JP2015168912A - Coating liquid for coated sheet and coated sheet using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating layer coating liquid, capable of achieving excellent printing characteristics, especially print density and print reproducibility even in any of information sheets for inkjet, pressure sensitivity and heat sensitivity.SOLUTION: A coating liquid for coated sheet includes a light calcium carbonate having specific physical properties and a binder. The light calcium carbonate is an aggregate obtained by aggregating primary particles formed by blowing carbon dioxide gas into a hydrated lime (calcium hydroxide) slurry and having an average particle size of 0.05-0.15 μm and a BET specific surface area of 15 m/g or more and 30 m/g or less. The pore volume of a fine pore formed by a nitrogen adsorption method and having a size of 1000 Å or less is 0.07 cm/G or more, and a portion of the pore volume of a fine pore having a size of 250Å or less is 35% or more.

Description

  The present invention relates to a coating liquid for coated paper and coated paper using the same, and more particularly to a coating liquid for coated paper suitable for information paper using light calcium carbonate as a pigment.

  In recent years, with the development of information equipment such as computers, printers and facsimiles, information paper such as PPC (Plain Paper Copier) paper, ink jet recording paper, thermal recording paper, and pressure sensitive recording paper specialized for these applications has been developed. Has been developed. As such information paper, coated paper coated with a predetermined pigment is often used in order to improve functions and characteristics such as printing characteristics, whiteness, and concealment of the base paper. As pigments contained in these coating layers, calcium carbonate, kaolin clay, silica, titanium dioxide and the like are used, and those having further enhanced functions of these pigments have been proposed.

For example, in Patent Document 1, in order to improve concealability, a calcium carbonate slurry having an average particle diameter of 0.5 to 1.5 μm and a specific gradient coefficient is used as a coating layer slurry for coated paper. It has been proposed to use. Patent Document 2 describes that whiteness and opacity can be improved by using calcium carbonate having a BET specific surface area of 100 m ² / g or more and a pore diameter of 2 to 50 nm for the coating layer of the coated paper. Has been.

  In the case of heat-sensitive recording paper, a heat-sensitive recording layer containing a leuco dye or the like is provided on the coated paper, and the coating layer functions as an undercoat layer for the heat-sensitive recording layer. In order to obtain high color development sensitivity in thermal paper, the undercoat layer is required to have high heat insulating properties. Patent Document 3 describes that kaolin and calcium carbonate are used in combination as a pigment for an undercoat layer of a thermal recording paper.

JP 2012-207346 A JP 2003-246617 A JP 2008-44227 A

  The function required for the coating layer of information paper is first printability or ink acceptability, but the recording method varies depending on the information paper, and it is difficult to cope with one kind of pigment. For this reason, the printability according to the recording method is acquired by making the kind of pigment differ according to uses, such as for inkjet, pressure-sensitive, and heat-sensitive, or making a coating layer into a some layer.

  It is an object of the present invention to provide a coating layer coating solution that can realize excellent printing characteristics, particularly printing density and printing reproducibility, in any of information sheets for ink jet, pressure sensitive, and heat sensitive.

The coating liquid for coated paper of the present invention that solves the above problems includes light calcium carbonate and a binder, and the light calcium carbonate is agglomerated with primary particles aggregated in a particle size of 0.05 μm or more and 0.15 μm or less. Calcium carbonate having a BET specific surface area of 15 m ² / g or more and 30 m ² / g or less, and a pore volume of 1000 Å or less by the nitrogen adsorption method having a pore volume of 0.07 cm ³ / g or more and 250 Å or less. This is a coating liquid for coated paper having a pore volume ratio of 35% or more. The BET specific surface area of light calcium carbonate is preferably 25 m ² / g or less.

  The coated paper of the present invention has a substrate and at least one coated layer on the substrate, and at least one layer of the coated layer is formed by the coated paper coating solution of the present invention. It is characterized by being.

