JP2003221797A - Coated paper for gravure process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide coated paper for gravure process that has a low density, a high glossiness, high rigidity and shows high opacity and improved speckle. <P>SOLUTION: The coated paper for gravure process is produced by forming coating layers including pigments and adhesive on the base paper. In this case, the coated layers comprise kaolin particles, as pigments, of which ≥65 vol.% of particles have particle sizes of 0.4-4.2 μm in an amount of ≥50 pts.wt. per 100 pts.wt. of the pigments and in addition, coated layers which include calcined kaolin may be formed between coated layers. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated paper for gravure printing which has an excellent white paper appearance and excellent printability.

[0002]

2. Description of the Related Art Gravure printing is an intaglio printing method in which ink in the depressions of a plate is transferred under pressure and has excellent gradation reproducibility, so it is used in the commercial printing field such as magazines, catalogs, and pamphlets. Therefore, there is a strong demand for weight reduction of printed matter from the viewpoint of resource saving, transportation and mailing cost, and there is a demand for low density and excellent printability.

In gravure printing, a plate is a hard metal roll as compared with offset printing, and it is difficult for the plate surface to completely adhere to the paper at the time of printing, so a phenomenon called speckle in which halftone dots do not normally transfer occurs. There are cases. When there are many speckles, the print quality is degraded.
The smoothness and cushioning property of the coated paper are important for suppressing the generation of speckles. In order to improve the smoothness of the coating layer surface of gravure printing paper, it is generally effective to blend a pigment with a high aspect ratio (delaminated clay, talc, etc.) into the coating layer composition. It is said that.

However, when a large amount of a pigment having a high aspect ratio is added to the coating layer composition, the viscosity of the coating liquid increases, handling during preparation is difficult, and coating defects such as streaks and scratches occur. Easy to cause. For this reason,
At present, it is not possible to increase the solid content concentration of the coating material, and as a result, it becomes necessary to strengthen the drying conditions, leading to higher costs. Also, pigments such as delaminated clay and talc, which have a high aspect ratio, were used in large amounts, as can be seen from the fact that they are generally used in low-gloss white paper applications such as matte coated paper. In this case, it has a characteristic that the white paper glossiness becomes low, and therefore, it is not suitable for applications requiring high white paper glossiness.

On the other hand, using organic pigments such as plastic pigments, high white paper glossiness, speckle prevention effect,
A method of imparting opacity or the like is known (Japanese Patent Laid-Open No. 64-20396). However, organic pigments are more expensive than inorganic pigments, resulting in higher costs, and coating liquids added with organic pigments tend to increase in viscosity under high shearing forces, causing streak, scratches, and other coating defects. Easy to cause. For this reason, it is the current situation that the solid content concentration of the paint cannot be increased so much, and as a result, it becomes necessary to strengthen the drying conditions, which causes a problem of high cost.

As a method of mechanically smoothing the surface of the coating layer of gravure printing coated paper and imparting a glossiness of white paper, a high-level pressure treatment using a super calender is usually performed. . The surface treatment with a super calendar has the effect of increasing the smoothness and the glossiness of the white paper, but at the same time, the density of the coated paper increases and the opacity and rigidity of the coated paper are lost. When the opacity is insufficient, the print pattern is transmitted to affect the print pattern on the back side, or the white surface feeling on the back side is impaired, resulting in deterioration in quality. Also, it is necessary to reduce the pressure treatment in order not to lose the opacity and rigidity, but usually, at the same time, the glossiness of the white paper decreases and the speckles at the time of gravure printing increase. The current situation is that the pressure cannot be reduced. Further, even when a soft nip calender is used, it is impossible to sufficiently reduce the pressure, and there is a problem that opacity and rigidity are lowered and roll stains occur. From the above background, it has been desired to develop a coating gravure having low density, high opacity and rigidity, high white paper glossiness, and good print quality.

[0007]

In view of such a situation, an object of the present invention is to provide gravure printing having low density, high white paper gloss and rigidity, and high opacity and speckle. An object is to provide a suitable coated paper for gravure printing.

[0008]

Means for Solving the Problems As a result of earnest studies on the above problems, the inventors of the present invention have found that, in a coated paper for gravure printing in which a coating layer having a pigment and an adhesive is provided on a base paper, a volume-based pigment Pigment of kaolin having a particle size distribution of 65% or more in the range of 0.4 to 4.2 μm
By providing a coating layer containing 50 parts by weight or more, preferably 3 to 20 parts by weight of calcined kaolin per 00 parts by weight, excellent gravure printing suitability of high white paper gloss and elimination of speckles despite low density. The present invention has been completed by discovering that it has high rigidity and high opacity.

