WO2006035661A1 - Ink jet recording paper - Google Patents

Abstract

[PROBLEMS] To provide an ink jet recording paper being excellent in opacity and the suitability to cutting, or an undercoated paper being excellent in ink-absorbing property and the strength of a coating layer. [MEANS FOR SOLVING PROBLEMS] An ink jet recording paper having a base paper and, provided thereon, an ink-receiving layer containing a pigment and a binder, wherein the base paper contains a filler of light calcium carbonate-silica composite particles comprising light calcium carbonate particles and silica covering the surface thereof, or an undercoated paper which contains the above light calcium carbonate-silica composite particles comprising light calcium carbonate particles and silica covering the surface thereof.

Description

 Specification

 Inkjet recording paper

 Technical field

 The present invention relates to an inkjet recording sheet.

 Background art

 The ink jet recording method is widely used with the rapid improvement of the printing performance due to the fact that full-coloring is easy and the printing noise is small! In addition, the ink jet recording method has been widely used as a color printer in homes and offices because the device is compact and inexpensive. The ink jet recording method ejects ink droplets toward recording paper such as nozzle force paper to form an image, and the recording paper and the printer do not come in direct contact with each other! is there.

 The inkjet recording method is, for example, recording of a document created by document creation software, recording of a digital image such as a digital photograph, recording (replication) after a scanner prints a beautiful print such as a silver salt photograph or a book, etc. To be used. Then, an inkjet recording sheet having a configuration suitable for each of these applications has been proposed. For example, for simple document recording, plain paper type recording paper which is not coated on base paper is used. Also, when resolution and color reproducibility comparable to silver halide photography are required, a coating type provided with a thick coating layer as an ink receiving layer on a base paper is used, and in particular when the gloss is required, the above coating A cast type recording sheet prepared by cast coating a working layer is used (see, for example, Patent Documents 1 and 2).

[0003] In the cast coating method, a coating liquid containing a pigment and a binder as main components is coated on a base paper to form a coating layer to be an ink receiving layer, and the coating is wet and plasticized. In this method, the work layer is pressed against a mirror-finished surface such as a cast drum to finish gloss. The cast coating method is (1) wet cast method (direct method) in which the coated layer is pressed and dried on a mirror-finished heating drum while the coated layer is wet, and (2) the coated layer in the wet state is ) After being dried, it is swelled and plasticized with rewetting liquid, pressed onto mirror surfaced heating drum and dried, and re-wet method (re-wetting method), (3) the wet coating layer is made into gel state by coagulation treatment Generally divided into three types: Gelie cast method (solidification method), which is pressed and dried on a mirror-finished heating drum be able to.

By the way, various fillers are used to increase the opacity of paper, but among them, titanium oxide is preferable because high opacity and whiteness can be obtained by addition of a small amount (for example, , Patent Documents 3 and 4). In addition, a bulky printing paper using as a filler an amorphous silica (white carbon, hydrous cayric acid) or a silicate having a bulk specific gravity of 0.3 g / cm ³ or less is disclosed (see, for example, Patent Document 5). In particular, in recent years, low density paper (bulk paper) is often used from the viewpoint of paper resource saving and weight reduction, and a filler for increasing the opacity is required.

 On the other hand, the ink for inkjet recording contains a large amount of solvent in the ink to form stable droplets. Therefore, in order to obtain good image quality, it is necessary to rapidly absorb recording paper force S ink droplets. In particular, in recent years, ink-jet recording paper is required to have higher ink absorbency by the use of high-speed or multi-color ink in printers. Therefore, a recording sheet provided with the above-mentioned ink receiving layer on a support is covered. The ink receiving layer is generally composed of a pigment which absorbs the ink, a binder which binds the pigment on the support, an ink fixing agent which fixes the ink to the ink receiving layer, and various auxiliary agents. As a pigment for the ink receiving layer, synthetic amorphous silica excellent in ink absorbability and transparency is generally used, but various properties for improving printing quality and workability (particle size, Silica having an oil absorption etc. has been proposed as a pigment (see, for example, Non-Patent Document 1).

For example, in Non-Patent Document 1, the average particle diameter is about 3 to 6 μm, and the oil absorption amount is 250 cm ³ Z100.

 It is described that eight or more silicas (123 of the same reference), average particle diameter of 2 to 15 111, oil absorption of 180 ml and 100 g or more of silica (pl46 of the same document) are suitable.

 Further, it contains synthetic amorphous silica having an oil absorption of 300 ml or more, and heavy calcium carbonate having a ratio of particles having an average particle diameter of 0.5 to 0.5 m and a particle diameter of 2 μm or less 95% or more. An ink jet recording sheet provided with an ink receiving layer is disclosed (see, for example, Patent Document 6).

At the same time, with the development of color reproducibility in recent printers, an inkjet recording sheet capable of absorbing more ink is desired. Such a force has been proposed to provide an under layer between the support and the ink receiving layer. For example, a technique of providing an under layer containing silica as a pigment in the lower layer of the ink receiving layer, or as an under layer pigment A technology using a mixture of silica and heavy calcium carbonate fine particles has been proposed (see Patents 7 and 8).

Patent Document 1: Japanese Patent Application Laid-Open No. 62-95285

 Patent Document 2: Japanese Patent Application Laid-Open No. 5-59694

 Patent Document 3: Japanese Patent Application Laid-Open No. 2004-18336

 Patent Document 4: Japanese Patent Application Laid-Open No. 2002-29739

 Patent Document 5: Japanese Patent Application Laid-Open No. 10-226982

 Patent Document 6: Japanese Patent Application Laid-Open No. 2003-170656

 Patent Document 7: Japanese Patent Application Laid-Open No. 2003-260862

 Patent Document 8: Japanese Patent Application Laid-Open No. 2003-285543

 Non-patent document 1: "Development technology of ink 'media' printer in ink jet recording", 1st print, Issuer Kazuhiro Takathin, Inc. Technical Information Association, Inc., August 28, 2000 pl23, p 146

 Disclosure of the invention

 Problem that invention tries to solve

 However, titanium oxide used to improve the opacity of paper itself is a relatively hard filler, and paper using titanium oxide tends to have a high density, so guillotine etc. There is a problem that when cutting is performed, the load on the cutting blade is large and chipping of the blade occurs, and cutting noise becomes extremely large. In addition, when a low specific gravity substance such as white carbon is used as a filler, the rigidity and size of the paper are lowered, and the opacity is lowered as compared with calcium carbonate and the like.

 When an under layer is provided below the ink receiving layer according to the technique described in Patent Document 7, although the ink absorbency of the pigment, which is a pigment, is high, the silica in the under layer coating solution has a high viscosity. In order to adsorb the binding agent (the amount of binding agent required is large), there is a problem that the amount of the effective binding agent is insufficient and the strength of the powder is further lowered. Also, if the blending amount of the binder is increased to secure the layer strength, the ink absorptivity decreases. On the other hand, when silica having a low oil absorption is used, the binder requirement is lowered but the ink absorption is poor.

Further, in the case of the technique described in Patent Document 8, although the strength of the under layer becomes high, Because of its low absorption characteristics, the ink absorption is poor.

 If the strength of the under layer is low, when the roll-like recording paper (paper) is wound up in the production process, the under layer or the ink receiving layer thereon may be missing and the paper may get caught between the paper and the like. It occurs. In this case, the paper surface may have irregularities such as depressions, which may impair the appearance, and is particularly remarkable in high-smooth cast paper.

 Therefore, an object of the present invention is to provide an ink jet recording sheet which is excellent in opacity and cutting processability, or higher in ink absorbability and sander strength.

 Means to solve the problem

 As a result of investigations to solve the above-mentioned problems, the present inventors have found that by using a specific filler in paper, the opacity and cutting processability can be improved.

 Therefore, the above object of the present invention is an ink jet recording sheet provided with an ink receiving layer containing a pigment and a binder on a base paper, wherein the surface of the light calcium carbonate particles is made of silica in the base paper. This is achieved by an ink jet recording sheet characterized in that it comprises a filler consisting of coated light calcium carbonate-silica composite particles.

 In addition, as a result of investigations to solve the above problems, the inventors have found that by using a specific filler in the under layer, it is possible to improve the ink absorbability and improve the under layer strength. . It is considered that this is because the pigment improves the balance of the absorption characteristics of the pigment and improves the ink absorption without adsorbing a large amount of the binder.

 Accordingly, the above object of the present invention is an ink jet recording paper provided with an under layer containing a pigment and a binder on at least one surface of a support and an ink receiving layer provided on the surface of the under layer. This is achieved by an ink jet recording sheet characterized in that the pigment of the under layer contains light calcium carbonate-silica composite particles coated with silica on the surface of light calcium carbonate particles.

 It is preferable that the solid content mass ratio (CaCO 2 / SiO 2) of the light calcium carbonate Z silica in the light calcium carbonate-silica composite particles is 25Z75 to 75Z25. Said

 3 2

 When light calcium carbonate / silica composite particles are contained in the base paper, the average particle size is

It is preferable that it is 1-30 m. In the light calcium carbonate-silica composite particles, the light calcium carbonate particles are secondary particles by aggregation of spindle-like primary particles. Preferably, it is a light rosette calcium carbonate calcium carbonate that forms a. The outermost surface of the ink receiving layer is brought into pressure contact with the 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 preferable to be provided.

