JP2006095861A - Inkjet recording paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide inkjet recording paper excellent in non-transparency and cutting suitability. <P>SOLUTION: An ink accepting layer containing a pigment and a binding agent is provided on base paper. In the base paper, a filler constituted of precipitated calcium carbonate light-silica composite particles prepared by coating the surfaces of rosette type calcite calcium carbonate light particles with silica is contained at 1-25 mass% in a solid content. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an inkjet recording paper, and more particularly to an inkjet recording paper excellent in opacity and cutting suitability.

  The ink jet recording method is used in many fields as printing performance is rapidly improved because full colorization is easy and printing noise is low. For example, recording of documents created by document creation software, recording of digital images such as digital photographs, and recording (duplication) after taking a beautiful printed material such as a silver halide photograph or book with a scanner can be used. An ink jet recording sheet having a configuration suitable for each of these uses has been proposed. For example, plain paper type recording paper that does not coat the base paper is used for simple document recording. When resolution and color reproducibility comparable to silver halide photography is required, a coating type in which a thick coating layer is provided on the base paper as an ink-receiving layer is used. Cast-type recording paper having a construction layer produced by a cast coating method is used (see, for example, Patent Documents 1 and 2).

  In the cast coating method, a coating liquid mainly composed of a pigment and a binder is applied onto a base paper to provide a coating layer that becomes an ink receiving layer, and the coating layer that is wet and plastic is cast. This is a method of pressing against a mirror-finished surface such as a drum to give a gloss finish. The cast coating method includes (1) a wet casting method (direct method) in which a coating layer is pressed against a heated drum that has been mirror-finished while the coating layer is in a wet state (dry method), and (2) a wet coating layer is temporarily (half-finished) ) Rewetting cast method (rewetting method) in which it is swelled and plasticized with a rewetting liquid after drying, and pressed onto a mirror-finished heating drum (drying method), (3) The wet coating layer is made into a gel state by coagulation treatment, Generally, it can be divided into three types, that is, a gelling cast method (coagulation method) in which pressure is applied to a heated mirror drum and dried.

By the way, various fillers are used to increase the opacity of paper. Among these, titanium oxide is suitable because high opacity and whiteness can be obtained by adding a small amount (for example, Patent Documents 3 and 4). reference). Moreover, a bulky printing paper using amorphous silica (white carbon, hydrous silicic acid) or silicate having a bulk specific gravity of 0.3 g / cm ³ or less as a filler is disclosed (for example, see Patent Document 5). Particularly in recent years, low-density paper (bulky paper) has been increasingly used from the viewpoint of paper resource saving and weight reduction, and a filler that increases opacity is desired.

JP-A-62-95285 JP-A-5-59694 JP 2004-18336 A JP 2002-29739 A Japanese Patent Laid-Open No. 10-226982

  However, titanium oxide itself is a relatively hard filler, and paper using titanium oxide tends to be high in density. Therefore, when cutting with guillotine, etc., the cutting blade is heavily loaded and the blade is not chipped. There is a problem that it occurs or the cutting sound becomes very loud. In addition, when a material having a low specific gravity such as white carbon is used as a filler, the stiffness and sizing of the paper are lowered, and the opacity is lowered as compared with calcium carbonate or the like.

  Therefore, an object of the present invention is to provide an ink jet recording paper excellent in opacity and cutting processability.

As a result of investigations to solve the above problems, the inventors have found that any of the above problems can be solved by using a specific paper filler.
Accordingly, the object of the present invention is an ink jet recording paper in which an ink receiving layer containing a pigment and a binder is provided on a base paper, and the surface of the light calcium carbonate particles is made of silica in the base paper. This was achieved by an ink jet recording paper characterized by containing a filler composed of coated light calcium carbonate-silica composite particles.

In the light calcium carbonate-silica composite particles, the light calcium carbonate / silica solid content mass ratio (CaCO ₃ / SiO ₂ ) is preferably 25/75 to 75/25, and the light calcium carbonate-silica composite particles The average particle diameter is preferably 1 to 30 μm. In the light calcium carbonate-silica composite particles, the light calcium carbonate particles are preferably Rosetta-type calcite light calcium carbonate in which spindle-shaped primary particles aggregate to form secondary particles. The outermost surface of the ink receiving layer is provided after the coating layer is pressed against a heated mirror surface while the surface of the coating layer formed by applying the coating material for the ink receiving layer is in a wet state, and then dried. It is preferred that

  According to the present invention, an ink jet recording paper excellent in opacity and cutting processability can be obtained.