  According to the present invention, information paper such as ink jet recording paper and pressure-sensitive recording paper having excellent print density and print reproducibility is provided. Further, by applying the coating liquid for coated paper of the present invention to the undercoat layer of the thermal recording paper, a thermal recording paper excellent in heat insulation effect and thereby capable of high quality printing is provided.

The figure which shows the SEM photograph of the light calcium carbonate (sample 1) used for the coated paper of this invention.

Embodiments of the present invention will be described below. First, the coating liquid for coated paper will be described.
The coating paper coating liquid of the present invention (hereinafter also simply referred to as coating liquid) contains light calcium carbonate and a binder. Light calcium carbonate is calcium carbonate generated by blowing carbon dioxide into slaked lime (calcium hydroxide) slurry, and specific agglomerated light calcium carbonate is used in the coating solution of the present invention.

  The crystal system of this agglomerated light calcium carbonate is calcite, the primary particles constituting the agglomerates are fine spindle-shaped particles, and the average particle diameter is 0.05 to 0.15 μm, preferably 0.08 to 0.13 μm. The average particle size of the aggregate (secondary particles) is 4.5 to 6.5 μm, preferably 5.5 to 6.0 μm. In the present invention, the average particle diameter is a value measured with a laser diffraction particle size distribution analyzer (LA950, manufactured by HORIBA). Moreover, a primary particle diameter is an average diameter which measured 50 particle | grain images of the SEM photograph with calipers.

Since this aggregated light calcium carbonate is an aggregate of small primary particles having an average particle size of 0.15 μm or less, it has a relatively small specific surface area and uniform pores. Specifically, the BET specific surface area is 15 m ² / g or more and 30 m ² / g or less, preferably 25 m ² / g or less. The ratio of the pore volume of pores having a diameter of 1000 mm or less by a nitrogen adsorption method (nitrogen gas adsorption: BJH method) of 0.07 cm ³ / g or more and a pore volume of 250 kg or less is 35% or more. It is.

According to the study by the present inventors, when the specific surface area of the pigment contained in the coating layer is large, the viscosity becomes high when the concentration of the pigment in the coating liquid is high, so that the handling of the coating liquid becomes difficult, and the coating process Have trouble. On the other hand, since the calcium carbonate of the present invention has a BET specific surface area of 25 m ² / g or less, the viscosity does not increase even with a high concentration coating solution, and good coating properties can be maintained. When the specific surface area is small, the oil absorption of the pigment particles themselves is low, but since the coating layer contains pigment particles at a high ratio, the ink absorbability is good. Further, since the pore volume of pores of 1000 mm or less is 0.07 cm ³ / g or more, the absorbed ink stays in the pores and does not spread and bleed into the coating layer, resulting in high print density. Can be realized.
In particular, since the ratio of the pore volume of pores of 250 mm or less is high, a high printing density and an effect of preventing the ink from coming off can be obtained.

  The agglomerated light calcium carbonate having the above-described characteristics is not limited, but can be produced by, for example, the following production method.

  First, lime milk is obtained by wet digestion of quicklime. Separately, calcium hydroxide (powder) is suspended in water, a calcium hydroxide suspension is prepared, carbon dioxide gas is blown into this suspension, and the carbonation is reduced to a carbonation rate of 20% or less. A calcium oxide suspension (partially carbonated calcium hydroxide suspension) is obtained. This colloidal calcium hydroxide suspension is added to the initially produced lime milk, carbon dioxide gas is blown into the lime milk, and the carbonation rate is reacted to 100%.

  Lime milk is obtained by digesting massive or powdered quicklime obtained by baking limestone with water, and a calcium hydroxide equivalent concentration of 100 to 120 g / L is preferable. The concentration of the calcium hydroxide suspension obtained by suspending calcium hydroxide in water is preferably 25 to 35 g / L in terms of calcium hydroxide.

