JPH0418077B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a matte coated paper for gravure printing, and in particular, a method for producing a matte coated paper for gravure printing that has low white paper gloss but high ink gloss, less misdots, and excellent halftone dot reproducibility. It is about law. Matte coated paper gives a more elegant and calm image compared to highly glossy coated paper, so
It is widely used as one of the important grades of coated paper for everything from monochrome printed materials such as text paper to various multicolored printed materials. On the other hand, gravure printing has good reproducibility from highlights to midtones and can print beautiful photographs, so it has recently been used in an increasingly wide range of fields. However, since gravure printing is a method in which ink is transferred directly from the concave surface of a metal roll to the paper surface, misdots and poor reproduction of halftone dots are likely to occur, which is a serious defect that impedes printing effectiveness. In particular, matte coated paper is coated with a coating composition containing a large amount of a pigment that is relatively coarser than the pigment used in ordinary coated printing paper, and is coated on the base paper in order to reduce the white paper gloss. Since the calendering treatment for smoothing is extremely light, such misdots and poor reproduction of halftone dots are more likely to occur, and matte coated paper for gravure printing with commercially satisfactory quality is still not available. It has not been done. Note that misdots are a phenomenon in which intaglio ink is not sufficiently transferred to the paper surface, and the main cause is that sufficient paper surface smoothness is not obtained even under pressure conditions during gravure printing. Poor halftone dot reproduction is a phenomenon in which the gravure ink spreads over the paper surface at the same time as it is transferred to the paper, causing poor reproduction of printed matter, and is likely to occur when the gravure ink is poorly absorbed into the paper surface. In view of the current situation, the present inventors have focused on improving the serious defects of gravure printing paper, such as missed dots and poor halftone reproducibility, in particular, with regard to the improvement of matte coating, which had previously been thought to have no room for improvement. In order to improve this on paper, we have conducted detailed studies and research not only on the coating composition used to manufacture printing paper, but also on the pulp fiber composition that makes up the base paper. By incorporating 50% by weight or more of heavy calcium carbonate as a pigment component, these properties are significantly improved, and when high-yield pulp with a specific fiber fraction is included in the base paper, the improvement effect is further enhanced. We have found remarkable things and have achieved the present invention. In the present invention, a coating composition containing 50% by weight or more of heavy calcium carbonate that satisfies the following conditions as a pigment component is coated on a base paper, dried, and a particle size of 15% by weight cumulative/85% by weight cumulatively is obtained. Particle size ≦15 This is a method for producing matte coated paper for gravure printing, which is characterized by smoothing treatment so that the white paper gloss (JISP8142 method) is 40% or less. The heavy calcium carbonate used in the present invention has a cumulative particle size of 15% by weight as described above, and a cumulative particle size of 85% by weight.
It is a specific heavy calcium carbonate in which the quotient of weight percent divided by particle size is 15 or less, more preferably 10 or less. The cumulative particle size of 15% by weight here refers to the cumulative weight of heavy calcium carbonate measured by measuring the particle size distribution using a Shimadzu-Micromeritics particle size distribution analyzer (Seday Graph 5000-01). % and particle diameter, and the cumulative weight % value is 15, which means the particle diameter.
Similarly, the cumulative particle size of 85% by weight means the particle size when the cumulative weight% value is 85. The desired effects of the present invention can only be obtained by using the ground calcium carbonate having such a specific particle size distribution, and the ground calcium carbonate having such a specific particle size distribution is used in the coating composition. It is contained in an amount of 50% by weight or more, more preferably 60% by weight or more of the total pigment components.
If the amount is less than 50% by weight, the resulting coated paper will have a high white gloss and will fall out of the category of matte coated paper. Heavy calcium carbonate is generally produced by crushing limestone, marble, calcite, white stone, etc., using crushers, hammer mills, micron mills, ball mills, jet mills, etc.
Grinding in dry or wet stages from the first to several stages using mechanical means such as a sand mill or attrition mill, and if necessary, classifying with elutriation, water elutriation, etc.