 Effect of the invention

 According to the present invention, it is possible to obtain an ink jet recording sheet which is excellent in opacity and cutting processability, or higher in ink absorbency and sander strength.

 BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described.

 1. An embodiment according to the first invention (containing light calcium carbonate / silica composite particles as a filler in base paper)

 The ink jet recording paper of the embodiment according to the first invention 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 embodiment contains pulp fibers and fillers as main components.

 (1) Pulp

 The type and blending amount of pulp used for the base paper are not particularly limited. For example, kraft pulp (

Chemical pulps such as KP), Stone Grand Pulp (SGP), Pressed Stone Grand Pulp (PG P), Refiner Grand Pulp (RGP), Chemi Grand Pulp (CGP), Thermo Grand Pulp (TGP), Ground Pulp (GP) Mechanical pulp (MP) such as Thermo-mechanic pulp (TMP), Chemotherme force-carp pulp (CTMP), Refiner-mechanic pulp (RMP), etc., and 1 or 2 from waste paper pulp such as deinked pulp (DIP) The species or more can be selected appropriately and used in combination.

(2) Filler (light calcium carbonate / silica composite particles)

As a 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 the whole or part of the filler in paper. The light calcium carbonate-silica composite particles have, for example, a particle diameter of about 0.9 to 9 / ζπι Silica (SiO 2) particles with a primary particle size of about 20 to 60 nm on the surface of light calcium carbonate

 2 It is a combination. Also, light calcium carbonate can be synthesized by, for example, calcining limestone and chemical reaction, but is not limited thereto.

 [0020] The crystal form (homomorphous) of light calcium carbonate (CaCO 3) is calcite, aragona

 3

 It may be any of them. The shape of the light calcium carbonate may be any of needle, column, spindle, sphere, cube, and rosette type. The rosette type refers to a shape in which spindle-shaped light calcium carbonate primary particles are aggregated into a chestnut-like shape, and the specific surface area and oil absorption are higher than those of other forms. In particular, it is preferable to use rosette type calcite-based light calcium carbonate, since light calcium carbonate-silica composite particles excellent in the effect of improving bulkiness and opacity when internally added to a base paper can be obtained. Light carbonated calcium carbonate may be used after being crushed.

 FIG. 1 is a SEM (electron microscope) image showing an example of the form of light calcium carbonate (Rosetta-type calcite system) in a dispersed state in a liquid, and FIG. 2 shows the dispersed state in a liquid. BRIEF DESCRIPTION OF THE DRAWINGS It is a SEM image which shows an example of the form of the light calcium calcium carbonate silica composite particle. According to FIG. 2, it can be seen that substantially spherical silica particles are bound (deposited) on the surface of light calcium carbonate. Also, in the example of FIG. 2, three composite particles are present. It is to be noted that the composite particles adhere to the surface of the knob fiber in a single or plural aggregated state after paper making.

 By using the above-described light calcium carbonate-silica composite particles as a filler in paper, the oil absorption can be increased, and the opacity of paper can be improved. In addition, light calcium carbonate-silica composite particles are less likely to wear the blade when cutting the paper which has lower hardness than titanium.

The light calcium carbonate-silica composite particles are required to be contained in the paper, and preferably 1 to 25% by mass as the filler in the paper. When the filler content in the paper is less than 1% by mass, the opacity of the ink jet recording sheet is not improved, and when it exceeds 25% by mass, the paper strength is reduced, paper breaks are generated during paper making, and paper powder is generated during processing. It will be easier. The filler content in the paper is more preferably 3 to 25% by mass, and most preferably 5 to 25% by mass. In addition, it can be measured by the ash content test method (525 ° C. combustion method) specified in the paper filler rate IS ISC P 8251. It is preferable that the solid content mass ratio (CaCO 2 / SiO 2) of the light calcium carbonate Z silica in the light calcium carbonate-silica composite particles is 25Z75 to 75Z25. The above ratio is

 3 2

 If it is less than 25Z75, the characteristics of the silica develop over the whole, so the opacity decreases and it becomes easy to cause the strike through of the recorded image. On the other hand, when the above ratio exceeds 75Z25, the characteristics of light calcium carbonate are largely developed, so the bulkiness is lowered and the air permeability of the support is lowered. The solid content mass ratio can be determined, for example, by fluorescent X-ray analysis of light calcium carbonate-silica composite particles to quantify Ca and Si.

The average particle diameter force of the light calcium carbonate / silica composite particles is preferably 30 μm. When the average particle size of the composite particles is less than 1 μm, the retention of filler during papermaking may decrease. On the other hand, when the average particle size exceeds 30 m, the paper strength may decrease, the filler distribution in the paper may become uneven, and the formation may be deteriorated. A more preferable average particle size 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 Z100 g. When the oil absorption amount of the composite particles is less than 70 ml and less than 100 g, when the coating amount of the ink receiving layer is small, the ink absorptivity deteriorates and problems such as bleeding easily occur in the ink jet recorded image. On the other hand, if the oil absorption exceeds 300 ml Z100 g, other additives may be absorbed excessively at the time of sheet making, and the effects of the agent may be reduced. More preferable oil absorption is 100 to 200 ml Z 100 g.

In addition, it is preferable that the light calcium carbonate-silica composite particles 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 the light scattering tends to be reduced and the opacity is reduced. On the other hand, when the BET specific surface area exceeds 110 m ² Zg, other additive chemicals may be absorbed excessively at the time of paper making, and the effects of the chemicals may be reduced. A more preferred BET specific surface area is 10 to 50 m ² Zg.

Since the light calcium carbonate / silica composite particles contain light calcium carbonate inside, when making the paper by acid papermaking, the light calcium carbonate inside the particles may be decomposed or dissolved. Therefore, in the present invention, it is preferable to make the paper by neutral paper making or alkaline paper making. (3) Other effects of light calcium carbonate / silica composite particles

 Furthermore, when light calcium carbonate / silica composite particles are used as a filler, there is an effect that low density paper (bulky paper) can be easily obtained. In particular, the present invention is effective when producing an inkjet recording sheet by a cast coating method. That is, in all of the cast coating methods, since it is necessary to press the coated layer against the cast drum to obtain a glossy surface, drying of the coated layer proceeds only from the side not in contact with the cast roll of the base paper. Therefore, the cast coating method can improve productivity by using a highly permeable base paper that has low drying speed and low productivity. Then, according to the present embodiment, the density of the base paper is reduced (the bulk is increased), and as a result, the air permeability of the base paper can be increased. As the density of the base paper, it is preferable to set the bulkiness to 3% or more. The higher the bulkiness rate, the better the cast operability, but if the bulkiness rate is too high, the paper strength tends to decrease, and there is a tendency for paper breaking to occur at the time of base paper production. For this reason, it is preferable to set the bulkiness to 20% or less. The bulk ratio is determined by measuring the density from the thickness and basis weight of the base paper before coating.

 Bulking ratio = (1−density of base paper with added filler / density of base without added filler) × 100.

(4) Method for producing light calcium carbonate / silica composite particles

 The light calcium carbonate-silica composite particles are prepared, for example, by adding a mineral acid to a mixture of light calcium carbonate and an aqueous solution of an alkaline metal silicate at a temperature not higher than the boiling temperature thereof. Obtained as 9. Incidentally, according to such a production method, it is considered that the surface of the light calcium carbonate will be a composite particle coated with silica.

 Specifically, first, the above-mentioned light calcium carbonate is dispersed in water. The dispersion amount in water is preferably set to 1 to 20% by mass in terms of solid content in consideration of the influence of addition of caiic acid described later. When the dispersed amount is less than 1% by mass, the production amount per batch decreases, and when it exceeds 20% by mass, the dispersibility decreases, and an alkali caic acid used for the reaction with the light calcium carbonate amount The viscosity of the reaction may increase and the operability S may decrease.

Next, an alkaline solution of silicic acid (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 0 = (3 to 3) 3.4) Zl) is generally available and readily available. The solid content mass ratio (CaCO 2 / SiO 2) of the intended light calcium carbonate-silica composite particles can be adjusted by adjusting the feed mass ratio of the light calcium carbonate to the alkali solution of silicic acid.

 3 2

 Next, these mixtures are stirred and dispersed by an agitator, a homomixer, a mixer or the like.

 If the light calcium carbonate is properly dispersed without excessive aggregation, the dispersion time, the strength of the agitation, etc. are not limited.

 Next, the reaction is neutralized with a mineral acid. Mineral acids can be anything cheap, such as sulfuric acid and hydrochloric acid. The mineral acid may contain an acidic metal salt such as a sulfuric acid band or magnesium sulfate. Addition of mineral acid (or acid containing the above acidic metal salt aqueous solution to mineral acid) is carried out at a temperature not higher than the boiling point of the above mixture, and precipitation of silicic acid on the surface of light calcium carbonate particles results in amorphous formation. Silica is formed and coated to obtain light calcium carbonate-silica composite particles. It is important to terminate this neutralization reaction at pH = 7 to 9. If the pH is less than 7, decomposition of light calcium carbonate occurs, and if the pH exceeds 9, precipitation of silicic acid is not sufficiently performed, and unreacted silicic acid Is not preferable because it causes a remaining loss.