  The carbonation reaction of the calcium hydroxide suspension has a reaction start temperature of 10 to 20 ° C., and the amount of carbon dioxide blown is preferably 3 to 12 L / min, more preferably in terms of pure carbon dioxide per kg of calcium hydroxide. Is performed at 4 to 8 L / min. The stirring condition is usually 2.6 to 7.8 m / sec. The carbon dioxide gas only needs to contain 20% by volume or more containing carbon dioxide gas, and exhaust gas from a firing furnace or an incinerator may be used. The carbonation reaction is carried out up to 20% in the first stage. In such a partially carbonated state, the calcium hydroxide suspension produces colloidal particles of calcium carbonate serving as the core of the aggregate. The calcium hydroxide suspension containing such colloidal particles is added to 15 to 25% by mass of lime milk with respect to the lime milk. By adjusting the addition amount of this calcium hydroxide suspension, the particle size of the primary particles can be adjusted, and a large amount of primary particles having a particle size of 0.05 to 0.15 μm can be obtained with the addition amount in the above range. It is done.

  In the reaction of carbonizing the lime milk to which the calcium hydroxide suspension is added to a carbonation rate of 100%, the reaction start temperature is set to 35 to 75 ° C., and the amount of gas blown is 12 in terms of pure carbon dioxide per kg of calcium hydroxide. It is preferable to carry out at -25 L / min.

  By reacting under such conditions, an aggregate calcium carbonate having a relatively small particle diameter and uniform pores can be obtained. Thereafter, classification and dehydration are performed as necessary to obtain powdery aggregate calcium carbonate. Or it is also possible to use for a coating liquid as a slurry of predetermined solid content concentration.

  The method for producing the aggregate calcium carbonate described above is an example, and even if calcium carbonate is produced by other production methods, it may have a predetermined primary particle diameter, specific surface area, pore volume, and the like. For example, it can be used as the coating liquid for coated paper of the present invention.

  The coating liquid for coated paper of the present invention comprises, in addition to aggregate calcium carbonate, calcium carbonate other than the above-mentioned aggregate calcium carbonate (light calcium carbonate, heavy calcium carbonate), kaolin, depending on the application of the coated paper. One or more inorganic pigments and organic pigments such as calcined kaolin, titanium dioxide, satin white, amorphous silica, and plastic pigment may be contained. For example, in the case of a general printing coated paper, it is preferable to use kaolin in addition to the aggregate calcium. In this case, the aggregate calcium and kaolin are preferably used in a weight ratio of 20:80 to 80:20. For information paper that requires opacity, titanium dioxide may be blended in an amount of 5 to 15% by weight of the total pigment. Further, for the purpose of improving gloss, satin white or plastic pigment may be blended. The blending amount in that case is, for example, 15% by weight or less of the whole pigment. Furthermore, for thermal paper and inkjet recording paper, amorphous silica can be blended in order to improve printing characteristics. Furthermore, when the coating liquid for coated paper of the present invention is used as a coating liquid for the undercoat layer of thermal paper, it may be used in combination with calcined kaolin.

  Next, the binder will be described. As the binder, water-soluble resins and emulsions generally used as a binder for coating paper coating liquids can be used. For example, celluloses such as polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, starch, modified starch, polyacrylic acid sodium, acrylic acid copolymer water soluble resin, styrene butadiene latex, vinyl acetate latex, acrylic An emulsion of a hydrophobic resin such as an acid copolymer latex can be used. These can be appropriately selected and used according to the type (printing method) of the information paper on which the coating paper coating liquid of the present invention is used. For example, water-soluble resins such as polyvinyl alcohol and celluloses are suitable for ink jet recording paper, and a hydrophobic resin emulsion such as styrene-butadiene latex and a water-soluble resin may be used in combination for pressure-sensitive paper and heat-sensitive paper. Good.

  The ratio of the pigment (the whole pigment containing aggregated calcium carbonate) and the binder in the coating solution varies depending on the type of information paper, but is generally preferably 100: 100 to 100: 10 by weight, and 100: 50 to More preferably, it is 100: 10.

  In addition to the binder and the pigment described above, other additives can be appropriately added to the coating liquid depending on the type of information paper to be applied and the position where the coating layer is provided. Examples of additives that can be added as appropriate include lubricants, water resistance agents, antifoaming agents, water retention agents, and dyes.

