JP2008106406A - Matte coated paper for printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a matte coated paper for printing, which is suitable for high-speed coating, and having a low density, high rigidity and smoothness, low white paper gloss and relatively high whiteness and printing gloss. <P>SOLUTION: The matte coated paper for printing is provided with a pigment coating layer applied to a base paper by a blade coating method. The base paper contains 1-10 mass% of amorphous silica or amorphous silicate as a filler based on the mass of the base paper, the pigment coating layer contains 2-20 mass% of kaolin having an average particle diameter (D<SB>50</SB>) of ≤2.0 μm measured by a laser diffraction method based on the total pigment mass, and 80-98 mass% of ground calcium carbonate having an average particle diameter (D<SB>50</SB>) of ≤1.5 μm, and the ground calcium carbonate contains ≥50 mass% of heavy calcium carbonate having an average particle diameter (D<SB>50</SB>) of ≤1.0 μm and ratio (D<SB>75</SB>/D<SB>25</SB>) of the particle diameter of 75 cumulative vol% (D<SB>75</SB>) to the particle diameter of 25% cumulative vol% (D<SB>25</SB>) in a particle diameter distribution curve of ≤2.0. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a matte coated paper for printing, suitable for high speed coating, low density, high rigidity and smoothness, low white paper gloss and relatively high whiteness and printing gloss. It relates to matte coated paper.

  In recent years, there has been a demand for a matte coated paper for printing that enhances the visual appeal of printed matter and has high printing workability due to high speed printing. For this reason, the stiffness, smoothness, whiteness, and print gloss quality of matte coated paper for printing are determined in terms of printing workability and ease of handling of printed materials as printing speed increases, and the smoothness. In addition, whiteness and print gloss have become important in terms of enhancing the visualization of printed matter. On the other hand, since high-speed coating and cost reduction for increasing production efficiency are more important than before, it is desired to cope with both.

  Therefore, as a method of increasing the stiffness, there is a method of reducing the press pressure and machine calender pressure during base paper making to reduce the base paper density, but the smoothness of the base paper is significantly reduced, and the smoothness of the coated paper is also large. The desired smoothness and printing gloss cannot be obtained.

  In addition, as a method for reducing the density of the base paper, a method is disclosed in which mechanical pulp is blended with pulp used in Patent Document 1 and amorphous silica or the like is used as a filler. However, mechanical pulp fibers are rigid. Although it tends to be bulky, there is a drawback that it is difficult to obtain smoothness because the coating liquid easily penetrates.

  On the other hand, as a method of obtaining a highly smooth coated paper, it is common to perform a surface treatment such as a super calendar. However, since these treatments press the paper to improve the smoothness, Since the thickness decreases and the rigidity decreases, and the glossiness of the white paper increases, it deviates from the category of matte coated paper.

  On the other hand, Patent Documents 2 and 3 propose a technique for obtaining low gloss without ink stains by using heavy calcium carbonate and kaolin having a specific particle size distribution in the pigment coating layer as matte coated paper. Has been made. In addition, Patent Document 4 discloses a technique for obtaining a coated paper having no gloss unevenness excellent in high-speed coating property by using a combination of specific heavy calcium carbonate and copolymer latex as a coated paper for printing. Yes. However, all of these are not sufficiently disclosed for obtaining high-whiteness and printing gloss with low density and relatively high production by high-speed coating desired in the matte coated paper for printing of the present application. .

Japanese Patent Laid-Open No. 11-279988 JP-A-6-212599 JP 2004-300605 A Japanese Patent Laid-Open No. 11-50390

  The object of the present invention is to provide a matte coated paper for printing that is suitable for high-speed coating, has low density, high rigidity and smoothness, low white paper gloss, and relatively high whiteness and printing gloss. There is to do.

