JP2007090606A - Inkjet recording sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording sheet which shows high printing density and ink absorbency even when water-based ink, not to mention non-water-based ink, is used, and moreover prevents strike through. <P>SOLUTION: In the inkjet recording paper, one or more ink accepting layers containing a pigment and a binder are formed on at least one side of base paper which is constituted by containing in pulp a loading material constituted mainly of a light calcium carbonate-silica composite having an average particle diameter of 1.0 μm or more and rosette type light calcium carbonate having an average particle diameter of 1.6 μm or more. The ash of the base paper stipulated in JIS-P 8251 is 15-40%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a coated paper type ink jet recording paper having 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 method is widely used for home use because it is easy to increase the speed and full color, and has low noise during recording and a low cost apparatus. On the other hand, in the field of commercial use, variable information (such as utility bills, credit bills, receipts, delivery slips, and advertisements) has been printed using non-impact (NIP) printing. It has been replaced with printing by a high-speed inkjet printer having a head.
Ink jet recording media are roughly classified into a plain paper type without an ink receiving layer containing a pigment and a coated paper type with an ink receiving layer. Usually, an inexpensive plain paper type is mainly used for printing business reports, and a coated paper type capable of reproducing a high-definition image is mainly used for image output of a digital camera. Along with the expansion of the application of such ink jet recording, a coated paper type ink jet recording medium capable of reproducing a high-definition image at low cost has been demanded.

In the case of a coated paper type ink jet recording medium, since an expensive material such as silica is generally blended in the ink receiving layer in a large amount, the ink receiving layer is made thin as a cost reduction measure. However, when the ink receiving layer is made thin, ink that cannot be absorbed by the ink receiving layer penetrates into the base paper, and a problem called back-through occurs in which a printed image can be seen through the back surface of the paper. In particular, in recent years, in order to obtain a higher definition image, there is a tendency to print by dropping a large amount of low density ink.
Also, when printing with pigment ink on a conventional ink jet recording medium, the printing density tends to be lower than when printing with dye ink. For these reasons, there is a need for an ink jet recording medium that has good color developability regardless of whether dye ink or pigment ink is used.

Therefore, a coated paper type in which light calcium carbonate is added as a filler to a base paper and an ink receiving layer is provided on the base paper as an ink jet recording medium having good ink absorbency even if the ink receiving layer is thin. Have been proposed (see, for example, Patent Document 1).
Further, as an ink jet recording paper for non-aqueous ink, a plain paper type ink jet recording paper in which Rosetta-type light calcium carbonate is added as a filler and ash content is 20 to 40% has been proposed (for example, see Patent Document 2). ).
In addition, as a coated paper type inkjet recording medium suitable for high-speed coating, a recording medium containing a light calcium carbonate-silica composite in the ink receiving layer has been proposed (for example, see Patent Document 3).
Japanese Patent Application Laid-Open No. 64-30780 JP 2005-193660 A JP-A-2005-96437

However, in the case of the technique described in Patent Document 1, the light calcium carbonate used for the filler has a small particle size and a low oil absorption, so the opacity of the base paper is low, and the effect of preventing back-through is not sufficient.
The technique described in Patent Document 2 is suitable for non-aqueous inks, but it is difficult to sufficiently prevent show-through when printing is performed using aqueous inks.
Further, in the case of the technique described in Patent Document 3, prevention of show-through is not sufficient.
Accordingly, an object of the present invention is to provide an ink jet recording paper that has high print density and ink absorbency and can prevent back-through even when water-based ink is used as well as non-water-based ink.

As a result of intensive studies, the present inventors have found that the above problem can be solved by using a base paper having a light calcium carbonate-silica composite having a predetermined particle size and rosetta-type calcium carbonate as a filler.
That is, in order to achieve the above object, the ink jet recording paper of the present invention comprises a light calcium carbonate-silica composite having an average particle diameter of 1.0 μm or more and a rosetta type light calcium carbonate having an average particle diameter of 1.6 μm or more. An ink-jet recording paper in which at least one ink receiving layer containing a pigment and a binder is formed on at least one surface of a base paper containing a filler mainly composed of The ash content specified in JIS-P8251 is 15 to 40%.

In the light calcium carbonate-silica composite and the rosetta-type light calcium carbonate in the base paper, the solid content mass ratio represented by (light calcium carbonate-silica composite / rosetta-type light calcium carbonate) is 70/30 to Preferably it is 30/70.
The light calcium carbonate-silica composite is preferably formed by coating the surface of light calcium carbonate fine particles with silica fine particles.
In the light calcium carbonate-silica composite, the solid content mass ratio represented by (CaCO ₃ / SiO ₂ ) is preferably 30/70 to 70/30, and the coating amount of the ink receiving layer is 2 to 7 g. / M ² is preferable.
The pigment of the ink receiving layer preferably contains 10 to 100% by mass of synthetic silica. The 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 size. It is preferable that it is 1.0-3.0 micrometers.

  According to the present invention, it is possible to obtain an ink jet recording sheet that has high print density and ink absorbency and prevents back-through even when water-based ink as well as non-water-based ink is used.