  In addition, as a material added according to the type of information paper, in the case of ink jet recording paper, a cationic auxiliary agent or the like is used. In general, the pressure-sensitive recording paper is generally used as a set of a paper on which a color developing layer containing a color developing agent is formed and a paper on which a color developing layer containing a developer is formed. When the coating paper coating liquid of the present invention is applied to a pressure-sensitive recording paper on which a color developing layer is formed, it is essential that a color developer be included in addition to the pigment and binder described above. As the developer, those generally used for pressure-sensitive recording paper can be used. For example, a novolac phenol resin and a polyvalent metal salt thereof, salicylic acid, a salicylic acid derivative and a polyvalent metal salt thereof can be used.

  The coating liquid for coated paper of the present invention is prepared by dissolving or dispersing the above-mentioned binder, pigment and additives and auxiliaries to be added as appropriate in an aqueous solvent so as to have a predetermined solid content concentration. . This coating solution can be applied to one or both sides of a support such as paper or plastic film to form a coated paper. It can also be used as an undercoat layer for thermal paper or the like. In that case, a functional layer such as a thermal layer is formed on the coating layer.

  Next, the coated paper of the present invention will be described. The coated paper of the present invention has one or more coating layers formed on a base paper, and at least one of the one or more coating layers is formed by the coating paper coating solution described above. It has been done. Specific examples of the coated paper of the present invention include inkjet recording paper, pressure-sensitive recording paper, and thermal recording paper.

  The base paper is not particularly limited, and high quality paper, medium quality paper, recycled paper, finely coated paper, and the like can be used.

  The specific configuration of the coating layer varies depending on the type. Hereinafter, typical paper will be exemplified.

In the case of inkjet recording paper, an intermediate layer is formed on the base paper as necessary, and a coating layer using the coating paper coating liquid of the present invention is formed thereon as an ink receiving layer. The amount of aggregated calcium carbonate contained as a pigment in the coating layer is preferably 30 to 100% by weight. The coating amount of the coating layer ^{is 5g / m 2 ~20g / m 2} . In the case of inkjet recording paper, it is preferable to perform supercalendering after forming a coating layer.

In the case of heat-sensitive recording paper, a coating layer using the coating paper coating solution of the present invention is formed as the undercoat layer of the heat-sensitive layer. The amount of aggregated calcium carbonate contained as a pigment in the coating layer is preferably 30 to 100% by weight. The coating amount of the coating layer ^{is 5g / m 2 ~12g / m 2} .

  In any case, the coating layer can be formed by a known coating method such as coating using a blade coater, curtain coater, spray coater, or wire bar. After the coating film is dried, the coated paper is obtained by subjecting it to moisture conditioning, calendering, and the like as necessary.

When the coated paper of the present invention has a coating layer containing specific agglomerated calcium carbonate on the outermost surface, the coated paper is excellent in absorbability and acceptability with respect to printing ink and toner, and a high printing density is obtained. In addition, since there is no bleeding of ink or the like, the print reproducibility is excellent.
In the coated paper of the present invention, when the coating layer containing the specific aggregated calcium carbonate is an undercoat layer of the heat-sensitive layer, the heat shielding property is good and high image quality is obtained.

  Examples of the coating liquid for coated paper of the present invention will be described below. In the following description, “%” and “part” are based on weight unless otherwise specified.

<< Production of Aggregated Calcium Carbonate >>
<Sample 1>
1. Preparation of raw lime milk 20 kg of quick lime (JIS special name quick lime, manufactured by Okutama Kogyo Co., Ltd.) was digested with 200 L of water at 60 ° C. and stirred for 1 hour to obtain lime milk. The concentration of this lime milk was 114 g / L.

2. Preparation of Colloidal Calcium Hydroxide Suspension On the other hand, 30 g of calcium hydroxide slurry obtained by suspending calcium hydroxide (super-specialized slaked lime, manufactured by Okutama Kogyo Co., Ltd.) in water was charged into a reaction vessel, After adjusting the slurry temperature to 15 ° C., carbon dioxide with a carbon dioxide concentration of 100% was blown, and when the carbonation rate reached 18%, the reaction was stopped to obtain a colloidal particulate calcium hydroxide suspension.

