, trifoam, and husk can also be used.

<Filler>
There is no restriction | limiting in particular in pH of the base paper in this invention, Any of acidic, neutral, and alkaline may be sufficient. As a filler to be used, it is essential to use rosette type light calcium carbonate. In addition, other fillers can be used according to the pH of the base paper as long as the effects of the present invention are not impaired. For example, conventionally used inorganic fine particles such as light calcium carbonate, heavy calcium carbonate, kaolin, talc, clay, silica, white carbon, aluminum hydroxide, zeolite, and the like in other shapes can be used. Note that the Rosetta-type light calcium carbonate is a particle in which primary particles of spindle-shaped light calcium carbonate are radially aggregated to form Rosetta-type secondary particles, and specifically, Specialty Minerals Inc. Products such as Albuquer HO, Albuquer 5970, Albuquer LO, etc. can be preferably mentioned. Here, the term “radial” refers, for example, to the longitudinal direction of each primary particle extending radially from the vicinity of the center of the secondary particle.

  Light calcium carbonate is superior in terms of production cost, operability, and high opacity with low addition amount.Rosetta-type light calcium carbonate has a special shape. The opacity is greatly improved, and the back-through during ink jet recording is effectively prevented. In addition, since the specific surface area is larger than that of conventional light calcium carbonate, a base paper excellent in ink absorbability can be obtained. In such a base paper, a great effect can be obtained particularly when the coating amount of an ink receiving layer described later is small.

  In the present invention, the average particle size of the rosetta type light calcium carbonate needs to be 1.6 μm or more, and preferably 1.6 to 5.0 μm. When the average particle diameter is less than 1.6 μm, the transparency of the base paper decreases as a result of improved light transmission. As a result, the print image can be seen through from the back side of the recording paper, resulting in back-through. On the other hand, when the average particle diameter exceeds 5.0 μm, the distribution of the filler becomes non-uniform, and the opacity of the base paper is lowered, and the quality stability tends to be lowered along with the occurrence of the back-through.

  The oil absorption of the rosetta type light calcium carbonate is required to be 90 to 200 ml / 100 g, and particularly preferably 90 to 140 ml / 100 g. When the oil absorption is less than 90 ml / 100 g, the ink absorbability of the obtained ink jet recording paper is lowered. On the other hand, when it exceeds 200 ml / 100 g, the absorbency of the base paper is too large, and when the ink receiving layer coating solution is applied, only the binder component easily penetrates into the base paper, and as a result, the surface of the ink receiving layer Since the strength is lowered, there are problems such as powder falling off during cutting, which is not preferable.

  FIG. 1 is an electron microscopic image showing an example of the form of Rosetta-type light calcium carbonate (secondary particles) in a state dispersed in a liquid. In this figure, the bases of the respective primary particles are aggregated, and each primary particle extends radially toward the tip. In addition, each primary particle has a slightly larger width (diameter) at the base and narrows toward the tip. In addition, micron in a figure shows micrometer.

<Ash content>
The base paper thus configured has an ash content defined in JIS-P8251 of 15 to 40%, preferably 15 to 30%. When the ash content is defined in this way, the opacity of the paper is increased, the double-sided printing suitability is improved, and the ink absorbability is improved, so that a printed matter with no image blur is obtained. Further, when printing is performed using an ink jet printer, back-through is prevented, and printability is improved. On the other hand, if the ash content is less than 15%, these effects cannot be obtained. If the ash content exceeds 40%, the ink jet recording paper becomes weak and the printer paper feeding performance is lowered. The ash content defined in JIS-P8251 represents the amount of ash residue after burning a sample (paper) at a temperature of 525 ± 25 ° C. as a percentage of the absolute dry weight of the sample.

<Other chemicals>
Further, in the base paper, in order to improve the visual whiteness, a paper strength enhancer, an antifoaming agent, a pH adjuster, a dye and a colored pigment for adjusting the hue, within a range not impairing the effects of the present invention. Internal additives for papermaking such as fluorescent dyes can be internally added.

