JP2024026131A - coated paper for printing - Google Patents

Abstract

To provide coated paper for printing, having high blank paper glossiness and high strength.SOLUTION: Coated paper for printing comprises a pigment coating layer on at least one side of base paper, wherein the outermost pigment coating layer includes calcium carbonate having an average particle diameter (D50) of over 0.50 μm and 0.80 μm or under and has blank paper glossiness (75°) of 60% or over.SELECTED DRAWING: None

Description

The present invention relates to a coated printing paper with high white paper gloss and high strength.

Coated paper is broadly divided into glossy coated paper and matte coated paper. Among glossy coated papers, high-gloss coated papers include art paper, super art paper, which was traditionally used for high-end printing, and coated paper used for catalogs, pamphlets, etc., and these have a white glossy finish in the printing finish. A glossy finish with high printing gloss and printing gloss. Furthermore, matte coated paper is coated paper that has lower white paper gloss and printing gloss than high-gloss coated paper, and includes dull coated paper and matte coated paper.

Generally, in high-gloss coated paper, white paper gloss is achieved by using a large amount of kaolin or clay, which are flat pigments, or by using plastic pigments with good gloss development properties. The main surface of a flat pigment such as kaolin or clay is acidic and the side surface is basic (Non-Patent Document 1), and adhesives such as latex commonly used in coated paper contain acidic groups. Therefore, since the main surface of kaolin or clay is acidic, it has low affinity with adhesives such as latex. On the other hand, since the side surfaces of kaolin or clay are basic, they have a high affinity with adhesives, but their area is small and a sufficient adhesion area cannot be achieved, resulting in a problem of low strength development efficiency.

Kaolin or clay is a pigment with a yellow to brown tint, and coated paper that uses a lot of it has a strong yellow tint, so the hue of high-gloss coated paper tends to be yellowish. Yellowness is indicated by b ^* in the L ^* a ^* b ^* colorimetric system, and paper with a strong yellowness tends to have a high b ^* value. When printing on paper with a strong yellow tinge, the yellow tinge of the entire printed material becomes strong, so the color development of the printed material tends to be poor.

Plastic pigments are very expensive materials, and it has been difficult to use them for general-purpose glossy coated paper such as flyers. In addition, there is an increasing number of cases in which the use of plastic pigments, which are organic pigments, are avoided due to environmental considerations.

In addition, regarding high-gloss coated paper, a technique has been proposed in which the gloss is improved using very fine calcium carbonate with an average particle size of 0.50 μm or less (Patent Document 2). However, calcium carbonate whose particle size is too small has a large specific surface area, which increases the amount of binder required, which may result in a decrease in paper strength.

Japanese Patent Application Publication No. 2007-231457 Japanese Patent Application Publication No. 7-229091

Paper and Pulp Technology Association Journal, Vol. 62 (2008) No. 6, p. 694-699

An object of the present invention is to provide a coated paper for printing that has high white paper gloss and high strength.

In view of the above-mentioned problems, the inventors of the present invention have made extensive studies and found that a coated printing paper provided with a pigment coating layer containing a specific particulate calcium carbonate solves the above-mentioned problems. That is, the above-mentioned problem is solved by the present invention described below.
[1] A pigment coating layer is provided on at least one side of the base paper,
The outermost pigment coating layer contains calcium carbonate having an average particle diameter (D50) of more than 0.50 μm and less than 0.80 μm,
A coated paper for printing that has a white paper glossiness (75°) of 60% or more.
[2] The coated paper for printing according to [1], 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.
[3] The coated paper for printing according to [1] or [2], wherein the calcium carbonate has an average particle diameter (D50) of 0.55 to 0.75 μm.
[4] The coated paper for printing according to any one of [1] to [3], wherein the printing gloss of the indigo-red printed area is 70% or more.
[5] The coated paper for printing according to [2], wherein 75 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.
[6] According to any one of [1] to [5], comprising a plurality of pigment coating layers, and the coating amount of the outermost pigment coating layer is greater than the coating amount of the innermost pigment coating layer. coated paper for printing.
[7] The coated paper for printing according to any one of [1] to [6], wherein the coating amount of the outermost coating layer is 7 g/m ² or more.

ADVANTAGE OF THE INVENTION According to the present invention, a coated paper for printing having high white paper gloss and high strength can be provided.