  Embodiments of the present invention will be described below. The ink jet recording paper of the present invention is provided with an ink receiving layer on a base paper and contains the following light calcium carbonate-silica composite particles as a filler in the base paper.

<Base paper>
The base paper used in the present invention is mainly composed of pulp fibers and fillers.
(1) Pulp The kind and blending amount of pulp used for the base paper are not particularly limited. For example, chemical pulp such as kraft pulp (KP), Stone Grand Pulp (SGP), Pressurized Stone Grand Pulp (PGP), Refiner Grand Pulp (RGP), Chemi Grand Pulp (CGP), Thermo Grand Pulp (TGP), Groundwood Pulp (GP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), refiner mechanical pulp (RMP) and other mechanical pulp (MP), and deinked pulp (DIP) and other waste paper pulp Two or more kinds can be appropriately selected and used in combination.

(2) Filler (light calcium carbonate-silica composite particles)
As the filler, light calcium carbonate-silica composite particles in which the surface of light calcium carbonate particles is coated with silica are used. The composite particles are used as a total amount or a part of the filler in paper. The light calcium carbonate-silica composite particles are obtained by bonding silica (SiO ₂ ) particles having a primary particle size of about 20 to 60 nm to the surface of light calcium carbonate having a particle size of about 0.9 to 9 μm, for example.

The crystal form (homogeneous image) of light calcium carbonate (CaCO ₃ ) may be either calcite or aragonite. The light calcium carbonate may have any of a needle shape, a column shape, a spindle shape, a spherical shape, a cubic shape, and a rosette type. The rosetta type refers to a shape in which spindle-shaped light calcium carbonate primary particles are aggregated in a chestnut shape, and has a higher specific surface area and oil absorption than those in other forms. In particular, the use of rosetta-type calcite light calcium carbonate is preferable because light calcium carbonate-silica composite particles that are bulky and excellent in improving opacity can be obtained. Light calcium carbonate may be used after being pulverized.

  FIG. 1 is an SEM (electron microscope) image showing an example of the form of light calcium carbonate (Rosetta calcite system) dispersed in a liquid, and FIG. 2 shows the light calcium carbonate dispersed in the liquid. -It is a SEM image which shows an example of the form of a silica composite particle. According to FIG. 2, it can be seen that substantially spherical silica particles are bonded (precipitated) to the surface of light calcium carbonate. In the example of FIG. 2, there are three composite particles. The composite particles are adhered to the surface of the pulp fiber in a single or a plurality of aggregated states after paper making.

  By using the light calcium carbonate-silica composite particles described above as a filler in paper, the oil absorption is increased and the opacity of the paper can be improved. Further, the light calcium carbonate-silica composite particles have a lower hardness than titanium, and the blades are less likely to be worn when the obtained paper is cut.

  The light calcium carbonate-silica composite particles must be contained in the paper, and preferably 1 to 25% by mass as a filler content in the paper. If the filler content in the paper is less than 1% by mass, the opacity of the ink jet recording paper will not be improved, and if it exceeds 25% by mass, the paper strength will be reduced, causing paper breakage during paper making or paper dust during processing. It becomes easy. The filler content in the paper is more preferably 3 to 25% by mass, and most preferably 5 to 25% by mass. The filler content in the paper can be measured by an ash content test method (525 ° C. combustion method) defined in JIS P P8251.

The light calcium carbonate / silica composite particle mass ratio (CaCO ₃ / SiO ₂ ) in the light calcium carbonate-silica composite particles is preferably 25/75 to 75/25. When the ratio is less than 25/75, 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 75/25, the characteristics of light calcium carbonate are greatly expressed, so that the opacity is lowered and the back-through easily occurs, and the bulkiness is lowered and the air permeability of the support is reduced. It tends to decrease. The solid content mass ratio can be obtained by, for example, analyzing light calcium carbonate-silica composite particles by fluorescent X-ray analysis and quantifying Ca and Si.