<Sizing agent>
The pulp described above is not only hydrophilic, but the gap between the pulp fibers absorbs water and oil by capillary action. Therefore, it is necessary to provide resistance to penetration of these liquids appropriately depending on the use of the paper. A sizing agent is used for this purpose. Any known sizing agent can be used. For example, rosin-based sizing agents, alkenyl succinic acid-based sizing agents, alkyl ketene dimer-based sizing agents, and high molecular compounds such as oxidized starch, polyvinyl alcohol, styrene / acrylic resins, polyamide resins, etc. The sizing agent is used alone or in appropriate combination. High molecular compounds can be classified into nonionic, cationic, anionic and amphoteric ones according to their ionic properties. Examples of the anionic polymer compound include a copolymer of a hydrophobic monomer and a negatively charged hydrophilic monomer. Examples of the cationic polymer compound include a copolymer of a hydrophobic monomer and a positively charged hydrophilic monomer. The nonionic polymer compound is a copolymer of a hydrophobic monomer or a copolymer of a hydrophobic monomer and a hydrophilic monomer having no charge. Examples of the amphoteric polymer compound include a polymer obtained by copolymerizing the above-described hydrophobic monomer, negatively charged hydrophilic monomer, positively charged anionic hydrophilic monomer, and optionally a hydrophilic monomer having no charge. The type is not particularly limited. Examples of these copolymers include styrene resin, alkyl dimer, higher fatty acid, petroleum resin, styrene acrylic acid copolymer resin, and styrene methacrylic acid copolymer resin.

  When the sizing agent is used as a surface sizing agent, a water-soluble binder can be added to the coating solution containing the sizing agent for the purpose of improving the surface strength. The water-soluble binder can be appropriately selected from known resins that are soluble in water and have film-forming properties. Specific examples of the water-soluble binder include starch or a modified product thereof, polyvinyl alcohol or a modified product thereof, casein, and polyacrylic acid amide, and these can be used alone or in combination. A preferable blending ratio (polymer compound / water-soluble binder) of the polymer compound and the water-soluble binder in the coating liquid is 1/1 to 1/15 in solid content. Further, the coating liquid is generally an ink jet recording paper such as a water retention agent, water resistance agent, pH adjuster, antifoaming agent, lubricant, preservative, surfactant, conductive agent, etc., as long as the effects of the present invention are not impaired. You may contain the additive used for.

<Ink receiving layer>
The ink receiving layer in the present invention is provided on at least one side of the base paper, and is composed of a pigment, a binder, and other auxiliary agents. In order to enable double-sided printing, an ink receiving layer can be applied to both sides of the base paper. The present invention is most suitable for double-sided printing because the back-through after printing is small. In addition, 2-7 g / m < ² > is essential per one side, and 4-7 g / m < ² > is especially preferable as the coating amount of an ink receiving layer. When the coating amount is less than 2 g / m ^2, it is difficult to uniformly coat the base paper surface as a support, resulting in uneven ink absorption, non-uniform solid printing, and greatly reduced inkjet suitability. To do. On the other hand, when the amount is more than 7 g / m ² , the ink-jet suitability such as ink absorption is good, but powder falling off during cutting of the recording medium or the like is likely to occur. Furthermore, since the ink receiving layer contains a large amount of expensive silica, it is difficult to reduce the cost.

<Pigment>
Synthetic silica is generally used as a pigment for the ink receiving layer in the present invention, but alumina, alumina hydrate (alumina sol, colloidal alumina, pseudoboehmite, etc.), aluminum silicate, magnesium silicate, calcium silicate, magnesium carbonate, light carbonate Calcium, heavy calcium carbonate, kaolin, talc, calcium sulfate, titanium dioxide, zinc oxide, zinc carbonate, aluminum hydroxide, calcined kaolin and other commonly used pigments for coated paper are used alone or in combination. be able to. Of the pigment in the ink receiving layer, it is essential to contain 10 to 100% by weight of synthetic silica, and more preferably 30 to 70% by weight.

<Synthetic silica>
The pigment used in the ink receiving layer is an oil absorption of 90 to 200 ml / 100 g, preferably 100 to 180 ml / 100 g, a BET specific surface area of 45 to ²⁰⁰ m ² / g, preferably 60 to ²⁰⁰ m ² / g, and an average particle size of 1.0. It is essential to contain ~ 3.0 μm synthetic silica.