The present invention will be explained in detail below. In the present invention, "~" includes its end points. That is, "X~Y" includes the values of X and Y. Moreover, "X or Y" means either one of X or Y, or both.

1. Coated Paper for Printing Coated paper for printing is paper for printing that has a pigment coating layer provided on a base paper. The pigment coating layer is a layer containing white pigment as a main component. In the coated printing paper of the present invention, the outermost pigment coating layer contains calcium carbonate having an average particle diameter (D50) of more than 0.50 μm and less than 0.80 μm. 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, inkjet method, electrophotographic method) on the surface of the paper, and can be used for books, Examples include, but are not limited to, magazines, posters, envelopes, calendars, etc.

(1) Pigment Coating Layer 1) Pigment The pigment coating layer contains calcium carbonate (hereinafter also referred to as "first calcium carbonate") having an average particle diameter (D50) of more than 0.50 μm and less than 0.80 μm. D50 is the 50% volume average particle diameter. The particle size distribution and D50 of the pigment by the sedimentation method can be measured using Mastersizer 3000 manufactured by Malvern Co., Ltd. or the like. The upper limit of D50 of calcium carbonate is preferably 0.75 μm or less, and preferably 0.70 μm or less. From the viewpoint of the specific surface area of the pigment and the amount of binder required, the lower limit is preferably 0.55 μm or more. If D50 is within the above range, the coating layer will be dense, resulting in high gloss, and the amount of binder required will be smaller than when using pigments of less than 0.50 μm, resulting in coated paper for printing with excellent strength. can be obtained.

When pigment coating layers are present on both sides of the base paper, the outermost pigment coating layer on at least one side may contain 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, and preferably 75 parts by weight or more based on 100 parts by weight of the pigment in the pigment coating layer. More preferably, the amount is 80 parts by weight or more. The entire amount may be used as the first calcium carbonate. The first calcium carbonate is preferably heavy calcium carbonate or light calcium carbonate produced in the causticizing step of the pulp manufacturing process (causticized light calcium carbonate, see Japanese Patent No. 5274077).

As the white pigment other than the first calcium carbonate in the pigment coating layer, pigments commonly used in the field can be used. Examples include kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, light calcium carbonate, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicates, colloidal silica, satin. Examples include inorganic pigments such as white and organic pigments such as solid type, hollow type, or core-shell type. These pigments may be used in combination.

As a 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 of more than 0.80 μm. Calcium carbonate has excellent binding properties with adhesives (binder) and improves whiteness, so high strength, whiteness, and printability can be achieved. 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, more preferably 100 parts by weight. When having two or more pigment coating layers, the total amount of the first and second calcium carbonate in the pigment coating layers other than the outermost coating layer is not limited, but is preferably within the above range. Preferably, the second calcium carbonate is ground calcium carbonate or causticized light calcium carbonate.

2) Adhesive The pigment coating layer contains an adhesive (binder) as a matrix. The adhesive is not limited, and any 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 alcohol such as fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol; casein, soybean Proteins such as proteins and synthetic proteins; etherified starches such as oxidized starch, positive starch, urea phosphate starch, and hydroxyethyl etherified starch; starches such as dextrin; cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxymethyl cellulose etc. These types can be used in combination.

From the viewpoint of printability and coating suitability, the amount of adhesive is preferably 5 to 30 parts by weight, and preferably 8 to 25 parts by weight, based on 100 parts by weight of the pigment in the entire pigment coating layer. More preferred. The upper limit is more preferably 20 parts by weight or less, most preferably 17 parts by weight or less. If the total amount of the adhesive exceeds 30 parts by weight, the viscosity of the pigment coating solution increases and operational troubles are likely to occur during coating. Furthermore, in this case, there is a tendency for the drying properties of the ink to decrease. On the other hand, if the total amount of adhesive is less than 5 parts by weight, it becomes difficult to obtain sufficient surface strength.