In a conventional formulation that uses a large amount of kaolin, it is easy to obtain characteristics such as high smoothness and high printing gloss, but on the other hand, it is easy to get a white gloss from its shape. There are aspects where the properties cannot be fully utilized. Conversely, when a large amount of calcium carbonate, especially heavy calcium carbonate is used, low gloss is obtained, but smoothness, printing gloss, etc. are difficult to achieve. Therefore, improvements are made by reducing the particle size. The fluidity during high-speed coating, which is an advantage, deteriorates.
In addition to the above, in order to solve the problem of obtaining high smoothness even when the density is reduced, the present inventors have made use of the characteristics of pigments used in the coating layer, particularly heavy calcium carbonate, to apply a matte coating. As a result of intensive studies on the relationship between high stiffness, smoothness, high whiteness and printing gloss as paper, the present invention has been completed. That is, in a matte coated paper for printing in which an aqueous coating liquid mainly composed of a pigment and an adhesive is coated on a base paper with a blade coater and dried to provide a pigment coating layer, the base paper filler as, at least one amorphous silica or amorphous silicate containing from 1 to 10 wt% with respect to the base paper weight, further the pigment coating measured average particle size by a laser diffraction method to be the layer in (D ₅₀₎ 2 to 20% by weight of kaolin having a particle size of 2.0 μm or less, and 80 to 98% by weight of heavy calcium carbonate having an average particle size (D ₅₀ ) of 1.5 μm or less. the ratio of the calcium carbonate, the average particle diameter _{(D 50)} 1.0μm or less, and a particle size of 75 cumulative% by volume in the particle size distribution curve _{(D 75)} and 25 cumulative volume percent of the particle diameter _{(D 25)} heavy that _(D 75 _{/ D 25)} of 2.0 or less The calcium, characterized by containing more than 50 wt%.

  According to the present invention, it is possible to obtain a matte coated paper for printing that is suitable for high-speed coating, has low density, has high rigidity and smoothness, has low white paper gloss, and has relatively high whiteness and printing gloss. it can.

The feature of the present invention is that amorphous silica or amorphous silicate is added to the base paper as a filler to ensure the bulkiness of the base paper and contribute to the improvement of smoothness and printing gloss on the base paper, but the white paper gloss is exhibited. It is a coating solution composed of a specific amount of kaolin that is easy to inferior to high-speed coating and excellent in high-speed coating with low white paper gloss, but smoothness tends to be low. By applying a coating solution obtained by blending heavy calcium carbonate having a mean particle size of 5% and a heavy calcium carbonate having a specific particle size and particle size distribution, drying and calendering, 1.0 g A matte coated paper for printing having a white paper gloss of 35% or less at a density of / cm ³ or less, high smoothness, rigidity, printing gloss, and high whiteness can be obtained.

  The base paper used in the present invention is mainly composed of a pulp component and a filler. As a pulp component, waste paper pulp made from various waste papers can be appropriately blended and used in addition to chemical pulp such as softwood bleached kraft pulp (NBKP) and hardwood kraft pulp (LBKP). However, in order to obtain a coated paper having sufficient smoothness, the pulp component of the base paper is composed only of chemical pulp, or it is classified into old paper (for example, upper white and card) that does not contain mechanical pulp. It is desirable to use waste paper pulp made from used paper (used paper classified as imitation / color).

In the present invention, a base paper having a low density can be obtained by internally adding at least one of amorphous silica or amorphous silicate as a filler to the base paper. Examples of the amorphous silica used include white carbon and hydrous silicic acid. In addition, the amorphous silicate has a general formula xM ₂ O · ySiO ₂ , xMO · ySiO ₂ , xM ₂ O ₃ · ySiO ₂ or the like (M is any of Al, Fe, Ca, Mg, Na, K, Ti, Zn: Examples thereof include those composed of silicate and / or silicon dioxide and a metal oxide represented by (x, y are arbitrary positive numerical values).

The average particle size of the amorphous silica and the amorphous silicate is preferably 16 to 40 μm. When the average particle size is less than 16 μm, the bulkiness effect when blended in paper is poor, and the average particle size exceeds 40 μm. In addition, the strength between the base paper layers is remarkably lowered, and the surface strength is also lowered due to dropping off of coarse particles present on the paper surface. In addition, the average particle diameter in this invention is a value which is measured by the laser diffraction method using SALD2100 (made by Shimadzu Corporation), and becomes 50% by volume integration.

