JP7309672B2 - Ink drying evaluation method and coated paper for printing - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for evaluating ink drying properties and a coated printing paper having ink drying properties.

In recent years, in the field of sheet-fed printing, there has been an increasing trend toward smaller lots and shorter delivery times. H-UV printing (hybrid UV printing) is also being adopted for printing presses, and powderless inks are being introduced into the market. Ink dryness is regarded as one of the important indices.

The absorption of the solvent component in the ink into the coating layer is determined by the coating layer material, coating layer structure, printing conditions, ink conditions, and the like. Therefore, in order to improve the drying property of the ink, we have added Satin White to the top coat layer, and by maintaining a certain void volume in the coating layer, we have improved the ink absorption and ink drying properties. Various studies have been made, such as a method of improving (Patent Document 1) and a method of using ink with excellent drying properties and stain resistance (Patent Document 2). In addition, many studies have been made focusing on the coating layer structure.

As for the relationship between the pigment coating layer and the solvent absorbency, the Lucas-Washburn equation shown in Equation (1), which captures a large number of fine pores present in the pigment coating layer as an aggregate of capillaries, is widely used. ing. Here, L is the penetration depth of the solvent, r is the average radius of the capillary, t is the time, γ is the surface tension of the solvent, θ is the contact angle between the capillary wall and the solvent, and η is the viscosity of the solvent. Assuming that the pore structure of the pigment coating layer is an array of n cylindrical pipes with an average radius of r, the ink solvent permeation amount ν into the pigment coating layer is expressed by the formula (2). (1) can be transformed into equation (3). d is the thickness of the pigment coating layer, V is the pore volume of the pigment coating layer, and k is the ink viscosity. That is, it is thought that the larger the pore diameter and pore volume in the pigment coating layer and the smaller the thickness of the pigment coating layer, the greater the amount of solvent permeation per certain period of time, and the better the ink drying property.

As a method for quantitatively evaluating the pore structure of paper, the mercury intrusion method is generally widely used (Patent Document 3). In recent years, an increasing number of companies and organizations are restricting their use out of consideration for human health and the environment.

By the way, among coated papers, there are matte coated papers with reduced glossiness. Among the matte coated papers, the demand for matte coated papers has been increasing in recent years because the difference between white paper glossiness and printing glossiness is large and characters after printing are easy to read. Methods for producing matte coated paper include using pigments with large particle diameters as coating pigments, and increasing unevenness on the paper surface by not performing calendering after pigment coating. are mentioned.

Furthermore, matte coated paper has a larger uneven surface than glossy coated paper, so the ink on the surface of the paper sinks easily. Therefore, in order to increase the print density, it is necessary to transfer a large amount of ink. Therefore, the amount of ink transferred to the matte coated paper increases, and the drying property tends to decrease. If the drying property of the ink is poor, the problem of "set-off" tends to occur, in which the ink is transferred to the other printed matter when the printed matter is overlaid. For this reason, in general, countermeasures are taken such as using powder such as starch to prevent printed matter from sticking to paper, or leaving the printed matter to stand so as not to cause rubbing after overlapping. Especially when performing double-sided printing, if the above-mentioned "set-off" occurs, the printed image will be damaged and the value of the printed matter will be significantly impaired. The ink must be dried until it no longer occurs. If the drying property of the ink is poor, the standing time will be longer, resulting in lower working efficiency. Furthermore, in double-sided printing, when the opposite side is printed, the printed image on the already printed side is rubbed by a roll or the like, so if the drying property of the ink is poor, the printed image may be damaged. Therefore, in order to cope with the improvement of printing speed and double-sided printing, particularly matte coated paper is required to have the ability to dry the ink quickly.

JP-A-11-247097 JP 2015-063667 A JP 2014-237898 A

As mentioned above, it is possible to evaluate the ink drying property from the pore diameter and pore volume of the paper. Mercury porosimetry is widely used as a method for quantitatively evaluating the pore structure of paper. Since it is a measurement, the pores may be deformed. In addition, when a pigment with a large particle size is used as a coating pigment, the larger the particle size of the pigment, the smaller the pore volume of the pigment coating layer and the lower the ink drying property. It was difficult to reconcile the sexes. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for accurately evaluating ink drying properties and a coated paper for printing, particularly matte, having ink drying properties.