If the oil absorption amount of the synthetic silica is less than 90 ml / 100 g, the ink absorbability of the obtained ink receiving layer is lowered, and if it exceeds 200 ml / 100 g, the surface strength of the ink receiving layer is lowered (for example, offset printability is lowered). ). Further, if the BET specific surface area of the synthetic silica is less than 45 m ² / g, the ink absorbability decreases, and if it exceeds 200 m ² / g, the viscosity of the coating liquid increases and the operability (for example, on-machine coating suitability). ) Tend to get worse. If the average particle size of the synthetic silica is less than 1.0 μm, the amount of voids in the silica is reduced, making it difficult to hold the ink, and the ink penetrates into the coating layer or the inside of the support to reduce the print density. Tend to. On the other hand, when the average particle diameter exceeds 3.0 μm, the opacity of the silica itself tends to increase and the print density tends to decrease. In addition, the average particle diameter of a silica can be measured using the laser method particle size measuring device (For example, the brand name: Mastersizer S type made from Malvern). By containing such synthetic silica in the ink receiving layer, the effect of preventing the breakthrough is further increased. This is considered because the opacity of the ink receiving layer is improved.
When the synthetic silica obtained by wet pulverizing a synthetic silica slurry obtained by neutralizing a sodium silicate aqueous solution with a mineral acid and / or an acidic metal salt aqueous solution is used as the synthetic silica, ink jet suitability and offset printing suitability are obtained. Are preferable.

  Examples of the metal element constituting the acidic metal salt aqueous solution include alkaline earth metal elements such as magnesium, calcium, strontium, and barium, or titanium, zirconium, nickel, iron, aluminum, and the like. Examples include acidic metal sulfates. In particular, it is preferable to use an aqueous solution of aluminum sulfate, which is an acidic metal sulfate, because not only can the solid concentration of the coating liquid be increased, but also the Hercules viscosity (high shear viscosity) can be kept low even when the solid concentration is high. .

Further, the blending amount of the acidic metal salt aqueous solution is preferably 5 to 60% (% relative to the neutralization equivalent) of the sodium silicate neutralization equivalent, and the other is preferably a mineral acid.
The mineral acid and / or acidic metal salt aqueous solution is used for neutralization when neutralizing sodium silicate to obtain a synthetic silica slurry, and preferably both mineral acid and acidic metal salt aqueous solution are used. A preferable mixing ratio is mineral acid: acidic metal salt aqueous solution = 95: 5 to 40:60 in an equivalent ratio. When both mineral acid and acidic metal salt aqueous solution are used, these may be used for neutralization one by one, or a mixture of these may be used for neutralization.
The synthetic silica can be obtained, for example, by wet pulverizing a synthetic silica slurry obtained by the method described in JP-A-2002-274837 with a known pulverizer (sand grinder, etc.). it can.
<Binder>

  The binder of the coating liquid is not particularly limited, and can be appropriately selected from, for example, known resins, but water-soluble polymer adhesives, synthetic emulsion adhesives, and the like that can be dissolved or dispersed in water. preferable. Examples of the water-soluble polymer adhesive include starch or a modified product thereof, polyvinyl alcohol and a modified product thereof, and casein. Synthetic emulsion adhesives include acrylic resin emulsions, vinyl acetate resin emulsions, styrene butadiene latexes, urethane resin emulsions, etc., but water-soluble polymer adhesives are used in terms of printing density. It is preferable to do. Specific examples include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, cation-modified polyvinyl alcohol, anion-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, oxidized starch, hydroxylethyl etherified starch, and phosphate esterified starch. Can be mentioned.

<Cationic resin>
In the present invention, in order to impart water resistance to the anionic inkjet ink, it is preferable that a cationic resin serving as a dye fixing agent is contained in the ink receiving layer (that is, in the coating liquid).
The cationic resin is a cationic water-soluble polymer, and it is more preferable to use a resin having an anion requirement of 5 meq / g or more and a molecular weight of 5,000 to 200,000 from the viewpoint of improving ink water resistance. The reason is presumed as follows. That is, it is considered that the ink for ink jet is adsorbed on the microscopic voids inside the pigment of the ink receiving layer or the pigment surface. Therefore, in order to make this ink water resistant, it is necessary to distribute the cationic resin that binds to the ink in the microvoids inside the pigment and the surface of the pigment in the ink receiving layer, but the molecular weight of the cationic resin is 200,000. When it exceeds, it cannot be distributed in the voids inside the pigment, and water resistance cannot be imparted to the ink that has entered the pigment. On the other hand, when the molecular weight of the cationic resin is less than 5,000, it tends to be distributed in minute voids inside the pigment, so that water resistance can be imparted to the ink that has entered the pigment. However, since the ink is fixed inside the pigment, the print density is greatly reduced. Further, if the anion requirement of the cationic resin is 5 meq / g or less, the ink fixing ability is not sufficient.

