JP2010236148A - Coated paper for printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide coated paper for printing, which has excellent stiffness and printing characteristics, especially the coated paper for printing which has high opacity though it is highly white, and has excellent print quality, such as strike through resistance, and has high rigidity and surface strength, in thin coated paper for printing. <P>SOLUTION: Printing paper having excellent stiffness and printing characteristics can be obtained by blending calcium aluminate monocarbonate particles, which have an average particle diameter of 2-15 μm, in a pigment coating layer. Preferably, the coated paper for printing has a basis weight of 30-60 g/m2. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a coated paper for printing excellent in rigidity and printing characteristics.

  In recent years, the demand for printing paper in the commercial printing field for the purpose of advertising and promotion such as flyers, catalogs, pamphlets and direct mails has been increasing year by year, and the production volume has been steadily increasing. In such a commercial printing field, photographs and designs are frequently used and color printing is often performed so that the contents can be transmitted visually and strongly to consumers. Therefore, coated paper with excellent print quality is desired. The

  On the other hand, in order to reduce costs in terms of resource saving, transportation, and mailing costs, there is a strong demand from paper users to reduce the weight of coated paper for printing, particularly to low basis weight products. Also, in the commercial printing field, if product information is transmitted to consumers, the purpose as an advertising / advertisement medium can be achieved, so that the printing paper itself is required to be inexpensive.

  Under such circumstances, in recent years, the growth rate of the production amount of thin coated paper and coated paper has been large. However, the two demands of excellent print quality and light weight are contradictory. Increasing the base paper weight and coating weight provides excellent print quality, but it is expensive and does not meet the demand for light weight and low price. . Therefore, there has been a demand for a technique for realizing a coated paper having a higher grade printing quality in a so-called lower grade coated paper having a low basis weight and a low coating weight.

  In general, the important qualities of the coated paper for printing include whiteness, opacity, white paper gloss, and print gloss. Furthermore, a thin coated paper with a low coating amount is required to have a quality such as a white paper surface or a print surface, and it is also important that it is difficult to see through. “Print through” is a phenomenon in which the printed surface can be seen through the printed surface (through surface). In low-coating thin-coated paper, opacity is reduced and the printed surface is exposed. It is easy and the improvement is an important issue.

  Further, when the rigidity of the printing paper is reduced due to the weight reduction, there may be a problem such as an ear fold (dog ear) in which the corner of the paper is bent during printing. When the ear break occurs, the printing speed must be reduced, and the printing work efficiency is remarkably lowered. Therefore, prevention of the ear break is also strongly required for the coated paper for printing. Therefore, it is very important to maintain rigidity in the low basis weight printing coated paper.

  Further, in the case of a low basis weight coated paper for printing, securing the surface strength of the printing paper is also a major technical problem. That is, when the coating amount is reduced due to weight reduction, the surface strength necessary for printing cannot be ensured, and there may be a problem that the surface of the coated paper or the pile is blurred during printing. In offset printing, in particular, ink with relatively strong tack is used, so that it is easy to generate piling, and it is necessary to maintain the surface strength of the coated paper for printing even if it is a low basis weight product.

  Generally, when reducing the weight of the coated paper, there are a method for reducing the basis weight of the base paper and a method for reducing the coating amount of the coating layer. If the base paper has a low basis weight, the paper thickness will be thin, and it will be easy to see through, and the rigidity will be lowered, so that it will be easy to cause a problem with corner folding in offset rotary printing. On the other hand, if the coating layer has a low coating amount, the base paper coverage of the coating layer is deteriorated, so that the whiteness and the printing surface are deteriorated, and the surface strength is lowered.

Further, when producing thin coated paper at a high operation speed such as 1000 m / min or more, if the base paper basis weight is lowered, paper breakage may occur and the operability may be greatly reduced. Therefore, for example, in a thin coated paper having a basis weight of 50 g / m ² or less, it is necessary to reduce the coating amount in order to prevent paper breakage, and a thin coating layer of 3 to 7 g / m ² is often provided on one side. . However, as described above, when the coating amount is reduced, the whiteness and the printing surface feeling are lowered, and it becomes difficult to ensure sufficient quality as a commercial printed matter.