The inventors have found that by obtaining the pore structure of the pigment coating layer using a nitrogen adsorption method that can be measured under low pressure conditions, the ink drying property can be evaluated more accurately. Further, in the present application, it is possible to provide a coated paper for matte printing excellent in ink drying property by setting the pore volume V of the pigment coating layer measured by the nitrogen adsorption method to 0.04 cm ³ /g or more. Found it. Therefore, the above problems are solved by the present invention described below.
(1) A step of measuring the pore volume V or the average pore diameter m of the base paper and the pigment coating layer provided thereon by a nitrogen adsorption method, and V or a step of evaluating the ink drying property based on the relationship that the larger m is, the higher the ink drying property is;
Ink dryness evaluation method including.
(2) further comprising a step of measuring the coating amount c of the pigment coating layer;
a step of evaluating the ink drying property based on the relationship that the greater the V/c or m/c, the higher the ink drying property;
The evaluation method according to (1), comprising:
(3) A coated printing paper comprising a base paper and a pigment coating layer provided thereon,
The pore volume V of the pigment coating layer measured by a nitrogen adsorption method is 0.04 cm ³ /g or more,
The white paper glossiness of the coated printing paper according to JIS-P8142 is less than 35%, and the JAPAN TAPPI Paper Pulp Test Method No. of the coated printing paper. A coated printing paper having a printing ink receptivity of 20 to 35 as measured by 46.
(4) The coated printing paper according to (3), wherein the average pore diameter m of the pigment coating layer measured by a nitrogen adsorption method is 30 nm or more.
(5) The coated printing paper according to (3) or (4), wherein the pore volume V is 0.09 cm ³ /g or less.
(6) The coated printing paper according to any one of (3) to (5), wherein the average pore diameter m is 60 nm or less.
(7) The outermost layer of the coated printing paper is a pigment-coated layer, and the static friction coefficient and dynamic friction coefficient of the outermost pigment-coated layer side measured according to ISO 15359 are static. The coated printing paper according to any one of (3) to (6), which has a higher coefficient of friction than the above.
(8) The coated printing paper of (7), wherein the outermost pigment coating layer contains 25 to 75% by weight of calcium carbonate in total pigment.
(9) The coated printing paper according to (8), wherein the calcium carbonate is ground calcium carbonate. (10) The coated printing paper according to (8), wherein the calcium carbonate is light calcium carbonate.
(11) The coated printing paper according to any one of (8) to (10), wherein the outermost pigment coating layer contains 20 to 50% by weight of kaolin or clay in total pigment.
(12) The coated printing paper according to any one of (7) to (11), wherein the outermost pigment coating layer contains an adhesive, and the adhesive contains 20 to 80% by weight of latex.
(13) The total pore volume (cm ³ /m ² ) defined by the pore volume V (cm 3 /g) × coating amount c ( ^g /m ² ) of the pigment coating layer is 0.55 The coated printing paper according to any one of (3) to (12), which is up to 4.50 cm ³ /m ² .

INDUSTRIAL APPLICABILITY According to the present invention, a method for accurately evaluating ink drying properties and a coated printing paper having ink drying properties can be provided.

Correlation diagram between ink drying speed and pore volume Correlation diagram between ink drying speed and average pore diameter

The present invention will be described in detail below. In the present invention, "X to Y" includes X and Y which are the end values. "X or Y" means either one or both of X and Y;

1. Ink drying property evaluation method (1) Pore structure measurement step A step of measuring the pore diameter m by a nitrogen adsorption method is included. The nitrogen adsorption method is a method in which nitrogen molecules are adsorbed on a pigment coating layer and the pore volume or average pore diameter is obtained from the behavior of pressure and adsorption amount. As an apparatus capable of measuring the pore structure by the nitrogen adsorption method, an apparatus such as Tristar 3000 manufactured by Shimadzu Corporation can be used.

(2) Evaluation Step As represented by the above formula (3), the larger the pore volume V or the average pore diameter m of the pigment coating layer, the higher the ink permeation rate, that is, the ink drying property. Therefore, based on this relationship, ink drying property can be evaluated when the same ink is used for paper having a pigment coating layer with a constant thickness.

As represented by the formula (3), the ink permeation rate is also affected by the coating weight of the pigment coating layer. Therefore, when the coating amount of the pigment coating layer is c, the larger the V/c or m/c is, the higher the ink drying property becomes. Based on this relationship, it is possible to make an evaluation considering the coating amount c. .

According to the evaluation method of the present invention, the optimum pore volume V or average pore diameter m of the pigment coating layer for exhibiting ink drying properties can be obtained.

2. Coated Paper for Printing The coated paper for printing of the present invention comprises a base paper and a pigment coating layer provided thereon, and the pigment coating layer has a pore volume V of 0.04 cm ³ / as determined by a nitrogen adsorption method. g or more, the white paper glossiness of the coated printing paper according to JIS-P8142 is less than 35%, and the JAPAN TAPPI Paper Pulp Test Method No. of the coated printing paper. The printing ink acceptance measured by 46 is 20-35. The coated printing paper of the present invention refers to paper that is used after being subjected to commercial printing such as offset printing, gravure printing, and on-demand printing (laser method, inkjet method) on the surface of the paper.

(1) Pore volume V
The pore volume V is determined by the nitrogen adsorption method. Since the coated printing paper of the present invention has a pore volume V of 0.04 cm ³ /g or more, it is excellent in ink drying property. The pore volume V is more preferably 0.045 cm ³ /g or more. The pore volume V is preferably 0.09 cm ³ /g or less, more preferably 0.08 cm ³ /g or less. Specifically, in the present invention, the pore volume is obtained from the desorption isotherm obtained by the nitrogen adsorption method. Tristar 3000 manufactured by Shimadzu Corporation can be used for measurement and analysis. In this application, the pore volume obtained with TriStar 3000 is considered the pore volume of the pigment coating layer.

Since the pigment coating layer is formed on the base paper, the pore volume V of the pigment coating layer can be measured by separating the base paper layer and the pigment coating layer. Alternatively, the pore volume of the laminate containing the base paper layer and the pigment coating layer is measured from the pigment coating layer side, and the obtained value is converted to the value per unit coating amount, thereby obtaining the pore size of the pigment coating layer. A volume V can be determined. The latter method is preferred in the present invention. Examples of the method for measuring the coating amount of the pigment coating layer include the method described in Japanese Patent No. 5827187.

(2) Total Pore Volume Total pore volume (cm ³ /m ² ) is defined by pore volume V (cm ³ /g)×coating amount c (g/m ² ), and its value is 0. It is preferably 55 cm ³ /m ² or more, more preferably 0.60 cm ³ /m ² or more, and even more preferably 0.65 cm ³ /m ² or more. The upper limit of the total pore volume is preferably 4.50 cm ³ /m ² or less, more preferably 3.60 cm ³ /m ² or less, even more preferably 2.70 cm ³ /m ² or less.