The ink jet recording paper of the present invention is of a coated paper type in which an ink receiving layer is provided on a base paper containing the following filler.
1. Base paper
<Pulp>
The base paper is made from paper made of wood pulp, fillers, auxiliaries and the like. Examples of the wood pulp include known chemical pulp, mechanical pulp, and deinked pulp. Moreover, these various pulps are used independently as needed, or are used together. As the pulp, conventionally known ones commonly 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 include chemical pulp such as (NBSP); mechanical pulp such as groundwood pulp (GP) and thermomechanical pulp (TMP); wood pulp such as waste paper pulp (DIP). Further, non-wood pulp such as cotton pulp, hemp, bagasse, kenaf, esparto, cocoon, trifoam, and husk can be used.
The pH of the base paper is not particularly limited and may be any of acidic, neutral, and alkaline.

<Filler>
The filler contains light calcium carbonate-silica composite and rosetta-type light calcium carbonate as essential components. An ink jet recording paper using a base paper containing both a light calcium carbonate-silica composite and a rosetta type light calcium carbonate has high ink absorptivity and prevention of see-through. In particular, when this is done, the ink absorptivity and back-through prevention effect of the base paper itself are increased. Therefore, even when the coating amount of the ink receiving layer is small, the ink absorption and back-through prevention effect are sufficiently obtained. Can be improved.

(Light calcium carbonate-silica composite)
The light calcium carbonate-silica composite is considered to have both the characteristics of silica and the characteristics of light calcium carbonate, and can achieve both ink absorbability and opacity (prevention of back-through).
The average particle size of the light calcium carbonate-silica composite needs to be 1.0 μm or more. When the average particle diameter is less than 1.0 μm, the amount of voids in the composite decreases, and the ink absorbability decreases. The average particle diameter is preferably 1.6 to 10.0 μm. When the average particle diameter exceeds 10.0 μm, the distribution of the particles in the base paper becomes non-uniform, the opacity of the base paper is lowered, and there is a tendency that the back-through occurs or a stable quality cannot be obtained. .
The oil absorption of the light calcium carbonate-silica composite is preferably 100 to 300 ml / 100 g, particularly preferably 100 to 200 ml / 100 g. If the oil absorption is less than 100 ml / 100 g, the ink absorbability may be lowered. On the other hand, when the oil absorption exceeds 300 ml / 100 g, the absorbability of the base paper becomes too large, and when the ink receiving layer coating liquid is applied, the binder component penetrates into the base paper and the surface of the ink receiving layer. Since the strength decreases, powder may fall off during cutting.

(Preferred form of light calcium carbonate-silica composite)
As the light calcium carbonate-silica composite, those obtained by coating light calcium carbonate fine particles as nuclei and coating the surface with silica fine particles are preferable. FIG. 2 is an SEM image showing an example of the form of light calcium carbonate-silica composite particles dispersed in a liquid. According to FIG. 2, it can be seen that substantially spherical silica primary particles are bonded (precipitated) to the surface of light calcium carbonate. In the example of FIG. 2, there are three composite particles.

As shown in FIG. 2, a light calcium carbonate-silica composite in which silica primary particles are deposited on the surface of light calcium carbonate fine particles can be specifically produced by the following method.
First, the light calcium carbonate is dispersed in water. The amount of dispersion in water is preferably 1 to 20% by mass in terms of solid content in consideration of the effect of addition of silicic acid described later. When the dispersion amount is less than 1% by mass, the production amount per batch is small and the productivity is low, and when it exceeds 20% by mass, the dispersibility is lowered, and the alkali silicate used for the reaction with the light calcium carbonate amount. In some cases, the concentration of is increased, the viscosity during the reaction is increased, and the operability is lowered.
Next, an alkali solution of silicic acid (alkali is, for example, sodium or potassium) is added to the slurry. Although the molar ratio of silicic acid and alkali is not limited, No. 3 silicic acid (SiO ₂ / Na ₂ O = (3-3.4) / 1) is generally easily available and can be suitably used. The solid mass ratio (CaCO ₃ / SiO ₂ ) of the intended light calcium carbonate-silica composite can be adjusted by adjusting the charging mass ratio between the light calcium carbonate and the alkali solution of silicic acid.
Next, these mixtures are stirred and dispersed with an agitator, a homomixer, a mixer or the like. Light calcium carbonate may be appropriately dispersed without excessive aggregation, and the dispersion time and the strength of agitation are not limited.

Next, this solution is neutralized with a mineral acid. Any mineral acid may be used, for example, sulfuric acid, hydrochloric acid, etc., which can be obtained at low cost. The mineral acid may contain an acidic metal salt such as a sulfate band or magnesium sulfate. Addition of mineral acid (or acid containing the above acidic metal salt aqueous solution in mineral acid) is performed at a temperature not higher than the boiling point of the above mixture, and deposits silicic acid on the surface of light calcium carbonate particles to form amorphous silicic acid. Form and coat to obtain a light calcium carbonate-silica composite. It is important to complete this neutralization reaction at pH = 7-9. If the pH is less than 7, decomposition of light calcium carbonate occurs. If the pH exceeds 9, precipitation of silicic acid is not performed sufficiently, and unreacted silicic acid remains. This is not preferable because it causes loss.
In addition, since the amount of the whole liquid will increase when the acid concentration is low, the acid concentration is preferably 0.05 N or more. However, when the acid concentration is increased, a portion having a low pH is generated in the liquid due to the addition of the acid, and light calcium carbonate is decomposed. Therefore, it is necessary to perform strong stirring using a homomixer or the like at the acid addition port. The acid addition may be performed in several times.