The coated printing paper of the present invention preferably contains 10 to 80% by weight of latex, more preferably 15 to 70% by weight of the total adhesive. Latex is an adhesive in the form of an emulsion. As the latex, styrene-butadiene latex is preferred. As mentioned above, calcium carbonate has better affinity with adhesives having acidic groups such as latex than kaolin or clay. Therefore, by using latex in the coated paper for printing of the present invention, a coated paper for printing with excellent strength development properties can be obtained. The coated paper for printing of the present invention has a pigment coating layer, but when it has two or more pigment coating layers, the layer closest to the base paper may contain 10 to 80% by weight of latex based on the total adhesive. Preferably, the layer remote from the base paper contains 30 to 60% by weight latex. It is particularly preferable to use starch as the other adhesive, and the amount thereof is preferably 30 to 90% by weight of the total adhesive in the layer closest to the base paper, and 40 to 70% by weight in the layer farthest from the base paper. It is preferable that there be.

3) Other additives The pigment coating layer may contain dispersants, thickeners, water retention agents, antifoaming agents, water resistance agents, dyes, coloring pigments, etc., as necessary, in addition to ordinary pigments for coated paper. It may also contain various auxiliary agents.

4) Coating amount The coating amount of the pigment coating layer is preferably 7 g/m ² or more in solid content per side, more preferably 10 g/m ² or more, and even more preferably 15 g/m ^{2 or} more. If the coating amount is less than 7 g/m ² , the unevenness on the surface of the paper base material cannot be sufficiently covered, so the receptivity of printing ink may be significantly reduced, and sufficient white paper glossiness may not be obtained. There is. On the other hand, the coating amount of the pigment coating layer is preferably 50 g/m ² or less, more preferably 40 g/m ² or less, and even more preferably 35 g/m ² or less. The coating amount is the total value of all pigment coating layers per side, but if there are two or more pigment coating layers, the amount of the innermost pigment coating layer (pigment coating layer adjacent to the base paper) The coating amount is preferably 2 to 15 g/m ² , more preferably 5 to 12 g/m ² . Further, the coating amount of the outermost pigment coating layer is preferably 7 g/m ² or more, more preferably 8 g/m ² or more. The upper limit is preferably 20 g/m ² or less, more preferably 15 g/m ² or less. Since the outermost coating layer has a large influence on gloss development, 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 Any 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), chemical ground pulp (CGP), and semi-chemical pulp (SCP). , waste paper pulp, etc. In the present invention, it is preferable to use chemical pulp. There are two types of chemical pulp: those manufactured by the kraft pulp method and those manufactured by the sulfite pulp method. Both can be used in the present invention, but the chemical pulp manufactured by the kraft method has a lower production cost. It is suitable from the viewpoint of The content of chemical pulp in the raw pulp is preferably 60% by weight or more in the total pulp, more preferably 80% by weight or more, even more preferably 90% by weight or more, particularly 95% by weight or more, from the viewpoint of whiteness etc. preferable.

2) Filler Known fillers may be used for the base paper. Known fillers include heavy calcium carbonate, light calcium carbonate, clay, silica, light calcium carbonate-silica composite, kaolin, calcined kaolin, delamic kaolin, white carbon, talc, magnesium carbonate, barium carbonate, barium sulfate, and water. Inorganic fillers such as amorphous silica produced by neutralizing aluminum oxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, zinc oxide, titanium oxide, and sodium silicate with mineral acids, urea-formalin resin, and melamine. Examples include organic fillers such as resins, polystyrene resins, and phenol resins. 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 above-mentioned first calcium carbonate or the second calcium carbonate, but light calcium carbonate is preferable. The filler percentage 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, etc., the content is more preferably 10 to 20% by weight.

3) Others Known paper-making additives can also be used. For example, internal additives for papermaking such as sulfuric acid, various anionic, cationic, nonionic, or amphoteric retention improvers, freeness improvers, various paper strength enhancers, and internal sizing agents are added as necessary. 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 or operability. Examples of internally added sizing agents include alkyl ketene dimers, alkenyl succinic anhydrides, and rosin sizing agents. Furthermore, dyes, pigments, optical brighteners, pH adjusters, antifoaming agents, pitch control agents, slime control agents, etc. can also be added as necessary.

4) Basis weight of base paper The basis weight of the base paper of the coated printing paper of the present invention is preferably 40 to 160 g/m ² , more preferably 45 to 150 g/m ² , and even more preferably 50 to 140 g/m ² .