 The acid concentration should be at least 0.05 N, as the amount of the whole solution will increase if the acid concentration is low. However, when the acid concentration becomes high, a low pH occurs in the solution due to the addition of acid, and light calcium carbonate is decomposed, so strong stirring is performed using a homomixer etc. at the addition port of acid. There is a need. Also, the acid addition may be performed 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 in the case of small scale production, filtration equipment such as filter paper or membrane filter is used, and in the case of medium scale or more, belt filter is used. And solid-liquid separation using filtration with a drum filter, etc., or centrifugation using a centrifuge, and removal of salts, which are by-products generated by neutralization reaction, is preferred. . If this salt remains, it may be converted to a poorly soluble metal salt (eg, calcium sulfate) in the papermaking process, which may cause scaling. Furthermore, the cake (usually having a solid concentration of 10 to 50%) subjected to solid-liquid separation may be re-dispersed with water or ethanol, and then solid-liquid separated again to further remove excess caiic acid or salt.

Furthermore, light calcium carbonate / silica composite particles obtained using a vibrating sieve or screen Among the particles, remove coarse particles (eg, 100 μm or more) as appropriate.

 The adjustment of the average particle size of the light calcium carbonate-silica composite particles can be carried out by vigorously stirring or grinding during aging during the neutralization reaction, or after completion of the neutralization reaction, or after wet separation of solid / liquid separated after completion of the reaction. It can be carried out by crushing using a machine. You may combine these methods. The term "aging" refers to temporarily suspending the addition of the acid to be added during neutralization and leaving it to be stirred only.

(5) Other filler

 As the filler, in addition to the light calcium carbonate-silica composite particles, other inorganic fillers and organic fillers may be used in combination as long as bulkiness, opacity, size and the like are not impaired. For example, fillers generally used in neutral papermaking and alkaline papermaking can be used without any limitation. For example, magnesium carbonate, barium carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, clay, calcined kaolin, delami kaolin, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, etc. One or more selected from fillers, fine particles of organic substances such as urea formalin resin, polystyrene resin, and phenol resin may be selected.

 The content of the total filler in the paper (light calcium carbonate / silica composite particles alone, or the total of this and other fillers) in the paper is preferably 1 to 40% by mass in solid content 3 to 40 mass % Is more preferably 5 to 40% by mass. If the content exceeds 40% by mass, the number of cut sheets due to the decrease in paper strength may increase, and the operability may decrease and the amount of paper dust generated during printing may increase.

(6) Production of base paper

The pulp and filler described above are mixed, and if necessary, paper strength improver, retention aid, wet paper strength improver, dye, optical brightener, antifoaming agent, pitch control agent, slime control agent , Add paper making auxiliary chemicals such as sizing agents, and make a paper sheet to make a base paper o In the case of neutral papermaking or alkaline papermaking, alkyl ketene dimer (AKD) based sizing agent, acrylic acid succinic anhydride (ASA) ) Known internally added neutral sizing agents such as sizing agents, neutral rosin sizing agents and the like can be used. However, AKD and ASA are more preferable than neutral rosin sizing agents because they can obtain lower density base paper. The content of these sizing agents is preferably from 0.1 to 1% by weight, preferably from 0.05 to 5% by weight, based on the absolute dry weight of the pulp. [0034] As a paper machine used for paper making of base paper, known devices such as a Fourdrinier paper machine, an on-top twin wire paper machine, a gear former and the like can be used.

 After papermaking, the surface may be coated on a base paper for the purpose of improving surface strength, imparting water resistance, and improving ink receptivity. There is no restriction on the coating device. The type of surface treatment agent used for surface coating is not particularly limited, and, for example, raw starch, oxidized starch, esterified starch, cationized starch, enzyme-modified starch, aldehyde-modified starch, hydroxylated starch and the like Modified starches; Cellulose derivatives such as carboxymethyl cellulose, hydroxyl cellulose and methyl cellulose; Modified alcohols such as polybul alcohol and carboxyl-modified polybul alcohol; styrene butadiene copolymer, polyvinyl acetate, polyvinyl chloride It is possible to use a rue acetate-bule copolymer, polyvinyl chloride, poly salt, vinylidene, polyacrylate, polyacrylamide, etc. alone or in combination. Furthermore, it is possible to apply a coating obtained by adding a surface sizing agent such as styrene acrylic acid, styrene maleic acid, an olefin based compound, or a cationic sizing agent to the surface treating agent.

 Force that can be processed by linear pressure within the normal operating range From the viewpoint of producing low-density paper, the linear pressure should be as low as possible, as long as the smoothness of the paper can be maintained. It is preferable to use soft calenders.

<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 thereof include silica (including colloidal silica), alumina (including colloidal alumina), aluminum hydroxide, kaolin, talc, calcium carbonate, titanium dioxide, clay, zinc oxide, etc. Alternatively, multiple mixtures can be used. Among them, alumina is an acid oxide of aluminum obtained by calcining aluminum hydroxide or the like, and can be exemplified by, for example, α-alumina, j8-anoremina, γ-alumina and the like. -It is preferable to use alumina because the gloss of the ink receiving layer is further improved. The particle diameter of alumina, BET specific surface area can be appropriately selected as necessary, but the average particle diameter (laser diffraction method It is preferable to use an alumina of 1. 0 to 4.0 m) because the glossiness of the ink receptive layer is improved. In particular, an anolemina of 1. 5 to 3. 3 / z m is preferably used. Prefer! /.

 (2) Binder

 The binding agent may be of any type as long as it is a polymer compound capable of forming a film. Specifically, completely acid or partially acid polyvinyl alcohol; carboxylic acid-defective polybule alcohol; silyl-modified polybule alcohol; acetatocetyl-modified polybule alcohol; polybutyl acetar resin; oxidized starch, Starches such as esterified starch; cellulose derivatives such as carboxymethyl cellulose and hydroxyl cellulose; polybutyl pyrrolidone; casein; gelatin; soy protein; styrene-one acrylic resin and derivatives thereof; styrene butadiene latex, acrylic resin, It is possible to use acetate alone or in combination with urethra chloride, urethan emulsion, urethan emulsion, urea emulsion, alkane aldehyde, and derivatives thereof alone or in combination. In particular, polyvinyl alcohol (including modified products) is preferable because it can improve the transparency of the ink receiving layer and impart the same glossiness as a silver salt photograph.

 The amount of the binder to be added is not particularly limited as long as the necessary layer strength can be obtained, but it is preferably 5 parts by mass to 30 parts by mass with respect to 100 parts by mass of the pigment 20 More preferably, it is at most parts by weight. If the blending amount is less than 5 parts by mass, the strength of the ink receiving layer decreases. If it exceeds 30 parts by mass, the ink absorption of the ink receiving layer tends to be reduced. Also

In the case where the polybule alcohol is blended in the binder, since the white paper gloss (the gloss of the recording layer before ink jet printing) tends not to be improved if the blend amount is small, the polybule alcohol in the binder is The proportion is preferably 30% by mass or more, more preferably 50% by mass or more.

(3) Formation of ink receiving layer

The ink receiving layer can be formed by applying a coating liquid for ink receiving layer. The coating method may be a known coater such as blade coater, air knife coater, roll coater, brush coater, kiss coater, squeeze coater, curtain coater, die coater, die coater, gravure coater, cast coater, etc. The power that can be selected appropriately from the coating methods used to obtain an inkjet recording sheet with particularly high gloss Cast coating (coating by cast coating) is preferred from the viewpoint of

 [0041] Method of Forming Ink Receptive Layer (Cast Coating Method)>

 When an ink jet recording sheet having high gloss is obtained, it is preferable to form an ink receptive layer by the V, conventional cast coating method, from the viewpoint of heat resistance. This cast coating method is performed by pressing the coated layer against a heated mirror surface while the surface of the coated layer coated with the paint for ink receiving layer is in a wet state, and then drying.

 The cast coating method is: (1) a wet casting method (direct method) in which the coated layer is pressed (pressure-welded) against a mirror-finished heating drum while it is in a wet state (as-coated); 1) The wet coated layer is once (semi) dried and then swell plasticized (wet) by rewet liquid, pressed onto a mirror-finished heating drum and dried (Rewet method), (3 The gel coating method can be generally divided into three types: gel cast method (coagulation method), in which the wet coating layer is made into a gel state by coagulation treatment such as coagulation liquid, and pressed onto a mirror-finished heated drum and dried. Ru.

 V, the same as the displacement method, except that the mirror surface (for example, a heated mirror drum or a metal mirror such as a flat mirror) is pressed against the coating layer in the wet state (including gel state in the wet state). is there.

 In the present invention, the rewetting method is preferable from the viewpoint of obtaining high strength and gloss which can also use the above-mentioned displacement method, and from the point of improving the productivity of the coagulation method.

In the case of the cast coating method of coagulation method, a treatment having the function of coagulating (or crosslinking) the binder while the coating layer coated with the coating liquid for ink receiving layer is in a wet state. Apply the solution, then press the coated layer on the heated mirror to give a gloss. For example, when polybule alcohol is used as a binder for the coating layer, any aqueous solution containing a compound having the function of coagulating polybule alcohol can be used, but in particular, Treatment solutions containing boric acid and borate are preferred. By mixing and using boric acid and a borate, it becomes easy to obtain a solidified state of appropriate hardness, and it is possible to obtain an inkjet recording sheet having a good gloss. When casein is used as a binding agent, an aqueous solution containing a compound having the function of coagulating casein is treated as a binder. It can be used as a fluid.