The amorphous silicate includes silicon-containing particles formed from silicon dioxide and / or silicate, and 0.1 to 8.0% by mass of metal in terms of oxide with respect to 100% by mass of the silicon-containing particles. It is preferable that the compound is contained, the specific surface area is 10 to 150 m ² / g, and the pore diameter is 0.10 to 0.80 μm. In addition, when the content of the metal compound is within the above range, a porous filler having an appropriate average particle diameter and a narrow particle size distribution can be obtained which is suitable for increasing the bulk of paper and opacity of white paper. Incidentally, the bonding force is weak between the specific surface area is less than 10 m 2 / ^g aggregate structure, the pulp slurry preparation time and pressing pressure, easily collapsed calendering pressure, if more than 150 meters 2 / ^g, a pore volume of By increasing, it becomes easy to be crushed by press pressure and calendering pressure, and the bulkiness when internally added to paper becomes insufficient, the particle size distribution becomes worse, the fine particles and coarse particles increase, the base paper interlayer strength And the surface strength decreases. When the pore diameter is less than 0.10 μm, the pore volume increases. When the pore diameter exceeds 0.80 μm, the cohesive strength of the agglomerated structure is weakened, and is easily crushed by press pressure and calendering pressure. The bulkiness of is insufficient. Here, the specific surface area is the surface area of all pores assuming that the pore shape is a geometric cylinder using a pore sizer 9230 (manufactured by Shimadzu Corporation), and is the pressure in the measurement range and the amount of mercury injected. The value obtained from the relationship. The pore diameter is also a median pore diameter obtained from an integral specific surface area curve using a pore sizer 9230 (manufactured by Shimadzu Corporation).

  As the amorphous silica and the amorphous silicate, those having a bulk specific gravity of 0.3 g / ml or less as measured in accordance with JIS K-5101 (stationary method) are effective. When amorphous silica or amorphous silicate having a bulk specific gravity exceeding 0.3 g / ml is used, a base paper having a sufficient paper thickness cannot be obtained. However, since the interlayer strength of the base paper decreases as the bulk specific gravity decreases, it is necessary to take measures against the strength of the base paper. Therefore, it is preferable to use one having a bulk specific gravity of 0.05 to 0.2 g / ml. In addition, a material having a low bulk specific gravity (a material having a large specific surface area) has an effect of improving opacity and whiteness. In the present invention, if the amorphous silica or amorphous silicate satisfies all of the specific surface area, pore diameter, average particle diameter and bulk specific gravity defined here, it is easy to balance the reduction in density of the base paper and the maintenance of the interlayer strength. Preferably used.

  The amount of use is 1 to 10% by mass relative to the mass of the base paper, and the paper stock is prepared. Incidentally, if it is less than 1% by mass, sufficient density reduction cannot be performed, and conversely if it exceeds 10% by mass, the bond between pulp fibers is weakened and the strength cannot be maintained.

  Here, in addition to amorphous silica or amorphous silicate, at least one or more other fillers such as talc, kaolin, heavy calcium carbonate, light calcium carbonate, titanium oxide, etc. are used for the purpose of adjusting papermaking suitability and strength characteristics of the base paper. May be used in combination.

The paper stock in which the filler is added to the pulp slurry is made by adding chemicals usually used in the paper making process, for example, a paper strength enhancer, a sizing agent, a fixing agent, a colorant, and the like as necessary. The paper making method is not particularly limited, and the long paper machine including the top wire, the round net machine, the twin wire machine, the round net machine, a combination machine of these, a Yankee dryer machine, etc. Paper can be made by the basic paper making method or the alkaline paper making method. In addition, the base paper of the present invention is pre-coated with starch, polyvinyl alcohol or the like using a two-roll size press, a gate roll coater, a pre-metering size press coater, or a coating containing a pigment and an adhesive. It is possible to pre-coat one or more working fluids. The basis weight of the base paper can be suitably about 30 to 150 g / m ² used for general coated paper, but the effect of the present invention is remarkably exhibited because of the opacity and bulk of the base paper. Is in the range of 30 to 100 g / m ² that is particularly required.