3. Synthesis of Calcium Carbonate 114g / L raw lime milk added with water and diluted to 100g / L is charged into a 30L reactor and adjusted to 70 ° C. 10 mass% was added at a converted weight ratio, carbon dioxide gas having a carbon dioxide concentration of 100% was blown at a reaction start temperature of 65 ° C., and the reaction was carried out until the carbonation rate was 100%, whereby a calcium carbonate slurry was obtained. The obtained slurry was dehydrated with a filter press, water was added to the calcium carbonate cake, and the mixture was stirred with a three-one motor to obtain a light calcium carbonate slurry having a solid content concentration of 30%.

The obtained calcium carbonate was an aggregate of primary particles having a particle size of about 0.13 μm, and the average particle size of the aggregate particles was 5.5 μm. The physical properties of the aggregated calcium carbonate are shown in Table 1, and the SEM photograph is shown in FIG.
The pore volume and pore distribution are values measured by a nitrogen adsorption method.

<Sample 2>
In the synthesis of calcium carbonate of Sample 1, a carbonation reaction was carried out in the same manner as Sample 1 except that 15% by mass of the colloidal calcium hydroxide suspension was added in a weight ratio in terms of calcium hydroxide, and a light solid having a solid content concentration of 30%. A calcium carbonate slurry was obtained. The particle diameter and physical properties of this calcium carbonate are also shown in Table 1.

<Sample 3>
In the synthesis of calcium carbonate of sample 1, a carbonation reaction was carried out in the same manner as in sample 1 except that 20% by mass of the colloidal calcium hydroxide suspension was added in a weight ratio in terms of calcium hydroxide, and a light solid having a solid content concentration of 30%. A calcium carbonate slurry was obtained. The particle diameter and physical properties of this calcium carbonate are also shown in Table 1.

<Sample 4>
In the synthesis of calcium carbonate of sample 1, a carbonation reaction was performed in the same manner as in sample 1 except that 25% by mass of the colloidal calcium hydroxide suspension was added in a weight ratio in terms of calcium hydroxide. A calcium carbonate slurry was obtained. The particle diameter and physical properties of this calcium carbonate are also shown in Table 1.

<Sample 5>
In the synthesis of calcium carbonate of Sample 1, a carbonation reaction was performed in the same manner as Sample 1 except that 3% by mass of the colloidal particulate calcium hydroxide suspension was added in terms of the weight ratio in terms of calcium hydroxide, and light weight with a solid content concentration of 30%. A calcium carbonate slurry was obtained. The particle diameter and physical properties of this calcium carbonate are also shown in Table 1.

<Sample 6>
The light calcium carbonate slurry of Sample 2 was treated with a coreless mixer at a diffusion peripheral speed of 25 m / sec for 20 minutes to obtain a light calcium carbonate slurry having a solid content concentration of 30%. In this calcium carbonate, since the particles are dispersed and the distance between the particles is reduced, the pore volume is greatly reduced as compared with the sample 2. Table 1 shows the particle diameter and physical properties.

<Sample 7>
The 114 g / L raw lime milk obtained in Sample 1 was added with water and diluted to 100 g / L and charged into a 30 L reactor, adjusted to 70 ° C., and a 10% citric acid solution was converted to calcium hydroxide. 5 mass% was added by weight ratio, carbon dioxide gas with a carbon dioxide gas concentration of 100% was blown at a reaction start temperature of 65 ° C., and the reaction was carried out until the carbonation rate reached 100% to obtain a calcium carbonate slurry. The obtained slurry was dehydrated with a filter press, water was added to the calcium carbonate cake, and the mixture was stirred with a three-one motor to obtain a light calcium carbonate slurry having a solid content concentration of 30%. The particle diameter and physical properties of this calcium carbonate are also shown in Table 1.