Heavy calcium carbonate, which can be obtained as a slurry or dry powder after dehydration treatment, has a high solid content and is wet-pulverized using a sand mill or the like. Since it is not necessarily excellent in improving the desired misdot and halftone dot reproducibility, it is not a particularly preferable heavy calcium carbonate. The heavy calcium carbonate used in the present invention preferably has a specific surface area of 1 to 3.5 m ² /g, more preferably 1.3 to 2.5 m ² /g. By using calcium carbonate, the effect of the present invention becomes even more certain. In addition to the specific heavy calcium carbonate, examples of pigment components in the coating composition used in the present invention include kaolin, light calcium carbonate, satin white, titanium dioxide, pyrofluorite clay, calcium sulfite, and calcium sulfate. , aluminum hydroxide, zinc oxide, talc, zeolite, barium sulfate, amorphous silica, plastic pigments, etc. can be blended. The adhesive components in the coating composition used in the present invention include styrene/butadiene, styrene/
Various copolymers such as acrylic, vinyl acetate/acrylic, ethylene/vinyl acetate, butadiene/methyl methacrylate, vinyl acetate/butyl acrylate, and alkali-sensitive or alkali-insensitive adhesives such as polyvinyl acetate; Furthermore, polyvinyl alcohol,
Synthetic adhesives such as maleic anhydride/styrene copolymer, isobutene/maleic anhydride copolymer, acrylic acid/methyl methacrylate copolymer,
Various commonly known adhesives such as oxidized starch, etherified starch, esterified starch, enzyme-modified starch, cold water-soluble starch obtained by flash-drying them, casein, soybean protein, and other natural adhesives are pigments.
It is used in an amount of about 3 to 20 parts by weight per 100 parts by weight.
Further, various auxiliary agents such as a dispersant, a thickener, a water retention agent, an antifoaming agent, a water resistance agent, a lubricant, a dye, and a PH regulator are appropriately blended as necessary. When preparing the coating composition, mixing using various mixers, kneaders, ball mills, sand mills, etc.
A stirrer is appropriately selected and used depending on the type of coating composition. The thus obtained coating composition of the present invention is coated in a single layer or in multiple layers on both sides or one side of the base paper to be coated.
In particular, the coating base paper has a 42 mesh fiber fraction content of 5 to 30 according to JISP8207 method.
% of high-yield pulp is more preferably used. By using such a base paper, the effect of improving the reproducibility of misdots and halftone dots can be more markedly obtained. The high yield pulp used in the present invention is
Mechanical pulps (MP) such as stone ground pulp, pressurized stone ground pulp (SGP), reflex-reiner ground pulp (RGP), thermomechanical pulp (TMP), chemi-thermomechanical pulp (CTMP), chemi-grand pulp (CGP), etc. chemical mechanical pulp (CMP),
Furthermore, it is a so-called ordinary high-yield pulp such as semi-chemical pulp (SCP), which is unbleached, semi-bleached, and bleached high-yield pulp that is widely used for newsprint, paperboard, medium-quality paper, medium-quality coated paper, bleached paper, etc. Pulp can be used alone or in combination. In the present invention, the fiber fraction distribution is measured by the JISP8207 method as described above.
12, 24, 42 mesh fiber fraction content expressed as total content of mesh sieve residue is 5 to 30
%, more preferably 10 to 25%, is particularly preferably used, and it is desirable that such high yield pulp is contained in at least 10% by weight or more in the base paper to be coated. Although it is not clear why the effect of improving misdot and halftone dot reproducibility becomes more pronounced by blending such high-yield pulp, it is clear that the blending of high-yield pulp with a specific fiber fraction content improves the cushioning of base paper. It is presumed that the properties have been significantly improved. In coating the base paper with the coating composition, the formulations of the coating compositions for both sides and the coating compositions constituting each layer in multilayer coating can be changed as appropriate according to a conventional method. The coating method is not particularly limited, and may be an air knife coater, a roll coater, a paddle and inverter type blade coater with a beveled or bent blade, or a bill blade, twin blade, or triplex coater. Various conventional coating devices such as various blade coaters and short dwell coaters are used. The coated paper coated with the coating composition and dried is then finished using a finishing device such as a super calender or a gloss calender, but in order to obtain the desired matte coated paper, such finishing treatment is It is finished under mild processing conditions so that the white paper gloss (JISP8142 method) is 40% or less. The thus obtained matte coated paper for gravure printing of the present invention has significantly improved miss dot and halftone dot reproducibility, and has an elegant white paper appearance and excellent ink gloss. The present invention will be described in more detail with reference to Examples below, but it is of course not limited thereto. Example 1 A pulp consisting of 50 parts of SGP and 50 parts of softwood bleached kraft pulp (hereinafter referred to as NBKP) prepared by post-refining to have a 42 mesh fiber fraction content (hereinafter referred to as 42 mesh content) of 20%. Composition (all parts by weight of bone dry pulp)
A paper stock containing 0.5 parts of rosin size, 2 parts of sulfuric acid, and 8 parts of talc as a filler is made into paper.