In this way, a suspension in which the surface of the light calcium carbonate particles is coated with silica is obtained. This suspension may be used as it is in the papermaking process, etc., but if the production is small, use filtration equipment such as filter paper or a membrane filter. It is preferable to perform solid-liquid separation using filtration using a drum filter or the like, or centrifugal separation using a centrifugal separator, and to remove as much as possible the salt that is a by-product generated by the neutralization reaction. If this salt remains, it changes into a hardly soluble metal salt (for example, calcium sulfate) in the paper making process, which may cause scaling. Further, the cake after the solid-liquid separation (usually the solid content concentration of 10 to 50%) may be re-dispersed with water or ethanol and then solid-liquid separated again to further remove excess silicic acid or salt.
Furthermore, coarse particles (for example, 100 μm or more) are appropriately removed from the obtained light calcium carbonate-silica composite using a vibrating sieve or a screen.
The average particle size of the light calcium carbonate-silica composite is adjusted by wet stirring or pulverization during aging during the neutralization reaction, or after completion of the neutralization reaction, or by solid-liquid separation after completion of the reaction. It can be performed by pulverization using a pulverizer. These methods may be combined. The aging means that the addition of the acid to be added at the time of neutralization is temporarily interrupted and left only after stirring.

In the light calcium carbonate-silica composite, the solid content mass ratio represented by (CaCO ₃ / SiO ₂ ) is preferably 30/70 to 70/30. When the ratio is less than 30/70, the characteristics of the silica are manifested as a whole, so that the opacity is lowered and the back-through of the recorded image is likely to occur. On the other hand, when the ratio exceeds 70/30, the characteristics of light calcium carbonate are greatly exhibited, so that the ink absorbability is lowered and the back-through is likely to occur, and the bulkiness is lowered and the transparency of the support is decreased. Temper is also likely to decrease.
Solid content mass ratio can be calculated | required by carrying out the fluorescent X ray analysis of a light calcium carbonate-silica composite, and quantifying Ca and Si, for example.

(Rosetta-type light calcium carbonate)
Rosette type light calcium carbonate is obtained by agglomerating primary particles of spindle-shaped light calcium carbonate in a radial manner to form rosette type secondary particles. 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.
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.

Light calcium carbonate is excellent in production cost and operability, and has a characteristic that high opacity can be obtained with a small addition amount. Furthermore, since the rosette type light calcium carbonate has the special shape described above, increasing the blending amount of the base paper improves the opacity of the base paper and effectively prevents back-through.
Specific examples of Rosetta-type light calcium carbonate include Specialty Minerals Inc. Preferable examples include products such as Albaca HO, Albaca 5970, and Albaca LO manufactured by SMI.

The average particle size of Rosetta-type light calcium carbonate must be 1.6 μm or more. When the particle diameter is less than 1.6 μm, light transmittance is improved, and the opaqueness of the base paper is lowered, so that the back-through occurs. The average particle size of the rosetta type light calcium carbonate is preferably 1.6 to 5.0 μm. When the average particle diameter exceeds 5.0 μm, the distribution of the particles in the base paper becomes non-uniform, the opacity of the base paper is lowered, and there is a tendency that the back-through occurs or a stable quality cannot be obtained. .
The oil absorption of Rosetta-type light calcium carbonate is preferably 90 to 200 ml / 100 g, and particularly preferably 90 to 140 ml / 100 g. If the oil absorption is less than 90 ml / 100 g, the ink absorbability may be lowered. On the other hand, if the oil absorption exceeds 200 ml / 100 g, the absorbability of the base paper becomes too large, and the binder component penetrates into the base paper when the ink receiving layer coating liquid is applied, and the surface of the ink receiving layer. Since the strength decreases, powder may fall off during cutting.

(Combination ratio of each filler)
In the light calcium carbonate-silica composite and the rosetta type light calcium carbonate in the base paper, the solid content mass ratio represented by (light calcium carbonate-silica composite / rosetta type light calcium carbonate) is 70/30 to 30-30. / 70 is preferable. When the ratio exceeds 70/30, the absorbability of the base paper becomes too large, and when the ink receiving layer coating liquid is applied, the binder component penetrates into the base paper and the surface strength of the ink receiving layer is increased. It may decrease, causing problems such as powder falling during cutting. On the other hand, when the ratio is less than 30/70, the opacity of the base paper is lowered, and it becomes easy to see through.