The average particle size of the light calcium carbonate-silica composite particles is preferably 1 to 30 μm. If the average particle size of the composite particles is less than 1 μm, the yield of the filler during papermaking may be lowered. On the other hand, when the average particle diameter exceeds 30 μm, the paper strength may be reduced, or the filler distribution in the paper may be uneven, and the formation may deteriorate. A more preferable average particle diameter is 3 to 20 μm, and a further preferable range is 3 to 10 μm.
The oil absorption of the light calcium carbonate-silica composite particles is preferably 70 to 300 ml / 100 g. When the oil absorption amount of the composite particles is less than 70 ml / 100 g, the ink absorbability deteriorates when the coating amount of the ink receiving layer is small, and problems such as bleeding are likely to occur in the ink jet recorded image. On the other hand, if the oil absorption exceeds 300 ml / 100 g, other additive chemicals may be excessively absorbed during paper making, and the effect of the chemicals may be reduced. A more preferable oil absorption is 100 to 200 ml / 100 g.
The light calcium carbonate-silica composite particles preferably have a BET specific surface area of 5 to 110 m ² / g. When the BET specific surface area of the composite particles is less than 5 m ² / g, the light scattering effect of the composite particles is reduced, so that light scattering is reduced and opacity tends to be lowered. On the other hand, when the BET specific surface area exceeds 110 m ² / g, other additive chemicals are excessively absorbed during paper making, and the effect of the chemicals may be reduced. A more preferable BET specific surface area is 10 to 50 m ² / g.

  In addition, since the light calcium carbonate-silica composite particles contain light calcium carbonate, the light calcium carbonate inside the particles may be decomposed or dissolved when the paper is made by acidic papermaking. Therefore, in the present invention, it is preferable to carry out papermaking with neutral papermaking or alkaline papermaking.

(3) Other effects of light calcium carbonate-silica composite particles Furthermore, when the light calcium carbonate-silica composite particles are used as a filler, there is an effect that low density paper (bulky paper) is easily obtained. In particular, the present invention is effective when manufacturing an inkjet recording paper by a cast coating method. That is, in any of the cast coating methods, it is necessary to press the coating layer against the cast drum to obtain a glossy surface, so that the drying of the coating layer proceeds only from the surface that does not contact the cast roll of the base paper. Therefore, the cast coating method has a low drying speed and low productivity, but the productivity can be improved by using a base paper with high air permeability. And according to this invention, since the density of a base paper falls (it becomes bulky), the air permeability of a base paper can be made high as a result. As the density of the base paper, the bulk ratio is preferably 3% or more. The higher the bulk factor, the better the cast operability. However, if the bulk factor becomes too high, the paper strength tends to decrease, and there is a tendency for paper breakage to occur during base paper production. For this reason, it is preferable that a bulkiness rate shall be 20% or less. The bulkiness ratio is a density measured from the paper thickness and basis weight of the base paper before coating, and the formula bulkiness ratio = (1-density of base paper with filler added / density of base paper without filler) × 100
Calculate according to

(4) Method for Producing Light Calcium Carbonate-Silica Composite Particles Specifically, in the production 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 content mass ratio (CaCO ₃ / SiO ₂ ) of the intended light calcium carbonate-silica composite particles can be adjusted by adjusting the charge 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, a neutralization reaction is performed 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 silicic acid is deposited on the surface of the light calcium carbonate particles to form amorphous silicic acid. It is formed and coated to obtain light calcium carbonate-silica composite particles. 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 the 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.

Further, coarse particles (for example, 100 μm or more) are appropriately removed from the obtained light calcium carbonate-silica composite particles using a vibrating sieve or a screen.
Adjustment of the average particle size of the light calcium carbonate-silica composite particles is carried out by vigorous stirring and 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.

