WO2018230682A1

WO2018230682A1 - Coated paper for use in printing

Info

Publication number: WO2018230682A1
Application number: PCT/JP2018/022833
Authority: WO
Inventors: 詩織柿木; 遼外岡; 吉松　丈博; 清畠山
Original assignee: 日本製紙株式会社
Priority date: 2017-06-15
Filing date: 2018-06-15
Publication date: 2018-12-20
Also published as: JPWO2018230682A1; JP6633251B2; TW201907077A

Abstract

Provided is a coated paper for use in printing, comprising at least one pigment coated layer on one surface of a base paper, wherein the white paper glossiness is 20-40%, the dynamic friction coefficient measured according to JIS P8147 is 0.25-0.45, and the pore volume of the pigment coated layer, measured by nitrogen adsorption, is 0.04 cm 3/g to 0.09 cm 3/g. This coated paper for use in printing has a matte-like and silky feeling, and ink dries exceptionally well on this coated paper.

Description

Coated paper for printing

The present invention relates to a coated paper for printing, and more particularly to a coated paper for silky printing.

In recent years, in the printing field, printed materials are required not only as a means of transmitting information but also to convey a texture that matches the concept. For that purpose, design and decoration are of course important, but the effects expected of paper are also increasing. Specifically, the image quality, such as image clarity and printing workability, which has been emphasized in the past, as well as high quality and natural atmosphere can be transmitted to the user more effectively. A paper with a texture is demanded (Patent Document 1). The required texture varies depending on the application. For example, when printing images with a natural atmosphere or retro image, the texture of uncoated paper with low smoothness such as kraft paper and a yellow to brown hue is exhibited. When it is desired to convey a clean and sharp atmosphere, the texture of coated paper with high whiteness and slightly bluishness tends to be preferred. As described above, the texture required for paper differs depending on the image required, but one of them is a silky texture with a high-class feeling. The silk-like texture is a texture that has a smooth and smooth texture, including a feeling of touch, and an elegant luster that is not gorgeous.

By the way, there is a matte coated paper with reduced glossiness. Among matte coated papers, demand for matte coated paper has been increasing in recent years because the difference between blank gloss and printed gloss is large and the character portion after printing is easy to read. In the field of coated paper for printing, in general, the 75 ° specular gloss (75 ° gloss) according to JIS P 8142 is often measured, but the 75 ° gloss of silk-coated paper is 20 About 40%, which is the 75 ° gloss range of matte coated paper. That is, the silk-like coated paper is a matte-coated paper that has a moist and smooth texture including touch.

Matte-coated paper generally uses techniques such as increasing the irregularities on the paper surface by using pigments with large particle diameters as coating pigments, or by not performing calendering after pigment coating. Manufactured. Matte-coated paper has larger surface irregularities than glossy coated paper that is smoothed by a calendar or the like, so that ink on the surface of the paper tends to sink. Therefore, it is necessary to transfer a large amount of ink in order to increase the printing density. Accordingly, the matte coated paper tends to have a low drying property because the amount of ink transferred increases. When the drying property of the ink is inferior, the problem of “setback” in which the ink is transferred to the other when the printed matter after printing is stacked is likely to occur. For this reason, in general, measures such as using a powder such as starch in order to prevent adhesion between the printed matter and paper, or taking a stand so as not to rub after overlapping are taken. In particular, when performing double-sided printing, if the above-mentioned “back-off” occurs, the printed image is soiled, and the value of the printed matter is significantly impaired. It is necessary to dry the ink until it no longer occurs. If the drying property of the ink is inferior, this standing time becomes longer, so that the working efficiency is lowered. Further, when printing on the opposite surface in double-sided printing, the printed image on the surface already printed by a roll or the like is rubbed, so that the printed image may be soiled if the drying property of the ink is inferior. Therefore, in order to cope with an improvement in printing speed and double-sided printing, particularly for matte coated paper, a performance for quickly drying the ink is required.

Generally, the absorption of the solvent component in the ink into the coating layer is determined by the material of the coating layer, the coating layer structure, the printing conditions, the ink conditions, and the like. So far, in order to improve the drying properties of the ink, satin white is blended into the top coating layer, and by maintaining a certain void volume in the coating layer, the absorption and ink absorption properties and ink drying properties are improved. Various studies have been made, such as a method for improving (Patent Document 2) and a method using an ink having excellent drying properties and stain resistance (Patent Document 3). Many studies have focused on the coating layer structure.