Under these circumstances, in order to realize lightweight coated paper with excellent quality, operational aspects such as materials such as pulp, filler, pigment, combinations thereof, operating conditions, paper making equipment and coating equipment Various studies have been made from the viewpoint of equipment. In recent years, an inexpensive synthesis method of calcium aluminate monocarbonate (3CaO · Al ₂ O ₃ · 11H ₂ O) has been developed, and as a new pigment for coated paper, calcium aluminum having a particle size of 0.5 to 1.5 μm. It has been reported that whiteness and opacity are improved when Nate monocarbonate is used for A2 grade coated paper (Patent Document 1).

JP 2008-196056 A

  As described above, various materials have been studied and various materials have been proposed in order to develop a coated paper for printing having excellent print quality. However, although the whiteness and opacity of the pigment constituting the pigment coating layer are studied, there are not many studies on maintaining the rigidity and surface strength of the thin coated paper by the pigment constituting the pigment coating layer. .

  In view of such a situation, an object of the present invention is to provide a coated paper for printing having excellent rigidity (rigidity) and printing quality in a coated paper for printing, particularly a thin coated paper for printing. It is. In particular, an object of the present invention is to provide a coated paper for printing having high whiteness, high opacity, excellent print quality such as back-through, and high rigidity and surface strength.

  As a result of various studies on pigments constituting the pigment coating layer in order to solve the above-mentioned problems, the present inventors have used calcium aluminate monocarbonate having an average particle diameter of 2 to 15 μm as the pigment of the pigment coating layer. When blended, it was found that a coated paper for printing with high rigidity and excellent print quality was obtained, and the present invention was completed.

Although this invention is not limited to this, It is related with the following invention.
(1) A printing coated paper having a base paper and a pigment coating layer, wherein the pigment coating layer comprises calcium aluminate monocarbonate having an average particle diameter of 2 to 15 μm. paper.
(2) The coated paper for printing as described in (1) whose average particle diameter of the said calcium aluminate monocarbonate is 2-10 micrometers.
(3) The coated paper for printing according to (1) or (2), wherein the basis weight is 30 to 60 g / m ² .

  According to the present invention, a coated paper for printing having excellent rigidity and printing quality can be obtained. In particular, the coated paper for printing of the present invention has high rigidity and surface strength while having a low basis weight, and is excellent in printing quality such as whiteness, opacity, and back-through.

  The present invention relates to a coated paper for printing having a base paper and a pigment coating layer, and uses calcium aluminate monocarbonate having an average particle diameter of 2 to 15 μm as a pigment constituting the pigment coating layer.

Coated paper for printing The coated paper for printing of the present invention can be suitably used for various printing applications. For example, it is used in printing systems such as planographic printing such as offset printing, intaglio printing such as gravure printing, and relief printing. can do. Since the coated paper for printing of the present invention is excellent in rigidity and back-through, it is suitable as a coated paper for low basis weight printing such as A3 coated paper, and is used for commercial printed materials such as flyers and catalogs. Is particularly suitable.

The basis weight of the printing coated paper of the present invention is not particularly limited, but according to the present invention, high rigidity and surface strength can be obtained even at a low basis weight, so 30 to 60 g / m ² is preferable, and 30 to 50 g / m. ² is more preferable, and 40 to 50 g / m ² is more preferable. Moreover, the ISO bending stiffness of the coated paper for printing of the present invention is not particularly limited, and can be determined as appropriate according to usage conditions such as a printing press and a printing speed. As one aspect, the machine direction ( Machine Direction: in bending stiffness MD) is preferably from 30~80μN · ^m 2 / ^m, more preferably 50~80μN · ^m 2 / ^m, more preferably 60~70μN · ^m 2 / ^m.

Calcium aluminate monocarbonate The coated paper for printing of the present invention contains calcium aluminate monocarbonate having an average particle diameter of 2 to 15 μm in the pigment coating layer. Calcium aluminate monocarbonate (hereinafter also referred to as monocarbonate) is a crystalline substance having a composition of 3CaO.Al ₂ O ₃ and is obtained in a state of being hydrated with water molecules. Monocarbonate has a layered structure, is composed of hexagonal plate-like primary particles similar to kaolin, and is generally synthesized from slaked lime and aluminum hydroxide.