(5) Other fillers In addition to light calcium carbonate-silica composite particles, other inorganic fillers and organic fillers may be used in combination as long as bulkiness, opacity, size, etc. are not impaired. Is possible. For example, any filler that is usually used for neutral papermaking or alkaline papermaking can be used without any limitation. Examples include inorganic fillers such as magnesium carbonate, barium carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, clay, calcined kaolin, deramikaolin, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, etc. And one or more selected from organic fine particles such as urea-formalin resin, polystyrene resin, and phenol resin.
The content of the total filler in the paper (only the light calcium carbonate-silica composite particles or the total of this and other fillers) in the paper is preferably 1 to 40% by mass, and 3 to 40% by mass. % Is more preferable, and 5 to 40% by mass is even more preferable. When the content exceeds 40% by mass, the number of paper breaks due to a decrease in paper strength increases, and the operability may decrease and the amount of paper dust generated during printing may increase.

(6) Manufacture of base paper The above pulp and filler are mixed, and paper strength improver, yield improver, wet paper strength enhancer, dye, fluorescent whitening agent, antifoaming agent, pitch as necessary. A base paper is manufactured by adding paper making chemicals such as a control agent, a slime control agent, and a sizing agent. In the case of neutral papermaking or alkaline papermaking, it is possible to use known internally added neutral sizing agents such as alkyl ketene dimer (AKD) sizing agents, alkenyl succinic anhydride (ASA) sizing agents, and neutral rosin sizing agents. it can. However, AKD and ASA are more preferable than neutral rosin sizing agents because a low-density base paper can be obtained. The content of these sizing agents is preferably 0.05 to 5% by mass, more preferably 0.1 to 1% by mass with respect to the absolute dry mass of the pulp.

  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.

  After papermaking, surface coating may be applied to the base paper for the purpose of improving surface strength, imparting water resistance, and improving ink deposition. There are no restrictions on the coating equipment. The type of surface treatment agent used for surface coating is not particularly limited. Cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose and methylcellulose; modified alcohols such as polyvinyl alcohol and carboxyl-modified polyvinyl alcohol; styrene-butadiene copolymer, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, polychlorinated Vinylidene, polyacrylic acid ester, polyacrylamide and the like can be used alone or in combination. Furthermore, what added surface sizing agents, such as a styrene acrylic acid, a styrene maleic acid, an olefin type compound, and a cationic sizing agent, can be applied with respect to the said surface treating agent.

  Although the calendering can be performed at a linear pressure within the normal operating range, from the viewpoint of producing low density paper, the linear pressure is set as low as possible within the range where the smoothness of the paper can be maintained, or the soft calendering is performed. It is preferable to use a render.

<Ink receiving layer>
The ink receiving layer contains a pigment and a binder.
(1) Pigment The pigment can be appropriately selected from known pigments. Specific examples include silica (including colloidal silica), alumina (including colloidal alumina), aluminum hydroxide, kaolin, talc, calcium carbonate, titanium dioxide, clay, and zinc oxide. These may be used alone or in combination. Can be used. Among these, alumina is an oxide of aluminum obtained by firing aluminum hydroxide and the like, and examples thereof include α-alumina, β-alumina, γ-alumina, and the like. This is preferable since the gloss of the ink receiving layer is further improved. The particle diameter and the BET specific surface area of alumina can be appropriately selected as necessary. When alumina having an average particle diameter (measured by laser diffraction method) of 1.0 to 4.0 μm is used, the gloss of the ink receiving layer is increased. In particular, it is preferable to use alumina having a thickness of 1.5 to 3.3 μm.

(2) Binder The binder may be any polymer compound that can form a film. Specifically, completely saponified or partially saponified polyvinyl alcohol; carboxylic acid-modified polyvinyl alcohol; silyl-modified polyvinyl alcohol; acetoacetyl group-modified polyvinyl alcohol; polyvinyl acetal resin; starches such as oxidized starch and esterified starch; carboxymethylcellulose; Cellulose derivatives such as hydroxyethyl cellulose; polyvinylpyrrolidone; casein; gelatin; soy protein; styrene-acrylic resin and derivatives thereof; styrene-butadiene latex, acrylic emulsion, vinyl acetate emulsion, vinyl chloride emulsion, urethane emulsion, urea emulsion, alkyd emulsion and These derivatives; etc. can be used alone or in combination. In particular, it is preferable to use polyvinyl alcohol (including a modified product) because the transparency of the ink receiving layer is improved and glossiness similar to that of a silver salt photograph can be imparted.