Japanese Patent Laying-Open No. 2015-193952 Japanese Patent Laid-Open No. 11-247097 Japanese Patent Laying-Open No. 2015-063667

Conventionally, there has not been sufficient study on printing paper with a texture that matches the concept of the printed matter, especially a high-quality silk-like textured coated paper. Furthermore, the relationship between the printing paper having such a texture and the ink drying property has not been studied. When a pigment having a large particle size is used as a coating pigment in order to achieve a matte tone, the pore volume of the pigment coating layer is reduced and the ink drying property is lowered. That is, it is difficult to achieve both matte and silky textures and ink drying properties. In view of such circumstances, an object of the present invention is to provide a coated paper for printing having a matte and silky texture and excellent ink drying properties.

The inventors have found that the above-described problems can be solved by setting the dynamic friction coefficient and the pore volume within a specific range. That is, the said subject is solved by the following this invention.
(Aspect 1) A coated paper for printing comprising at least one pigment coating layer on one side of a base paper,
Blank paper gloss is 20-40%,
The third dynamic friction coefficient measured according to JIS P8147 is 0.25 to 0.45,
A coated paper for printing, in which the pore volume of the pigment coated layer measured by a nitrogen adsorption method is 0.04 to 0.09 cm ³ / g.
(Aspect 2) The coated paper for printing according to aspect 1, wherein the coating amount of the pigment coating layer is 2 to 50 g / m ² .
(Aspect 3) The coated paper for printing according to aspect 1 or 2, wherein the outermost pigment coating layer contains calcium carbonate having an average particle diameter (D50) of 0.80 μm or less.
(Aspect 4) The coated paper for printing according to aspect 3, wherein 40 parts by weight or more of the calcium carbonate is contained in 100 parts by weight of the pigment in the outermost pigment coating layer.
(Aspect 5) The coated paper for printing according to any one of aspects 1 to 4, wherein the pigment in the pigment coating layer contains 100% by weight of calcium carbonate.
(Aspect 6) The coated paper for printing according to any one of Aspects 1 to 5, wherein the average pore diameter measured by a nitrogen adsorption method is 20 to 80 nm.

According to the present invention, a coated paper for printing having a matte and silky texture and excellent ink drying properties can be provided.

Hereinafter, the present invention will be described in detail. In the present invention, “˜” includes its end points. That is, “X to Y” includes the values of X and Y. “X or Y” means one or both of X and Y.

1. Coated paper for printing The coated paper for printing is a paper for printing provided with a pigment coating layer provided on a base paper. A pigment coating layer is a layer which has a white pigment as a main component. The coated paper for printing of the present invention can be subjected to commercial printing such as offset printing, gravure printing, on-demand printing (laser method, ink jet method, electrophotographic method), etc. on the paper surface. Examples include, but are not limited to, magazines, posters, envelopes, and calendars.

(1) Pigment coating layer 1) Pigment The pigment coating layer may be one layer or two or more layers. In the present invention, known pigments can be used. Examples include heavy calcium carbonate, light calcium carbonate, kaolin, clay, engineered kaolin, delaminated clay, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicate, colloidal silica, satin. Examples thereof include inorganic pigments such as white and organic pigments such as a solid type, a hollow type, and a core-shell type.

The outermost pigment coating layer preferably contains calcium carbonate having an average particle diameter (D50) of 0.80 μm or less (hereinafter also referred to as “first calcium carbonate”). D50 is a 50% volume average particle size. The particle size distribution and D50 of the pigment by the precipitation method can be measured with a master sizer 3000 manufactured by Malvern. The upper limit of D50 of calcium carbonate is preferably 0.75 μm or less, and preferably 0.70 μm or less. The lower limit is preferably 0.50 μm or more.

When the outermost pigment coating layer is present on both sides of the base paper, it is preferable that the outermost pigment coating layer on at least one side contains the first calcium carbonate.

The lower limit of the amount of the first calcium carbonate in the outermost pigment coating layer is preferably 40 parts by weight or more, preferably 45 parts by weight or more, in 100 parts by weight of the pigment in the pigment coating layer. preferable. However, if the amount of the first calcium carbonate in the outermost pigment coating layer is too large, the glossiness of the white paper is excessively increased and the matte tone is impaired, so the upper limit is in 100 parts by weight of the pigment in the pigment coating layer. 70 parts by weight or less, more preferably 60 parts by weight or less, and even more preferably 55 parts by weight or less. The first calcium carbonate is preferably heavy calcium carbonate or light calcium carbonate produced in the causticizing step of the pulp production step (causticized light calcium carbonate, see Japanese Patent No. 5274077).

As the white pigment other than the first calcium carbonate in the outermost pigment coating layer, a pigment usually used in the field as described above can be used. As the white pigment other than the first calcium carbonate, it is preferable to use heavy calcium carbonate or light calcium carbonate (hereinafter also referred to as “second calcium carbonate”) having a D50 exceeding 0.80 μm. Since calcium carbonate has excellent binding properties with an adhesive (binder) and improves whiteness, it can improve ink drying properties and achieve higher whiteness and printability. In 100 parts by weight of the pigment in the outermost pigment coating layer, the total amount of the first and second calcium carbonates is preferably 90 parts by weight or more, and more preferably 100 parts by weight. The total amount of the first and second calcium carbonates in the other pigment coating layers is not limited, but is preferably in the above range. The second calcium carbonate is preferably heavy calcium carbonate or causticized light calcium carbonate.