  Examples of cationic resins include polyethylenimine quaternary ammonium salt derivatives; ammonia / dialkylamine / epihalohydrin condensation polymers; polyamine polyamide epihalohydrins, dicyanamide / formaldehyde resins; diethylenetriamine / dicyandiamide / ammonium chloride polymers; dimethyldiallylammonium chloride polymers, etc. Is exemplified. Among these, the fixability of the inkjet ink is particularly high. A polycondensation product obtained by reacting ammonia, amines and epihalohydrins is preferred.

  Examples of amines used in the condensation polymerization product include primary amines, secondary amines, tertiary amines, polyalkylpolyamines, and alkanolamine monoamines. Specific examples of the secondary amine include dimethylamine, diethylamine, dipropylamine, methylethylamine, methylpropylamine, methylbutylamine, methyloctylamine, methyllaurylamine, and dibenzylamine. Specific examples of the tertiary amine include trimethylamine, triethylamine, tripropylamine, triisopropylamine, tri-n-butylamine, tri-sec-butylamine, tri-tert-butylamine, tripentylamine, trihexylamine, and trioctyl. Examples include amines and tribenzylamine. Of these, the secondary amines dimethylamine and diethylamine are particularly preferred.

  Specifically, the epihalohydrins in the polycondensate can be used from one or more selected from epichlorohydrin, epibromohydrin, epiiodohydrin, methyl epichlorohydrin, etc., and epichlorohydrin is particularly preferable.

  As a method for synthesizing the polycondensate, for example, known methods described in JP-A-10-152544 and JP-A-10-147057 can be used. About the obtained said condensation polymer, 1 type individual may be mix | blended with a coating liquid, and the thing of different polymerization degree may be mixed and you may mix | blend with a coating liquid. In addition, the said condensation polymer may use what was synthesize | combined appropriately, and may use a commercial item.

<Other chemicals>
In addition, the sizing agent, dye, fluorescent dye, water-retaining agent, water-resistant agent, pH adjuster, antifoaming agent, lubricant, preservative in the coating liquid to be the ink-receiving layer as long as the effect of the present invention is not impaired. It is possible to use additives such as surfactants, conductive agents, ultraviolet absorbers, and antioxidants. In particular, the addition of the sizing agent improves the sharpness of the printed part, so it is preferable to add it. In addition, when using various additives, it is preferable that it is cationic or nonionic from the point of compatibility with the said cationic resin.

<Coating method>
The method for adding a surface sizing liquid containing a sizing agent, a water-soluble binder, etc. to the base paper, and the method for adding the coating liquid for providing the ink receiving layer to the base paper are not particularly limited, and are known coatings. The base paper can be coated or impregnated by a construction method or an impregnation method. For example, as an impregnation method, impregnation using an impregnation type size press apparatus can be performed, and coating methods include various blade coaters, roll coaters, air knife coaters, bar coaters, curtain coaters, gravure coaters, gate roll coaters, Coating using a known coating apparatus such as a die coater can be performed.

<Drying method>
Next, the base paper is impregnated with the coating liquid and then dried. As a drying method, for example, a normal method using a steam heater, a gas heater, an infrared heater, an electric heater, a hot air heater, a microwave, a cylinder dryer, or the like can be performed. After drying, if necessary, finishing processes such as post-processing such as super calender and soft calender may be performed to impart smoothness, or other general paper processing means may be used. In addition, if necessary, one surface can be subjected to adhesive processing, lamination processing, or the like, and a coating layer for imparting various functions such as transportability, antistatic property, and writing property can also be provided.

<Example>
EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example. The following “parts” and “%” refer to “parts by weight” and “% by weight”, respectively, unless otherwise specified.