 [0043] In the case of the rewetting cast coating method, a treatment liquid having a function of drying the coated layer coated with the coating liquid for the ink receiving layer and plasticizing the binder of the coated layer Solution is applied to the coated layer, and then the coated layer is pressure-bonded to the heated mirror surface to impart gloss. In this method, when the treatment liquid is applied, the ink receiving layer is in a dry state, so that it is difficult to copy the surface of the mirror drum surface. However, productivity can be improved because the coating speed can be increased as compared with other methods.

 Further, in the above-mentioned treatment liquid (coagulation liquid and plasticization treatment liquid), if necessary, a pigment dispersant, a water retention agent, a thickener, an antifoamer, an antiseptic agent, a coloring agent, a water resistant agent, a wetting agent An agent, a fluorescent dye, an ultraviolet absorber, a cationic polymer electrolyte, etc. can be added as appropriate. The method for applying the treatment liquid may be, for example, a roll, a spray, or a curtain method.

 2. An embodiment according to the second invention (containing the light calcium carbonate-silica composite particles in the under layer)

 The ink jet recording sheet of the embodiment according to the second aspect of the present invention is configured by providing an undercoat layer and an ink receiving layer in this order on a support.

[Support]

 As the support, a known material can be appropriately selected and used. It is particularly preferable to use paper (coated paper, uncoated paper, etc.) as the base paper.

As a support, since the same pulp and auxiliary agent used in the embodiment according to the first invention are used, the description of the same parts will be omitted. As the filler, it is also possible to use a conventionally known inorganic filler and organic filler in combination. Any filler that is usually used in neutral papermaking and alkaline papermaking can be used without any limitation. For example, magnesium carbonate, barium carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, clay, calcined kaolin, delami kaolin, titanium dioxide, zinc oxide, silicon oxide, amorphous silica Etc., and fine particles of organic substances such as urea formalin resin, polystyrene resin, and phenol resin. One or more selected. Also, the light calcium carbonate / silica composite particles according to the first invention may be used. The method for producing a support, the surface coating after paper making, and the surface treatment are also the same as in the embodiment according to the first invention. The explanation is omitted.

 <Under Layer>

 An under layer is present between the base paper and the ink receiving layer to aid in the uniform coating and ink absorption of the ink receiving layer. The under layer contains a pigment and a binding agent, and the pigment contains light calcium carbonate-silica composite particles.

 [Pigment]

 As the pigment, the same light calcium carbonate-silica composite particles as used in the embodiment according to the first invention are used, so the description of the same parts will be omitted. The same applies to the form (homomorphous image) of light calcium carbonate crystals.

 In particular, the light calcium carbonate calcium carbonate power of the Rosetta-type light calcium carbonate-mosilica composite particles obtained has good absorption characteristics, and when this is used as a pigment of the under layer, the ink absorbability of the ink jet recording paper is obtained. Is preferable because it improves. Since the light calcium carbonate-silica composite particles obtained by the above-mentioned Rosetta-type light calcium carbonate carbonate and the like have a light calcium carbonate particle serving as a core, they have a large number of voids in the composite particles and the ink absorbability is improved. It is thought that.

 The reason for improving the ink absorbability and the strength of the under layer by using the above-described light calcium carbonate-silica composite particles as a pigment is not clear, but is considered as follows. That is, in the case of light calcium carbonate-silica composite particles, since primary particles of silica are attached to the surface of light calcium carbonate, a large amount of ink having an oil absorption larger than that of calcium carbonate having the same particle diameter is contained in the pigment. Can be absorbed. In particular, when light calcium carbonate serving as a core forms secondary particles, a space is formed between primary particles of calcium carbonate, resulting in a further increase in oil absorption.

 Further, in the case of the above composite particles, since the silica is disposed around light calcium carbonate, the specific surface area and the ratio of the pigment adsorbing the binder are smaller than that of a single silica of the same particle diameter. Since the amount is reduced (as the required amount of binder is decreased), it is considered that an effective amount of binder is secured and the strength of the under layer is increased. In addition, when the specific surface area of the pigment decreases, the stability of the paint containing it also increases.

[0050] The light calcium carbonate-silica composite particles have the characteristics of silica and the characteristics of light calcium carbonate. It is considered that the combination of these properties is considered, and there is an advantage that the ink absorbency, print density, or sharpness can be properly adjusted by adjusting the blending ratio of these. Here, the vividness is an index for clearly printing an image, and is an evaluation that integrates the printing density, the image reproducibility, and the presence or absence of image unevenness. From these facts, the solid mass ratio (CaCO 2 / SiO 2) of the light calcium carbonate Z silica in the light calcium carbonate silica composite particles is

 3 2

It is preferable that it is 25Z75-75Z25. When the above ratio is less than 25/75, the properties of the silica are exhibited overall, and the strength of the under layer is apt to decrease because the adsorption property is too high and the binding agent is adsorbed. On the other hand, when the above ratio exceeds 75Z25, the characteristic of light calcium carbonate is largely developed, the adsorption characteristic is lowered, and the ink absorptivity and the printing density are easily lowered. The solid content mass ratio can be determined, for example, by measuring light calcium carbonate-silica composite particles with a fluorescent X-ray to quantify Ca and Si.

 The oil absorption of the light calcium carbonate-silica composite particles is preferably 100 to 250 ml Z 100 g. If the oil absorption of the composite particles is less than 100 ml ZlOOg, the ink absorption may decrease, and if it exceeds 250 ml Zl 00g, the under layer strength may decrease. A more preferable oil absorption amount is 120 to 200 ml Z 100 g, and a further preferable range is 140 to 180 ml Z 100 g.

 Oil absorption can be measured according to IS K5101.

Further, it is preferable that the BET specific surface area of the light calcium carbonate / silica composite particles is 5 to 150 m ² Zg. When the BET specific surface area of the composite particles is less than 5 m ² Zg, the ink absorptivity decreases, and when it exceeds 150 m ² Z g, the strength of the under layer decreases and the viscosity of the coating liquid increases and the operability decreases. There is. A more preferable BET specific surface area is 10 to: LOOm ² Zg, and a further preferable range is 20 to 50 m ² Zg.

 The BET specific surface area can be measured by a nitrogen adsorption method.

The average particle diameter of the light calcium carbonate-silica composite particles is preferably 1 to 10 μm. When the average particle size of the composite particles is less than 1 μm, the voids in the composite particles are reduced and the ink absorbability is reduced. On the other hand, when the average particle size exceeds 10 m, the smoothness of the under layer may be impaired, and it may be difficult to uniformly provide the ink receiving layer. A more preferable average particle diameter is 2 to 9 μm, and a further preferable range is 3 to 8 μm. The average particle size can be measured using a laser method particle size measuring apparatus (for example, a trade name of Master Malvern, Inc .: Master-I sizer-type).

[Other Effects of Light Calcium Carbonate-Silica Composite Particles]

 Furthermore, when light calcium carbonate / silica composite particles are used as the pigment of the under layer, there is an effect that the air permeability of the recording paper becomes high. In particular, the present invention is effective when producing an inkjet recording sheet by a cast coating method. That is, in the cast coating method, since it is necessary to press the coated layer against the cast drum to obtain a glossy surface, drying of the coated layer proceeds only from the side not in contact with the cast roll of the support. Therefore, although the cast coating method has a low drying speed and low productivity, the productivity can be improved by increasing the air permeability of the under layer.

 The reason is considered to be that the light calcium carbonate-silica composite particles contain voids as described above. In order to increase the air permeability of the under layer, it is preferable to set the average particle size of the composite particles to 1 m or more. Further, the above-mentioned Rosetta-type light calcium carbonate calcite has a great effect of improving the air permeability of the under layer having many voids because of the chestnut-like shape.

 The air permeability of the support provided with the under layer is preferably 300 seconds or less, more preferably less than 100 seconds.

[Method of producing light calcium carbonate / silica composite particles]

 The method for producing the composite particles is the same as the method for producing the embodiment according to the first aspect of the present invention, so the description will be omitted.

[Other pigments]

As the pigment of the under layer, in addition to the light calcium carbonate-silica composite particles, it is also possible to use an inorganic pigment and an organic pigment in combination, if necessary, as long as the effects of the present invention are not impaired. These pigments can be used without any limitation as long as they are pigments generally used in coated paper. For example, synthetic silica, alumina and alumina hydrate (alumina sol, colloidal alumina, pseudoboehmite etc.), aluminum silicate, magnesium silicate, magnesium carbonate, light calcium carbonate, calcium carbonate, kaolin, talc, calcium sulfate, dioxide Titanium, zinc oxide, zinc carbonate, calcium silicate, aluminum hydroxide Inorganic pigments such as urea; organic pigments such as urea formalin resin, polystyrene resin and phenol resin; and one or more selected from kabuto etc. can be used in combination. When light calcium carbonate / silica composite particles and other pigments are used in combination, light calcium carbonate / silica composite particles are preferably contained in an amount of 60% by mass or more in all pigments.

[Binder]

 The same binder as the binder for the ink receiving layer in the embodiment according to the first invention can be used as the binder for the under layer, so the description will be omitted. The use of polyvinyl alcohol (including modified products) is preferable because it improves the transparency of the under layer and improves the color developability of the ink remaining in this layer.

 The amount of the binder contained in the under layer is not particularly limited as long as the necessary layer strength can be obtained, but it is preferably 3 to 70 parts by mass with respect to 100 parts by mass of the pigment. It is more preferred that If the blending amount of the binder is small, the strength of the under layer decreases. If the blending amount is too large, the ink absorbability tends to be reduced.