5) Clear coating layer The coated paper for printing of the present invention may have a clear (transparent) coating layer on one or both sides of the above-mentioned base paper. By applying a clear coating to the base paper, the surface strength and smoothness of the base paper can be improved, and the suitability for pigment coating can also be improved. The amount of clear coating is preferably 0.1 to 3.0 g/m ² in solid content per side, more preferably 0.2 to 2.0 g/m ² , and even more preferably 0.5 to 2.0 g/m 2 . ^m2 .

In the present invention, clear coating refers to coating of starch, oxidized starch, A coating liquid (surface treatment liquid) containing starches such as various modified starches (self-modified, cationic modified, etc.) and water-soluble polymers such as polyacrylamide and polyvinyl alcohol is applied onto base paper ( size press). Coating can also be carried out by adding a sizing agent to the clear coating solution. In the present invention, it is preferable to coat with starch.

2. Manufacturing method The coated paper for printing of the present invention can be manufactured by a known method, but it is preferably manufactured by coating a pigment coating liquid containing a pigment and an adhesive onto a 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 papermaking method. For example, using a Fourdrinier paper machine including a top wire, an on-top former, a gap former, a circular wire paper machine, a paperboard machine using a combination of a Fourdrinier paper machine and a circular wire paper machine, a Yankee dryer machine, etc. I can do it. The pH during papermaking may be acidic, neutral, or alkaline, but preferably neutral or alkaline. Paper making speed is also not particularly limited. The base paper used in the present invention may be single-layer or multi-layer, but single-layer base paper is preferably used.

(2) Smoothing treatment of base paper Before applying a pigment coating liquid to the obtained base paper, it is preferable to perform a smoothing treatment on the base paper using various calender devices. As such a calender device, commonly used calender devices such as a super calender and a soft calender can be appropriately used. 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 depending on the required quality. Calendering the base paper improves the smoothness of the base paper and improves its suitability for pigment coating.

(3) Preparation of pigment coating liquid The pigment coating liquid can be prepared by dispersing or dissolving the pigment, adhesive, and, if necessary, additives in water. The composition of each component is adjusted so that the pigment coating layer described above can be formed. When blade coating is performed, the solid content concentration of the pigment coating liquid is preferably 40 to 70% by weight, more preferably 60 to 70% by weight. The viscosity of the pigment coating liquid is preferably a type B viscosity in the range of 500 to 5000 mPa·s measured at 60 rpm at room temperature. Further, when coating is performed using a roll coater, the solid content of the pigment coating liquid is preferably 30 to 60% by weight, more preferably 40 to 60% by weight. If the solid content weight is too low, backflow will occur during blade coating, while if it is too high, the blade load will increase and blade wear will progress, and in roll coaters, operability will be affected, such as boiling occurring.

(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 also not particularly limited, but it is preferably 400 to 1,800 m/min in the case of a blade coater, and 400 to 2,000 m/min in the case of a roll coater. In the present invention, a single pigment coating layer may be applied using a blade coater, it may be applied using a roll coater and then a blade coater, or it may be applied using a blade coater and then a blade coater. Although it may be coated, it is preferable to use a blade coater for coating the outermost coated layer because the surface smoothness can be improved.

The coated paper for printing of the present invention has a pigment coating layer on at least one side, and may have two or more pigment coating layers. When the number of pigment coating layers is two or more, fiber coverage is improved and smoothness is also increased. When the number of layers is three or more, the coating amount can be increased and the quality of the coated paper is improved, but from the viewpoint of cost and operability, the number of layers is preferably one or two. As described above, a clear coating layer may be provided on the base paper, and a pigment coating layer may be provided thereon.

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

For the coated paper for printing of the present invention, the coated paper produced as described above may be surface-treated, and in order to obtain high gloss, it is preferable to perform a calender treatment. When calendering is performed, commonly used calendering devices such as super calendars and soft calendars can be used as appropriate. Calender finishing conditions include the temperature of the rigid roll, calender pressure, number of nips, roll speed, and paper moisture before calendering, which are appropriately selected depending on the required quality. It is more preferable to perform hot soft nip calender treatment. The processing conditions are a linear pressure of 140 to 300 kN/m, a temperature of 70 to 300° C., and preferably 5 nips or more. The processing speed is about 200 to 800 m/min.