(3) average pore diameter m
The average pore diameter m is determined by the method described above. From the viewpoint of ink drying property, the average pore diameter m is preferably 30 nm or more. The upper limit of the average pore diameter m is preferably 60 nm or less. Specifically, in the present invention, the average pore diameter is obtained from the desorption isotherm obtained by the nitrogen adsorption method. For the purposes of this application, the average pore diameter obtained with Tristar 3000 is considered the average pore diameter of the pigmented coating.

(4) Glossiness of white paper The glossiness of white paper is an index indicating the degree of glossiness of white paper, and is measured according to JIS-P8142 in the present invention. Since the coated printing paper of the present invention is a matte coated printing paper with a large difference between white paper gloss and printing gloss as described above, the white paper glossiness is less than 35%. Although the lower limit of the white paper glossiness is not limited, it is preferably 15% or more.

(5) Printing ink acceptability The printing ink acceptability is an index showing how easily the ink dries. 46. Specifically, printing ink receptivity is evaluated by applying a certain amount of ink to paper, wiping off the ink after a certain amount of time has passed, and evaluating the difference in whiteness between before and after applying the ink. A higher value means better ink drying properties. In the present invention, the printing ink receptivity is 20 or higher, preferably 21 or higher, and more preferably 22 or higher. Also, the printing ink acceptability is 35 or less, preferably 33 or less, more preferably 31 or less. If the printing ink acceptability is less than 20, the ink will not dry sufficiently. On the other hand, if the printing ink receptivity exceeds 35, the ink will dry excessively and the printing glossiness will decrease.

(6) Coefficient of Friction The coated printing paper of the present invention preferably has a coefficient of dynamic friction greater than its static coefficient of friction. Coated paper for printing may cause problems such as paper becoming slippery and not aligned, making it difficult to set the paper in the printing machine, or making it difficult to cut. This problem can be solved by having a large dynamic friction coefficient. Conventionally, adjusting the coefficient of friction of paper has been considered in order to avoid the problem. Generally, it is known that the coefficient of dynamic friction of paper is smaller than the coefficient of static friction. For this reason, if the static friction coefficient is increased to some extent, a moderately high dynamic friction coefficient can be obtained, so the prior art has mainly focused on adjusting the static friction coefficient. There is also a technique that focuses on the relationship between the dynamic friction coefficient and the static friction coefficient (for example, JP-A-08-060597), but this technique also assumes that the dynamic friction coefficient is smaller than the static friction coefficient. . However, according to the present invention, the problem can be solved by a concept different from the conventional concept.

The coefficient of friction is measured according to ISO 15359. In ISO 15359, the same sample is used to measure the static friction coefficient and the dynamic friction coefficient three times each, the first and third values are adopted for the static friction coefficient, and the dynamic friction coefficient is the third measurement. adopt the value of In the present invention, the first value is adopted for the static friction coefficient. Although not limited, the increase rate calculated by [(dynamic friction coefficient) - (static friction coefficient)] / (static friction coefficient) is preferably 2 to 25%, and is 3 to 20%. is more preferable. Although the specific friction coefficient is not limited, the static friction coefficient is preferably 0.3 to 0.7, more preferably 0.4 to 0.6. When the coefficient of friction is within this range, the problems before printing and problems in the printing press are eliminated.

(7) Base paper 1) Pulp The base paper of the present invention can be a known pulp, but chemical pulp is preferably used. Chemical pulp includes those manufactured by the kraft pulp method and those manufactured by the sulfite pulp method, and both of them can be used in the present invention, but the chemical pulp manufactured by the kraft method is lower in production cost. It is suitable from the aspect. The content of the chemical pulp in the raw material pulp is 60% by weight or more, more preferably 80% by weight or more, still more preferably 90% by weight or more, and particularly 95% by weight or more, from the viewpoint of whiteness etc. preferable.

2) Fillers In the present invention, known fillers may be used for the base paper. Known fillers include heavy calcium carbonate, light calcium carbonate, clay, silica, light calcium carbonate-silica composite, kaolin, calcined kaolin, delaminated kaolin, white carbon, talc, magnesium carbonate, barium carbonate, barium sulfate, water. Inorganic fillers such as amorphous silica produced by neutralizing aluminum oxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, zinc oxide, titanium oxide, sodium silicate minerals, urea-formalin resin, melamine type Organic fillers such as resins, polystyrene resins and phenolic resins can be used. Among these, when heavy calcium carbonate and light calcium carbonate, which are typical fillers in neutral papermaking and alkaline papermaking, are used, a high effect of improving opacity can be obtained. As the light calcium carbonate, light calcium carbonate (causticized light calcium carbonate) produced in the causticizing process of the pulp production process described in Japanese Patent No. 5274077 may be used. The filler content in paper is not particularly limited, but is preferably 1 to 40% by weight, more preferably 10 to 35% by weight.

3) Others In the present invention, known papermaking additives can also be used. For example, aluminum sulfate, various anionic, cationic, nonionic, or amphoteric retention improvers, drainage improvers, various paper strength agents, internal sizing agents, and other internal additives for papermaking are added as needed. can be used Examples of dry strength improvers include polyacrylamide and cationized starch, and examples of wet strength improvers include polyamidoamine epichlorohydrin. These chemicals are added within a range that does not affect formation, workability, and the like. Examples of internal sizing agents include alkyl ketene dimer, alkenyl succinic anhydride, and rosin sizing agents. Furthermore, dyes, fluorescent whitening agents, pH adjusters, antifoaming agents, pitch control agents, slime control agents and the like can be added as necessary.

4) Basis Weight of Base Paper The basis weight of the base paper of the present invention is preferably 40 to 160 g/m ² , more preferably 45 to 150 g/m ² , even more preferably 50 to 130 g/m ² .