  The blending amount of the binder is not particularly limited as long as the required layer strength can be obtained. More preferably. When the blending amount is less than 5 parts by mass, the strength of the ink receiving layer tends to be lowered, and when it exceeds 30 parts by mass, the ink absorbability of the ink receiving layer tends to be lowered. Also, when polyvinyl alcohol is blended in the binder, if the blending amount is small, the gloss of the white paper (the gloss of the recording layer before ink jet printing) tends not to improve, so the proportion of polyvinyl alcohol in the binder is 30. It is preferable to set it as mass% or more, More preferably, you may be 50 mass% or more.

(3) Formation of ink receiving layer The ink receiving layer can be formed by applying an ink receiving layer coating solution. As a coating method, a coating method using a known coating machine such as a blade coater, an air knife coater, a roll coater, a brush coater, a kiss coater, a squeeze coater, a curtain coater, a die coater, a bar coater, a gravure coater, or a cast coater. Although it can select suitably from the inside, the cast coat method (coating with a cast coater) is preferable from the point which can obtain the inkjet recording paper which has especially high glossiness.

<Method for forming ink receiving layer (cast coating method)>
In view of obtaining an inkjet recording paper having high gloss, it is preferable to form the ink receiving layer by a so-called cast coating method. This cast coating method is performed by pressing the coating layer against a heated mirror surface and then drying it while the surface of the coating layer to which the ink receiving layer coating is applied is in a wet state.
The cast coating method includes (1) a wet casting method (direct method) in which a coating layer is pressed (pressure-welded) to a mirror-finished heating drum while the coating layer is still wet (direct method), (2) Rewetting cast method (rewetting method) in which a wet coating layer is once (semi-) dried and then swollen and plasticized (wet) with a rewetting liquid, and pressed onto a mirror-finished heating drum (drying method), (3) wet state The coating layer is generally made into a gel state by a coagulation treatment such as a coagulating liquid, and can be generally classified into three types: a gelation cast method (coagulation method) in which the coating layer is pressed against a mirror-finished heating drum and dried.
Both methods are similar in that a mirror surface (for example, a metal mirror surface such as a heated mirror drum or a flat mirror surface) is pressed against a coating layer in a wet state (including a gel state in a wet state).
In the present invention, any of the methods described above can be used, but the coagulation method is preferable from the viewpoint of obtaining high gloss, and the rewet method is preferable from the viewpoint of improving productivity.

  In the case of the coagulation method cast coating method, while the coating layer to which the ink receiving layer coating solution is applied is in a wet state, a treatment solution that solidifies (or crosslinks) the binder is applied thereto. Then, the coated layer is pressure-bonded to the heated mirror surface to give gloss. For example, when polyvinyl alcohol is used as the binder for the coating layer, any aqueous solution containing a compound capable of coagulating polyvinyl alcohol can be used. And a treatment liquid containing borate is preferable. By mixing and using boric acid and borate, it becomes easy to obtain a solidified state having an appropriate hardness, and an ink jet recording paper having a good gloss feeling can be obtained.

  In the case of the rewet method cast coating method, the treatment layer that has the effect of drying the coating layer coated with the coating solution for the ink receiving layer and plasticizing the binder of the coating layer (plasticization treatment solution) Is applied to the coating layer, and then the coating layer is pressure-bonded to a heated mirror surface to give gloss. In this method, since the ink receiving layer is in a dry state when applying the treatment liquid, it is difficult to copy the surface of the mirror drum, there are many fine irregularities on the surface, and the glossiness tends to be slightly lowered. Since the coating speed can be increased as compared with this method, productivity is improved.

  In addition, the above treatment liquids (coagulation liquid and plasticizing liquid) include pigment dispersants, water retention agents, thickeners, antifoaming agents, antiseptics, colorants, water resistance agents, wetting agents, fluorescent agents as necessary. A dye, an ultraviolet absorber, a cationic polymer electrolyte, and the like can be appropriately added. Examples of the method for applying the treatment liquid include, but are not limited to, a roll, a spray, and a curtain method.

<Example>
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples. Further, the following “parts” and “%” represent “parts by mass” and “mass%” unless otherwise specified.