  The average particle size (volume basis) of the calcium aluminate monocarbonate of the present invention is 2 to 15 μm. By using a monocarbonate having such a particle size, the calcium aluminate monocarbonate has excellent rigidity and surface strength and is also suitable for printing. Excellent coated paper for printing can be obtained. When the average particle size of monocarbonate is less than 2 μm, the glossiness of the pigment coating layer is improved, but the rigidity and surface strength are lowered. On the other hand, when the average particle diameter of monocarbonate exceeds 15 μm, the smoothness of the pigment coating layer is lowered, and it becomes difficult to obtain a good printing surface. In consideration of blank paper glossiness and printing glossiness, the average particle size (volume basis) of the calcium aluminate monocarbonate of the present invention is preferably 2 to 10 μm, and more preferably 5 to 10 μm. Here, the particle size defined in the present invention is a volume-based average particle size measured by a laser diffraction method, and is measured using, for example, a laser diffraction particle size distribution measuring instrument such as Mastersizer of MALVERN Instruments. be able to. In addition, the particle diameter of the pigment can also be measured by a sedimentation method, and for example, Sedigraph manufactured by Micromeritics can be used.

  The blending amount of the calcium aluminate monocarbonate of the present invention may be appropriately determined according to the use and the like, and is not particularly limited, but may be 5 parts by weight or more out of 100 parts by weight of the pigment constituting the pigment coating layer. Preferably, the pigment coating layer can be formed using only calcium aluminum monocarbonate as a pigment. In a preferred embodiment, the amount of calcium aluminate monocarbonate is 10 to 50 parts by weight, more preferably 10 to 40 parts by weight. With such an amount, the coated paper for printing of the present invention having excellent rigidity and surface strength can be obtained without adversely affecting workability during pigment coating.

  In the present invention, when calcium aluminate monocarbonate having an average particle diameter of 2 to 15 μm is blended in the pigment coating layer, the reason why a coated paper for printing having excellent rigidity and surface strength and excellent printing quality can be obtained. Details are not clear, and the present invention is not limited to this, but the calcium aluminate monocarbonate of the present invention has a lower specific gravity than pigments such as kaolin and calcium carbonate, so it contains calcium aluminate monocarbonate. Then, since a bulky pigment coating layer is formed, it is estimated that the rigidity is improved. The calcium aluminate monocarbonate of the present invention has a relatively regular plate shape, and the surface strength of the coating layer is improved by blending such a pigment into the pigment coating layer. When the average particle size is 2 μm or more, it is presumed that the pigment is less likely to drop off from the pigment coating layer, and that piling and smearing during printing are reduced.

The calcium aluminum monocarbonate of the present invention may be a commercially available product or a synthesized product. Monocarbonate are known to produce cement cured product in the same manner as satin white _{(3CaO · Al 2 O 3 ·} 3CaSO 4). The particle size is a hexagonal plate with monocarbonate having a layered structure, whereas satin white has a needle shape, and when used as a pigment for coated paper, it tends to be oriented flat on the paper surface. Calcium aluminum monocarbonate can be synthesized by a known method, for example, a method in which anhydrous calcium aluminate is reacted with calcium carbonate in water (Damon et al., “3CaO · Al ₂ O ₃ —CaSO ₄ · 2H ₂ O -CaCO ₃ —Na ₂ SO ₄ —H ₂ O Hydrate ”,“ Inorganic Materials ”, page 196, vol.4, 1997), mechanochemically slaked lime and carbonate by grinding aluminum hydroxide Examples include a method of reacting calcium in the presence of water (see JP 2008-37664 A). In addition, when the monocarbonate having a particle size of 2 μm to 15 μm used in the present invention is synthesized by the method described in Japanese Patent Application Laid-Open No. 2008-37664, the grinding time of aluminum hydroxide is shortened and the time until completion of the reaction is lengthened. Can be synthesized.

Base Paper The base paper used in the present invention is not particularly limited, and general paper such as high-quality paper, medium-quality paper, and recycled paper can be used, and it may be acid paper or neutral paper. The basis weight of the base paper of the present invention is not particularly limited, coated paper of the present invention formulated with carbonate hardly strike, because high surface strength, preferably ^{25~55g / m 2, 30~50g / m} 2 Is more preferable, and 35-45 g / m < ² > is still more preferable.

  The pulp used for the base paper of the present invention is not particularly limited, but, for example, raw materials for printing paper such as mechanical pulp (MP), regenerated pulp, hardwood kraft pulp (LKP), conifer kraft pulp (NKP), etc. In general, those commonly used can be suitably used, and one or two or more of these can be used as appropriate. Examples of the mechanical pulp include groundwood pulp (GP), refiner groundwood pulp (RGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), chemiground pulp (CGP), semi-chemical pulp (SCP), and the like. . In addition to general wood pulp, non-wood pulp such as linter pulp, hemp, bagasse, kenaf, esparto grass, and straw, semi-synthetic fibers such as rayon and acetate, synthetic fibers such as polyolefin, polyamide, and polyester Etc. can be used.