In the present invention, the pigment coating layer provided on the base paper contains a specific kaolin and a specific heavy calcium carbonate. In other words, kaolin having an average particle diameter (D ₅₀ ) of 2.0 μm or less measured by a laser diffraction method on the pigment layer is 2 to 20% by mass of the total pigment, and the average particle diameter (D ₅₀ ) is 1.5 μm or less. In the amount of 80 to 98% by weight of the total pigment. Kaolin having an average particle diameter of more than 2.0 μm has little effect of improving the smoothness and printing gloss of white paper, and the whiteness is also low. Here, in order to maintain the printability such as the stability and surface strength of the paint, the average particle diameter of kaolin is preferably 0.2 μm or more. In addition, the use of heavy calcium carbonate having an average particle diameter exceeding 1.5 μm cannot provide high smoothness due to the presence of coarse particles, resulting in a decrease in printing gloss. Moreover, it is preferable that an average particle diameter is 0.2 micrometer or more from a viewpoint of maintaining the fluidity | liquidity of the coating liquid which is the characteristic of heavy calcium carbonate. Here, when the amount of kaolin used exceeds 20% by mass of the total pigment, the smoothness increases, but the whiteness decreases and the white paper gloss increases, making it difficult to finish the matte tone. Since the viscosity of the liquid also increases, the suitability for high-speed coating deteriorates. On the other hand, if it is less than 2% by mass, the effect of enhancing the coating stability by mixing with heavy calcium carbonate is lost.

Furthermore, in the present invention, the desired smoothness and printing gloss cannot be obtained simply by using heavy calcium carbonate having an average particle diameter of 1.5 μm or less, and further, heavy carbonate having a specific particle size distribution is obtained. Based on the knowledge that calcium contributes greatly to smoothness and printing gloss, and supplements the properties of kaolin, a particle size of 75 cumulative volume% (D ₇₅ ) and a particle diameter of 25 cumulative volume% (D ₂₅ ) It is extremely important to contain 50% by mass or more of heavy calcium carbonate having a ratio (D ₇₅ / D ₂₅ ) of 2.0 or less. Here, D ₇₅ / D ₂₅ is an index indicating the sharpness of the particle size distribution, and the smaller the value, the narrower the particle size distribution. Incidentally, when the ratio exceeds 2.0, the particle size distribution becomes wide, the desired smoothness is hardly obtained, and the printing gloss is also lowered. Moreover, if content of this heavy calcium carbonate is less than 50 mass%, the effect which raises to the desired smoothness will not be acquired. The average particle size D _{50 referred to} here is a particle size corresponding to 50 cumulative volume% of the particle size distribution curve measured using a laser diffraction particle size distribution measuring device (SALD-2100) manufactured by Shimadzu Corporation. means. D ₇₅ means a particle diameter corresponding to 75 cumulative volume% of the particle size distribution curve, and D ₂₅ means a particle diameter corresponding to 25 cumulative volume%.

  Examples of the pigment used in combination with the above-mentioned heavy calcium carbonate and kaolin having a specific average particle diameter include heavy calcium carbonate and kaolin that deviate from the specific average particle diameter, and further calcium hydroxide, light calcium carbonate, titanium dioxide, One or more kinds of coating pigments such as satin white, calcium sulfate, talc, and plastic pigment can be appropriately used as long as the desired effects of the present invention are not impaired.

  Furthermore, examples of the adhesive used together with the pigment component include proteins such as casein and soybean protein, conjugated diene polymer latex such as styrene-butadiene copolymer and methyl methacrylate-butadiene copolymer, and acrylic acid. Acrylic polymer latex such as ester and methacrylic acid ester polymers or copolymers, vinyl polymer latex such as ethylene-vinyl acetate copolymer, or these various polymers and copolymers can be converted to carboxyl groups, etc. Synthetic resin adhesives such as alkali-soluble or alkali-insoluble polymer latexes modified with functional group-containing monomers, polyvinyl alcohols, olefin-maleic anhydride resins, melamine resins, and positive starches , Starches such as oxidized starch, phosphate starch, enzyme-modified starch, carbox Methylcellulose, cellulose derivatives such as hydroxyethyl cellulose, various adhesives known for general coated paper is used alone or in combination. The total amount of the adhesive used is about 3 to 15 parts by mass per 100 parts by mass of the pigment.