The pigment coating layer other than the outermost coating layer may contain any pigment, but is preferably calcium carbonate. Considering the cost and the like, the calcium carbonate other than the outermost layer is preferably the second calcium carbonate.

2) Adhesive The pigment coating layer contains an adhesive (binder) as a matrix. The adhesive is not limited, and a known adhesive can be used. Examples include styrene / butadiene copolymers, styrene / acrylic copolymers, ethylene / vinyl acetate copolymers, butadiene / methyl methacrylate copolymers, vinyl acetate / butyl acrylate copolymers, anhydrous Latex such as maleic acid copolymer, acrylic acid / methyl methacrylate copolymer; polyvinyl alcohols such as fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol; casein, soybean Proteins such as protein and synthetic protein; oxidized starch, positive starch, urea phosphated starch, etherified starch such as hydroxyethyl etherified starch, starch such as dextrin; carboxymethylcellulose, hydroxyethylcellulose, hydride Cellulose derivatives such as carboxymethyl cellulose and the like. These multiple types can be used in combination.

The amount of the adhesive is preferably 5 to 30 parts by weight and preferably 8 to 25 parts by weight with respect to 100 parts by weight of the pigment in the total pigment coating layer from the viewpoint of printability and coating suitability. More preferred. When the total amount of the adhesive exceeds 25 parts by weight, the viscosity of the pigment coating solution becomes high and operational troubles are likely 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 the adhesive is less than 5 parts by weight, it becomes difficult to obtain sufficient surface strength.

The coated paper for printing of the present invention preferably contains 10 to 80% by weight of the total adhesive, and contains a styrene / butadiene copolymer latex in the form of an emulsion, and preferably contains 15 to 70% by weight of latex. preferable. The coated paper for printing of the present invention comprises two or more pigment coated layers. The layer closest to the base paper preferably contains 10 to 80% by weight of latex in the total adhesive, and the layer far from the base paper has 30 to 30 layers. Preferably it contains 60% by weight latex. As other adhesives, it is particularly preferable to use starches, and the amount thereof is preferably 30 to 90% by weight in the total adhesive in the layer closest to the base paper, and 40 to 70% by weight in the layer far from the base paper. Preferably there is. Compared with latex, starches increase the water retention of the pigment coating liquid, so that the coating liquid is less likely to sink into the base paper, and the base paper can be effectively coated with the pigment coating layer. In other words, when starches are used, the coverage of the base paper by the pigment coating layer is improved. As a result, an improvement in printing quality, particularly printing glossiness, and an improvement in ink drying property can be expected. In the present invention, the ratio of latex to starch is preferably 3: 5 to 5: 7.

3) Other additives The pigment coating layer can be applied to ordinary coated paper pigments such as dispersants, thickeners, water retention agents, antifoaming agents, water resistance agents, dyes, and coloring pigments as necessary. Various auxiliaries to be blended may be included. In the present invention, it is preferable to use organic particles having a particle size larger than that of the aforementioned white pigment. By including the organic particles in the outermost coating layer farthest from the base paper, paper surface contamination due to rubbing between printed papers can be reduced, and printability can be improved. The organic particles are preferably non-steamed starch granules, and the above effect can be obtained by adding 0.5 to 10% by weight of the above-mentioned pigment. The organic particles preferably have an average particle size (D50) of 8 to 25 μm as measured with a laser diffraction particle size distribution analyzer.

4) Coating amount The coating amount of the pigment coating layer 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 terms of solid content per side. If the coating amount is less than 5 g / m ² , the unevenness on the surface of the paper substrate cannot be sufficiently covered, and the acceptability of the printing ink may be lowered. On the other hand, the coating amount of the pigment coating layer is preferably 50 g / ^{m 2} or less, more preferably ^{^{40g / m 2, 35g / m}} 2 or less is more preferred. The coating amount is a total value of all the pigment coating layers per side, but the coating amount of the innermost pigment coating layer (pigment coating layer adjacent to the base paper) is preferably 2 to 15 g / m ^2. More preferably, it is 5 to 12 g / m ² . The coating amount of the outermost pigment coating layer is preferably 6 to 20 g / m ² , more preferably 8 to 15 g / m ² . Since the outermost coating layer has a great influence on the texture including ink drying properties and touch, the coating amount of the outermost coating layer is preferably larger than the coating amount of the innermost pigment coating layer.