(Production of light calcium carbonate-silica composite particles)
1) Light calcium carbonate-silica composite particles A
In a reaction vessel (12 L), 603 g of commercially available Rosetta-type light calcium carbonate (trade name: Albuquer 5970, manufactured by Specialty Minerals Inc., average particle size 3.0 μm, oil absorption 150 ml / 100 g) was dispersed in water. 3,400 g of a sodium silicate solution (SiO ₂ concentration 18.0 wt / wt%, Na ₂ O concentration 6.1 wt / wt%) was added, and 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 light calcium carbonate-silica composite particles A having a light calcium carbonate / silica mass ratio of 50/50 were obtained. The oil absorption of the composite particles was 160 ml / 100 g, the BET specific surface area was 28 m ² / g, and the average particle size was 6.1 μm. For the measurement of oil absorption, etc., the sample after suction filtration was re-dispersed in ethanol so that the filtrate had a solid content of 10% by mass, filtered, and dried at 105 ° C. It was.

<Production of light calcium carbonate-silica composite particles 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 particles A. Light calcium carbonate-silica composite particles 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 were obtained.

(Manufacture of base paper)
To a pulp slurry consisting of 100 parts of LBKP with a beating degree of 370 ml, light calcium carbonate-silica composite particles A were added as a filler so that the filler content in the paper would be 7%, and papermaking was performed. At the time of papermaking, starch was applied to both sides so that the solid content per side was 2.5 g / m ² to obtain a base paper having a basis weight of 65 g / m ² .

(Formation of under layer)
On one side of this base paper, an under layer was provided by coating the coating liquid A with a blade coater so that the coating amount was 15 g / m ² .
Coating liquid A: 100 parts of synthetic silica (Fine Seal X-37B: Tokuyama Co., Ltd.) as a pigment, 5 parts of SB latex (LX438C: Sumitomo Chemical Co., Ltd.) as a binder, and polyvinyl alcohol ( 20 parts of PVA117: product name of Kuraray Co., Ltd. and 5 parts of sizing agent (Polymaron 360: product name of Arakawa Chemical Co., Ltd.) were blended to prepare a coating solution having a solid content concentration of 20%.

(Formation of ink receiving layer)
Next, 10 g / m ^{2 of} coating liquid B is applied onto the coating surface of coating liquid A with a roll coater, and solidified using coagulating liquid C while the coating layer is in a wet state, and then pressed. The coated layer was pressure-bonded to the heated mirror-finished surface through a roll, the mirror surface was copied, and dried to obtain an inkjet recording paper having a basis weight of 90 g / m ² .
Coating liquid B: 100 parts of high-purity alumina (UA5605: trade name, manufactured by Showa Denko Co., Ltd., average particle size: 2.8 μm) is blended as a pigment, and a completely saponified polyvinyl alcohol (polymerization degree 500) is used as a binder. 15 parts of PVA105: Kuraray Co., Ltd. trade name, saponification degree 98.5) was blended, and 0.2 part of antifoaming agent was blended to prepare a coating solution having a concentration of 30%.
Coagulating liquid C: 2% borax, 2% boric acid (mass ratio of borax / boric acid = 1/1, calculated in terms of Na ₂ B ₄ O ₇ and H ₃ BO ₃ ), release agent (FL-48C: Toho Coagulation liquid was prepared by blending 0.2% (made by Chemical Industry Co., Ltd.).

  Except that instead of the light calcium carbonate-silica composite A, the light calcium carbonate-silica composite B was blended so that the filler content in the paper would be 7% as the base paper filler, exactly as in Example 1. Inkjet recording paper was obtained.

As the ink receiving layer coating liquid, the following coating liquid B1 is used instead of the coating liquid B, and the coating is performed with an air knife coater so that the coating amount is 12 g / m ^2, and then coagulated with the coagulating liquid C. Ink jet recording paper was obtained in exactly the same manner as in Example 1 except that it was dried as it was without being subjected to cast coating.
Coating liquid B1: 70 parts of synthetic amorphous silica (nip gel AY-603: manufactured by Nippon Silica Industry) and 30 parts of synthetic amorphous silica (Mizukasil P-50: manufactured by Mizusawa Chemical Co., Ltd.) as a binder, 35 parts of polyvinyl alcohol (PVA-117: manufactured by Kuraray) and 25 parts of ethylene vinyl acetate copolymer latex (Likabond BE-7000: manufactured by Chuo Rika Kogyo), 2 parts of cationic sizing agent (Polymaron 360: manufactured by Arakawa Chemical Industries), A dye fixing agent (PAS-H-10L: manufactured by Nitto Boseki Co., Ltd.), 5 parts, an antifoaming agent, dilution water and the like were appropriately mixed to prepare a coating solution having a solid content concentration of 18%.