  In addition to the above-mentioned pigments and adhesives, the paint contains a dispersant, a thickener, a water retention agent, an antifoaming agent, a water-resistant agent, a lubricant, a dye, a pH adjuster, etc. as necessary. The solid content concentration is adjusted to about 60 to 70%.

  Next, the prepared pigment coating solution is applied by an on-machine or off-machine blade coater capable of high-speed coating of 1000 m / min or more. As the blade coater, various blade coaters such as a bevel or bent type coater, a rod blade, and a show duel are preferably used. And it apply | coats and dries each on both surfaces of a base paper.

  As a method for drying the pigment coating solution, various drying methods such as a heating cylinder, a heated hot air air dryer, a gas heater dryer, an electric heater dryer, and an infrared heater dryer can be used alone or in combination. In the present invention, when a multilayer pigment coating layer is formed on a base paper, it is possible to form the specific pigment coating layer of the present invention on both the outermost layer and the base paper side coating layer in contact with the outermost layer. However, in general, the specific pigment layer of the present invention is formed on the outermost layer, and another pigment layer is formed on the coating layer on the base paper side in contact with the specific pigment layer.

The coating amount of the pigment coating layer is determined according to the desired quality of the matte coated paper. For example, when the basis weight of the base paper is 45 g / m ² , the specific pigment coating layer is formed on both sides. If the coating amount is about 12 to 30 g / m ^{2 in} total, sufficient coverage, high smoothness, and printed surface gloss can be obtained.

  The coated paper on which the specific pigment coating layer thus obtained is formed is passed through a multi-stage super calender process or a nip composed of a metal roll and a resin elastic roll as necessary, and is subjected to a soft calender process. However, the calendar conditions such as the number of paper feeding nips, the metal roll temperature, the nip linear pressure, and the paper feeding speed are not particularly limited, and are appropriately adjusted according to the required quality.

In the present invention, as a filler, kaolin having an average particle diameter (D ₅₀ ) of 2.0 μm or less is contained in a base paper containing 1 to 10% by mass of amorphous silica or amorphous silicate with respect to the base paper mass. Of the heavy calcium carbonate having an average particle diameter (D ₅₀ ) of 1.5 μm or less and the heavy calcium carbonate, the average particle diameter (D ₅₀ ) is 1.0 μm or less and a cumulative 75% particle diameter (D ₇₅ ) And a 25% cumulative particle size (D ₂₅ ) ratio (D ₇₅ / D ₂₅ ) of 2.0 or less, a coating solution containing 50% by weight or more of heavy calcium carbonate is applied and dried to finish the coating process. The matte coated paper for printing finished with a multi-stage calendar or a soft calendar is measured in accordance with JIS P-8143-1996 in longitudinal stiffness (A), lateral stiffness (B) and JIS P. -81 4: When the basis weight (C) measured according to 1998 is (A + B) / C> 1.0, the Oken smoothness (JAPAN TAPPI paper pulp test method No5-2) is 250 seconds or more. By finishing in such a manner, it is possible to obtain a matte coated paper for printing which is further excellent in printing workability and printing finish. Incidentally, when (A + B) / C is less than 1.0, the stiffness with respect to the rice tsubo is lowered, and particularly in the case of a lightweight coated paper, the workability at the time of printing and the page turning suitability of the printed matter are deteriorated. Here, a preferable basis weight having an effect is 80 g / m ² or less.

  Examples of the present invention will be described below, but the present invention is not limited to these examples. In the examples, “parts” and “%” indicate parts by mass and mass% unless otherwise specified.