(Other fillers)
As long as the effects of the present invention are not impaired, fillers other than the light calcium carbonate-silica composite and the rosetta type light calcium carbonate can be blended according to the pH of the base paper. For example, conventionally used inorganic fine particles such as light calcium carbonate, heavy calcium carbonate, kaolin, talc, clay, silica, white carbon, aluminum hydroxide, and zeolite, which have a different shape from the above composite, are used as fillers. can do.

<Ash content>
The ash content defined in JIS-P8251 of the base paper is required to be 15 to 40%, preferably 15 to 30%. When the ash content is 15 to 40%, the opacity of the paper is increased, and the effect of preventing see-through is improved. In addition, the ink absorbability is improved and a printed matter without blurring of the image can be obtained, and further, see-through is prevented. 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 mass of the sample.
In addition, since the ink jet recording paper of the present invention uses the above-mentioned base paper, the back-through after printing is small and suitable for double-sided printing.

<Basic papermaking>
As the paper machine used for making the base paper, known apparatuses such as a long net paper machine, an on-top twin-wire paper machine, and a gap former can be used. Further, in the base paper, a paper strength enhancer, an antifoaming agent, a pH adjusting agent, a dye or colored pigment for adjusting the hue, and a visual whiteness are improved within a range not impairing the effects of the present invention. Internal additives for papermaking such as fluorescent dyes can be internally added.

2. Ink-receiving layer The ink-receiving layer is provided on at least one side of the base paper and contains a pigment and a binder. When performing double-sided printing, the ink receiving layer can be applied to both sides of the base paper.
<Pigment>
Synthetic silica can be used as the pigment, but alumina and alumina hydrate (alumina sol, colloidal alumina, pseudoboehmite, etc.), aluminum silicate, magnesium silicate, calcium silicate, magnesium carbonate, light calcium carbonate, heavy carbonate Those usually used as coated paper pigments such as calcium, kaolin, talc, calcium sulfate, titanium dioxide, zinc oxide, zinc carbonate, aluminum hydroxide, and calcined kaolin can be used alone or in combination.

(Synthetic silica)
The pigment preferably contains 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. 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.
More preferably, the synthetic silica has an oil absorption of 100 to 180 ml / 100 g and a BET specific surface area of 60 to ²⁰⁰ m ² / g.
When the oil absorption amount of the synthetic silica is less than 90 ml / 100 g, the ink absorbability of the ink receiving layer decreases, and when the oil absorption amount exceeds 200 ml / 100 g, the surface strength of the ink receiving layer tends to decrease.
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 ink receiving layer or the base paper, resulting in a decrease in printing 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).
In addition, it is preferable that the content rate of a synthetic silica is 10-100 mass% with respect to the whole pigment in an ink receiving layer, More preferably, it is 30-70 mass%.

When the synthetic silica slurry obtained by neutralizing a sodium silicate aqueous solution with a mineral acid and / or acidic metal salt aqueous solution as a result of wet pulverization is used as the synthetic silica, ink jet suitability and offset printing suitability are used. 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, and aluminum. Examples of the acidic metal salt aqueous solution include acidic metal sulfate. In particular, it is preferable to use an aluminum sulfate aqueous solution that is an acidic metal sulfate because the solid content concentration of the coating solution can be increased.
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 sodium silicate is neutralized 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 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 are 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 binders 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 ester. Examples include modified starch.

<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.
The cationic resin is a cationic water-soluble polymer, and it is more preferable to use 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 the 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 exceeds 200,000. In some cases, the ink 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 may be greatly reduced. Further, if the anion requirement of the cationic resin is 5 meq / g or less, the ink fixing ability may not be sufficient.

Examples of the cationic resin include polyethylenimine quaternary ammonium salt derivatives; ammonia, dialkylamine, epihalohydrin condensation polymer; polyamine polyamide epihalohydrin, dicyanamide, formaldehyde resin; diethylenetriamine, dicyandiamide, ammonium chloride polymer; dimethyldiallylammonium chloride polymer, etc. Is exemplified. Among these, it is particularly preferable to use a polycondensation product obtained by reacting ammonia, amines and epihalohydrins since ink fixing properties are improved.
Examples of the amines used in the polycondensation 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, as the epihalohydrin in the polycondensate, one or more selected from epichlorohydrin, epibromohydrin, epiiodohydrin, methyl epichlorohydrin, and the like can be used, and epichlorohydrin is particularly used. It is 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. One of the above condensation polymers may be blended alone in the ink-receiving layer coating solution, or one having a different polymerization degree may be mixed and blended in the coating solution. In addition, the said polycondensate may use what was synthesize | combined appropriately, and may use a commercial item.

<Other ingredients>
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 add additives such as a surfactant, a conductive agent, an ultraviolet absorber, and an antioxidant. In particular, the addition of a sizing agent is preferable because the sharpness of the printed portion is improved. In addition, as each above-mentioned additive, it is preferable to use a cationic or nonionic thing from a compatible point with the said cationic resin.