[Comparative Example 1]
As a base paper filler, in place of the light calcium carbonate-silica composite A, Rosetta-type light calcium carbonate (trade name: Albuquer 5970, Specialty Minerals Inc.) is used as it is without being combined, and the paper filler ratio is 7 Inkjet recording paper was obtained in exactly the same manner as in Example 1, except that it was blended so that the content was%.

[Comparative Example 2]
As a filler for the base paper, instead of the light calcium carbonate-silica composite A, a spindle-shaped light calcium carbonate (trade name: TP121, manufactured by Okutama Kogyo Co., Ltd.) is not combined and the filler content in the paper is 7% as it is. An ink jet recording paper was obtained in exactly the same manner as in Example 1 except that it was blended. TP121 consists of spindle-shaped primary particles, and the primary particles do not aggregate and do not form secondary particles.

[Comparative Example 3]
In place of light calcium carbonate-silica composite A as a base paper filler, white carbon (trade name: TIXOLEX17, manufactured by Rhdia Silica Korea) is not compounded so that the filler content in the paper is 7%. Except that, an ink jet recording paper was obtained in the same manner as in Example 1.

[Comparative Example 4]
As a filler for base paper, instead of light calcium carbonate-silica composite A, white carbon (trade name: TIXOLEX17, manufactured by Rhdia Silica Korea) and commercially available rosetta-type light calcium carbonate (trade name: Albuquer 5970, Specialty Minerals Inc. Inkjet recording paper is obtained in exactly the same manner as in Example 1 except that a mixture of 50:50 (not made) is blended so that the total filler content in the paper is 7%. It was. The mixed filler had an average particle size of 3.8 μm and an oil absorption of 137 ml / 100 g.

[Comparative Example 5]
As a base paper filler, in place of the light calcium carbonate-silica composite A, titanium oxide (FA-50: manufactured by Furukawa Machine Metal Co., Ltd.) was used except that the filler content in the paper was 2%. Inkjet recording paper was obtained exactly as in Example 1.

[Comparative Example 6]
An ink jet recording paper was obtained in the same manner as in Example 1 except that no filler was added to the base paper.

[Comparative Example 7]
As a base paper filler, in place of the light calcium carbonate-silica composite A, titanium oxide (FA-50: manufactured by Furukawa Machine Metal Co., Ltd.) was used except that the filler content in the paper was 2%. Inkjet recording paper was obtained in exactly the same manner as in Example 3.

The physical property values of the fillers blended in the base paper, the inkjet recording papers of the examples and comparative examples were evaluated by the following methods.
1) Physical property value of each filler (1-1) Filler content in paper: according to JIS P8251, each uncoated base paper is baked at 525 ° C., and the amount of ash is measured. Minute conversion).
(1-2) Oil absorption: According to the method of JIS K5101.
(1-3) Average particle diameter: A slurry of each filler was added dropwise to pure water to which a dispersant (sodium hexametaphosphate 0.2% by mass) was added to form a uniform dispersion. (Part number: Mastersizer S type) was used to measure the particle size, and the average particle size was determined.
(1-4) Light calcium carbonate / silica solid content mass ratio (CaCO ₃ / SiO ₂ ): Light calcium carbonate-silica composite particles were analyzed by fluorescent X-rays, and Ca and Si were determined.

2) Evaluation of each ink-jet recording paper (2-1) Whiteness of base paper: The uncoated base paper was measured with a color difference meter (Murakami Color Research Laboratory) according to JIS P8148.
(2-2) Opacity of base paper: The uncoated base paper was measured with a color difference meter (manufactured by Murakami Color Research Laboratory) according to JIS P8138. It can be said that the opacity is good when the opacity is approximately 83% or more.
(2-3) Bulkiness ratio of base paper: For uncoated base paper, the density is measured from the paper thickness and basis weight, and the following formula: Bulkiness ratio = (1− (density of filler-added product / filler-free product) Density)) × 100
Calculated according to It can be said that it is bulky when the bulkiness ratio is approximately 4% or more.