Example 1
<Preparation of base paper>
LBKP65 parts (freeness 440ml / csf), NBKP35 parts (freeness 46
0 ml / csf) as a filler, amorphous silicate (average particle diameter: 18.0 μm, bulk specific gravity: 0.12 g / ml, specific surface area 60 m ² / g, pore diameter 0.21 μm) It is added so that it may become 8 mass%, Furthermore, 0.01 parts of AKD sizing agent (brand name: size pine K-902, Arakawa Chemical Co., Ltd.) as an internal sizing agent with respect to 100 parts of pulp (solid content conversion) And 0.6 parts of aluminum sulfate (in terms of solid content) was added to prepare a paper stock. Paper is made using this stock, and further, oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.) is used to apply 2.0 g / m ^{2 on} both sides with a gate roll size press coater, and 50 g / m ^{2 2} high quality paper coated base paper was obtained. In addition, the average particle diameter and bulk specific gravity of the filler internally added to the base paper are the average particle diameter, which is a value corresponding to 50 cumulative volume% measured with a laser diffraction particle size distribution analyzer (SALD-2100, manufactured by Shimadzu Corporation). The bulk specific gravity is a value measured in accordance with JIS K 5101 (standing method).

<Preparation of pigment coating solution>
15 parts of fine kaolin (trade name: Hydra Gloss 90, manufactured by Huba Co., Ltd., Kaolin A) having an average particle diameter D ₅₀ of 0.6 μm, an average particle diameter D ₅₀ of 0.7 μm, and D ₇₅ / D ₂₅ of 1.8 Of ultrafine heavy calcium carbonate (trade name: Seta curve HG, manufactured by Bihoku Flour & Chemical Co., Ltd., heavy calcium carbonate A), average particle size D ₅₀ is 1.2 μm, and D ₇₅ / D ₂₅ is 2.4. To a pigment made of 35 parts of fine calcium carbonate (trade name: FMT-90, manufactured by Pfematec Co., Ltd., Heavy Calcium Carbonate B), 0.05 part of sodium polyacrylate as a dispersant was added as a dispersant. And a pigment slurry having a solid content of 72% was prepared. Into this pigment slurry, 8 parts of styrene-butadiene copolymer latex (trade name: OJ-2000, manufactured by JSR) per 100 parts of inorganic pigment (solid content), 4 parts of oxidized starch (trade name: Ace A, supra) (Solid content) and other auxiliary agents were added to finally prepare a pigment coating solution having a solid content concentration of 65%.

The above-mentioned base paper is coated on both sides with a blade coater at a coating speed of 1300 m / min so that the dry coating amount on one side becomes 10 g / m ² , and the paper moisture is 5.0%. It dried so that it might become, and double-sided coated paper was manufactured. The double-sided coated paper thus obtained was passed through a soft nip calender consisting of a metal roll and an elastic roll of a resin cover so that one side was in contact with the metal roll once to obtain a matte coated paper for printing.

Example 2
A matte coated paper for printing was obtained in the same manner as in Example 1 except that the pigment coating solution of Example 1 was changed to 70 parts of heavy calcium carbonate A and 15 parts of heavy calcium carbonate B.

Example 3
A matte coated paper for printing was obtained in the same manner as in Example 1 except that the pigment coating solution in Example 1 was changed to 85 parts of heavy calcium carbonate A.

Example 4
Matte coated paper for printing in the same manner as in Example 1 except that the preparation of the pigment coating solution of Example 1 was changed to 5 parts of kaolin A, 70 parts of heavy calcium carbonate A and 25 parts of heavy calcium carbonate B25. Got.

Example 5
At the preparation of the base paper in Example 1 to give a coating base paper for fine paper by changing the basis weight 50 g / m ² to 95 g / m ^2. A matte coated paper for printing was obtained in the same manner as in Example 1 except that the coated base paper was used.

Comparative Example 1
A coated base paper was obtained in the same manner as in Example 1 except that in the preparation of the base paper of Example 1, an amorphous silicate filler was added to 0.5% by mass. A matte coated paper for printing was obtained in the same manner as in Example 1 except that the coated base paper was used.

Comparative Example 2
A coated base paper was obtained in the same manner as in Example 1 except that in the preparation of the base paper of Example 1, an amorphous silicate filler was added to 12% by mass. A matte coated paper for printing was obtained in the same manner as in Example 1 except that the coated base paper was used.

Comparative Example 3
In the preparation of the base paper of Example 1, the amorphous silicate filler was light calcium carbonate (average particle size: 6.1 μm, bulk specific gravity: 0.23 g / ml, specific surface area: 4 m ² / g, pore size: 0.58 μm) A matte coated paper for printing was obtained in the same manner as in Example 1 except that the above was changed.