(8) Pigment Coating Layer 1) Pigment A known pigment can be used in the present invention. Examples include kaolin, clay, engineered kaolin, delaminated clay, ground calcium carbonate, light calcium carbonate, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silica, silicates, colloidal silica, satin. Inorganic pigments such as white and organic pigments such as solid, hollow, or core-shell types are included. These pigments may be used in combination of multiple types. As the light calcium carbonate, causticized light calcium carbonate may be used.

In order to achieve the aforementioned white paper glossiness, printing ink receptivity, coefficient of friction, etc., it is preferable to use calcium carbonate and kaolin or clay as pigments in the present invention. In particular, in order to achieve the aforementioned coefficient of friction, the outermost layer of the coated printing paper is a pigment-coated layer, and the outermost pigment-coated layer contains 25 to 75% by weight of calcium carbonate in the total pigment. preferable. Other pigments are not limited, but preferably contain 20 to 50% by weight of kaolin or clay in the total pigments of the outermost pigment coating layer. The calcium carbonate is preferably ground calcium carbonate or light calcium carbonate. More preferably, the precipitated calcium carbonate is causticized precipitated calcium carbonate.

In the present invention, the pore volume V and the average pore diameter m can be easily achieved by adjusting the average particle diameter of the pigment. Specifically, for example, the volume 50% average particle diameter (D50) of calcium carbonate is preferably 0.5 to 6.0 μm, more preferably 0.5 to 2.0 μm. The 50% volume average particle size (D50) of kaolin or clay is preferably 1.0 to 6.0 μm, more preferably 2.0 to 5.5 μm. The particle size of these pigments can be measured with a laser diffraction particle size distribution analyzer such as Mastersizer S manufactured by Malvern.

2) Adhesive The pigment coating layer contains an adhesive (binder) as a matrix. The adhesive used in the present invention is not limited, and known adhesives can be used. Adhesives include styrene/butadiene, styrene/acrylic, ethylene/vinyl acetate, butadiene/methyl methacrylate, vinyl acetate/butyl acrylate copolymers, maleic anhydride copolymers, acrylic acid/ Latexes such as methyl methacrylate copolymers; polyvinyl alcohols such as completely saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and acetoacetyl-modified polyvinyl alcohol; proteins such as casein, soybean protein, synthetic protein; Etherified starch such as oxidized starch, positive starch, urea phosphate esterified starch, hydroxyethyl etherified starch, starches such as dextrin; cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose and hydroxymethyl cellulose. These multiple types can be used in combination. Preferred are styrene/butadiene copolymers, oxidized starch, and dextrin.

In the present invention, various copolymers such as styrene/butadiene, styrene/acrylic, ethylene/vinyl acetate, butadiene/methyl methacrylate, and vinyl acetate/butyl acrylate are used as the adhesive for the outermost coating layer. It is preferable to use latexes such as maleic anhydride copolymers and acrylic acid/methyl methacrylate copolymers.
It is more preferable to use a butadiene-based copolymer. By adjusting the average particle size and the glass transition temperature of the latex measured by the dynamic light scattering method, it becomes easy to obtain high ink drying property in the coated paper for matte printing. The preferred average particle size of the latex is 70-150 nm, more preferably 70-120 nm. If the average particle size is small, the latex may migrate during drying, preventing the formation of a uniform pigment coating layer and causing uneven ink application. On the other hand, when the average particle size is large, although the drying property of the ink is improved, the ink sinks into the pigment coating layer, which may deteriorate the printing gloss. The glass transition temperature of the latex is preferably about -30°C to 30°C, preferably -25°C to 20°C, more preferably -20°C to 15°C. If the glass transition temperature is too low, the coating runnability may deteriorate. On the other hand, if the glass transition temperature is too high, the surface strength of the coated paper will be insufficient and the white paper glossiness will be excessive, making it difficult to obtain the matte white paper glossiness desired in the present invention.

The amount of the adhesive is preferably 5 to 20 parts by weight, more preferably 8 to 16 parts by weight, based on 100 parts by weight of the pigment, from the viewpoint of printability and coatability. If the total amount of the adhesive exceeds 20 parts by weight, the viscosity of the pigment coating liquid becomes high, and operational troubles tend to occur during coating. Furthermore, there is a tendency that the drying property of the ink is lowered. On the other hand, when the total amount of adhesive is less than 5 parts by weight, it becomes difficult to obtain sufficient surface strength.

In the present invention, in order to achieve the above physical properties, the outermost pigment coating layer preferably contains 20 to 80% by weight of latex, more preferably 25 to 75% by weight of latex in the total adhesive. , 25-50% by weight latex. Starches, particularly oxidized starch and dextrin, are preferably used as other adhesives. The reason why starches are preferred is that compared to latex, starches have a higher water retention capacity for pigment coating liquids, so the coating liquids are less likely to sink into the base paper, and the pigment coating layer effectively covers the base paper. It is considered possible. In other words, when starches are used, the coverage of the base paper with the pigment coating layer is improved. As a result, an improvement in print quality, especially print glossiness, and an improvement in ink drying property can be expected.

3) Others The pigment coating layer contains, if necessary, dispersants, thickeners, water retention agents, antifoaming agents, water resistance agents, and various auxiliaries that are usually blended with pigments for coated paper. good too.

3. Manufacturing Method The coated printing paper of the present invention can be manufactured by a known method, but it is preferable to coat one or two layers of a pigment coating solution containing a pigment and an adhesive on the base paper. It is preferable to manufacture with a roll coater or a blade coater.