[Other Auxiliary Agents]

 In order to improve the fixing property of the dye ink and to make the fixed dye ink water resistant, the under layer may contain a cationic polymer compound.

 Examples of the cationic polymer compound include primary amine, secondary amine, tertiary amine, quaternary ammonium salt and cyclic amine, or a polymer compound using these salts as monomers. Specific examples include berylimine, alkylamine, alkyleneamine, buramine, allylamine, cycloaliphatic amine, epihalohydrin, dialkylaminoethyl methacrylate, dialkylaminoalkyl arylate, dialkylaminoalkyl acrylamide, diallyldimethyl So-called polyethylenimine type oils, polyamine type oils, polyamide type oils, polyamidoepichlorohydrin, which are cationic polymer compounds having monomers such as ammonium salts, acrylamides, amidoamines and amidines. There may be mentioned series fats, polyamine pychlorohydrin based fats, polyamide polyamines pychlorohydrin based fats, polydiarylamine based fats, dicyandiamide condensates and the like. Also, two or more of these cationic polymer compounds can be used in combination.

In particular, the printing quality is excellent regardless of whether the dye ink or the pigment ink is used, and the printing density is particularly high. Condensates (homopolymers), copolymers and derivatives of dialkyl (alkylene) amines, lohydrins and diaryl dimethyl ammonium salts, which increase the degree and water resistance, are preferred. And, dialkyl (alkylene) amines, polymers of lohydrin (homopolymers), copolymers, and derivatives are most preferable because they have low molecular weight and are not likely to inhibit the ink absorption of the ink receiving layer.

In the under layer, if necessary, pigment dispersants, flow improvers, water retention agents, thickeners, antifoaming agents, foam inhibitors, mold release agents, surface property modifiers, foaming agents, penetrants, coloring dyes, coloring Pigments, optical brighteners, UV absorbers, antioxidants, preservatives, fungicide, _P H adjusting agents, softeners, may be added various aids.

Coating method>

 Next, a method of providing an under layer on a support will be described.

The under layer can be formed as one or more layers on one side or both sides of the support. When a plurality of under layers are provided, the components of the coating liquid may be different within the range specified in the present invention. Further, for example, the coating material may be layered in plural layers by a slide die coater or the like, coated on a support and then dried. Usually, when the paint is applied a plurality of times, an interface exists between the coating layers, and the interface is observed, for example, by observing the cross section of the ink receiving layer with an electron microscope or an optical microscope, or by a gas adsorption method or mercury porosimeter. It can be identified by measuring the pore size distribution. The coating amount of the under layer and more preferably it is preferred instrument is 3～30GZm ² is 5~20gZm ^2. If it is less than 3 gZm ² , the support can not be covered sufficiently and coating unevenness may occur. If it exceeds 30 g Zm ² , the strength of the coated layer may be reduced to cause the under layer peeling.

In practice, when a predetermined paint is applied, the physical properties of the coated paper may differ between the case where it is applied at one time and the case where it is applied twice. Also, in this case, as described above, the interface of the coated layer can be easily observed in the case of double coating by microscopic observation or the like.

Then, in the case where the coating and the coating are performed once, the physical properties of the coated paper may differ due to binder migration and the like, so the number of times of coating may be determined according to the required characteristics and the like. In addition, in order to apply a predetermined coating amount at one time, the drying load of the coater is large, and it is affected by the equipment, so in the case of a small coater, it may be necessary to coat twice.

[0062] As an apparatus for coating the under layer, various blade coaters, roll coaters, air knives: ~ "ta '~", no ~ ~ "~ ~ ~ ~ ~ ~, r ~ ~ ~ ~" / Vn '~' ta '~' ij ~ ~ te, no ~ 'ta' ~ set ^ ¹ ~ ~ 1, short-dwell coater, gravure coater, flexo gravure coater, spray coater, size press, etc. The device can be used on-machine or off-machine.

 It is also possible to surface-treat with a calender device such as a machine calender, a super calender, a soft calender, etc. before or after applying the under layer.

 <Ink Receiving Layer>

 The ink receiving layer contains a pigment and Z or a binder, and retains colored components in the ink. The pigment, the binder, and the pigment for the ink receiving layer in the embodiment according to the first aspect of the invention can be used in the ink receiving layer, so the description will be omitted. If necessary, various assistants similar to those of the under layer can be added.

 [Coating Amount of Ink Receptive Layer]

The coating amount of the ink receiving layer can be optionally adjusted within the range in which sufficient ink absorbency can be obtained while covering the surface of the under layer, but from the viewpoint of achieving both recording density and ink absorbency, one side It is preferable that it is 3-30 g / m < ² > in solid content conversion. A further preferred range is 5 to 20 g / m ² . If the coating amount is less than 3 g / m ² , the under layer may not be covered sufficiently and coating unevenness may occur, and if it exceeds 30 g / m ² , the coating layer in the case of the cast method described later. The peelability of the mirror drum force is reduced, and the coating layer may be attached to the mirror drum.

 [Method of Forming Ink Receiving Layer]

 The ink receiving layer can be formed by applying a coating liquid for ink receiving layer. As the application method, the same method as the application method of the ink receiving layer in the embodiment according to the first aspect of the present invention can be used, so the description will be omitted.

[Method of forming ink receiving layer (cast coating method)] When it is possible to obtain an ink jet recording sheet having the same high gloss as that of a silver salt photograph, it is preferable to form an ink receiving layer by a V-like cast coating method from the point of view. This cast coating method is carried out by pressing the coated layer against a heated mirror surface while the surface of the coated layer coated with the paint for ink receiving layer is in a wet state, and then drying. Here, in the present invention, since the first layer contains the light calcium carbonate-silica composite particles, an appropriate void is formed in the layer, and when the coating liquid for the ink receiving layer is pressed against the cast drum and dried, Since the vapor evaporated from the coating liquid is easily released, the cast drum may be dried immediately and the cast drum may be fogged or any trouble may be reduced if the coating layer adheres to the cast drum.

 The cast coating method can be generally divided into three types, a direct method, a rewetting method, and a coagulation method. These are the same as those described in the first embodiment of the present invention. , I omit the explanation.

 In the present invention, the rewetting method is preferable from the viewpoint of obtaining high strength and gloss which can also use the above-mentioned displacement method, and from the point of improving the productivity of the coagulation method.

In addition, in the treatment liquid (coagulation liquid and plasticization treatment liquid), if necessary, a pigment dispersant, a water retention agent, a thickener, an antifoamer, an antiseptic agent, a coloring agent, a water resistant agent, a wetting agent Fluorescent dyes, ultraviolet absorbers, cationic polymer electrolytes and the like can be added as appropriate. Examples of the method for applying the treatment liquid include, but not limited to, roll, spray and curtain methods.

 <Other Layers>

 In the present invention, an overcoat layer comprising a coating layer containing organic fine particles, inorganic fine particles, or a polymer compound, etc. is provided on the ink receiving layer for the purpose of adjusting the glossiness and the coefficient of friction. It can also be done. In addition, if necessary, a back layer may be provided on the support opposite to the side on which the ink receiving layer is provided to provide writability, antistatic properties, antifouling properties, slipperiness, and the like. Is also possible.

 [Examples of Examples]

The present invention will be described more specifically by the following examples. The present invention is not limited to the following examples. Moreover, the following "parts" and "%" represent "mass part" and "mass%" unless there is particular notice. Example according to the first invention (when internally adding composite particles to base paper)>

 (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 (Alpaca 5970: manufactured by Speciality Minerals Inc., average particle size 3.0 m, oil absorption 150 ml ZlOOg) is dispersed in water, and sodium silicate is dispersed therein. Solution (SiO concentration 18. OwtZwt%

 2, Na O concentration 6. lwt

 2

/ wt%) After adding 3,400 g, water was added to make the total amount 12 liters. The mixed slurry was heated to 85 ° C. while being sufficiently stirred by a laboratory agitator. To this slurry, a 10% sulfuric acid solution was added by a rotary pump, and at this time, it was added immediately below the stirring blade of the laboratory agitator so that the sulfuric acid-added portion was sufficiently stirred. Under the conditions described above where the added sulfuric acid is sufficiently dispersed, sulfuric acid is added at a constant temperature and at a constant rate so that the final pH of the slurry after the addition of sulfuric acid is 8.0 and the total sulfuric acid addition time is 240 minutes. did. The obtained slurry was subjected to 100 mesh sieve to separate coarse particles, and suction filtration was performed using No. 2 filter paper. Furthermore, the filtrate was re-dispersed in water so that the solid matter was 10% by mass, and light calcium carbonate-silica composite particles A of 50 Z 50 in weight ratio of light calcium carbonate Z silica were obtained. The oil absorption capacity of this composite particle was 160 ml Z 100 g, the BET specific surface area was 28 m ² Z g, and the average particle size was 6.1 μm. To measure the oil absorption, etc., the sample after the above suction filtration is redispersed in ethanol so that the filtrate has a solid content of 10% by mass, followed by filtration, and the powder sample dried at 105 ° C. Using.

2) Light calcium carbonate-silica composite particles B

The weight ratio of light calcium carbonate Z silica is 70 Z30, and the oil absorption amount is 150 ml Z 100 g, in the same manner as in the production of the light calcium carbonate-silica composite particles A except that the dispersion amount of the rosetta light calcium carbonate is 1407 g. A light calcium carbonate-silica composite particle B having a BET specific surface area of 26 m ² Z g and an average particle size of 4.6 m was obtained.