<Evaluation of fillers and pigments>
Measurement of average particle size: Sample (filler) slurry was dropped and mixed in pure water to which sodium hexametaphosphate 0.2% was added as a dispersant to prepare a uniform dispersion, and laser particle size measuring machine (Mastersizer S type: Malvern) The measurement was performed using
Oil absorption: Measured according to JIS-K5101.
BET specific surface area: Calculated from nitrogen adsorption amount using Gemini 2360 type (manufactured by Micromeritics).

<Evaluation of the base paper>
Ash content: Measured according to JIS-P8251.
Opacity: Measured according to ISO-2471 (JIS-P8149).

<Example 1>
For 100 parts of pulp slurry made of hardwood kraft pulp (freezing degree 350 ml csf), Rosetta type light calcium carbonate (Albuquer LO: manufactured by SMI, average particle size 2.4 μm, oil absorption 101 ml / 100 g) 20 parts, 0.4 part of internal sizing agent (NT-87: manufactured by Arakawa Chemical Co., Ltd.) and 0.8 part of cationized starch were added, and the paper was made to a basis weight of 80 g / m ² with a long net paper machine. A base paper was obtained. The ash content of the base paper was 16.2% and the opacity was 91.1%.
On both sides of this base paper, silica as a pigment (Fine Seal X37: manufactured by Tokuyama Corporation, oil absorption: 260 ml / 100 g, average particle diameter: 2.7 μm), 100 parts, and polyvinyl alcohol (PVA103: manufactured by Kuraray Co., Ltd.) as a binder 50 Part, 20 parts of cationic resin (polyamine ammonia epichlorohydrin, anion requirement 6 meq / g, molecular weight 100,000), 10 parts of cationic sizing agent (SE2250: manufactured by Seiko PMC) (solid content) 28%, B-type viscosity 300 mPa · s) at a blade coater of 500 m / min. The ink-receiving layer was formed by coating at a speed of, and after drying, calendering (linear pressure 1960 N / cm (200 kgf / cm) · 2 NIP) was performed to prepare an ink jet recording paper. The coating amount per side was 4.8 g / m ² .

<Example 2>
An ink jet recording paper was prepared by coating the base paper in the same manner as in Example 1 except that 100 parts of the synthetic silica A produced as described below was used. The coating amount per side was 4.9 g / m ² .
・ Synthetic silica A
(Production of synthetic silica A 1)
First step: Commercially available No. 3 sodium silicate (SiO ₂ : 20.0%, Na ₂ O: 9.5%) was diluted with water in a reaction vessel (200 L) to obtain 6.7% by mass as SiO _2. 200 L of diluted sodium silicate solution was prepared.
After heating this sodium silicate solution to 85 ° C., a dropping rate of 200 g / min of aluminum sulfate (concentration of 8% by mass or less of Al ₂ O ₃ minutes or less, indicated as “band”) corresponding to 20% of the neutralization equivalent. Then, an amount of sulfuric acid (concentration 98% by mass) corresponding to 30% of the neutralization equivalent was added under sufficient strong stirring as described above. After completion of the addition, the partially neutralized liquid obtained was aged while being stirred, and at the same time, the target particle size was 7 μm using a vertical sand grinder (capacity 7.57 L, filling rate of glass beads with a diameter of 1 mm of 70%). Was circulated and ground. This aging and pulverization treatment was performed for 3 hours.

Second step: Next, the slurry temperature is raised to 90 ° C., and sulfuric acid having the same concentration as in the first step is added up to 80% of the neutralization equivalent under the same conditions as in the first step. Aged. Third step: Subsequently, sulfuric acid having the same concentration as that described above was similarly added to the slurry after aging at an addition rate of 76 g / min, and the slurry pH was adjusted to 6.
Grinding by wet grinding; the slurry after completion of the third step was filtered, washed with water, repulped into pure water, and the hydrated silica slurry was recovered. The obtained slurry is diluted to a concentration indicating a liquid state, and this diluted slurry is put into a horizontal sand grinder having a filling rate of 80% of glass beads having a bead diameter of 0.6 to 0.8 mm (manufactured by Toyo Ballotini), Wet grinding was performed.
The wet pulverization time was adjusted to obtain synthetic silica A of silica having an oil absorption of 147 ml / 100 g, a BET specific surface area of 80 m ² / g, and an average particle size of 2.1 μm.