In the present invention, as the coating pigment, kaolin having a particle size distribution of 65% or more contained in a range of 0.4 to 4.2 μm on a volume basis is blended in an amount of 50 parts by weight or more per 100 parts by weight of the pigment. It is necessary, and preferably 80 parts by weight or more. 0.4-4.2 μm on a volume basis
When the content of kaolin having a particle size distribution of 65% or more in the range is less than 40% by weight, white paper glossiness or printing glossiness is lowered or speckle is increased. When kaolin containing less than 65% of particles falling within a range of 0.4 to 4.2 μm on a volume basis and having a large volume distribution of particles is used, the white paper glossiness is high, but the printing glossiness is Low, speckle number increases. In addition, 0.4 to 4.2
When less than 65% of particles fall within the μm range and kaolin containing a large amount of particles having a large volume distribution is used,
Although the number of speckles is small, the glossiness of the white paper is too low, and it is difficult to produce a coated paper for gravure printing which has both an excellent white paper appearance and printability. Further, it is necessary to blend calcined kaolin as a coating pigment, and the blending amount is preferably 3 to 20 parts by weight.
It is more preferably 5 to 15 parts by weight. It was found that the number of speckles was significantly reduced by combining calcined kaolin and kaolin having a narrow particle size distribution in a specific amount. The reason for this is that kaolin in the range of 0.4 to 4.2 μm, for example engineered kaolin, tends to be bulky because the coating layer structure is difficult to be densely packed. On the other hand, the calcined clay is structured by sintering and has a shape with many voids. It is considered that by combining these, the synergistic effect of both makes the coating layer more bulky, and the coverage of the base paper is good, resulting in high smoothness and good cushioning, and thus the number of speckles is reduced. .

The kaolin having a defined particle size distribution used in the present invention has a larger distribution in a relatively large particle size than that of a commonly used coating pigment. It provides high printability and high white paper gloss under conditions of lower pressure than the calendering process. Therefore, it is possible to suppress an increase in the density due to the calendar treatment, and it is possible to increase the opacity and the rigidity as compared with the conventional gravure-coated paper.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The coating composition used in the coated paper for gravure printing of the present invention will be described below. The pigment used in the present invention may be a combination of other pigments besides kaolin having a specific particle size distribution and calcined kaolin.
Other pigments include kaolin, clay, delaminated clay, heavy calcium carbonate, light calcium carbonate, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, and silicic acid that have been conventionally used for coated paper. , Inorganic pigments such as silicate, colloidal silica and satin white, and organic pigments such as plastic pigment
It can be used by mixing more than one kind.

As the adhesive used in the present invention, a copolymer latex may be used alone or as a mixture of several kinds, but other adhesives such as starch may be used in combination within a range not impairing the object of the present invention. You can The copolymer latex is not limited to rubber latex, but includes synthetic resin emulsions, styrene / butadiene copolymer, conjugated diene copolymer latex such as methacrylate / butadiene copolymer, acrylic ester, and Alternatively, vinyl-based polymer latexes such as polymers or copolymers of methacrylic acid esters, or alkali-soluble, alkali-swellable or alkali-insoluble polymer latexes obtained by modifying these various polymer latexes with carboxyl groups and the like, One or more kinds of various synthetic resin polymers called binder pigments are appropriately selected and used. In the present invention, the glass transition temperature of the copolymer latex is preferably -50 ° C to 0 ° C. By using a material in this range, a coated paper having a hardness suitable for calendering and a cushioning property suitable for gravure printing can be obtained. That is, since the coating layer formed by using the copolymer latex having a glass transition temperature exceeding 0 ° C. becomes hard, the cushioning property becomes insufficient and the speckle during gravure printing tends to increase.
When a copolymerized latex having a glass transition temperature of less than −50 ° C. is used, the stickiness of the latex becomes high, roll stains are likely to occur during super calender treatment, and papers are adhered to each other during product winding. Blocking is likely to occur, which is not preferable in operation. The copolymer latex is preferably used in an amount of 3 to 10 parts by weight based on 100 parts by weight of the pigment as a solid content.
The coated paper produced with less than 3 parts by weight of the copolymer latex tends to weaken the surface strength of the coating layer, which is not preferable for gravure printing. In addition, the coated paper produced with the amount of the copolymerized latex exceeding 10 parts by weight has a tendency that the coating layer becomes hard, the cushioning property becomes insufficient, and the speckle at the time of gravure printing tends to increase. Is not preferable.