(1) Preparation of base paper The base paper is as described above. The base paper is manufactured by a known papermaking method. For example, using a fourdrinier machine including a top wire, an on-top former, a gap former, a cylinder paper machine, a paperboard machine using both a fourdrinier paper machine and a cylinder paper machine, a Yankee dryer machine, etc. can be done. The pH during papermaking may be acidic, neutral or alkaline, preferably neutral or alkaline. The papermaking speed is also not particularly limited.

(2) Smoothing Treatment of Base Paper It is preferable to smoothen the base paper by various calendering devices before coating the obtained base paper with the pigment coating liquid. As such a calender, a generally used calender such as a super calender and a soft calender can be appropriately used. As calender finishing conditions, rigid roll temperature, calender pressure, number of nips, roll speed, paper moisture content before calendering, etc. are appropriately selected according to the required quality.

(3) Preparation of Pigment Coating Liquid The pigment coating liquid of the present invention can be prepared by dispersing or dissolving a pigment, an adhesive, and, if necessary, additives in water. The blending of each component is adjusted so that the pigment coating layer can be formed. When blade coating is performed, the solid content concentration of the pigment coating solution is preferably 40 to 70% by weight, more preferably 60 to 70% by weight. The viscosity of the pigment coating liquid is preferably in the range of 500 to 3000 mPa·s in B-type viscosity measured at 60 rpm at room temperature.

(4) Coating method The coating method is not limited, and known coating machines such as roll coaters and blade coaters can be used. Although the coating speed is not particularly limited, it is preferably 400 to 1800 m/min for a blade coater and 400 to 2000 m/min for a roll coater. In the present invention, it is preferable to use a blade coater for coating the outermost coating layer.

One or more pigment coating layers can be provided. Alternatively, a clear coating layer may be provided on the base paper, and a pigment coating layer may be provided thereon. The outermost layer is preferably a pigment coating layer.

The coating amount c (g/m ² ) of the pigment coating layer in the present invention is preferably 2 g/m ² or more, more preferably 5 g/m ² or more, and even more preferably 10 g/m ² or more in solid content per side. . If the coating amount is less than 5 g/m ² , the irregularities on the surface of the paper substrate cannot be sufficiently covered, and the receptivity of the printing ink may be remarkably lowered. On the other hand, the coating amount of the pigment coating layer is preferably 50 g/m ² or less, more preferably 40 g/m ² or less, and even more preferably 30 g/m ² or less.

Although the basis weight of the coated printing paper of the present invention is not particularly limited, it is about 50 g/m ² or more and 260 g/m ² or less.

(5) Other steps The method for drying the wet pigment coating layer is not limited, and for example, a steam heating cylinder, a heated hot air dryer, a gas heater dryer, an electric heater dryer, an infrared heater dryer, etc. can be used.

The coated printing paper of the present invention may be subjected to a smoothing treatment by various calendering devices after drying the wet pigment coating layer to such an extent that the matte texture is not impaired. As such a calender, a generally used calender such as a super calender and a soft calender can be appropriately used. As calender finishing conditions, rigid roll temperature, calender pressure, number of nips, roll speed, paper moisture content before calendering, etc. are appropriately selected according to the required quality.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited by these. Parts by weight and % by weight are values in terms of solid content.

<Evaluation method>
(1) Measurement of pore volume and average pore diameter The pore volume and average pore diameter of the coated paper were determined by the nitrogen adsorption method. Tristar 3000 manufactured by Shimadzu Corporation was used for the measurement.
(Sample preparation)
A paper sample of 40 cm long×15 cm wide was divided into two layers so as to be even in the thickness direction to obtain a laminate containing a pigment coating layer and a base paper layer. In the case of double-sided coated paper, two such laminates are obtained, and in the case of single-sided coated paper, one such laminate and one layer consisting mainly of the base paper layer are obtained. A laminate containing a pigment coating layer and a base paper layer was used as a sample sheet for the measurement. In the case of double-sided coated paper, one of them was used as a sample sheet for measurement. The basis weight t (g/m ² ) of the sample sheet was measured. After selecting arbitrary four points in one sample sheet and cutting it into strips, the measurement sample was placed in a measurement cell so that the absolute dry weight was about 1 to 2 g. The absolute dry weight at this time was defined as w (g). Pretreatment was carried out overnight under vacuum at a treatment temperature of 120°C.

(measurement)
The pore volume and the average pore diameter were measured from the pigment coating layer side of the measurement sample using the above apparatus. Specifically, the pore volume and average pore diameter of the measurement sample are obtained from the desorption isotherm using the BJH method, the average value of the 4 samples is taken, and the pore volume V' and average pore diameter of the measurement sample are obtained. m'. The pore volume V' was converted to a value per unit coating weight and defined as the pore volume V of the pigment coating layer of the present invention. The obtained average pore diameter m' was taken as the average pore diameter m of the pigment coating layer of the present invention. The pigment coating layer weight of the measurement sample is pigment coating layer weight (g) = absolute dry weight w (g) of measurement sample × coating amount c (g/m ² ) ÷ basis weight of sample sheet t (g/ m ² ). The coating amount c (g/m ² ) was obtained by the measurement method described later.

The pore volume and average pore diameter of the coated paper were also determined by the mercury intrusion method in the same manner as the nitrogen adsorption method. Auto Pore 9500 manufactured by Shimadzu Corporation was used for the measurement. Samples were prepared similarly to the nitrogen adsorption method. However, the amount of the measurement sample was about 0.13 g (absolute dry weight).