 Example 1

[0073] (Production of base paper)

To a pulp slurry consisting of 100 parts of LBKP with a freeness of 370 ml c 's' f, add light carbonic acid calcium sulfate silica composite particles A as a filler so that the filler percentage in the paper is 7%, and use a paper machine Paper was made with During papermaking, starch in per one side solids 2. Ensure a 5GZm ² was applied to both surfaces, to obtain a base paper having a basis weight 65gZm ^2.

[0074] (Formation of an under layer)

On one side of this base paper, using a blade coater, the coating solution A was coated to a coating amount of 15 g / m ² to form an under layer.

 Coating solution A: 100 parts of silica as a pigment (Fine Seal X-37B: manufactured by Tokuma Co., Ltd.), 5 parts of SB latex (LX438C: manufactured by Sumitomo Chemical Co., Ltd.) as a binding agent, and polyvinyl alcohol (PVA 117: stock 20 parts of Kuraray Co., Ltd. and 5 parts of sizing agent (Polymeron 360: Arakawa Chemical Industry Co., Ltd.) were blended to prepare a coating liquid having a solid content concentration of 20%.

(Formation of Ink Receptive Layer)

Next, 10 g / m ^{2 of} coating solution B is coated on the coated surface of coating solution A with a roll coater, and while the coating layer is in a wet state, coagulate using coagulating solution C, and then press The coated layer was pressure-bonded to the heated mirror-finished surface via a roll, the mirror surface was copied, and dried to obtain an inkjet recording sheet with a basis weight of 9 OgZm ² .

 Coating solution B: 100 parts of high purity alumina (UA5605: manufactured by Showa Denko KK, average particle diameter: 2.8 m) as a pigment is blended, and completely densified poly vinyl alcohol having a polymerization degree of 500 (PVA 105: Kuraray Co., Ltd., 15 parts of oxidation degree 9) was blended, and 0.2 parts of an antifoaming agent was blended to adjust a coating liquid having a concentration of 30%.

 Solidifying solution C: Borax 2%, boric acid 2% (mass ratio of borax Z boric acid = 1Z1, Na B O

 2 4 7 and BO calculated), mold release agent (FL-48C: made by Toho Chemical Industry Co., Ltd.) 0.2% distributed

3 3

 The coagulation solution was adjusted.

 Example 2

 [0076] Except that light calcium carbonate-silica composite particles B were mixed as a filler for the base paper instead of the light calcium carbonate-silica composite particles A so that the filler content in the paper would be 7%, the same procedure as in Example 1 was performed. An ink jet recording sheet was obtained in the same manner.

 Example 3

[0077] As a coating liquid for the ink receiving layer, using the following coating liquid B1 instead of the coating liquid B, the coating liquid is coated with an air one-knife coater to a coating amount of 12 gZm ² and then a coagulating liquid C Coagulation and An ink jet recording sheet was obtained in exactly the same manner as in Example 1, except that it was dried as it was without cast coating.

 Coating solution B1: Silica as a pigment (Nipp JEL AY-603: manufactured by Tosoh Silica Corporation) 70 parts and silica (Mizkasil P-50: manufactured by Mizusawa Chemical Industry Co., Ltd.) 30 parts, as a binder 35 parts of alcohol (PVA-117: manufactured by Kuraray Co., Ltd.) and 25 parts of ethylene acetate vinyl copolymer latex (Likabond BE-7000: manufactured by Chuo Ri-i Kogyo Co., Ltd.), force size (Polymeron 360: 2 parts of Araiso 11 Chemical Industry Co., Ltd., 5 parts of dye fixing agent (PAS-H-10L: made by Nitto Boseki Co., Ltd.), an antifoaming agent, dilution water, etc. are appropriately blended, and the solid concentration is 18% The coating solution of

Comparative Example 1

 As the filler for the base paper, instead of the light calcium carbonate-silica composite particles A, Rosetta type light calcium carbonate (Alpaca 5970, Specialty Minerals Inc.) is not complexed and the filler ratio in the paper is 7 as it is. Ink jet recording paper was obtained in exactly the same manner as in Example 1 except that it was formulated to be%.

Comparative Example 2

 As a filler for the base paper, in place of the light calcium carbonate-silica composite particles A, spindle-like light calcium carbonate (TP121, manufactured by Okutama Kogyo Co., Ltd.) is blended so as to have a loading rate S7% in the paper as it is. An inkjet recording paper was obtained in exactly the same manner as in Example 1 except for the above. TP121 is composed of spindle-shaped primary particles, and the primary particles do not aggregate and do not form secondary particles.

Comparative Example 3

 As a filler for the base paper, instead of the light calcium carbonate-silica composite particles A, white carbon (TIXOLEX 17, manufactured by Rhdia Silica Korea) was blended as it is so that the filler percentage in the paper would be 7% without complexation. An ink jet recording sheet was obtained in the same manner as in Example 1 except for the above.

Comparative Example 4

As a filler for the base paper, white carbon (TIXOLEX 17, manufactured by Rhdia Silica Korea) and a light sales rosetta type light calcium carbonate (a) are used instead of the light calcium carbonate-silica composite particle A. The same as Example 1, except that a mixture of Lubaker 5970 and Specialty Minerals Inc.) at 50:50 (not composited) was blended so that the total filler ratio in paper would be 7%. The ink jet recording paper was obtained. The average particle diameter of the above mixed filler was 3.8 m, and the oil absorption amount was 137 ml / 100 g.

Comparative Example 5

 As a filler for the base paper, titanium oxide (FA-50: manufactured by Furukawa Machine Metals Co., Ltd.) was blended in place of the light calcium carbonate-silica composite particles A so that the filler content in the paper would be 2%, except that In the same manner as in Example 1, an inkjet recording sheet was obtained.

Comparative Example 6

 An inkjet recording paper was obtained in exactly the same manner as in Example 1 except that no filler was added to the base paper.

Comparative Example 7

 As a filler for the base paper, titanium oxide (FA-50: manufactured by Furukawa Machine Metals Co., Ltd.) was blended in place of the light calcium carbonate-silica composite particles A so that the filler content in the paper would be 2%, except that An ink jet recording sheet was obtained in the same manner as in Example 3.

The physical property values of the respective fillers blended in the base paper, and the inkjet recording paper of each Example and Comparative Example were evaluated by the following method.

 1) Physical property value of each filler

 (1-1) Content ratio of filler in paper: According to JIS P8251, each uncoated base paper was baked at 525 ° C., the ash content was measured, and this value was taken as the content ratio (solid content conversion) .

 (1-2) Oil absorption: It was based on the method of JIS K5101.

 (1-3) Average particle size: A slurry of each filler is added dropwise to pure water to which a dispersing agent (sodium hexametaphosphate 0.2% by mass) is added to make a uniform dispersion, and a laser method particle size measuring machine (Malva The particle size was measured by an Onen Corporation model number: Master Sizer 1 S type), and the average particle size was determined. (1-4) Solid content mass ratio of light calcium carbonate Z silica (CaCO 2 / SiO 2): light carbonation power

 3 2

The fluorescent-silica composite particles were analyzed by fluorescent X-ray to determine Ca and Si, thereby obtaining [0086] 2) Evaluation of each inkjet recording paper (2-1) Whiteness of base paper: The uncoated base paper was measured with a color difference meter (manufactured by 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. If the opacity is about 83% or more, it can be said that the opacity is good.

 (2-3) Bulk ratio of base paper: With respect to an uncoated base paper, the density is measured from the paper thickness and basis weight, and the following formula

 Bulking factor = (1 (density of filler additive / density of non-filler)) × 100

 Calculated according to It can be said that the bulkiness is about 4% or more.

[0087] (2-4) Cutting aptitude

 i) Abrasion of blade at guillotine cutting

 After overlapping 200 sheets of the ink jet recording paper and cutting the other part of the paper 10 times with a guillotine cutter from the side opposite to the ink receiving layer surface, the chipping condition of the blade was visually evaluated.

 ○: There is no chipping

 Slightly missing

 X: Missing in several places

 iO cutting sound

 Two hundred ink jet recording sheets were stacked, and the magnitude of the sound when cut with a guillotine cutter from the side opposite to the ink receiving layer surface was evaluated.

 :: The sound is small! / ヽ (about normal cutting work)

 :: The sound is a little louder

 X: There is vibration at the time of cutting when the sound is loud

(2-5) Strikethrough

A predetermined pattern is recorded on the ink receiving layer with black ink by an ink jet printer (PM-950C: trade name of Seiko Epson Corporation) using dye ink, and the ink receiving layer is viewed from the side opposite to the ink receiving layer. The degree of transparency of the printed image on the side was observed. The strike-through rating indicates the opacity of the paper. If the strike through is 不透明, it can be said that the opacity is excellent :: The image can not be seen from the opposite side

 :: The image looks slightly transparent from the opposite side

 X: The image is clearly visible through the opposite side

(2-6) Cast operability

 When the coating liquid B (or B1) was applied and the coagulating liquid C was applied, the coating layer was attached to the cast drum to make it dirty and the maximum value of the coating speed in the range was evaluated. If the cast operability is 〇, it can be said that the cast operability is excellent.