  The filler used in the base paper of the present invention is not particularly limited. For example, calcium carbonate such as heavy calcium carbonate and light calcium carbonate, titanium oxide, clay, silica, talc, kaolin, calcined kaolin, deramikaolin. , Magnesium carbonate, barium carbonate, zinc oxide, silicon oxide, amorphous silica, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, titanium oxide, bentonite, etc .; urea-formalin resin, polystyrene resin , Organic fillers such as melamine resin, phenol resin, and fine hollow particles can be used alone or in appropriate combination of two or more. In addition, recycled fillers made from papermaking sludge, deinking floss, etc. can also be used. In particular, in the present invention, it is preferable to use calcium carbonate as a filler because it is inexpensive and excellent in optical properties. A composite filler such as a calcium carbonate-silica composite (for example, a light calcium carbonate-silica composite described in JP2003-212539A or JP2005-219945A) can also be used. In acidic papermaking, a filler obtained by removing acid-soluble ones from the filler used in the neutral papermaking is used, and used alone or in appropriate combination of two or more. As a compounding quantity of a filler, it is preferable to contain 5-25 weight% per base paper total weight.

  In the present invention, in addition to pulp and filler, papermaking chemicals generally used for the production of base paper can be used as appropriate. For example, sizing agents such as rosin-based sizing agents, synthetic sizing agents, petroleum resin-based sizing agents, and neutral sizing agents can be used as the internal sizing agent in the present invention. In addition, paper strength enhancer, retention agent, freeness improver, coagulant, sulfuric acid band, bentonite, silica, dye, pH control agent, antifoaming agent, pitch control agent, UV inhibitor, anti-fading agent, An internal additive for papermaking such as a slime control agent can be appropriately added depending on the purpose.

Pigment coating layer The coated paper for printing of the present invention comprises a pigment coating layer on a base paper. The pigment coating layer of the present invention comprises a pigment and a binder, and can be provided on the base paper by a known method. The pigment coating layer of the present invention is provided on one side or both sides of the base paper, and may be a single layer or two or more layers.

In the present invention, the coating amount of the pigment coating layer is not particularly limited, but since the carbonate of the present invention can exert its effect even at a low coating amount, it is ² to 10 g / m ² per side. it is preferred, more preferably from 2 to 8 g / ^{m 2,} further preferably 3 to 6 g / ^{m 2.}

  The coated paper for printing of the present invention may contain other pigments as long as carbonate having an average particle diameter of 2 to 15 μm is contained in the pigment coating layer. Examples of the pigment used in the coating layer of the present invention include, but are not limited to, kaolin, clay, delaminated clay, heavy calcium carbonate, light calcium carbonate, talc, titanium dioxide, barium sulfate, calcium sulfate, and oxidation. Inorganic pigments such as zinc, silicic acid, silicate, colloidal silica, and satin white can be used in combination with monocarbonate.

  In general, various binders are used in the pigment coating layer in addition to the pigment, but various binders can also be used in the present invention. Examples of the adhesive used in the coating layer of the present invention include, for example, various copolymers such as styrene / butadiene, styrene / acrylic, ethylene / vinyl acetate, butadiene / methyl methacrylate, vinyl acetate / butyl acrylate, Or synthetic adhesives such as polyvinyl alcohol, maleic anhydride copolymer, acrylic acid / methyl methacrylate copolymer, proteins such as casein, soy protein, synthetic protein, oxidized starch, cationized starch, urea phosphate esterification One or more types can be appropriately selected and used from binders such as starches, starches such as hydroxyethyl etherified starch, and cellulose derivatives such as carboxymethyl cellulose, hydroxymeter cellulose, and hydroxyethyl cellulose. The compounding amount of the adhesive is about 5 to 50 parts by weight, preferably 10 to 30 parts by weight with respect to 100 parts by weight of the pigment.

  In addition, the pigment coating layer of the present invention contains various auxiliary agents that are generally blended in pigment coating liquids, such as dispersants, thickeners, water retention agents, antifoaming agents, colorants, and printability improvers. It can be used as appropriate.