<Coating of ink receiving layer>
The coating amount of the ink receiving layer is preferably ² to 7 g / m ² , particularly preferably 4 to 7 g / m ² per side. When the coating amount is less than 2 g / m ^2, it is difficult to uniformly coat and coat the surface of the base paper, and thus ink absorption unevenness occurs, and the inkjet suitability tends to be greatly reduced (non-solid printing failure). Uniform). On the other hand, when the coating amount is more than 7 g / m ² , the ink absorbability is good, but powder falling off easily occurs when the recording paper is cut. Further, since the amount of silica used in the ink receiving layer increases, the cost may increase.
(Coating method)
The method for coating the ink receiving layer is not particularly limited, and a known coating method or impregnation method can be applied. For example, impregnation using an impregnation type size press apparatus can be performed. As a coating method, it is possible to perform coating using a known coating apparatus such as various blade coaters, roll coaters, air knife coaters, bar coaters, curtain coaters, gravure coaters, gate roll coaters, die coaters and the like.
The same applies to a method of adding a surface sizing solution containing a sizing agent, a water-soluble binder, and the like to the base paper.
(Drying method)
As a method for drying the coating liquid, 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. Further, after drying, if necessary, finishing processes such as super calendering and soft calendering which are post-processing may be performed to impart smoothness, or other general paper processing means may be used. Further, if necessary, adhesive processing, laminating processing, or the like can be performed on one side of the recording paper, 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 mass” and “mass%”, respectively, unless otherwise specified.

<Production of light calcium carbonate-silica composite>
1) Light calcium carbonate-silica composite A
In a reaction vessel (12 L), 603 g of commercially available Rosetta-type light calcium carbonate (Albaca 5970: manufactured by SMI, average particle size 1.9 μm, oil absorption 123 ml / 100 g) was dispersed in water, and this was mixed with a sodium silicate solution (SiO 2 ₍₂ concentration 18.0 wt / wt%, Na ₂ O concentration 6.1 wt / wt%) 3400 g was added, then water was added to make the total volume 12 L. This mixed slurry was heated to 85 ° C. with sufficient stirring with a laboratory agitator. A 10% sulfuric acid solution was added to the slurry by a rotary pump, and at this time, the sulfuric acid-added portion was added immediately below the stirring blade of the laboratory agitator. Under the above conditions in which the added sulfuric acid was sufficiently dispersed, sulfuric acid was added at a constant temperature and at a constant rate so that the final pH of the slurry after completion of sulfuric acid addition was 8.0 and the total sulfuric acid addition time was 240 minutes. After the obtained slurry was passed through a 100 mesh sieve to separate coarse particles, No. Suction filtration was performed using 2 filter papers. Further, the filtrate was redispersed in water so that the solid content was 10% by mass, and a light calcium carbonate-silica composite A having a light calcium carbonate / silica mass ratio of 50/50 was obtained.
The composite had an oil absorption of 160 ml / 100 g, a BET specific surface area of 28 m ² / g, and an average particle size of 6.1 μm. The sample after suction filtration was redispersed in ethanol so that the filtrate was 10% by mass in solids, filtered, and dried at 105 ° C to measure oil absorption and the like. Provided.
2) Light calcium carbonate-silica composite B
Except that the amount of dispersion of the Rosetta-type light calcium carbonate was 1407 g, the light calcium carbonate / silica mass ratio was 70/30 and the oil absorption was exactly the same as the production of the light calcium carbonate-silica composite A. A light calcium carbonate-silica composite B having 150 ml / 100 g, a BET specific surface area of 26 m ² / g, and an average particle size of 4.6 μm was obtained.

For 100 parts of pulp slurry consisting of hardwood kraft pulp (freeness 350 ml csf), as filler, 10 parts of light calcium carbonate-silica composite A and Rosetta type light calcium carbonate (Albaca LO: manufactured by SMI, 10 parts of average particle size 2.4 μm, oil absorption 101 ml / 100 g) was added, 0.4 parts of internal sizing agent (NT-87: Arakawa Chemical Co., Ltd.) and 0.8 parts of cationized starch were added. Paper was made with a long paper machine to a basis weight of 80 g / m ² to obtain a base paper. In addition, the yield regulator was added to adjust the yield of the filler, and the solid content mass ratio represented by 16.2% ash content (light calcium carbonate-silica composite / rosetta type light calcium carbonate) was 50/50, A base paper with an opacity of 91.8% was obtained.
Synthetic silica as a pigment (Fine Seal X37: manufactured by Tokuyama Corporation, oil absorption: 260 ml / 100 g, average particle size: 2.7 μm) on both surfaces of the base paper, and polyvinyl alcohol (PVA103: manufactured by Kuraray Co., Ltd.) as a binder. 50 parts, 20 parts of cationic resin (polyamine ammonia epichlorohydrin, anion requirement 6 meq / g, molecular weight 100,000), and 10 parts of cationic sizing agent (SE2250: manufactured by Seiko PMC) ( Solid content 28%, B-type viscosity 300 mPa · s) with a blade coater 500 m / min. The ink-receiving layer was provided by coating at a speed of
After the ink receiving layer was dried, it was further calendered (linear pressure 1960 N / cm (200 kgf / cm) · 2 NIP) to prepare an ink jet recording paper. The coating amount of the ink receiving layer per side was 4.8 g / m ² .