 ○: Coating speed is 25mZ or more

 :: Coating speed is more than 20mZ minutes and less than 25mZ minutes

 X: Coating speed is less than 20 mZ

 The obtained results are shown in Tables 1 and 2.

[table 1]

Filler in base paper

 Light calcium carbonate average particle size, oil absorption, BET specific surface area in ink base paper

 Type Content ratio (%) Receptive layer

/ Silica) mass ratio (m) (ml / 100g) (m ² / g)

 Light calcium carbonate

Example 1 1 50/50 6.1 160 28 Cast Coat Silica Composite Particles A

 Light calcium carbonate

Example 2 7 70/30 4.6 150 26 Cast Coat-Silica Composite Particles B

 Light calcium carbonate

Example 3 1 7 50/50 6.1 160 28 matte silica composite particles A

Comparative Example 1 Rose 'Ivy Type Calcium Carbonate 7-3.0 121 12 Cast Coat Comparative Example 2 Spindle-like Calcium Carbonate 7-1.2 50 5 Cast Co-Composite Comparative Example 3 Hot Car Hon 7-8.2 152 52 Cast Co-Composite Hot force-Hon 'and calcium carbonate

Comparative Example 4 7 50/50 3.8 137 23 Mixture of cast irons

Comparative Example 5 Titanium Dioxide 2-0.6 24 8 Cast Coat Comparative Example 6-Mono----Cast Coat Comparative Example 7 Titanium Dioxide 2 1 0.6 24 8 Matte

[Table 2]

表 1、 2から明らかなように、各実施例の場合、不透明度及び断裁適性のいずれも 優れていた。又、各実施例の場合、基紙の嵩高率が高ぐキャスト操業性にも優れて いた。

As apparent from Tables 1 and 2, in each of the examples, both the opacity and the cutability were excellent. Moreover, in the case of each embodiment, the base paper is also excellent in cast operability with a high bulk ratio. It was.

 On the other hand, in the case of Comparative Examples 1 and 2 in which only light calcium carbonate was used as the filler, both the opacity decreased and the cast operability with low bulkiness also decreased. In the case of Comparative Example 3 in which white carbon was used as the 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 and the cast operability with low bulkiness also decreased. In the case of Comparative Examples 5 and 7 in which titanium dioxide was used as the filler, the cutting aptitude deteriorated, and the cast operability with low bulkiness also decreased. In the case of Comparative Example 6 in which no filler was added, the opacity was significantly degraded.

 As described above, by using the light calcium carbonate / silica composite particles as a filler, it is possible to obtain an ink jet recording sheet excellent in opacity and cutting aptitude.

 Example according to the second invention (when the under layer contains the composite particles)>

 (Production of light calcium carbonate / silica composite particles)

 1) Light calcium carbonate silica composite particles C

In a reaction vessel (12 L), 262 g of commercially available Rosetta-type light calcium carbonate (Alpaca 5970, manufactured by Speciality Minerals Inc., average particle size 3.0 m, BET specific surface area: 12 m ² Zg, oil absorption amount 120 ml Z 100 g) Dispersed in water, sodium silicate solution (SiO concentration 18. Ow

 2

 tZwt%, Na 2 O concentration 6. lwt / wt%) After adding 3,400 g, add water to make the total volume 12 liters

 2

The The mixed slurry was heated to 85 ° C. while being sufficiently stirred by a laboratory agitator. To this slurry, a 10% sulfuric acid solution was added by a rotary pump, and at this time, it was added immediately below the stirring blade of the laboratory agitator so that the sulfuric acid-added portion was sufficiently stirred. Under the above conditions where the added sulfuric acid is sufficiently dispersed, the final pH of the slurry after the addition of sulfuric acid is 8.0 and the total sulfuric acid addition time is 240 minutes so that the temperature is constant and the sulfuric acid is added at a constant rate. did. The resulting slurry is separated by a 100 mesh sieve to separate coarse particles, and suction filtered using No. 2 filter paper to obtain a light calcium carbonate-silica composite particle C with a weight ratio of light calcium carbonate Z silica of 30 Z 70. Obtained. The oil absorption of the composite particles was 180 ml / 100 g, the BET specific surface area was 30 m ² Zg, and the average particle size was 7.3 μm.

2) Production of light calcium carbonate-silica composite particles D

Other than the dispersion of the above Rosetta light calcium carbonate being 612 g, the above light In exactly the same manner as in the preparation of calcium carbonate-silica composite particles C, a light weight of light calcium carbonate Z silica 50 Z 50, oil absorption 160 ml Z 100 g, BET specific surface area 28 m ² Z g, average particle diameter 4.4 m Calcium carbonate-silica composite particles D were obtained.

3) Production of light calcium carbonate-silica composite particles E

The weight ratio of light calcium carbonate Z silica is 70 Z30, and the oil absorption is 140 ml Z 100 g, in the same manner as in the production of the light calcium carbonate silica composite particles C except that the dispersion amount of the rosetta light calcium carbonate is 1436 g. Light calcium carbonate-silica composite particles E having a BET specific surface area of 26 m ² Z g and an average particle size of 3.6 m were obtained.

 Example 4

(Production of Support)

Pulp consisting of 100 parts of hardwood bleached kraft pulp (L BKP) with 350 ml c 's' f freeness, 4 parts of acid titanium, cationic starch (Kate 304L: Nippon NSC Co., Ltd.) 0.4 parts, aluminum sulfate 1.0 part, 0.1 part of synthetic sizing agent, and 0.02 part of retention aid were added to obtain a norp slurry. Papermaking was carried out using this slurry strength paper machine, and starch was impregnated on both sides by a size press so that the dry coating amount per one side was 1.5 gZm ² to obtain a support.

(Formation of Under Layer)

A coating solution D was coated on one side of this support using a blade coater to give a coating amount of lOgZm ² to form an under layer, and a coated paper with a basis weight of 180 g Zm ² was obtained.

 Coating solution D: 100 parts of light calcium carbonate-silica composite particles C as pigment, 30 parts of polybul alcohol (PVA 117: manufactured by Kuraray Co., Ltd.) as binder and ethylene glycol acetate (BE7000: Central Rikko Kogyo Co., Ltd.) 5 parts, cationic resin (polyamine ammonia epichlorohydrin, molecular weight 100,000) 5 parts, sizing agent (Polymeron 360: Arakawa Chemical Industrial Co., Ltd.) 2 parts, antifoam agent 0.5 part A coating solution (solid content: 23%) was prepared.

(Formation of Ink Receptive Layer)

Next, apply ²⁰ g of a coating solution E to a coating surface of the coating solution D with a roll coater, and while the coating layer is in a wet state, coagulate using the coagulating solution F, and then press roll. The coated layer is pressed onto a mirror-finished surface with a surface temperature of 100 ° C, the mirror surface is copied, dried and dried. An ink jet recording sheet of 200 g / m ² was obtained.

 Coating solution E: 100 parts of silica as a pigment (Fine Seal X-37: manufactured by Tokuama Co., Ltd.), 5 parts of SB latex (LX438C: manufactured by Sumitomo Chemical Co., Ltd.) as a binding agent, and polyvinyl alcohol (PVA 117: Kuraray Co., Ltd. An aqueous coating solution E having a concentration of 20% was prepared by blending 24 parts of a product, and 5 parts of a sizing agent (Polymeron 360: manufactured by Arakawa Chemical Industry Co., Ltd.).

 Solidifying solution F: Borax 2%, boric acid 2% (mass ratio of borax Z boric acid = 1Z1, Na B O

 2 4 7 and

Calculated in HBO conversion), mold release agent (FL- 48C: made by Toho Chemical Industry Co., Ltd.) 0.2% blended

3 3

 The coagulation liquid was adjusted.

 Example 5

 An ink jet recording sheet was prepared in the same manner as in Example 4, except that the light calcium carbonate / silica composite particles C were replaced with 100 parts of the light calcium carbonate / silica composite particles D as a pigment for the coating liquid D. Obtained.

 Example 6

 Inkjet was carried out in exactly the same manner as in Example 4, except that 100 parts of the light calcium carbonate-silica composite particles E were blended instead of the light calcium carbonate / silica composite particles C as a pigment for the under layer coating liquid D. I got a recording sheet.

 Example 7

 [0101] As a coating liquid for the ink receiving layer, Example 4 was used except that the following coating liquid E1 was used instead of the coating liquid E, and the coagulating liquid F1 was used instead of the coagulating liquid F. Ink jet recording paper was obtained in the same manner as in.

 Coating solution E1: 100 parts of silica as a pigment (Fine seal X-37: manufactured by Tokuma Co., Ltd.), 30 parts of an aqueous urethane resin (HUX- 980: manufactured by Asahi Denka Kogyo Co., Ltd.) as a binding agent, and Zein (ALACID) 10 parts of lactic case, and 5 parts of a release agent (Nopcoat SYC: manufactured by San Nopco Co., Ltd.) were mixed to prepare an aqueous coating liquid E1 having a concentration of 30%.

 Coagulation solution F1: 5% of calcium formate (manufactured by Asahi Chemical Industry Co., Ltd.) and 1% of a dye fixing agent (Dyfix YK-50: manufactured by Daiwa Chemical Co., Ltd.) were mixed to prepare a coagulation solution.