Comparative Example 4
At the preparation of the pigment coated liquid of Example 1, 2 grade kaolin of A15 parts of kaolin average particle diameter _{D 50} 4.4 [mu] m: changed (trade name HT, manufactured by Engelhard Corporation .. Kaolin B) to 15 parts of Except for the above, a matte coated paper for printing was obtained in the same manner as in Example 1.

Comparative Example 5
Matte coated paper for printing was obtained in the same manner as in Example 1 except that the pigment coating solution of Example 1 was changed to 15 parts of heavy calcium carbonate A and 70 parts of heavy calcium carbonate B.

Comparative Example 6
In the preparation of the pigment coating solution of Example 1, the kaolin A was changed to 35 parts and the heavy calcium carbonate A65 parts, but the finished paint viscosity measured with a B-type viscometer was high, and the coating amount was too much to control. Since it was not possible, a matte coated paper for printing was obtained in the same manner as in Example 1 except that the solid content concentration was diluted to 63% by mass.

Comparative Example 7
At the preparation of the pigment coated liquid of Example 1, ground calcium carbonate A50 parts average particle diameter _{D 50} of the _{0.9μm, D} 75 _/ D ₂₅ of 2.2 fine ground calcium carbonate (trade name: FMTOP Matte coated paper for printing was obtained in the same manner as in Example 1 except that it was changed to 50 parts of -2A, manufactured by Pfematec Co., Ltd./heavy calcium carbonate C).

Comparative Example 8
In the preparation of the pigment coating solution of Example 1, 50 parts of heavy calcium carbonate A and 35 parts of heavy calcium carbonate B were finely divided heavy particles having an average particle diameter D ₅₀ of 1.6 μm and D ₇₅ / D ₂₅ of 2.4. Matte coated paper for printing was obtained in the same manner as in Example 1 except that the calcium carbonate (trade name: Escalon # 2200, Sankyo Flour Mills Co., Ltd. · heavy calcium carbonate D) was changed to 85 parts.

Comparative Example 9
Matte coated paper for printing was obtained in the same manner as in Example 1 except that kaolin was not used in the preparation of the pigment coating solution of Example 1 and the heavy calcium carbonate A was changed to 100 parts. However, the coating amount was difficult to attach, and the dry coating amount was 9 g / m ² .

  The matte coated printing paper obtained in each example and comparative example was evaluated based on the following evaluation method, and the results are shown in Table 1.

<Measurement of pigment particle size by laser diffraction method>
The particle size of the pigment by the laser diffraction method was measured using a laser diffraction particle size distribution analyzer SALD-2100 manufactured by Shimadzu Corporation. The particle diameter when the cumulative volume% was 50% was the average particle diameter (D ₅₀ ), and the particle diameter when the cumulative volume% was 75% and 25% was D ₇₅ and D ₂₅ , respectively. The pigment dispersion used for the measurement was a pigment slurry prepared by adding 0.05% of a dispersant (sodium polyacrylate) to the pigment, and a 0.1% aqueous solution of a phosphate dispersant (nancarin). Diluted to a concentration of about 1%.

<Glossiness of blank paper>
The resulting matte coated paper for printing was conditioned in an environment of 23 ± 1 ° C. and (50 ± 2)% RH, and then the gloss meter (GM-26D type, Murakami Color Technology) under the same environment. 75 degree glossiness was measured using a laboratory product (based on ISO 8254-Part 1).

<Smoothness>
The resulting matte coated paper for printing was conditioned in an environment of 23 ± 1 ° C. and (50 ± 2)% RH, and then in the same environment, the JAPAN TAPPI paper pulp test method No. 5-2 “Air Micro It was measured based on the “smoothness / air permeability test method of paper and board using a meter type tester”.

<Density>
Measured based on JIS P 8118: 1998.