(Coating amount)
The coating amount was measured according to the method described in Japanese Patent No. 5827187. Specifically, it was measured by the following procedure.
1) A measurement sample (paper) was cut into a size of 5 cm×5 cm, and the weight x was measured after conditioning at a temperature of 23° C. and a relative humidity of 50%.
2) The sample was placed on a styrene polymer plate so that the pigment-coated layer was in contact with the sample, sandwiched between a watch glass and fixed with a clip.
3) Placed in a drier at 120 to 150°C to melt the styrene polymer and adhere it to the pigment coating layer, allow to cool, and then adjust the humidity for about half a day at a temperature of 23°C and a relative humidity of 50% to measure the weight y. .
4) After immersing the measurement sample obtained in the previous step in the copper ethylenediamine solution for about 3 to 4 hours, the base paper layer and the pigment coating layer were carefully peeled off using a brush. This process was repeated until no pulp fibers adhered to the pigment coating layer.
5) The pigment coating layer was washed with water and dried, and after about half a day of humidity conditioning at a temperature of 23° C. and a relative humidity of 50%, the weight z was measured.
6) The coating amount was calculated by the following formula.
Coating amount c (g/m ² ) = (xA) x 400
A = y-z

(2) White Paper Glossiness Measured based on JIS-P8142.
(3) Printing ink receptivity JAPPAN TAPPI paper pulp test method No. 46: Paper and Paperboard--Printing Ink Acceptance Test Method--Measured based on the K&N ink method. The whiteness was measured under conditions including UV light (UV-In).
(4) Static Friction Coefficient and Dynamic Friction Coefficient Measured according to ISO 15359. However, in three repeated measurements, the first measured value was used for the static friction coefficient, and the third measured value was used for the dynamic friction coefficient.

(5) Ink drying property Using offset sheet-fed ink (NEX-M manufactured by Toyo Ink) on a Roland sheet-fed offset printing machine (4 colors) at a printing speed of 8000 sheets / hr, ink density of solid area After printing so that the black was 2.00, the black solid printed portion was touched with a fingertip every 10 minutes immediately after printing, and the speed of ink drying was sensory evaluated. If the evaluation is 4 or 3, there is no practical problem.
4: Very good 3: Good 2: Slightly inferior 1: Poor

(6) Halftone dot unevenness Using offset sheet-fed ink (NEX-M manufactured by Toyo Ink Co., Ltd.) with a Roland sheet-fed offset printing machine (4 colors), solid ink at a printing speed of 8000 sheets / hr Crimson (CM) was printed in order so that the inking density was 1.60 indigo and 1.50 in red. Inking unevenness of the indigo red (CM) halftone (50%) printed portion of the resulting printed matter was visually evaluated. If the evaluation is 4 or 3, there is no practical problem.
4: Very good 3: Good 2: Slightly inferior 1: Poor

(7) Print glossiness (difference in glossiness)
Offset sheet-fed ink (NEX-M manufactured by Toyo Ink Co., Ltd.) was used on a Roland sheet-fed offset printing machine (4 colors) at a printing speed of 8000 sheets/hr, and the ink density of the solid area was indigo 1. 0.60 and red 1.50 were printed in the order of magenta (CM). The glossiness of the magenta (CM) solid printed portion of the obtained print was measured according to JIS P-8142.
The value obtained by subtracting the white paper glossiness from the print glossiness is defined as the glossiness difference. If the glossiness difference is 20 or more, a sufficient gloss difference is obtained between the printed portion and the white paper portion, and there is no practical problem.
Glossiness difference (%) = printing glossiness (%) - white paper glossiness (%)

(Base paper)
A fine paper having a density of 0.73 g/cm ³ and a basis weight of 98 g/m ² containing 100% by weight of chemical pulp as a base paper and 13% by weight of light calcium carbonate as a filler was prepared.

[Example 1]
55 parts by weight (solid content) and 2 of heavy calcium carbonate slurry 1 (manufactured by Fimatech, trade name: FMT97, ratio of particles having a particle size of 2 μm or less by sedimentation method: 97%, D50 = 0.64 μm) as a pigment Grade clay (manufactured by IMERYS, trade name: KCS, D50 = 4.9 μm) 45 parts by weight (solid content) was used, and styrene-butadiene copolymer latex 2 (manufactured by A&L, trade name: PB9501) was used as an adhesive. , average particle diameter 80 nm, glass transition temperature -12 ° C.) 4 parts by weight, 6 parts by weight of oxidized starch (manufactured by Japan Corn Starch Co., Ltd., trade name: SK200), and water is added to solid content concentration 66% by weight. A pigment coating liquid 1 was obtained.
Pigment coating solution 1 was coated on both sides of the base paper with a blade coater so that the dry coating amount per one side was 15.0 g/m ² , and then dried to obtain a coated printing paper.

[Example 2]
55 parts by weight (solid content) and 2 of heavy calcium carbonate slurry 1 (manufactured by Fimatech, trade name: FMT97, ratio of particles having a particle size of 2 μm or less by sedimentation method: 97%, D50 = 0.64 μm) as a pigment Grade clay (manufactured by IMERYS, trade name: KCS, D50 = 4.9 μm) 45 parts by weight (solid content) was used, and styrene-butadiene copolymer latex 2 (manufactured by A&L, trade name: PB9501) was used as an adhesive. , average particle diameter 80 nm, glass transition temperature -12 ° C.) and 3 parts by weight of oxidized starch (manufactured by Japan Corn Starch Co., Ltd., trade name: SK200) are blended, and water is added to solid content concentration 66% by weight. A pigment coating liquid 2 was obtained.
A coated printing paper was obtained in the same manner as in Example 1, except that the pigment coating liquid 2 was used instead of the pigment coating liquid 1.