 Comparative Example 8

The light calcium carbonate-silica composite particles C as a pigment for the under layer coating liquid D And Example 4 with the exception that 100 parts of silica (AY-603: Tosoh 1. Silica Corporation, oil absorption: 290 ml ZlOOg, BET specific surface area 300 m ² / g, average particle size 6.5 m) was blended. An ink jet recording sheet was obtained in exactly the same manner.

[Comparative Example 9]

Rosetta type light calcium carbonate (Alpaca 5970, manufactured by Specialty Minerals Inc., oil absorption amount 120 ml Z 100 g, BET specific surface area 12 m ² Z g instead of light calcium carbonate-silica composite particle C as a pigment for the coating liquid D for the under layer An ink jet recording sheet was obtained in the same manner as in Example 4 except that 100 parts of an average particle diameter of 3.O / zm were blended.

[Comparative Example 10]

 50 parts of silica (AY-603) and 50 parts of rosetta type light calcium carbonate (Alpaca 5 70 70) instead of the light calcium carbonate-silica composite particles C as a pigment for the under layer coating liquid D An ink jet recording sheet was obtained in the same manner as in Example 4 except for the above.

 The physical property values of the pigment of the under layer, and the inkjet recording papers of Examples and Comparative Examples were evaluated by the following methods.

 1) Physical property value of pigment in under layer

 (1-1) Solid mass ratio of light calcium carbonate Z silica (CaCO 2 / SiO 2): light carbonation power

 3 2

 Calculated by fluorescent X-ray analysis of Russium-silica composite particles and quantification of Ca and Si

(1-2) Average particle size: A slurry of each pigment is added dropwise to pure water added with a dispersant (sodium hexametaphosphate 0.2% by mass) to obtain a uniform dispersion, and a laser method particle size measurement machine (Malva (Maruba) The particle size was measured by an Onen Corporation model number: Master Sizer 1 S type), and the average particle size was determined. (1-3) Oil absorption: It was according to the method of JIS K5101.

 (1-4) BET specific surface area: The specific surface area was measured by a nitrogen adsorption amount using an automatic specific surface area measuring apparatus by volume method (Diemi-2360 manufactured by Micromeritics Co., Ltd.). When the sample was a slurry, it was dispersed in ethanol so as to have a solid content of 10%, dried at 105 ° C., and then the BET specific surface area was measured.

2) Evaluation of each inkjet recording sheet About each item below, if evaluation is (circle) and (double-circle), it can be used without a problem on practical use.

 (2-1) Underlayer strength

 For the sample provided with only the under layer on the base paper without the ink receiving layer, a Sellotape (registered trademark, transparent adhesive tape) with a width of 18 mm is attached to the surface of the under layer, and one end of the tape is sandwiched with a digital force gauge. When the tape was peeled off the surface of the under layer, the maximum value read with a digital force gauge was taken as the following measurement value. By peeling off the tape, the strength of the coated layer of the under layer can be measured. The following "paper peeling" indicates the case where the base paper strength is peeled not the under layer but the case where the peeling strength is the lowest and the part is the base paper. In this case, adhesion of the base paper fiber to the tape can be visually confirmed. The occurrence of paper peeling indicates that the strength of the interface between the under layer and the base paper is low, and indicates that peeling of the coated layer or cast coatability is deteriorated.

 :: The measured value is lOOogf (9.81N) or more, no paper peeling!

 Good: Measured value is 700gf (6.86N) or more, no paper peeling! ,.

 Δ: The measured value is 500 gf (4.90 N) or more and less than 700 gf (6.86 N). Or more than that there is paper peeling.

 X: The measured value is less than 500 gf (4.90 N).

(2-2) Ink absorbency (bleeding)

 A red and green solid image is recorded on a recording sheet with a spreadsheet software “Etacel” using an ink jet printer (PM-950C: trade name of Epson Corporation) using dye ink, and a red and green mixed color is used. Bleeding was visually evaluated at the boundaries of parts.

 :: The color boundary is clearly divided! /,

 :: Bleeding is small among those with some bleeding at the color boundary!

 :: At a color boundary, among those with slight blur, those with a relatively large degree of blur

X: At the border of color, the blur is very large

(2-3) vividness

A predetermined pattern was printed on a recording sheet using an ink jet printer (PM-950C: trade name of Epson Corporation) using a dye ink, and the vividness of the image area was visually evaluated. Vividness is an index by which an image is printed beautifully, and printing density and image The evaluation is a comprehensive evaluation of the appearance and the presence or absence of image unevenness. Here, the following evaluation was made by visually judging the printed image.

 :: very vivid

 ○: Vivid

 Slightly less vivid

 X: I can not see vividly

(2-4) Permeability

 The air permeability of the recording paper before forming the ink receiving layer (only the under layer is formed on one side of the support) was measured according to the Papers and Pulp Technical Association Ci. TAPPI No. 5.

 :: The measured value is less than 100 s.

 :: The measured value is at least 100 s but less than 300 s.

 Δ: The measured value is 300 seconds or more and less than 600 seconds.

 X: The measured value is 600 s or more.

(2-5) Cast Layer Appearance

 Visual observation of the surface of the ink receiving layer (cast layer) after forming the ink receiving layer by casting method

○: Unevenness due to the missing under layer is not seen.

 X: There is unevenness due to the missing under layer.

 (2-6) Cast operability

 The dirt on the above-mentioned mirror finished surface (cast drum surface) when casting the ink receiving layer was visually evaluated.

 ○: There is no dirt on the surface

 :: The surface is slightly cloudy

 X: A part of the coating layer (ink receiving layer) adheres to the surface

 The obtained results are shown in Tables 3 and 4.

[Table 3] Underlayer pigment

 (Light calcium carbonate Average particle size Oil absorption BET specific surface area Type

/ Silica) mass ratio (im) (ml / 100g) (m ² / g) Example 4 light calcium carbonate 30/70 7.3 180 30 monosilica composite particle C

Example 5 light calcium carbonate 50/50 4.4 160 28 monosilica composite particles D

 Light calcium carbonate

Example 6 70/30 3.6 140 26 Monosilica Composite Particles E

 Light calcium carbonate

Example 7 30/70 7.3 180 30

 —Silica composite particles C

Comparative Example 8 Silica-6.5 290 300 Comparative Example 9 Rosetta light calcium carbonate-3.0 120 12

 Silica + Respectively each Comparative example 10-

Rose 'tta type light calcium carbonate 6.5, 3.0 290, 120 300, 12

As is apparent from Tables 3 and 4, in each of the examples, both the under layer strength and the ink absorbability were excellent. In each of the examples, the castability (the appearance of the cast layer, operability) having high air permeability was also excellent. Furthermore, in the case of each example, the vividness of the recorded image was also excellent.

On the other hand, in the case of Comparative Example 8 in which only silica was used as the pigment of the under layer, the under layer strength deteriorated and the air permeability decreased, and the cast aptitude (the appearance of the cast layer, operability) also decreased. . The reason for this is that the oil absorption of silica is too large to adsorb the binding agent and the effective binding agent It is thought that the amount decreased.

 In addition, in the case of Comparative Example 9 in which only light calcium carbonate was used as the pigment of the under layer, the ink absorption deteriorated, and the sharpness of the recorded image also decreased. It is considered that this is because calcium carbonate alone has a small oil absorption.

 Also in the case of Comparative Example 10 in which a mixture of silica and light calcium carbonate was used as the pigment of the under layer, the ink absorption deteriorated. From this, it has been found that simply mixing silica and light calcium carbonate can not improve the ink absorbency.

As described above, by using the light calcium carbonate-silica composite particles as the pigment of the under layer, it is possible to obtain an ink jet recording sheet excellent in the under layer strength and the ink absorptivity.

 Brief description of the drawings

 FIG. 1 is a view showing an example of the form of light calcium carbonate (Rosetta-type calcite system) dispersed in a liquid.

 FIG. 2 is a view showing an example of the form of light calcium carbonate / silica composite particles dispersed in a liquid.

Claims

The scope of the claims  [1] An ink jet recording sheet provided with an ink receiving layer containing a pigment and a binder on a base paper, wherein the base paper comprises a light calcium carbonate particle whose surface is coated with silica. Ink-jet recording paper characterized by containing calcium-silica composite particle filler.  [2] An inkjet recording sheet provided with an under layer containing a pigment and a binder on at least one surface of a support, and an ink receiving layer provided on the surface of the under layer, wherein the pigment of the above-mentioned single layer is provided An ink jet recording sheet comprising a light calcium carbonate-silica composite particle wherein the surface of the light calcium carbonate particle is coated with silica.  [3] A solid content mass ratio (CaCO 2 / SiO 2) of light calcium carbonate Z silica in the light calcium carbonate-silica composite particles is 25Z75 to 75Z25.  3 2  An ink jet recording sheet according to item 1 or 2. [4] The ink jet recording sheet according to any one of claims 1 to 3, wherein an average particle diameter of the light calcium carbonate-silica composite particles is 1 μm to 30 μm. [5] In the light calcium carbonate-silica composite particles, the light calcium carbonate particles are rosetta type calcite-based light calcium carbonate formed by aggregation of spindle-like primary particles to form secondary particles. The ink jet recording sheet according to any one of claims 1 to 4, characterized in that  [6] The outermost surface of the ink receiving layer is brought into pressure contact with the heated mirror surface while the surface of the coated layer formed by applying the coating material for ink receiving layer is in a wet state, The ink jet recording sheet according to any one of claims 1 to 5, which is provided by drying.