3. Paper quality (1) White paper glossiness White paper glossiness is an index indicating the degree of glossiness of white paper, and in the present invention, it is measured according to JIS-P8142 and is specular glossiness at an angle of 75° to the normal line of the paper surface. be. The coated paper for printing of the present invention is a high-gloss coated paper for printing with high white paper gloss. The white paper gloss of the coated printing paper of the present invention is 60% or more, preferably 65% or more, and more preferably 70% or more. The upper limit of white paper glossiness is not limited, but is 100% or less.

(2) Print Glossiness Print glossiness is an index indicating the glossiness of printed matter after printing, and is measured by the method described below in the present invention. The print glossiness (CM) of the indigo-red printed area is preferably 70 or more, preferably 75% or more.

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

<Evaluation method>
(1) Basis weight Measured according to JIS P 8124.
(2) ISO whiteness: Measured in accordance with JIS P8148 using a color difference meter CMS-35SPX manufactured by Murakami Color Co., Ltd. under conditions including ultraviolet light.
(3) White paper glossiness Measured based on JIS-P8142.
(4) Printing glossiness Using offset sheet-fed ink (NEX-M manufactured by Toyo Ink Co., Ltd.) on a Roland offset sheet-fed printing machine (4 colors), the ink in the solid area was printed at a printing speed of 8000 sheets/hr. Printing was performed in the order of blue and red (CM) so that the ink density was 1.60 for blue and 1.50 for red. The glossiness of the blue-red (CM) solid printed area of the obtained printed matter was measured based on JIS P-8142.
(5) Printing surface strength After printing using a printing ink (NEX-Y manufactured by Toyo Ink) using a RI-I type printing machine (manufactured by Mei Seisakusho), the printing marks on the rubber roll were manually transferred to transfer paper. The degree of picking was visually evaluated. The evaluation criteria are as follows.
A = Rarely occurs, B = Occurs

<Materials>
The following was used.
(1) Heavy calcium carbonate manufactured by Fimatec Co., Ltd., product name: FMT97, D50 = 0.88 μm
Manufactured by Fimatec Co., Ltd., product name: FMT75, D50 = 1.65 μm
Manufactured by Fimatec Co., Ltd., product name: Carbital 90, D50 = 1.22 μm
Manufactured by Fimatec Co., Ltd., product name: FMT100YF, D50=0.59μm
Manufactured by Fimatec Co., Ltd., product name: FMT100, D50=0.65μm
Manufactured by Imerys Minerals Japan Co., Ltd., product name: Carbital 97, D50 = 0.88 μm
(2) Clay Made by Kamin, Hydragloss D50=0.22μm
Made by Imerys Minerals Japan, Premier, D50=2.055μm
(3) Adhesive Styrene-butadiene copolymer latex Starch:
Dynacoat 68NB (manufactured by GSL Japan Co., Ltd.)
Biolatex (manufactured by Ecosynthetix)
(4) Dye Purple dye (manufactured by Mikuni Shiki Co., Ltd.)
Blue dye (manufactured by Mikuni Shiki Co., Ltd.)
Black dye (manufactured by Mikuni Shiki Co., Ltd.)
Fluorescent dye: canwhite (manufactured by Canada Japan)

<Series 3>
[Example 1]
A base paper with a basis weight of 75 g/m ² was prepared using 100% by weight of chemical pulp and containing 13.5% by weight of light calcium carbonate as a filler.

100 parts by weight of heavy calcium carbonate (manufactured by Fimatec Co., Ltd., product name: FMT97, D50 = 0.88 μm) was used as a pigment, 3 parts by weight of styrene-butadiene copolymer latex and oxidized starch were used as an adhesive. 6 parts by weight were added, and water was further added to obtain an undercoat pigment coating liquid with a solid content concentration of 65% by weight.

Using 100 parts by weight of fine grained ground calcium carbonate (manufactured by Fimatec Co., Ltd., trade name: 100YF, D50=0.59 μm), which is the first calcium carbonate, 7 parts of styrene-butadiene copolymer latex was added as an adhesive. .7 parts by weight, 1.3 parts of starch-based binder "Biolatex" (denoted as BLx in the table), each dye as shown in Table 1, and water was added to obtain a solid content of 66% by weight. A top coat pigment coating solution was obtained.