<< Manufacture of coated paper (inkjet recording paper) >>
<Example 1>
Apply the coating liquid for the coating layer of the following prescription to a commercially available high-quality paper (trade name: Shirai: Nippon Paper Industries Co., Ltd., basis weight: 52.3 g / m ² ) with a wire bar so that the application amount is 10 g / m ^2. And dried at 100 ° C. for 3 minutes. Thereafter, humidity was controlled for 24 hours in a constant temperature and humidity environment (23 ° C., humidity 50%). Thereafter, the paper was passed once through a super calendar (linear pressure: 50 kg / cm, temperature: 55 ° C.) to prepare a coated paper for ink jet recording.

<< Coating layer coating liquid (solid content concentration 20%) >>
・ Calcium carbonate of sample 1 (slurry concentration 30%) 333 parts ・ Polyvinyl alcohol (trade name: POVAL JP05, Nippon Acetate ・ POVAL)
35 parts, cationic auxiliary agent (trade name: SN Dispersant 7347C, San Nopco)
10 copies

<Example 2>
A coated paper for inkjet recording was prepared in the same manner as in Example 1 except that the calcium carbonate used in the coating solution of Example 1 was replaced with the calcium carbonate of Sample 2.

<Example 3>
A coated paper for ink-jet recording was prepared in the same manner as in Example 1 except that the calcium carbonate used in the coating solution of Example 1 was replaced with the calcium carbonate of Sample 3.

<Example 4>
A coated paper for ink jet recording was prepared in the same manner as in Example 1 except that the coating liquid of Example 1 was replaced with the following formulation.

<< Coating layer coating liquid (solid content concentration 20%) >>
-Sample 1 calcium carbonate (slurry concentration 30%) 67 parts-Silica (trade name: Mizukasil P-78A, Mizusawa Chemical Industry Co., Ltd.)
Dispersed slurry concentration 20%) 400 parts ・ Polyvinyl alcohol (Brand name: POVAL JP05, Nippon Acetate / Poval)
35 parts, cationic auxiliary agent (trade name: SN Dispersant 7347C, San Nopco)
10 copies

<Example 5>
A coated paper for inkjet recording was prepared in the same manner as in Example 4 except that the calcium carbonate and silica ratio in Example 4 was changed from 2: 8 to 5: 5.

<Example 6>
A coated paper for ink jet recording was prepared in the same manner as in Example 1 except that the calcium carbonate used in the coating solution of Example 1 was replaced with the calcium carbonate of Sample 4.
<Comparative Example 1> to <Comparative Example 3>
A coated paper for ink-jet recording was prepared in the same manner as in Example 1 except that the calcium carbonate used in the coating solution of Example 1 was replaced with the calcium carbonate of Samples 5 to 7.

<Reference Example 1>
Inkjet recording was carried out in the same manner as in Example 1 except that the calcium carbonate used in the coating solution of Example 1 was replaced with silica (trade name: Mizukasil P-78A, Mizusawa Chemical Co., Ltd.) commercially available for inkjet. Coated paper was prepared. The silica used had a specific surface area of 331 m ² / g, a pore volume of 0.68, and a proportion of pores of 250 mm or less was 36.2%.

  About the inkjet recording paper obtained by Examples 1-6, Comparative Examples 1-3, and Reference Example 1, it printed on the coating surface using an inkjet printer (EPSON PX-V630), and print density, bleedability (printing) Three items were evaluated: reproducibility) and strikethrough (concealment). The results are shown in Table 2. The evaluation method is as follows.

Printing density: Solid printing was performed with black ink, and the density of the recording surface was measured with a Macbeth reflection densitometer.
Smearability: An image was printed, and the degree of blurring at the boundary of the printed part was visually evaluated. As a result, “◎” indicates that no blurring was observed at the printing boundary, “○” indicates that slight blurring was observed at the printing boundary but there was no problem in use, and there was bleeding at the printing boundary. Was judged as difficult.

  Back-through: Printed with black ink, and the back-through of the ink on the printed back after 10 minutes was measured with a Macbeth reflection densitometer. In addition, the numerical value of Table 2 shows that there are few show-throughs, so that a numerical value is low.