<Print glossiness>
The resulting matte coated paper for printing was conditioned in an environment of 23 ± 1 ° C. and (50 ± 2%) RH, and in that environment, the printing ink (Varius G) Printed using 0.3 ml of black ink N type (Dainippon Ink Co., Ltd.), left to stand for 1 day, and measured 60 ° gloss using a gloss meter (GM-26D, manufactured by Murakami Color Research Laboratory) did.

<Whiteness>
In accordance with JIS P 8148: 2001, measurement was performed with a C / 2 light source using a spectral whiteness meter (manufactured by Suga Test Instruments Co., Ltd.).

<Surface strength>
The resulting matte coated paper for printing was conditioned in an environment of 23 ± 1 ° C. and (50 ± 2)% RH, and then in that environment, the printing ink (SD50 red) The product was printed using 0.6 ml of Toyo Ink Co., Ltd., and the degree of picking on the printed surface was visually evaluated.
A: Picking does not occur at all and the surface strength is extremely good.
○: Picking is slightly occurring, but it is a good level as coated paper.
(Triangle | delta): Picking generate | occur | produces and surface strength is inferior.
X: A lot of picking occurs and the surface strength is considerably inferior.

<(A + B) / C>
The resulting matte coated paper for printing was conditioned in an environment of 23 ± 1 ° C. and (50 ± 2)% RH, and then JIS P 8143-1996 “Paper Clark Stiffness Tester” The stiffness in the vertical direction (A) and the stiffness in the horizontal direction (B) measured based on the “stiffness test method”. Moreover, (A + B) / C when the basis weight measured according to JIS P 8124: 1998 was (C) was calculated.

As shown in Table 1, each of Examples 1 to 5 is a matte coated paper for printing having a low density of 1.0 g / cm ³ or less, high rigidity, high smoothness, high whiteness and excellent printing gloss. Has been obtained. In contrast, Comparative Example 1 has a low amount of amorphous silicate, so a low density cannot be obtained. Conversely, Comparative Example 2 has a large amount of amorphous silicate, especially in terms of surface strength. Inferior. In Comparative Example 3, since amorphous silicate was not used, the density was high at 1.0 g / cm ³ or more, no bulkiness, and the rigidity was inferior. Further, Comparative Example 4 using kaolin having a large average particle size is inferior in smoothness, printing gloss and whiteness, and Comparative Examples 5, 7 and 8 are all heavy in which D ₇₅ / D ₂₅ is 2 or less. Since only 50% by weight or less of calcium carbonate is used, the smoothness and printing gloss are inferior. In Comparative Example 6 in which kaolin was used in excess of 20% by weight of the total pigment, the paint properties were inferior, the glossiness increased, and the desired low gloss was not obtained. In Comparative Example 9, since kaolin is not used, the coating property of the paint is inferior and the desired quality is not obtained. As described above, according to the present invention, it is possible to obtain a coated paper that is suitable for high-speed coating, has low density, high rigidity and smoothness, low white paper gloss, and relatively high whiteness and printing gloss. became.

Claims (2)

In a matte coated paper for printing, in which an aqueous coating liquid mainly composed of a pigment and an adhesive is coated on a base paper with a blade coater and dried to provide a pigment coating layer, as a filler for the base paper, At least one amorphous silica or amorphous silicate is contained in an amount of 1 to 10% by mass based on the mass of the base paper, and the average particle diameter (D ₅₀ ) measured by a laser diffraction method in the pigment coating layer is 2 A heavy calcium carbonate having an average particle diameter (D ₅₀ ) of 2 to 20% by mass of the total pigment and 80 to 98% by mass of the total pigment of kaolin of 0.0 μm or less; of an average particle diameter _{(D 50)} 1.0μm or less, and the ratio between the particle size of 75 cumulative% by volume in the particle size distribution curve _{(D 75)} and 25 cumulative volume percent of the particle diameter _{(D 25)} (D ₇₅ / _{D 25)} of 2.0 or less heavy bicarbonate Printing matte coated paper, characterized by containing a calcium least 50 mass%.   When the longitudinal stiffness (A), lateral stiffness (B), and basis weight (C) measured according to JIS P 8143-1996, (A + B) / C> 1.0, Oken The matte coated paper for printing according to claim 1, wherein the formula smoothness is 250 seconds or more.