(2-4) Cutting suitability
i) Abrasion of blades when cutting guillotine 200 sheets of inkjet recording paper were stacked, and after cutting another portion of the paper 10 times with a guillotine cutter from the opposite side of the ink receiving layer surface, the degree of chipping of the blade was visually evaluated. .
○: No chipping △: Slight chipping is observed ×: Chipping is observed at multiple locations
ii) Cutting sound 200 ink jet recording sheets were stacked, and the loudness when cutting with a guillotine cutter from the opposite side of the ink receiving layer surface was evaluated.
○: Low sound (about normal cutting work)
Δ: Sound is slightly loud ×: Sound is loud and there is vibration when cutting

(2-5) Back-through A predetermined pattern is recorded on the ink receiving layer with black ink by an ink jet printer (PM-950C: trade name manufactured by Seiko Epson Corporation) using dye ink, and the surface opposite to the ink receiving layer The transparency of the printed image on the ink receiving layer side was observed from the side. The evaluation of show-through indicates the opacity of the paper. If the strikethrough is ○, the opacity is excellent.
○: The image is not visible from the opposite side. Δ: The image is slightly transparent from the opposite side. X: The image is clearly transparent from the opposite side. (2-6) Cast operability Coating with coating liquid B (or B1) Then, when the coagulation liquid C was applied, the maximum value of the coating speed was evaluated in a range where the coating layer did not adhere to the cast drum and became dirty. If the cast operability is ○, it can be said that the cast operability is excellent.
○: Coating speed is 25 m / min or more. Δ: Coating speed is 20 m / min or more and less than 25 m / min. X: Coating speed is less than 20 m / min.

  As is clear from Tables 1 and 2, in each example, both opacity and cutting suitability were excellent. In each example, the bulkiness of the base paper was high and the cast operability was excellent.

  On the other hand, in the case of Comparative Examples 1 and 2 using only light calcium carbonate as a filler, both the opacity deteriorated, the bulkiness was low, and the cast operability was also lowered. In the case of Comparative Example 3 using white carbon as a filler, the opacity deteriorated. In the case of Comparative Example 4 in which a mixture of light calcium carbonate and white carbon was used as a filler, the opacity deteriorated, the bulkiness was low, and the cast operability was also lowered. In Comparative Examples 5 and 7 using titanium dioxide as a filler, cutting suitability deteriorated, bulkiness was low, and cast operability was also lowered. In the case of the comparative example 6 which did not mix | blend a filler, the opacity deteriorated significantly.

  As described above, by using the light calcium carbonate-silica composite particles as a filler, an ink jet recording paper excellent in opacity and cutting suitability can be obtained.

It is a figure which shows an example of the form of the light calcium carbonate (Rosetta-type calcite type) of the state disperse | distributed in the liquid. 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 (5)

  An ink jet recording paper provided with an ink receiving layer containing a pigment and a binder on a base paper, wherein the light calcium carbonate-silica composite particles are obtained by coating the surface of the light calcium carbonate particles with silica in the base paper. An ink jet recording paper comprising a filler comprising: _2. The inkjet recording according to claim 1, wherein the light calcium carbonate / silica composite particles have a light calcium carbonate / silica solid content mass ratio (CaCO ₃ / SiO ₂ ) of 25/75 to 75/25. Paper.   3. The inkjet recording paper according to claim 1, wherein the light calcium carbonate-silica composite particles have an average particle diameter of 1 μm to 30 μm.   2. The light calcium carbonate-silica composite particles, wherein the light calcium carbonate particles are Rosetta calcite light calcium carbonate in which spindle-shaped primary particles are aggregated to form secondary particles. Item 4. The inkjet recording paper according to any one of Items 1 to 3.   The outermost surface of the ink receiving layer is provided after the coating layer is pressed against a heated mirror surface while the surface of the coating layer formed by applying the coating material for the ink receiving layer is in a wet state, and then dried. The ink jet recording paper according to claim 1, wherein the ink jet recording paper is used.