An undercoat pigment coating solution was applied onto both sides of the base paper using a blade coater so that the dry coating amount per side was 9.5 g/m ² and dried. Furthermore, a top coat pigment coating liquid was applied on both sides using a blade coater so that the dry coating amount per side was 8.5g/ ^m2 , and the coating was nipped between a resin roll and a metal roll, and the temperature and nip were adjusted. Calendar treatment was performed under the linear pressure conditions shown in Table 1 to obtain coated paper for printing. The coated paper for printing was evaluated using the method described above.

[Example 2]
Coated paper for printing was produced and evaluated in the same manner as in Example 1, except that the amount of latex in the undercoat coating liquid was changed.

[Comparative Examples 1 and 2]
Coated paper for printing was produced and evaluated in the same manner as in Example 1, except that the coating liquid shown in Table 1 was used.

<Series 1>
[Examples 3 and 4]
A base paper with a basis weight of 69 g/m ² was prepared using 100% by weight of chemical pulp and containing 13.5% by weight of light calcium carbonate as a filler.
An undercoat pigment coating liquid with a solid content concentration of 65% by weight was obtained using the pigments and adhesives shown in Table 1. Using the pigments and adhesives shown in Table 1, a top coat pigment coating liquid with a solid content concentration of 65% by weight was obtained.
Using these, coated paper for printing was manufactured and evaluated in the same manner as in Example 1.

[Comparative Examples 3 and 4]
Coated paper for printing was produced and evaluated in the same manner as in Example 3, except that the top coating liquid was changed as shown in Table 1.

<Series 2>
[Examples 5 to 8]
A base paper with a basis weight of 75 g/m ² was prepared using 100% by weight of chemical pulp, containing 13.5% by weight of light calcium carbonate as a filler, and was pressed to a starch size. A pigment coating solution having a concentration of 65% by weight was obtained.
Using these, coated printing paper having one pigment coating layer was produced and evaluated in the same manner as in Example 1.

[Comparative example 5]
Coated paper for printing was produced and evaluated in the same manner as in Example 5, except that the coating liquid was changed as shown in Table 1.

In Examples 3 and 4 of Series 1, by using calcium carbonate with a D50 of 0.80 μm or less, the printing surface strength was improved compared to Comparative Example 4 in which clay was blended, suggesting the possibility of reducing the amount of binder. . Further, in Examples 3 and 4, high gloss was obtained even under the same calendering conditions as in Comparative Example 3 using calcium carbonate having a large average particle diameter.

Series 2 concerns coated paper for printing with single coating. In Examples 5 to 8, in which calcium carbonate with a D50 of 0.80 μm or less was blended, similar to Series 1 (double coating), the gloss was higher than in Comparative Example 5, which used calcium carbonate with a large average particle size. Obtained. Further, in Example 8, the amount of starch as a binder was reduced by 1 part by weight compared to Example 5, but the printing surface strength was maintained at a level that caused no problems in printing, and no major difference was observed between the two.

From Series 3, by using calcium carbonate with a D50 of 0.80 μm or less, compared to using clay or kaolin, it is possible to improve strength while maintaining the same white paper gloss, and to reduce the amount of adhesive. It is clear that a coated printing paper with the same strength could be obtained even if the amount was reduced. From the above, it is clear that the coated paper for printing of the present invention has high white paper gloss and excellent strength.

Claims (7)

A pigment coating layer is provided on at least one side of the base paper,
The outermost pigment coating layer contains calcium carbonate having an average particle diameter (D50) of more than 0.50 μm and less than 0.80 μm,
A coated paper for printing that has a white paper glossiness (75°) of 60% or more. The coated paper for printing according to claim 1, wherein the calcium carbonate is contained in an amount of 40 parts by weight or more in 100 parts by weight of the pigment in the outermost pigment coating layer. The coated paper for printing according to claim 1 or 2, wherein the calcium carbonate has an average particle diameter (D50) of 0.55 to 0.75 μm. The coated paper for printing according to any one of claims 1 to 3, wherein the printing gloss of the indigo-red printed area is 70% or more. The coated paper for printing according to claim 2, wherein 75 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 printing coating according to any one of claims 1 to 5, comprising a plurality of pigment coating layers, and the coating amount of the outermost pigment coating layer is greater than the coating amount of the innermost pigment coating layer. paper. The coated paper for printing according to any one of claims 1 to 6, wherein the coating amount of the outermost coating layer is 7 g/m ² or more.