Ink jet recording was carried out in the same manner as in Example 1, except that 10 parts of light calcium carbonate-silica composite B and 10 parts of rosetta type light calcium carbonate (Albaca LO) were added as fillers for the base paper. A paper was prepared.
The ash content of the base paper was 16.0%, and the ratio of light calcium carbonate-silica composite / Rosetta-type light calcium carbonate 9 was 50/50, and the opacity was 91.6%. The coating amount per unit was 5.0 g / m ² .

An ink jet recording paper was produced in the same manner as in Example 1 except that 100 parts of synthetic silica A produced by the following method was used instead of the silica as a pigment in the ink receiving layer coating solution. The coating amount per side of the ink receiving layer was 4.9 g / m ² .
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 as SiO _2. A 200% by weight diluted sodium silicate solution 200L 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. And added with sufficient vigorous stirring so that no coarse gel was generated. Thereafter, an amount of sulfuric acid (concentration: 98% by mass) corresponding to 30% of the neutralization equivalent was added with sufficient vigorous stirring as described above. After completion of the addition, the partially neutralized liquid obtained was aged while being stirred, and at the same time, a vertical sand grinder (capacity 7.57 L, filling rate of glass beads having a diameter of 1 mm of 70%) was used to target a particle size of 7 μm. As a circulating pulverization process. The aging and pulverization processes were performed for 3 hours.
(2) Second step: Next, the slurry temperature is raised to 90 ° C., 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, and 32 with stirring. Aged for a minute.
(3) 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 to adjust the slurry pH to 6.
(4) 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 showing a liquid state, and this diluted slurry is put into a horizontal sand grinder filled with glass beads having a bead diameter of 0.6 to 0.8 mm (manufactured by Toyo Ballotini) at a filling rate of 80%. Wet pulverization was performed.
The wet pulverization time was adjusted to obtain synthetic silica A 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.

Ink jet recording paper was prepared in exactly the same manner as in Example 1 except that the amount of Rosetta-type light calcium carbonate in the base paper filler was changed to 25 parts.
The ash content of the base paper was 28.1%, the ratio of (light calcium carbonate-silica composite / rosetta type light calcium carbonate) was 29/71, and the opacity was 92.9%. The coating amount per side of the ink receiving layer was 5.0 g / m ² .

Of the base paper filler, as Rosetta-type light calcium carbonate, it was carried out except that 10 parts of the trade name Albaca 5970 (manufactured by SMI, average particle size 1.9 μm, oil absorption 123 ml / 100 g) was blended instead of the above. Inkjet recording paper was prepared exactly as in Example 1.
The ash content of the base paper was 15.9%, the ratio of (light calcium carbonate-silica composite / rosetta type light calcium carbonate) was 50/50, and the opacity was 91.6%. The coating amount per side of the ink receiving layer was 5.0 g / m ² .

An ink jet recording paper was prepared in exactly the same manner as in Example 1 except that the coating amount per side of the ink receiving layer was 6.8 g / m ² .

An ink jet recording paper was prepared in exactly the same manner as in Example 1 except that the coating amount per side of the ink receiving layer was 1.5 g / m ² .

<Comparative Example 1>
Of the base paper filler, 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 used instead of the above rosette type light calcium carbonate (Albaca LO). An ink jet recording paper was produced in the same manner as in Example 1 except that 10 parts were blended.
The base paper had an ash content of 16.1% and an opacity of 90.5%. The coating amount per side of the ink receiving layer was 4.9 g / m ² .

<Comparative Example 2>
Of the base paper filler, 10 parts of spindle-shaped light calcium carbonate (PC: manufactured by Shiraishi Kogyo Co., Ltd., average particle size 3.0 μm, oil absorption 40 ml / 100 g) instead of the above rosette type light calcium carbonate (Albaca LO) An ink jet recording paper was produced in the same manner as in Example 1 except that it was blended.
The ash content of the base paper was 16.0%, and the opacity was 90.4%. The coating amount per side of the ink receiving layer was 5.0 g / m ² .

<Comparative Example 3>
Of the base paper filler, as Rosetta-type light calcium carbonate, it was implemented except that 10 parts of the trade name Albaca HO (manufactured by SMI, average particle size 1.3 μm, oil absorption 125 ml / 100 g) was blended instead of the above. Inkjet recording paper was prepared exactly as in Example 1.
The base paper had an ash content of 15.9% and an opacity of 90.8%. The coating amount per side of the ink receiving layer was 5.0 g / m ² .

<Comparative Example 4>
Among the fillers of the base paper, the blending amount of the light calcium carbonate-silica composite A is changed to 7 parts, and the blending amount of the rosetta type light calcium carbonate (Albaca LO) is changed to 7 parts blending, An ink jet recording paper was prepared in exactly the same manner as in Example 1.
The ash content of the base paper was 11.2%, and the opacity was 89.1%. The coating amount per side of the ink receiving layer was 5.1 g / m ² .