[Example 3]
As pigments, causticized light calcium carbonate slurry 1 (D50 = 1.02 µm) 55 parts by weight (solid content) and secondary clay (manufactured by IMERYS, trade name: KCS, D50 = 4.9 µm) 45 parts by weight (solid content) 4 parts by weight of styrene-butadiene copolymer latex 1 (manufactured by A&L, trade name: PB1537, average particle diameter 110 nm, glass transition temperature 10 ° C.) as an adhesive, and oxidized starch (manufactured by Japan Corn Starch Co., Ltd., product Name: SK200) was mixed with 6 parts by weight, and water was further added to obtain a pigment coating liquid 3 having a solid content concentration of 66% by weight.
A coated printing paper was obtained in the same manner as in Example 1, except that Pigment Coating Solution 3 was used instead of Pigment Coating Solution 1.

[Comparative Example 1]
100 parts by weight (solid content) of heavy calcium carbonate slurry 1 (manufactured by Fimatech, trade name: FMT97, ratio of particles having a particle diameter of 2 μm or less by sedimentation method: 97%, D50 = 0.64 μm) was used as a pigment. , 8 parts by weight of styrene-butadiene copolymer latex 2 (manufactured by A&L, trade name: PB9501, average particle diameter 80 nm, glass transition temperature -12 ° C.) as an adhesive, and oxidized starch (manufactured by Nippon Corn Starch Co., Ltd., trade name : SK200) was blended, and water was further added to obtain a pigment coating liquid 4 having a solid concentration of 66% by weight.
A coated printing paper was obtained in the same manner as in Example 1, except that Pigment Coating Solution 4 was used instead of Pigment Coating Solution 1.

[Comparative Example 2]
As pigments, causticized light calcium carbonate slurry 1 (D50 = 1.02 µm) 95 parts by weight (solid content), fine clay (manufactured by IMERYS, trade name: Astraglaze, D50 = 0.23 µm) 5 parts by weight (solid content) 5.8 parts by weight of styrene-butadiene copolymer latex 1 (trade name: PB1537, average particle size 110 nm, glass transition temperature 10 ° C.) as an adhesive, and oxidized starch (manufactured by Japan Corn Starch Co., Ltd., trade name : SK200) was blended, and water was further added to obtain a pigment coating liquid 5 having a solid content concentration of 66% by weight.
Next, 20 parts by weight (solid content) of causticized light calcium carbonate slurry 1 (D50 = 1.02 µm) and 80 parts by weight (solid content) of causticized light calcium carbonate slurry 2 (D50 = 1.38 µm) were used as pigments. , 2.5 parts by weight of styrene-butadiene copolymer latex 1 (trade name: PB1537, average particle size: 110 nm, glass transition temperature: 10°C) as an adhesive, and oxidized starch (manufactured by Japan Corn Starch Co., Ltd., trade name: SK200). ) was blended, and water was further added to obtain a pigment coating liquid 6 having a solid content concentration of 66% by weight.
The pigment coating solution 6 was coated on both sides of the base paper with a blade coater so that the dry coating amount per side was 4.5 g/m ² , and then dried to obtain a lower layer coated paper. Pigment coating liquid 5 is coated on both sides of the lower layer coated paper with a blade coater so that the dry coating amount per side is 10.5 g/m ² , and then dried to obtain a coated printing paper. rice field.

[Reference example 1]
70 parts by weight of heavy calcium carbonate slurry 1 (manufactured by Fimatech, trade name: FMT97, D50 = 0.64 µm) and 30 parts by weight of primary clay (manufactured by IMERYS, trade name: Premier, D50 = 3.22 µm) as pigments (solid content), 7 parts by weight of styrene-butadiene copolymer latex 2 (manufactured by A&L, trade name: PB9501, average particle size 80 nm, glass transition temperature -12 ° C.) as an adhesive, and oxidized starch ( 3 parts by weight of SK200 (manufactured by Japan Corn Starch Co., Ltd.) was blended, and water was further added to obtain a pigment coating solution 7 having a solid content concentration of 66% by weight.

100 parts by weight (solid content) of heavy calcium carbonate slurry 1 (manufactured by Fimatech, product name: FMT97, D50 = 0.64 µm) was used as a pigment, and styrene-butadiene copolymer latex 1 (product Name: PB1537, average particle diameter 110 nm, glass transition temperature 10 ° C.) 7 parts by weight, 3 parts by weight of oxidized starch (manufactured by Japan Corn Starch Co., Ltd., trade name: SK200), and water is added to solid content concentration 66 A pigment coating liquid 8 of weight % was obtained.
The pigment coating solution 8 was coated on both sides of the base paper with a blade coater so that the dry coating amount per side was 8.5 g/m ² , and then dried to obtain a lower layer coated paper. The pigment coating liquid 7 is coated on both sides of the lower layer coated paper with a blade coater so that the dry coating amount per side is 20.0 g/m ² , and then dried to obtain a coated printing paper. rice field.

[Reference example 2]
70 parts by weight of heavy calcium carbonate slurry 2 (manufactured by Fimatech, trade name: FMT90, ratio of particles having a particle size of 2 μm or less by sedimentation method: 90%, D50 = 0.94 μm) as a pigment, first-class clay (IMERYS) (product name: Premier, D50 = 3.22 μm) 30 parts by weight (solid content), and styrene-butadiene copolymer latex 2 (manufactured by A&L, product name: PB9501, average particle size 80 nm) is used as an adhesive. , glass transition temperature -12 ° C.), 3 parts by weight of oxidized starch (manufactured by Japan Corn Starch Co., Ltd., trade name: SK200), and water is added to obtain a pigment coating solution with a solid content concentration of 66% by weight. got 9.
A printed coated paper was obtained in the same manner as in Reference Example 1 except that Pigment Coating Solution 9 was used instead of Pigment Coating Solution 7 as the coating solution.