<Example 3>
Except for using 50 parts of synthetic silica A and 50 parts of light calcium carbonate (Tamapearl 123CS: manufactured by Okutama Kogyo Co., Ltd.), the pigment was applied to the base paper in the same manner as in Example 1 to prepare an ink jet recording paper. The coating amount per side was 4.7 g / m ² .

<Example 4>
Except that the pigment was 50 parts of silica (Fine Seal X37) and 50 parts of calcined kaolin (Ansilex 90: manufactured by Engelhard), it was coated on the base paper in the same manner as in Example 1 to prepare an ink jet recording paper. . The coating amount per side was 4.9 g / m ² .

<Example 5>
Except that the pigment was 50 parts of silica (Fine Seal X37) and 50 parts of light calcium carbonate (Tama Pearl 123CS: manufactured by Okutama Kogyo Co., Ltd.), it was coated on the base paper in the same manner as in Example 1 to prepare an ink jet recording paper. . The coating amount per side was 4.9 g / m ² .

<Example 6>
Example 1 except that the amount of Rosetta-type light calcium carbonate, which is a filler internally added to the base paper, was changed to 35 parts, the ash content of the base paper was 27.5%, and the opacity was 92.7%. Inkjet recording paper was produced in exactly the same manner. The coating amount per side was 5.0 g / m ² .

<Example 7>
An ink jet recording paper was prepared in exactly the same manner as in Example 1 except that the coating amount per side was 6.8 g / m ² .
< Comparative Example 5 >
An ink jet recording paper was produced in the same manner as in Example 1 except that the coating amount per side was 1.8 g / m ² .

<Example 8 >
As a filler internally added to the base paper, 20 parts of Rosetta-type light calcium carbonate (Albaca 5970: manufactured by SMI, average particle size 1.9 μm, oil absorption 123 ml / 100 g) was blended, and the ash content of the base paper was 15.7%. An ink jet recording paper was prepared in exactly the same manner as in Example 1 except that the opacity was 90.6%.

<Comparative Example 1>
As a filler to be internally added to the base paper, 20 parts of cubic light calcium carbonate (Unibur-70: manufactured by Shiraishi Kogyo Co., Ltd., average particle size 2.4 μm, oil absorption 50 ml / 100 g) is blended, and the ash content of the base paper is 15 An ink jet recording paper was prepared in exactly the same manner as in Example 1 except that the content was 0.7% and the opacity was 86.4%. The coating amount per side was 4.9 g / m ² .
<Comparative example 2>
As a filler to be internally added to the base paper, 20 parts of spindle-shaped light calcium carbonate (PC: manufactured by Shiroishi Kogyo Co., Ltd., average particle size 3.0 μm, oil absorption 40 ml / 100 g) is blended, and the ash content of the base paper is 15.7. %, And an opacity of 87.8%, an ink jet recording paper was prepared in exactly the same manner as in Example 1. The coating amount per side was 4.8 g / m ² .

<Comparative Example 3>
20 parts of Rosetta type light calcium carbonate (Albuquer HO: manufactured by SMI, average particle size 1.3 μm, oil absorption 125 ml / 100 g) was blended as a filler internally added to the base paper, and the ash content of the base paper was 15.9%. An ink jet recording paper was prepared in exactly the same manner as in Example 1 except that the opacity was 87.8%. The coating amount per side was 5.0 g / m ² .

<Comparative example 4>
Example 1 except that the amount of Rosetta-type light calcium carbonate, which is a filler internally added to the base paper, was changed to 15 parts, the ash content of the base paper was 11.2%, and the opacity was 88.9%. Inkjet recording paper was produced in exactly the same manner. The coating amount per side was 5.1 g / m ² .

<Evaluation of coated paper: inkjet recording with dye ink>
For each recording paper, inkjet recording was performed using a commercially available dye inkjet printer PM-G820 (manufactured by Seiko Epson Corporation), and printability was evaluated according to the following evaluation items. The evaluation results are shown in Table 1.
<Evaluation items>
1) Print density (color development)
After printing a black solid print pattern with the inkjet printer, the print density on the print surface was measured with a Macbeth densitometer (RD918).

  If the following evaluations are ◎, ○, △, they can be used practically without problems.

A: Density value exceeds 1.60 O: Density value exceeds 1.50 and 1.60 or less Δ: Density value exceeds 1.40 and 1.50 or less X: Density value 2) Back-through The black solid print pattern was printed with the inkjet printer, and then the print density on the back side of the print surface was measured with a Macbeth densitometer (RD918).