<Comparative Example 5>
Of the filler of the base paper, the blending amount of the light calcium carbonate-silica composite A was changed to 20 parts, and the Rosetta-type light calcium carbonate (Albaca LO) was not blended. In the same manner, an inkjet recording paper was produced.
The ash content of the base paper was 16.2% and the opacity was 92.5%. The coating amount per side of the ink receiving layer was 5.1 g / m ² .

<Comparative Example 6>
Except that the light calcium carbonate-silica composite A was not blended in the base paper filler, and the amount of the Rosetta light calcium carbonate (Albaca LO) was changed to 20 parts, it was exactly the same as Example 1. Thus, an inkjet recording paper was prepared.
The base paper had an ash content of 16.4% and an opacity of 90.9%. The coating amount per side of the ink receiving layer was 4.8 g / m ² .

<Comparative Example 7>
An ink jet recording paper was prepared in the same manner as in Example 1 except that 10 parts of the synthetic silica A was blended in place of the light calcium carbonate-silica composite A in the base paper filler.
The base paper had an ash content of 16.1% and an opacity of 90.5%. The coating amount per side of the ink receiving layer was 5.0 g / m ² .

<Evaluation>
1. Characteristics of filler and pigment (1) Measurement of average particle diameter: Sample (filler or pigment) slurry is dropped and mixed into pure water to which 0.2% sodium hexametaphosphate is added as a dispersant to form a uniform dispersion, and laser It measured using the method particle size measuring machine (Mastersizer S type | mold: Malvern company make).
(2) Oil absorption: measured in accordance with JIS-K5101.
(3) BET specific surface area: It was calculated from the nitrogen adsorption amount using Gemini 2360 type (manufactured by Micromeritics).
2. Characteristics of base paper (1) Ash content: Measured according to JIS-P8251.
(2) Opacity: Measured according to ISO-2471 (JIS-P8149).

3. Water-based dye ink suitability For the ink-jet recording paper of each Example and Comparative Example, the following pattern was recorded using a commercially available ink-jet printer for water-based dye ink (PM-G820, manufactured by Seiko Epson Corporation). The suitability of the water-based dye ink was evaluated.
(1) Print density (color development)
After printing a black solid print pattern, the print density on the print surface was measured with a Macbeth densitometer (RD918) and evaluated according to the following evaluation criteria. If evaluation is (double-circle), (circle), (triangle | delta), it can be used practically without a problem.
A: Print density exceeds 1.60 B: Print density exceeds 1.50 and 1.60 or less Δ: Print density exceeds 1.40 and 1.50 or less X: Print density is 1.40 (2) Back-through After printing a black solid print pattern, the print density on the back side of the print surface was measured with a Macbeth densitometer (RD918) and evaluated according to the following evaluation criteria. If evaluation is (double-circle), (circle), (triangle | delta), it can be used practically without a problem.
A: Print density is 0.10 or less. B: Print density is over 0.10 and 0.12 or less. Δ: Print density is over 0.12 and 0.15 or less. X: Print density is 0.00. More than 15 (3) Ink absorbability The ink absorbability when a black solid print pattern was printed was visually evaluated and evaluated according to the following evaluation criteria. If evaluation is (double-circle), (circle), (triangle | delta), it can use without a problem practically.
◎: Absorption is very fast ○: Absorption is fast △: Absorption is a little slow ×: Absorption is slow, and dirt on the device and printed parts occur

3. Water-based pigment ink suitability The following patterns were recorded on the ink-jet recording paper of each Example and Comparative Example using a commercially available (water-based) ink-jet printer for pigment ink (PX-G920, manufactured by Seiko Epson Corporation). The water-based pigment ink suitability was evaluated for the items.
(1) Print density (color development)
After printing a black solid print pattern, the print density on the print surface was measured with a Macbeth densitometer (RD918) and evaluated according to the following evaluation criteria. If evaluation is (double-circle), (circle), (triangle | delta), it can be used practically without a problem.
A: Print density exceeds 1.80 B: Print density exceeds 1.60 and 1.80 or less Δ: Print density exceeds 1.40 and 1.60 or less X: Print density is 1.40 The following (2) Back-through evaluation was performed according to the same measurement method and evaluation standard as used for the suitability of the aqueous dye ink. If evaluation is (double-circle), (circle), (triangle | delta), it can be used practically without a problem.
(3) Ink absorbability The ink was evaluated according to the same measurement method and evaluation criteria as those used for water-based dye ink suitability. If evaluation is (double-circle), (circle), (triangle | delta), it can be used practically without a problem.

4). Non-aqueous ink suitability For the inkjet recording paper of Example 1, Comparative Example 6 and Comparative Example 7, the following pattern was used using a commercially available inkjet printer for non-aqueous (oil-based) pigment ink (ORPHIS HC5000, manufactured by Riso Kagaku). It was recorded and the pigment ink suitability was evaluated for the following evaluation items.
(1) Print density (color development)
After printing a black solid print pattern, the print density on the print surface was measured with a Macbeth densitometer (RD918) and evaluated according to the following evaluation criteria. If evaluation is (double-circle), (circle), (triangle | delta), it can be used practically without a problem.
A: Print density exceeds 1.30 B: Print density exceeds 1.20 and is 1.30 or less Δ: Print density exceeds 1.10 and is 1.20 or less ×: Print density is 1.10 The following (2) Back-through evaluation was performed according to the same measurement method and evaluation standard as used for the suitability of the aqueous dye ink. If evaluation is (double-circle), (circle), (triangle | delta), it can be used practically without a problem.
(3) Ink absorbability The ink was evaluated according to the same measurement method and evaluation criteria as those used for water-based dye ink suitability. If evaluation is (double-circle), (circle), (triangle | delta), it can be used practically without a problem.