(2) Base paper 1) Pulp Known pulp can be used for the base paper. Known pulps include chemical pulp, groundwood pulp (GP), refiner groundwood pulp (RGP), thermomechanical pulp (TMP), chemothermomechanical pulp (CTMP), chemiground pulp (CGP), and semichemical pulp (SCP). And waste paper pulp. In the present invention, it is preferable to use chemical pulp. There are chemical pulps 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. From the aspect, it is preferable. The content of the chemical pulp in the raw material pulp is preferably 60% by weight or more, more preferably 80% by weight or more, still more preferably 90% by weight or more, particularly 95% by weight or more from the viewpoint of whiteness and the like. preferable.

2) Filler A known filler 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, deramikaolin, white carbon, talc, magnesium carbonate, barium carbonate, barium sulfate, water Inorganic fillers such as amorphous silica produced by neutralization of aluminum oxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, zinc oxide, titanium oxide, sodium silicate with mineral acid, urea-formalin resin, melamine Organic fillers such as resin, polystyrene resin, phenol resin and the like. Among these, heavy calcium carbonate and light calcium carbonate, which are typical fillers for neutral papermaking and alkaline papermaking, are preferably used to improve opacity. The calcium carbonate used as the filler may be the first calcium carbonate or the second calcium carbonate described above, but light calcium carbonate is preferred. The filler content in the paper is not particularly limited, but is preferably 1 to 40% by weight, more preferably 10 to 35% by weight. Considering the strength of the base paper, it is more preferably 10 to 20% by weight.

3) Others Known paper additives can also be used. For example, sulfuric acid bands and various anionic, cationic, nonionic or amphoteric yield improvers, drainage improvers, various paper strength enhancers and internal additive sizing agents, etc. Can be used. Examples of the dry paper strength improver include polyacrylamide and cationized starch, and examples of the wet paper strength improver include polyamidoamine epichlorohydrin. These chemicals are added within a range that does not affect the formation and operability. Examples of the internal sizing agent include alkyl ketene dimer, alkenyl succinic anhydride, and rosin sizing agent. Furthermore, dyes, pigments, fluorescent brighteners, pH adjusters, antifoaming agents, pitch control agents, slime control agents and the like can be added as necessary.

4) The basis weight of base paper coated printing paper having a basis weight of the present invention of the base paper is preferably 40 ~ 160g / ^{m 2,} more preferably 45 ~ 150g / ^{m 2,} more preferably 50 ~ 140g / ^{m 2.}

5) Clear coating layer The printing coated paper of the present invention may have a clear (transparent) coating layer on one side or both sides of the base paper described above. By performing clear coating on the base paper, the surface strength and smoothness of the base paper can be improved, and the coating suitability when applying pigment can be improved. The amount of the clear coating is preferably 0.1 ~ 3.0g / ^{m 2} by solid per side content, more preferably 0.2 ~ 2.0g / ^{m 2,} more preferably 0.5 ~ 2.0 g / a m ^2.

In the present invention, clear coating refers to, for example, a starch, oxidized starch, a coater (coating machine) such as a 2-roll pound size press, a gate roll coater, a pre-metering size press, a curtain coater, or a spray coater. Coating and coating liquids (surface treatment liquids) mainly composed of starches such as various modified starches (self-modified, cation-modified, etc.) and water-soluble polymers such as polyacrylamide and polyvinyl alcohol are coated on the base paper ( Size press). The clear coating liquid can be coated with a sizing agent. In the present invention, it is preferable to apply starch.

2. Production Method The coated paper for printing of the present invention can be produced by a known method, but it is preferably produced by applying a pigment coating solution containing a pigment and an adhesive on the base paper.
(1) Preparation of base paper The raw materials used for the base paper used in the present invention are as described above. The base paper is manufactured by a known paper making method. For example, use a long paper machine including top wire, on-top former, gap former, round paper machine, paperboard machine using a combination of long paper machine and round paper machine, Yankee dryer machine, etc. Can do. The pH during papermaking may be acidic, neutral or alkaline, but neutral or alkaline is preferred. The paper making speed is not particularly limited. The base paper used in the present invention may be a single layer or multiple layers, but a single layer base paper is preferably used.

(2) Smoothing treatment of base paper Before applying the pigment coating liquid to the obtained base paper, it is preferable to smooth the base paper with various calendar devices. As such a calendar device, a commonly used calendar device such as a super calendar or a soft calendar can be used as appropriate. As the calendar finishing conditions, the temperature of the rigid roll, the calendar pressure, the number of nips, the roll speed, the paper moisture before the calendar, and the like are appropriately selected according to the required quality. In the present invention, it is preferable to perform a calendar process on the base paper in order to impart smoothness while maintaining the matte texture. By applying a calendar treatment to the base paper, the smoothness of the base paper is improved and the pigment coating suitability is improved.