[Example 4]
70 parts by weight of heavy calcium carbonate slurry 3 (Fimatec Co., Ltd., trade name: FMT75, proportion of particles having a particle size of 2 μm or less by sedimentation method: 75%, D50 average particle size of 1.65 μm) as a pigment, first grade clay ( Made by IMERYS, trade name: Premier, D50 = 3.22 μm) 30 parts by weight (solid content), and styrene-butadiene copolymer latex 2 (manufactured by A&L, trade name: PB9501, average particle size) is used as an adhesive. diameter 80 nm, glass transition temperature −12° C.) and 3 parts by weight of oxidized starch (manufactured by Japan Corn Starch Co., Ltd., trade name: SK200), and water is added to form a pigment coating with a solid content concentration of 66% by weight. A working solution 10 was obtained.
A printed coated paper was obtained in the same manner as in Reference Example 1, except that Pigment Coating Solution 10 was used instead of Pigment Coating Solution 7 as the coating solution.

Table 1 shows the formulations and evaluation results of Examples 1-4, Comparative Examples 1-2, and Reference Examples 1-2.

As is clear from Table 1, in the coated printing paper comprising the base paper and the pigment coating layer thereon, the pore volume V or the average pore diameter m of the pigment coating layer measured by the nitrogen adsorption method is large. The higher the ink drying property, the higher the ink drying property. Further, when the coating amount of the pigment coating layer of the coated printing paper is c, the larger the V/c or m/c, the higher the ink drying property.

Furthermore, the coated paper for printing of the present invention is a coated paper for matte printing having a large difference between the white paper glossiness and the printing glossiness. It is clear that a coated paper for matte printing having good ink drying property and printing ink receptivity can be obtained by having a diameter. In addition, the coated matte printing papers of Examples 1 and 3 are given a dynamic friction coefficient higher than a static friction coefficient, thereby suppressing paper slippage and providing excellent paper alignment.
On the other hand, Comparative Examples 1 and 2 have low pore volumes and average pore diameters, and are accordingly inferior in printing ink receptivity and ink drying properties. Further, as shown in Reference Examples 1 and 2, if the white paper glossiness is higher than 35%, by reducing the particle size of the coating pigment, the pore volume and average pore diameter are reduced to the range of the present application. Although it is easy to obtain excellent printing ink receptivity and ink drying property by adjusting to , achieved the ink drying property.

[Comparison between nitrogen adsorption method and mercury intrusion method]
The coated printing papers obtained in Reference Examples 1 and 2 and Example 4 were quantitatively evaluated for quick ink drying by the following method.

<Quantitative Evaluation of Quick Drying of Ink>
Using an RI printing tester (RI-3 type, manufactured by Ishikawajima Sangyo Kikai Co., Ltd.), 0.8 cc of standard tack ink for lithography was spread on a rubber roll, and the printing was performed at a printing speed of 130 rpm three times so that the amount of ink was uniform. Printed on coated printing paper. Every 2 minutes from 2 minutes to 20 minutes after printing, the ink printed on the coated paper is transferred to the paper, and the Y value (brightness) of the ink transferred to the paper is measured with a portable spectrodensitometer (manufactured by X-Rite, Inc.). Measured by X-Rite 520). The Y value indicates the degree of ink transferred to the paper without drying. Y=80 was used as a standard for quick drying of the ink, and the time required to achieve this was used as a quantitative index for drying.

The results are shown in Table 2, Figures 1 and 2. As the pore volume and average pore diameter measured by the nitrogen adsorption method increase, the quick drying property of the ink improves. This tendency conforms to the relationship of the above-described formula (3). On the other hand, this correlation was not observed in the mercury intrusion method. From the above, it is clear that the rapid drying of ink can be measured more accurately by using the nitrogen adsorption method.

Claims (9)

A coated printing paper comprising a base paper and a single pigment coating layer provided thereon,
The pore volume V of the pigment coating layer measured by a nitrogen adsorption method is 0.04 cm ³ /g or more,
The white paper glossiness of the coated printing paper according to JIS-P8142 is less than 35%, and the JAPAN TAPPI Paper Pulp Test Method No. of the coated printing paper. a printing ink receptivity of 20 to 35 as measured by 46;
The outermost layer of the paper is the pigment coating layer, and the outermost pigment coating layer is
25 to 55% by weight of calcium carbonate having a D50 of 0.5 to 1.02 μm in all pigments;
In the static friction coefficient and dynamic friction coefficient on the outermost pigment coating layer side measured according to ISO15359, the dynamic friction coefficient is larger than the static friction coefficient,
Coated paper for printing. 2. The coated printing paper according to claim 1, wherein the pigment coating layer has an average pore diameter m of 30 nm or more as measured by a nitrogen adsorption method. The coated printing paper according to claim 1 or 2, wherein the pore volume V is 0.09 cm ³ /g or less. The coated printing paper according to any one of claims 1 to 3, wherein said average pore diameter m is 60 nm or less. The coated printing paper according to any one of claims 1 to 4 , wherein the calcium carbonate is ground calcium carbonate. The coated printing paper according to any one of claims 1 to 4 , wherein the calcium carbonate is light calcium carbonate. Coated printing paper according to any of claims 1 to 6 , wherein said outermost pigment coating layer contains 20 to 50% by weight of kaolin or clay in total pigment. The coated printing paper according to any one of claims 1 to 7 , wherein said outermost pigment coating layer comprises an adhesive, and 20 to 80% by weight of latex in said adhesive. The total pore volume (cm ³ /m 2 ) defined by pore volume V (cm 3 /g)×coating amount c ( ^g /m ^{2 )} of the pigment coating layer is 0.55 to 4.0. The coated printing paper according to any one of claims 1 to 8 , which has a density of 50 cm ³ /m ² .