  As can be seen from the results shown in Table 2, the ink jet recording papers of Examples 1 to 6 had a performance equivalent to or close to that of the case where only silica for ink jet was used as a pigment (Reference Example 1). In particular, the ink jet recording papers of Examples 2 and 3 using calcium carbonate having a pore volume of 0.1 (Sample 2 and Sample 3) showed the same characteristics as Example 5 using silica together. It has been shown that some or all of the expensive silica can be substituted.

  On the other hand, in Comparative Example 1 using calcium carbonate (Sample 5) having a large primary particle size, all items were inferior to those of Examples. In Comparative Example 2 using calcium carbonate (Sample 6) having a small proportion of pores of 250 mm or less by dispersing the calcium carbonate of Sample 2 (used in Example 2), the print density and The evaluation of the strikethrough was slightly inferior.

  Further, the ink jet recording paper of Comparative Example 3 using calcium carbonate having a large specific surface area (Sample 7) has a large pore volume of the calcium carbonate and a large proportion of pores of 250 mm or less, but the printed image is blurred. It was judged that it was difficult to use.

<< Manufacture of coated paper (pressure-sensitive recording paper) >>
<Example 7>
The coating solution for coating layer having the following formulation was applied to a commercially available high-quality paper (trade name: Shirai: Nippon Paper Industries Co., Ltd., basis weight: 52.3 g / m ² ) with a wire bar so that the coating amount was 6 g / m ^2. And dried at 100 ° C. for 3 minutes. Then, humidity was adjusted for 24 hours in a constant temperature and humidity environment (23 ° C., humidity 50%) to prepare a coated paper (developed sheet) for pressure-sensitive recording.

<< Coating liquid for coating layer (solid content concentration 40%) >>
Sample Calcium carbonate (slurry concentration 30%) 333 parts Styrene butadiene rubber (0692, JSR)
10 parts starch (MS4600, Nippon Food & Chemicals) 2 parts developer (trade name: Celica A960, San Nopco) 8 parts

<Examples 8 and 9>
A coated paper for pressure-sensitive recording was produced in the same manner as in Example 7, except that the calcium carbonate used in the coating solution of Example 7 was replaced with the calcium carbonate of Samples 2 and 3, respectively.

<Comparative Examples 4-6>
A coated paper for pressure-sensitive recording was produced in the same manner as in Example 7, except that the calcium carbonate used in the coating solution of Example 7 was replaced with the calcium carbonate of Samples 5-7.

  On the pressure-sensitive recording paper obtained in Examples 7 to 9 and Comparative Examples 4 to 6, a commercially available pressure-sensitive recording paper upper paper (carbonless writing paper 303N, KOKUYO) was superposed, and a super calendar (50 kg / cm) once to develop pressure. The hue (b value) of the colored surface after 10 seconds, 1 hour, and 24 hours after color development was measured using a whiteness meter. The results are shown in Table 3.

As can be seen from the results shown in Table 3, in the thermal papers of Examples 7 to 9, a high color density was obtained in a very short time after color development, and the color density after 24 hours also showed a high value. On the other hand, the pressure sensitive recording paper of Comparative Example 4 using calcium carbonate (sample 5) in which the primary particle size is large and the BET specific surface area does not satisfy 15 m ² / g or more, and conversely, the calcium carbonate having a large BET specific surface area. In the pressure-sensitive recording paper of Comparative Example 6 using (Sample 7), the time until color development was slow and the final color density was low. The pressure sensitive recording paper of Comparative Example 5 was not as fast as Comparative Examples 4 and 6, but the color development speed was slower than Examples 7-9. From these results, it can be seen that in the case of pressure-sensitive recording paper, the particle size and specific surface area of primary particles are particularly important factors.