(3) Preparation of pigment coating liquid The pigment coating liquid can be prepared by dispersing or dissolving a pigment, an adhesive, and, if necessary, an additive in water. The composition of each component is adjusted so that the pigment coating layer can be formed. When performing blade coating, 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 solution is preferably in the range of 500 to 5000 mPa · s as measured by the B-type viscosity measured at 60 rpm at room temperature. When coating is performed with a roll coater, the solid content of the pigment coating solution is preferably 50 to 70% by weight, more preferably 60 to 70% by weight. If the solid weight is too low, backflow or the like occurs, and if it is too high, the blade load increases and blade wear increases, which affects operability.

(4) Coating method The coating method is not limited, and known coating methods such as a roll coater and a blade coater can be used. The coating speed is not particularly limited, but is preferably 400 to 1800 m / min in the case of a blade coater and 400 to 2000 m / min in the case of a roll coater. In the present invention, the pigment coating layer may be applied with a single layer blade coater, may be applied with a roll coater and then applied with a blade coater, or may be applied with a blade coater and then applied with a blade coater. Although coating may be performed, since the smoothness of the surface can be improved, it is preferable to use a blade coater for coating the outermost coating layer.

The printing coated paper of the present invention is preferably provided with two or more pigment coating layers in order to increase the printing gloss. By providing two or more pigment coating layers, the fiber coverage is improved and the smoothness is also increased. When the number of layers is three or more, the coating amount can be increased, so that the quality of the coated paper is improved. However, the number of layers is preferably two from the viewpoint of cost and operability. As described above, a clear coating layer may be provided on the base paper, and two or more pigment coating layers may be provided thereon.

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

The coated paper for printing according to the present invention may be surface-treated as necessary with the coated paper produced as described above. However, since it is difficult to obtain the matte texture of the present invention, no calendar treatment is performed. It is desirable. When performing calendar processing, a commonly used calendar device such as a super calendar or a soft calendar can be used as appropriate. As the calender finishing conditions, the temperature of the rigid roll, the calender pressure, the number of nips, the roll speed, the paper moisture before the calender, etc. are appropriately selected according to the required quality, but in the coated paper for printing of the present invention In order to give a matte texture, calendering at low pressure is preferable.

3. Paper quality (1) Blank paper glossiness Blank paper glossiness is an index indicating the glossiness of white paper, and is measured according to JIS-P8142 in the present invention. Since the coated paper for printing of the present invention is a matte printing coated paper having a large difference between the gloss of the blank paper and the printed gloss as described above, the glossiness of the blank paper is 20 to 40%. The upper limit is preferably 35% or less, and more preferably less than 30%.

(2) Dynamic friction coefficient The dynamic friction coefficient is measured according to JIS P8147. In JIS P8147, the dynamic friction coefficient is measured three times using the same sample. In the present invention, the third value is set as the dynamic friction coefficient. The dynamic friction coefficient is 0.25 to 0.45. A moist texture is obtained when the dynamic friction coefficient is within this range. From this viewpoint, the lower limit of the dynamic friction coefficient is preferably 0.3 or more, and the upper limit is preferably 4.0 or less. The static friction coefficient is similarly measured according to JIS P8147, and the first value is adopted in the present invention. The static friction coefficient is preferably 0.3 to 0.7.

(3) Ink drying property The coated paper for printing of the present invention is excellent in ink drying property although the printing glossiness is high. The superiority or inferiority of the ink drying property of the coated paper for printing is generally identified by confirming the settling of the ink transferred to the other when the printed matter after printing is overlaid, or the rubbing stain on the printed surface.

(3-1) Evaluation by pore volume, etc. In the present invention, by using a nitrogen adsorption method that can be measured under a low pressure condition, the pore structure of the pigment coating layer is evaluated in an established manner, so that the coated paper for printing is used. The ink drying property can be evaluated. Regarding the relationship between the pigment coating layer and the solvent absorptivity, the Lucas-Washburn formula shown in formula (1), in which a large number of fine pores existing in the pigment coating layer are regarded as aggregates 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 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 cylindrical structure of the pigment coating layer has n cylindrical ridges having an average radius r, the ink solvent permeation amount ν into the pigment coating layer is expressed by Formula (2). (1) can be transformed as shown in 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 viscosity of the ink. That is, it is considered that the larger the pore diameter and pore volume in the pigment coating layer, and the smaller the pigment coating layer thickness, the greater the amount of solvent permeation per fixed time and the more the ink drying property. In the present invention, the pore volume obtained by the Tristar 3000 is regarded as the pore volume of the pigment coating layer, and the average pore diameter is regarded as the average pore diameter of the pigment coating layer.