  In the present invention, the apparatus for providing the coating layer on the base paper is not particularly limited. For example, a film such as a 2-roll size press coater, a gate roll coater, a blade metering size press coater, a rod metering size press coater, or a shim sizer. In addition to transfer type roll coater, hradette nip / blade coater, jet fountain / blade coater, and short dwell time applicator type coater, rod metering coater and curtain coater using grooved rod, plain rod, etc. instead of blade , And a known coater such as a die coater. It is also possible to use an on-line coater to increase operational efficiency.

  A general dryer can be used to dry the coating layer applied by the coater, and various types of dryers such as a heated hot air dryer, a heating cylinder, a gas heater dryer, an electric heater dryer, and an infrared heater dryer can be used. These can be used alone or in combination. Since the dry state affects the curl of the paper, it is preferable to use an apparatus capable of controlling the dry balance between the front and back sides in the present invention.

  In the present invention, the pigment coating layer of the coated paper thus obtained can be surface-treated in order to increase the smoothness and the like. The calendar process may be performed using a super calendar, a gloss calendar, a soft calendar, or the like usually used for the smoothing process of the coated paper, or these may be used in combination. From the viewpoint of improving the balance between the printing surface quality and the printing workability, it is particularly preferable to perform a high temperature hot soft calendering treatment.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples. In the present specification, “part” and “%” are based on weight unless otherwise specified, and “part by weight” and “% by weight” respectively represent “part by weight” and “% by weight”.

Evaluation Method Details of various evaluation methods in the present invention are as follows.
(1) Average particle size
It was measured by Mastersizer2000 (manufactured by MALVERN Instruments, laser method) and Sedigraph (manufactured by Micromeritics, precipitation method).
(2) Basis weight / paper thickness Basis weight was measured according to JIS P8124, and paper thickness was measured according to JIS P8118.
(3) ISO bending stiffness
According to ISO 2493, the bending stiffness with a bending angle of 15 degrees was measured with an L & W Bending Tester (manufactured by Lorentzen & Wettre).
(4) ISO whiteness ISO whiteness (JIS P8148) by a diffuse illumination method was measured.
(5) ISO opacity ISO opacity (JIS P8149) was measured.
(6) Glossiness of printing Using a Roland sheet-fed printing press (4 colors) and using a sheet-fed printing ink (manufactured by Toyo Ink) at a printing speed of 8000 sheets / hour in the order of black, indigo, red, yellow Print and measure the surface gloss of the printed matter (indigo single color, indigo red 2 color, indigo red 3 color solid print part) at an angle of 75 degrees according to JIS P-8142, and calculate the average value. Calculated.
(7) Back-through Using a Roland sheet-fed printing press (4 colors), printing is performed in the order of ink, indigo, red, yellow using a sheet-fed printing ink (manufactured by Toyo Ink) at a printing speed of 8000 sheets / hour. Then, the degree of through-through of the obtained printed matter was visually evaluated. The evaluation criteria are as follows.
◎ = very good, ○ = good, △ = slightly inferior, x = slightly inferior (8) Dry pick surface strength evaluation After monochromatic solid printing of indigo color ink on A3 size sample on a sheet-fed printing press R202 made by Roland The number of peeled pulp fibers appearing on the surface was visually evaluated. The evaluation criteria are as follows.
-O: Occurrence of pulp fiber peeling was hardly observed.-: Pulp fiber peeling occurred in a small amount.-X: Pulp fiber peeling occurred in a large amount [Example 1]
<Synthesis of monocarbonate>
As the monocarbonate, monocarbonate (manufactured by Kotegawa Sangyo Co., Ltd.) having an average particle size of 8.1 μm and 1.0 μm was used. Monocarbonate having an average particle size of 8.1 μm is obtained by grinding aluminum hydroxide as described in JP-A-2008-37664 and causing mechanochemical reaction in the presence of slaked lime and calcium carbonate in the presence of water. However, the grinding time of aluminum hydroxide was shortened and the time until completion of the reaction was lengthened. Monocarbonate having an average particle size of 1.0 μm was synthesized by the method described in JP-A-2008-37664.

<Manufacture of base paper>
The pulp composition constituting the base paper was KP 40% by weight, GP 10% by weight, TMP 10% by weight and DIP 42% by weight, containing 11% by weight of light calcium carbonate (average particle size: 2.2 μm) internally added, and polyacrylamide A paper stock was prepared by adding 0.03% by weight of a paper strength agent and 0.8% by weight of a sulfuric acid band as a fixing agent.

This stock was made at 1200 m / min with a twin wire paper machine to obtain a base paper having a basis weight of 41 g / m ² .