  If the following evaluations are ◎, ○, △, they can be used practically without problems.

A: Concentration value is 0.10 or less. O: Concentration value exceeds 0.10 and 0.12 or less. Δ: Concentration value exceeds 0.12 and 0.15 or less. 3) Ink absorbability with a value exceeding 0.15 The ink absorbability when a black solid print pattern was printed by the inkjet printer was visually evaluated.

  If the following evaluations are ◎, ○, △, they can be used practically without problems.

◎: Absorption is very fast ○: Absorption is fast △: Absorption is a little slow ×: Absorption is slow, and dirt on the device and printed parts occur

<Evaluation of coated paper: inkjet recording with water-based pigment ink>
For each recording paper, inkjet recording was performed using a commercially available pigment inkjet printer PX-G920 (manufactured by Seiko Epson Corporation), and printability was evaluated according to the following evaluation items. The evaluation results are shown in Table 1.
<Evaluation items>
4) Print density (color development)
After printing a black solid print pattern with the inkjet printer, the print density on the print surface was measured with a Macbeth densitometer (RD918).

  If the following evaluations are ◎, ○, △, they can be used practically without problems.

A: Density value exceeds 1.80 O: Density value exceeds 1.60 and is 1.80 or less Δ: Density value exceeds 1.40 and is 1.60 or less ×: Density value 5) Back-through After printing a black solid print pattern with the above-mentioned inkjet printer, the print density on the back side of the print surface was measured with a Macbeth densitometer (RD918).

  If the following evaluations are ◎, ○, △, they can be used practically without problems.

A: Concentration value is 0.10 or less. O: Concentration value exceeds 0.10 and 0.12 or less. Δ: Concentration value exceeds 0.12 and 0.15 or less. The value exceeds 0.15. 6) Ink Absorbency The ink absorbency when a black solid print pattern was printed by the inkjet printer was visually evaluated.

  If the following evaluations are ◎, ○, △, they can be used practically without problems.

◎: Absorption is very fast ○: Absorption is fast △: Absorption is a little slow ×: Absorption is slow, and dirt on the device and printed parts occur

As shown in Table 1, in each example, the evaluation of printing density, anti-through-through property, and ink absorbency was good. In Example 6 in which Rosetta-type light calcium carbonate was blended in a high amount, the printing density of the dye ink was slightly inferior, but the printing density of the pigment ink was sufficiently high. Further, Comparative Example 5 in which the coating amount of the ink receiving layer was 1.8 g / m ² per side was slightly inferior in print density and ink absorbability . On the other hand, Comparative Example 1 using prismatic light calcium carbonate, Comparative Example 2 using spindle-shaped light calcium carbonate, Comparative Example 3 in which the particle size of Rosetta-type light calcium carbonate is less than 1.6 μm, base paper In Comparative Example 4 in which the ash content was 15% or less, show-through occurred during printing.

It is a figure which shows an example of the electron microscope image of the secondary particle shape of a rosetta type light calcium carbonate.

Claims (3)

Pigment and binder on at least one side of a base paper mainly composed of pulp and a filler mainly composed of rosetta-type light calcium carbonate having an average particle size of 1.6 μm or more and an oil absorption of 90 to 200 ml / 100 g an inkjet recording sheet which is provided one or more layers an ink receiving layer containing, at 15% to 40% ash content prescribed in JIS-P8251 of the base paper, coating amount of the ink receiving layer 2～7G / 10 to 100% by weight of synthetic silica having an oil absorption of 90 to 200 ml / 100 g, a BET specific surface area of 45 to ²⁰⁰ m ² / g, and an average particle size of 1.0 to 3.0 μm as a pigment in the ink receiving layer at m ² ink-jet recording paper to be. The inkjet recording paper according to claim 1, wherein the synthetic silica is obtained by wet-grinding a synthetic silica slurry obtained by neutralizing a sodium silicate aqueous solution with a mineral acid and / or an acidic metal salt aqueous solution. The inkjet recording paper according to claim 2, wherein the synthetic silica is a synthetic silica obtained by neutralizing a sodium silicate aqueous solution with an aluminum sulfate aqueous solution.

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