The pore volume V of the coated paper for printing of the present invention is 0.04 to 0.09 cm ³ / g. When the pore volume V is in this range, the ink drying property is excellent. From this viewpoint, the lower limit of the pore volume V is preferably 0.05 cm ³ / g or more. The upper limit is preferably 0.085cm ³ / g or less, and more preferably less 0.08 cm ³ / g.

The total pore volume (cm ³ / m ² ) of the printing coated paper of the present invention is defined by pore volume V (cm ³ / g) × coating amount c (g / m ² ), and the value is 0.55 cm ³ / m ² or more is preferable, 0.60 cm ³ / m ² or more is more preferable, and 0.80 cm ³ / m ² or more is more preferable. The upper limit of the total pore volume is preferably 1.00 cm ³ / ^{m 2} or less, more preferably 0.95cm ³ / ^{m 2.}

The average pore diameter m of the coated paper for printing of the present invention is preferably 20 to 80 nm. The upper limit of the average pore diameter m is preferably 60 nm or less, and the lower limit is preferably 30 nm or more. Specifically, in the present invention, the average pore diameter is determined from a desorption isotherm obtained by a nitrogen adsorption method. In the present application, the average pore diameter obtained by the Tristar 3000 is regarded as the average pore diameter of the pigment coating layer.

(4) Print glossiness (Glossiness difference)
The print glossiness is an index indicating the glossiness of the printed material after printing, and is measured by the method described later in the present invention. The print gloss (CM) is preferably 45 or more, more preferably 50% or more, and further preferably 70% or more. The upper limit of the print glossiness is not limited, but is preferably less than 75%. In the present invention, if the difference in glossiness obtained by subtracting the blank paper glossiness from the print glossiness is 15 or more, a sufficient difference in gloss between the printed portion and the blank paper portion is obtained, and the printed matter is clearer. It can be said.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. Parts by weight and% by weight are values in terms of solid content.

<Evaluation method>
(1) Basis weight: Measured according to JIS P 8124.
(2) Paper thickness: Measured according to JIS P 8118.
(3) Density: Determined from basis weight and paper thickness according to JIS P 8118.
(4) Blank paper glossiness Measured based on JIS-P8142.

(5) Ink drying property Ink density of solid part at a printing speed of 8000 sheets / hr using offset sheet-fed ink (NEX-M manufactured by Toyo Ink) with an offset sheet-fed printing machine (4 colors) manufactured by Roland. After printing so that the ink became black 2.00, the black solid printing part was touched with a fingertip every 10 minutes immediately after printing, and the degree of ink drying speed was sensory evaluated according to the following criteria.
A: Good B: Bad

(6) Print glossiness (Glossiness difference)
Using offset sheet-fed ink (NEX-M manufactured by Toyo Ink Co., Ltd.) with an offset sheet-fed printing machine (4 colors) manufactured by Roland, the ink thickness of the solid part is indigo at a printing speed of 8000 sheets / hr. .60 and Crimson (CM) were printed in order of Crimson 1.50. The glossiness of the indigo red (CM) solid printed part of the obtained printed matter was measured based on JIS P-8142. The value obtained by subtracting the white paper glossiness from the printing glossiness is defined as the glossiness difference. If the glossiness difference is 15 points or more, the difference in glossiness between the printed portion and the white paper portion is sufficiently obtained, and it can be said that the printed matter looks good. .
Gloss level difference = printing gloss level (%)-blank paper gloss level (%)

(7) Pore volume, etc. (i) Sample preparation and measurement The pore volume, total pore volume, and average pore diameter of the coated paper were determined by the nitrogen adsorption method.
(Sample preparation)
A paper sample having a length of 40 cm and a width of 15 cm was divided into two layers so as to be uniform in the thickness direction to obtain a laminate including 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 mainly composed of a base paper layer are obtained. A laminate including a pigment coating layer and a base paper layer was used as a sample sheet for measurement. In the case of double-sided coated paper, either one was used as a sample sheet for measurement. The basis weight t (g / m ² ) of the sample sheet was measured. Arbitrary four points in one sample sheet were selected, cut into strips, and then placed in a measurement cell so that the measurement sample had a dry weight of about 1 to 2 g. The absolutely dry weight at this time was set to w (g). Pretreatment was performed overnight in a vacuum state at a treatment temperature of 120 ° C.

(Measurement)
Using the apparatus, the pore volume and average pore diameter were measured from the pigment coating layer side of the measurement sample. Specifically, the pore volume and average pore diameter of the measurement sample were determined from the desorption isotherm using the BJH method, and the average value of four samples was taken, and the pore volume V ′ and average pore diameter of the measurement sample were taken. m ′. The pore volume V ′ was converted to a value per unit coating amount and used as the pore volume V of the pigment coating layer of the present invention. The obtained average pore diameter m ′ was directly used 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 t (g / g of sample sheet) m ² ). The coating amount c (g / m ² ) was determined by the measurement method described later. For the measurement and analysis, Tristar 3000 manufactured by Shimadzu Corporation was used.