<< Characteristics for thermal recording paper >>
<Example 10>
A commercially available OHP film (thickness: 100 μm, KOKYO) is coated with a coating solution for coating layer having the following formulation with a wire bar so that the coating amount is 30 g / m ² , dried at 100 ° C. for 3 minutes, and coated film A sheet was produced.
<< Coating liquid for coating layer (solid content concentration 40%) >>
Sample Calcium carbonate (slurry concentration 30%) 333 parts Styrene butadiene rubber (0692, JSR)
20 parts ・ Polyvinyl alcohol (Brand name: POVAL JP05, Nippon Vinegar POVAL)
20 copies

<Examples 11 and 12>
A coated film sheet for pressure-sensitive recording was produced in the same manner as in Example 10 except that the calcium carbonate used in the coating solution of Example 10 was replaced with the calcium carbonate of Sample 2 and Sample 3, respectively.

<Comparative Examples 7-9>
A coated film sheet for pressure sensitive recording was prepared in the same manner as in Example 10 except that the calcium carbonate used in the coating solution of Example 10 was replaced with the calcium carbonate of Samples 5-7.

<Reference Example 2>
For pressure-sensitive recording in the same manner as in Example 10, except that the calcium carbonate used in the coating solution of Example 10 was replaced with calcined kaolin (trade name: Alphatex, Imeris Minerals Japan) for the thermal paper undercoat layer. A coated film sheet was prepared.

  The thermal conductivity of the coating film sheets (coating layers) of Examples 10 to 12, Comparative Examples 7 to 9, and Reference Example 2 was measured using a rapid thermal conductivity meter (QTM-500, Kyoto Electronics Industry Co., Ltd.). did. The results are shown in Table 4.

  As can be seen from the results shown in Table 4, the coated film sheets of Examples 10 to 12 have a lower thermal conductivity, that is, a higher heat insulating effect than the coated film sheets of Comparative Examples 7 to 9, and a thermal paper undercoat layer. It was close to the calcined kaolin (Reference Example 2). Therefore, it was found that the calcium carbonates of Samples 1 to 3 can be partially or wholly replaced with calcined kaolin.

According to the present invention, a coating liquid for coated paper is provided that is suitable for information paper such as ink jet recording paper, heat-sensitive recording paper, pressure-sensitive recording paper, and the like, and can improve the printing performance.

Claims (9)

A coating liquid for coated paper containing light calcium carbonate and a binder,
The light calcium carbonate is agglomerated calcium carbonate in which primary particles having a particle size of 0.05 μm or more and 0.15 μm or less are aggregated, and has a BET specific surface area of 15 m ² / g or more and 30 m ² / g or less, and 1000 kg by a nitrogen adsorption method. A coating liquid for coated paper, wherein the pore volume ratio of the following pores is 0.07 cm ³ / g or more and the pore volume ratio of the pores of 250 mm or less is 35% or more. The coating liquid for coated paper according to claim 1, wherein light calcium carbonate having a BET specific surface area of 25 m ² / g or less is used as the light calcium carbonate.   The coating liquid for coated paper according to claim 1, comprising 20 to 65% by weight of the light calcium carbonate.   The coating liquid for coated paper according to any one of claims 1 to 3, further comprising at least one pigment selected from heavy calcium carbonate, silica particles, kaolin, calcined kaolin, and titanium. Coating liquid for coated paper.   The coating liquid for coated paper according to claim 4, wherein the ratio of light calcium carbonate to pigment is 400 parts by weight or less of pigment with respect to 100 parts by weight of light calcium carbonate. Coating liquid.   A base material and at least one coating layer on the base material, wherein at least one of the coating layers is a layer formed by the coating paper coating solution according to any one of claims 1 to 5. Coated paper characterized by being.   7. The coated paper according to claim 6, wherein the coated layer is an ink jet recording layer, and is a layer formed by the coated paper coating solution according to any one of claims 1 to 5. Characterized coated paper.   It is a coated paper of Claim 6, Comprising: The said coating layer is a pressure-sensitive recording layer, It is a layer formed with the coating liquid for coated paper as described in any one of Claim 1 thru | or 5. Coated paper characterized by A thermal printing paper having a base material and an under layer and a thermal recording layer in order on the base material, wherein the under layer is formed from the coating paper coating solution according to any one of claims 1 to 5. Thermal printing paper characterized by being a layer.

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