5. Surface Strength A cello tape (registered trademark) having a width of 18 mm was affixed to the white paper surface of the ink receiving layer of the ink jet recording paper of each Example and Comparative Example. Next, the peel strength when peeled to the side opposite to the sticking surface was measured with a force gauge and evaluated according to the following evaluation criteria. If evaluation is (circle) and (triangle | delta), it can be used without a problem practically.
○: Peel strength is 4.9 N (500 gf) / 18 mm or more. Δ: Peel strength is 3.92 N (400 gf) / 18 mm or more and less than 4.9 N (500 gf) / 18 mm. X: Peel strength is 3. It is less than 92N (400gf) / 18mm

  The obtained results are shown in Tables 1 and 2.

As is apparent from Tables 1 and 2, in the case of each example, the print density and ink absorbency were high even when water-based inks as well as non-water-based inks were used, and the back-through could be prevented.
Note that the ratio expressed by (light calcium carbonate-silica composite / rosetta type light calcium carbonate) in the base paper is less than 30/70 (that is, the ratio of the rosetta type light calcium carbonate is large). In the case of No. 4, the print density when using the dye ink was slightly inferior to the other examples, but the print density when using the pigment ink was higher.
Further, in Example 6 in which the coating amount of the ink receiving layer was less than 2 g / m ² , the print density and ink absorbability were slightly inferior to those of other examples, but the back-through could be sufficiently prevented. .

On the other hand, in the case of Comparative Examples 1 and 2 in which Rosetta-type light calcium carbonate was not blended as a filler for the base paper, the opacity of the base paper was lowered and a breakthrough occurred. Further, in the case of Comparative Example 3 in which the particle size of Rosetta-type light calcium carbonate serving as a filler was less than 1.6 μm, the opacity of the base paper was lowered, resulting in breakthrough.
In the case of Comparative Example 4 in which the ash content of the base paper was less than 15%, the opacity of the base paper was lowered to cause back-through.

In the case of Comparative Example 5 in which Rosetta-type light calcium carbonate was not blended as a filler for the base paper and the blending amount of the light calcium carbonate-silica composite was increased, the surface strength of the ink receiving layer was lowered. This is presumably because the absorbency of the base paper became too large, and the binder penetrated into the base paper when the ink receiving layer was applied, thereby reducing the strength of the ink receiving layer.
In addition, in the case of Comparative Example 6 in which the light calcium carbonate-silica composite was not blended as the filler of the base paper and the amount of rosetta type light calcium carbonate was increased instead, The preventive effect disappeared and a strike-through occurred.
In addition, in the case of Comparative Example 7 in which the light calcium carbonate-silica composite was not blended as the filler of the base paper, but synthetic silica was blended instead, the effect of preventing the back-through by the light calcium carbonate-silica composite disappeared, A strike-through occurred.

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. It is a figure which shows an example of the form of the light calcium carbonate-silica composite particle of the state disperse | distributed in the liquid.

Claims (7)

At least on one side of a base paper containing a filler composed mainly of a light calcium carbonate-silica composite having an average particle size of 1.0 μm or more and a rosetta type light calcium carbonate having an average particle size of 1.6 μm or more. An ink jet recording paper in which one or more ink receiving layers containing a pigment and a binder are formed, and the ash content defined in JIS-P8251 of the base paper is 15 to 40%. In the light calcium carbonate-silica composite and the rosetta-type light calcium carbonate in the base paper, the solid content mass ratio represented by (light calcium carbonate-silica composite / rosetta-type light calcium carbonate) is 70/30 to The inkjet recording paper according to claim 1, which is 30/70. The inkjet recording paper according to claim 1 or 2, wherein the light calcium carbonate-silica composite is formed by coating silica fine particles on the surface of light calcium carbonate fine particles. The inkjet recording paper according to any one of claims 1 to 3, wherein the light calcium carbonate-silica composite has a solid content mass ratio of 30/70 to 70/30 represented by (CaCO ₃ / SiO ₂ ). The inkjet recording paper according to any one of claims 1 to 4, wherein a coating amount of the ink receiving layer is ² to 7 g / m2. The inkjet recording paper according to any one of claims 1 to 5, wherein the pigment of the ink receiving layer contains 10 to 100% by mass of synthetic silica. The oil absorption amount of the synthetic silica is 90 to 200 ml / 100 g, the BET specific surface area is 45 to 200 m ² / g, and the average particle size is 1.0 to 3.0 μm. 2. Inkjet recording paper described in 1.