(Coating amount)
The coating amount was measured according to the method described in Japanese Patent No. 5827187. Specifically, it measured by the following procedures.
1) A measurement sample (paper) was cut into a size of 5 cm × 5 cm, and the weight x after humidity adjustment was measured at a temperature of 23 ° C. and a relative humidity of 50%.
2) The sample was placed so that the pigment coating layer was in contact with the styrene polymer plate, and was sandwiched with a watch glass and fixed with a clip.
3) Put into a dryer at 120 to 150 ° C., melt the styrene polymer, adhere to the pigment coating layer, allow to cool, adjust the humidity at about 23 ° C. and 50% relative humidity for about half a day, and measure the weight y. .
4) After the measurement sample obtained in the previous step was immersed in a 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 there was no pulp fiber adhering to the pigment coating layer.
5) The pigment coating layer was washed with water and dried. After conditioning for about half a day 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 ) = (x−A) × 400
A = yz

(8) Coefficient of friction Measured according to JIS P8147. However, in the three repeated measurements, the first measured value was adopted as the static friction coefficient, and the third measured value was adopted as the dynamic friction coefficient.

(9) Silk tone The silky texture was sensory evaluated according to the following criteria.
A: Good B: Bad

(10) Halftone dot unevenness Ink on the solid part at a printing speed of 8000 sheets / hr using offset sheet-fed ink (NEX-M manufactured by Toyo Ink Co., Ltd.) on an offset sheet-fed printing machine (4 colors) manufactured by Roland. Printing was performed in the order of indigo red (CM) so that the inking density was 1.60 indigo and 1.50 in red. The printed material obtained was visually evaluated for unevenness in the indigo color (CM) halftone (50%) printed part. If the evaluation is 4 or 3, there is no practical problem.
4: Very good 3: Good 2: Slightly inferior 1: Inferior

[Example 1]
Light calcium carbonate was added using 100% by weight of chemical pulp so that the ash content in the paper was 13.5% by weight, and a base paper having a basis weight of 97.9 g / m ² was prepared.
Heavy calcium carbonate (manufactured by Pimatech Co., Ltd., trade name: NP, D50 = 0.6 μm) as a pigment and 45 parts by weight of heavy calcium carbonate (Pimatec Co., Ltd., trade name: FMT97, D50 = 0.88 μm) 55 parts by weight, 4 parts by weight of styrene / butadiene copolymer latex and 6 parts by weight of oxidized starch as an adhesive are added to this, and water is added to obtain a pigment coating solution having a solid content concentration of 66% by weight. Obtained.
On the base paper, the pigment coating solution was coated on both sides with a blade coater and dried to obtain a coated paper for printing. The dry coating amount per side was 15.0 g / m ² . The coated paper for printing was evaluated by the method described above.

[Example 2]
A coated paper for printing was produced and evaluated in the same manner as in Example 1 except that the coating amount on one side of the outermost layer was changed to 15.3 g / m ² .

[Example 3]
100 parts by weight of heavy calcium carbonate (trade name: FMT97, D50 = 0.88 μm) made of heavy calcium carbonate as a pigment, 7 parts by weight of styrene / butadiene copolymer latex as an adhesive, and oxidized starch 3 parts by weight was added and water was further added to obtain an undercoat pigment coating solution having a solid content concentration of 66% by weight.
As a pigment, 44.5 parts by weight of heavy calcium carbonate (manufactured by Pimatech, Inc., trade name: FMT100, D50 = 0.66 μm) and heavy calcium carbonate (tradename: FMT97, D50 = 0.0.6 μm). 88 μm), 55 parts by weight, 4 parts by weight of styrene / butadiene copolymer latex as an adhesive, 6 parts by weight of oxidized starch, and uncooked starch granules (trade name: Y- 3P) was added in an amount of 0.5 parts by weight, and water was further added to obtain a topcoat pigment coating solution having a solid concentration of 66% by weight.
On the base paper, an undercoat pigment coating solution was coated on both sides with a blade coater so that the dry coating amount per side was 10.0 g / m ² and dried. Further, a top coat pigment coating solution was coated on both sides with a blade coater so that the dry coating amount per side was 8.0 g / m ² to obtain a coated paper for printing. The coated paper for printing was evaluated by the method described above.