A coated base paper of g/m ² was obtained. Using 80 parts of heavy calcium carbonate and 20 parts of kaolin (manufactured by EMC, HT clay) as a dispersing agent, 0.2 parts of sodium polyacrylate was used as a dispersant, and the quotient of the cumulative particle size of 15% by weight and the cumulative particle size of 85% by weight was 6.0. The solid content was dispersed in water to give a solid content concentration of 70%, and then an alkali-sensitive emulsion and an alkali-insensitive emulsion were blended as adhesives with a solid content of 0.4 parts and 7 parts, respectively, and mixed with NaOH. pH 9.5
A coating composition with a concentration of 60% was obtained. This was coated on coated base paper using a blade coater so that the coating amount was 24 g on both sides, dried, and further treated with a super calender to obtain a matte coated paper for gravure printing. The quality of the obtained coated paper was evaluated and the results are listed in Table 1. The quotient of the cumulative particle size of 15% by weight and the cumulative particle size of 85% by weight of heavy calcium carbonate was calculated using a Shimadzu-Micromeritics particle size distribution analyzer (Sedaygraph 5000).
-01). Example 2 25 parts of RGP with a 42 mesh content of 15%,
Pulp composition consisting of 40 parts of NBKP and 35 parts of NBKP (all parts by weight of bone dry pulp) and rosin size
0.5 parts, 2 parts of sulfate and 8 parts of talc as filler.
The paper stock to which the above-mentioned amount was added was made into paper to obtain coated base paper of 40 g/m ² . A coating composition was obtained in the same manner as in Example 1, except that 100 parts of ground calcium carbonate was used, in which the quotient of the cumulative particle size of 15% by weight and the cumulative particle size of 85% by weight was 8.5.
A matte coated paper for gravure printing was obtained in the same manner as in Example 1, and its quality was evaluated and the results are shown in Table 1. Example 3 A matte coated paper for gravure printing was obtained in the same manner as in Example 1, except that heavy calcium carbonate having a quotient of 11.5 between the cumulative particle diameter of 15% by weight and the cumulative particle diameter of 85% by weight was used. The quality was evaluated and the results are listed in Table 1. Example 4 A pulp composition consisting of 50 parts of TMP and 50 parts of NBKP (all parts by weight of bone-dry pulp) adjusted to a 42 mesh content of 20% by post-refining, 0.5 part of rosin size, 2 parts of sulfate band, and Paper stock with 8 parts of talc added as a filler is made into 40g/
m ² of coated base paper was obtained. The same procedure as in Example 1 was used except that 60 parts of heavy calcium carbonate and 40 parts of kaolin (manufactured by EMC, HT clay) whose quotient of the cumulative particle size of 15% by weight and the cumulative particle size of 85% by weight was 4.8 were used. A coating composition was obtained, and a matte coated paper for gravure printing was obtained in the same manner as in Example 1. The quality of the paper was evaluated and the results are shown in Table 1. Comparative Example 1 A matte coated paper for gravure printing was obtained in the same manner as in Example 1, except that heavy calcium carbonate having a quotient of 17.0 between the cumulative particle diameter of 15% by weight and the cumulative particle diameter of 85% by weight was used. The quality was evaluated and the results are shown in Table 1, but the miss dots were extremely poor. Comparative Example 2 In Example 1, the amount of heavy calcium carbonate used was 40 parts, and kaolin (manufactured by EMC, HT clay)
A matte coated paper for gravure printing was obtained in the same manner except that the amount used was 60 parts, but the paper had a high white gloss and could not be called a matte coated paper.

[Table] As is clear from the results in Table 1, the matte coated paper for gravure printing obtained in each example of the present invention has less misdots and mesh than the coated paper of each comparative example. It had extremely excellent dot reproducibility, an elegant appearance, and excellent ink gloss.

Claims (1)

[Scope of Claims] 1 A coating composition containing 50% by weight or more of heavy calcium carbonate that satisfies the following conditions as a pigment component is coated on base paper and dried to give a cumulative particle diameter of 15% by weight/cumulative 8.5. A method for producing matte coated paper for gravure printing, characterized by smoothing the particle size in weight%≦15 so that the white paper gloss (JISP8142 method) is 40% or less. 2. The method for producing coated paper according to claim 1, wherein the base paper is a base paper containing high-yield pulp having a 42 mesh fiber fraction content of 5 to 30% according to JISP8207 method.