<Preparation of coating solution>
30 parts by weight of fine kaolin (average particle diameter of 0.22 μm by laser method, Hydragros / Imerys), 30 parts by weight of engineered kaolin (average particle diameter of 3.56 μm by laser method, manufactured by Contour1500 / Imerys), average A pigment composed of 30 parts by weight of monocarbonate having a particle size of 8.1 μm and 10 parts by weight of rutile titanium dioxide was added to water mixed with 0.2 parts by weight of a polyacrylic acid soda dispersant and dispersed with a serie mixer. A pigment slurry having a solid content concentration of 55% by weight was prepared. On this pigment slurry, 9 parts by weight of styrene / butadiene copolymer latex (Lx: NP100B, manufactured by JSR, etc.) and 7.5 parts by weight of hydroxyethyl etherified starch (M210: Sumida Chemical) are printed. Add 0.5 parts by weight of suitability improver (SPI106N: manufactured by Seiko PMC), 0.5 parts by weight of lubricant (SN231SP: manufactured by San Nopco), 150 ppm of black dye (SA Black A035: manufactured by Gokoku Dye), Water was added to obtain a pigment coating solution having a solid concentration of 55% by weight.

<Preparation of coated paper>
Apply the above coating solution on both sides of the base paper using a short duel type blade coater at a coating speed of 1200 m / min so that the coating amount per side becomes 3.5 g / m ^2. After passing through a scuff dryer, the paper was dried with a cylinder dryer so that the moisture in the paper was 5.5%.

<Calendar processing>
Subsequently, surface treatment was performed using an online soft nip calender to produce a coated paper for printing. The soft calender was subjected to surface treatment under the conditions of a metal roll temperature of 150 ° C., an elastic roll with a Shore D hardness of 85, a paper feed speed of 1200 m / min, a linear pressure of 200 kN / m, and a calender nip number of 4 nips.

[Comparative Example 1]
A coated paper for printing was obtained in the same manner as in Example 1 except that 30 parts by weight of monocarbonate having an average particle diameter of 1.0 μm was used instead of monocarbonate having an average particle diameter of 8.1 μm.

[Comparative Example 2]
A coated coated paper for printing was obtained in the same manner as in Example 1 except that monocarbonate having an average particle size of 8.1 μm was not blended and fine kaolin was increased by 30 parts by weight.

[Comparative Example 3]
Example 1 is the same as Example 1 except that monocarbonate having an average particle size of 8.1 μm is not blended and secondary kaolin (average particle size by laser method: 1.50 μm, manufactured by KCS / Imerys) is blended by 30 parts by weight. Thus, a coated paper for printing was obtained.

[Comparative Example 4]
A coated paper for printing was obtained in the same manner as in Example 1 except that monocarbonate having an average particle size of 8.1 μm was not blended and engineered kaolin (Contour 1500, manufactured by Imerys) was added by 30 parts by weight.

  Table 1 shows the evaluation results. As is apparent from Table 1, the coated paper of the present invention of Example 1 is excellent in all aspects such as opacity, stiffness (bending stiffness), back-through, dry pick strength, whiteness, and printing gloss. As a result, it was confirmed that the coated paper for printing such as offset printing was good.

  When Example 1 (average particle size: 8.1 μm) using carbonates having different particle sizes was compared with Comparative Example 1 (average particle size: 1.0 μm), Example 1 was glossy as compared with Comparative Example 1. Although it is slightly inferior, it is confirmed that the bending stiffness and the dry pick strength are significantly high, and the coated paper for printing of the present invention is less likely to bend or pile during printing.

  In addition, the coated coated paper of Example 1 is particularly resistant to bending stiffness (stiffness), back-through, and dry pick strength (surface) as compared to Comparative Examples 2 and 3 using kaolin, which is the same plate-like pigment as carbonate. Strength). As described above, it was confirmed that by using the carbonate having a relatively large particle diameter according to the present invention as a pigment, the rigidity and back-through of the coated paper for printing and the surface strength of the pigment coated layer can be improved.

Claims (3)

A printing paper having a base paper and a pigment coating layer,
The above coated paper for printing, wherein the pigment coating layer comprises calcium aluminate monocarbonate having an average particle diameter of 2 to 15 µm.   The coated paper for printing of Claim 1 whose average particle diameter of the said calcium aluminate monocarbonate is 2-10 micrometers. The coated paper for printing of Claim 1 or 2 whose basic weight is 30-60 g / m < ² >.