[Example 4]
1. 3 parts by weight of self-made light calcium carbonate (D50 = 1.02 μm) and 97 parts by weight of self-made light calcium carbonate (D50 = 1.38 μm) were used as pigments, and styrene / butadiene copolymer latex was used as an adhesive. 5 parts by weight and 21 parts by weight of oxidized starch were added, and water was further added to obtain an undercoat pigment coating solution having a solid concentration of 50% by weight.
As a pigment, 55 parts by weight of self-made light calcium carbonate (D50 = 1.02 μm) and 44.5 parts by weight of self-made light calcium carbonate (D50 = 0.64 μm) were used, and 4 styrene / butadiene copolymer latex was used as an adhesive. Part by weight, 6 parts by weight of oxidized starch, 0.5 parts by weight of uncooked starch granules (trade name: Y-3P, manufactured by Nippon Cornstarch Co., Ltd.), water added, and solid content concentration of 66 weights % Topcoat pigment coating solution was obtained.
On the base paper, the undercoat pigment coating solution was coated on both sides with a gate roll coater so that the dry coating amount per side was 4.5 g / m ² and dried. Further, a top coat pigment coating solution was coated on both sides with a blade coater so that the dry coating amount per side was 10.5 g / m ² , thereby obtaining a coated paper for printing. The coated paper for printing was evaluated in the same manner as in Example 1.

[Comparative Example 1]
100 parts by weight of heavy calcium carbonate (manufactured by Phymatech Co., Ltd., trade name: FMT97, D50 = 0.88 μm) as a pigment, 8 parts by weight of a styrene / butadiene copolymer latex as an adhesive, and 6 parts by weight of oxidized starch Then, water was added to obtain a pigment coating solution having a solid content concentration of 66% by weight. Using the coating solution, a coated paper for printing having one pigment coating layer was produced in the same manner as in Example 1, and evaluated.

[Comparative Example 2]
1. 20 parts by weight of self-made light calcium carbonate (D50 = 1.02 μm) and 80 parts by weight of self-made light calcium carbonate (D50 = 1.38 μm) are used as pigments, and styrene / butadiene copolymer latex is used as an adhesive. 5 parts by weight and 21 parts by weight of oxidized starch were added, and water was further added to obtain an undercoat pigment coating solution having a solid concentration of 50% by weight.
95 parts by weight of self-made light calcium carbonate (D50 = 1.02 μm) and 5 parts by weight of fine clay (Imeris, trade name: Astra Grace, D50 = 0.23 μm) are used as pigments, and styrene / butadiene as an adhesive. 5.8 parts by weight of latex and 5.3 parts by weight of oxidized starch were added, and water was further added to obtain a topcoat pigment coating solution having a solid content concentration of 66% by weight.
On the base paper, the undercoat pigment coating solution was coated on both sides with a gate roll coater so that the dry coating amount per side was 4.5 g / m ² and dried. Further, a top coat pigment coating solution was coated on both sides with a blade coater so that the dry coating amount per side was 10.5 g / m ² , thereby obtaining a coated paper for printing. The coated paper for printing was evaluated in the same manner as in Example 2.

[Comparative Examples 3 to 5]
The undercoat pigment coating solution and the topcoat pigment coating solution were changed to those shown in Table 1, and the undercoat pigment coating solution was coated with a blade coater at a dry coating amount of 10.5 g / m ² on one side. A coated paper for printing was produced and evaluated in the same manner as in Example 3, except that the liquid was coated on both sides with a blade coater so that the dry coating amount per side was 8.5 g / m ² .

[Comparative Examples 6 and 7]
A coated paper for printing was produced and evaluated in the same manner as in Example 1 except that the topcoat pigment coating solution was changed to that shown in Table 1.

It is apparent that the coated paper for printing of the present invention has a matte and silky texture and is excellent in ink drying properties.

Claims

A coated paper for printing comprising at least one pigment coating layer on one side of a base paper,
Blank paper gloss is 20-40%,
The third dynamic friction coefficient measured according to JIS P8147 is 0.25 to 0.45,
A coated paper for printing, in which the pore volume of the pigment coated layer measured by a nitrogen adsorption method is 0.04 to 0.09 cm 3 / g.
The coated paper for printing according to claim 1, wherein the coating amount of the pigment coating layer is 2 to 50 g / m 2 .
The coated paper for printing according to claim 1 or 2, wherein the outermost pigment coating layer contains calcium carbonate having an average particle diameter (D50) of 0.80 µm or less.
The coated paper for printing according to claim 3, wherein 40 parts by weight or more of the calcium carbonate is contained in 100 parts by weight of the pigment in the outermost pigment coating layer.
The coated paper for printing according to any one of claims 1 to 4, comprising 100% by weight of calcium carbonate in the pigment in the pigment coating layer.
The coated paper for printing according to any one of claims 1 to 5, wherein an average pore diameter measured by a nitrogen adsorption method is 20 to 80 nm.