As an adhesive other than latex,
For example, proteins such as casein, soybean protein, and synthetic protein; synthetic resin adhesives such as polyvinyl alcohol, olefin / maleic anhydride resin, and melamine resin; oxidized starch, positive starch, urea phosphate esterified starch, hydroxyethyl ether starch, etc. One or more ordinary coating adhesives such as etherified starch, starches such as dextrin; carboxymethyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, cellulose derivatives and the like may be appropriately selected and used. Further, as additives to be added as necessary, various auxiliaries to be added to ordinary coated paper pigments such as a dispersant, a thickener, a water retention agent, a defoaming agent, a water resistant agent, and a colorant. Used as appropriate.

As the coated base paper, pulp for papermaking such as chemical pulp, waste paper pulp, mechanical pulp and the like is beaten to obtain pulp slurry. In order to improve the opacity and the rigidity, it is preferable to add 10% by weight or more of mechanical pulp to the total pulp, and more preferably 20 to 60% by weight of mechanical pulp.
It is to mix. If necessary, a filler that is usually used in the papermaking process, such as talc, kaolin, heavy calcium carbonate, light calcium carbonate, titanium dioxide, etc., is added to the adjusted pulp slurry, and chemicals such as a paper strengthening agent and a sizing agent are added. Add paper, defoaming agent, coloring agent, etc. to make paper. The papermaking method is not particularly limited, using a Fourdrinier machine including a top wire etc., a round net machine, a paperboard machine using both of them, a Yankee dryer machine, etc.
It may be an acidic papermaking paper, a neutral papermaking paper, or a base paper made by an alkaline papermaking method. Further, a base paper pre-coated with starch, polyvinyl alcohol or the like using a size press, a gate roll coater or a pre-metering size press can also be used. The basis weight of the base paper is 40
˜200 g / m ² is preferred. In the present invention, the prepared coating liquid is applied onto the base paper. As the coating method, a blade coater, a bar coater, a roll coater, an air knife coater, a reverse roll coater, a curtain coater, a size press coater, a gate roll coater, etc. are used, and one side or two or more layers per side are coated on the base paper. Work. The coating amount of the present invention is preferably 7 to 16 g / m ^{2 on} one side, and more preferably 7 to 1
It is 3 g / m ² .

As a method for drying the wet coating layer, various methods such as a steam heating cylinder, a heated hot air dryer, a gas heater dryer, an electric heater dryer, an infrared heater dryer and a high frequency heater dryer can be used alone or in combination. .

The gravure coated paper coated and dried as described above can have high printability and high white paper gloss by adding a specific pigment, so that it is possible to reduce super calendar conditions. Is. It is also possible to perform treatment with a high temperature soft nip calender at 100 ° C. or higher using an elastic roll having a high hardness and a metal roll.

[0017]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Unless otherwise specified, parts and% in the examples represent parts by weight and% by weight, respectively.

The obtained coated paper for gravure printing is
Then, the test was conducted based on the evaluation method shown below. (Particle size distribution measurement method) Laser diffraction / scattering type particle size distribution measurement
Ware (Malvern Co., Ltd. equipment name Mastersizer S)
The volume distribution particle size of the pigment was measured using 0.4 μm
Calculate the percentage of pigment that falls within the 4.2 μm range
I asked more. (Blank gloss) Measured according to JIS P 8142
It was (Number of speckles: number of missing dots) Ministry of Finance gravure printing machine
Halftone dot gravure plate (175
40m printing speed using line number) and gravure printing ink
/ Min., Printing pressure 10 kgf / cm, printed matter obtained
Of 10% halftone dots (35mm x 30mm) of
The number was visually evaluated using a magnifying glass (15 times). (Stiffness) Measured according to JIS P 8143 and evaluated.
The following criteria were used. ○: Good, △: Slightly inferior (Opacity) Measured according to JIS P 8138,
The evaluation was performed based on the following criteria. ○: Good, △: Slightly inferior [Example 1] [Preparation of coating liquid] Engineered kaolin
(Engelhard ECLIPS 650, volume distribution
Particle size 0.40 to 4.20 μm: 66%) 90 parts, calcined power
Olin (Imeris Alphatex, volume distribution particles
Diameter 0.40 to 4.20 μm: 64%) Face consisting of 10 parts
Sodium polyacrylate as a dispersant for pigments.
Add 2 parts and disperse with a serie mixer to obtain solid concentration
A 70% pigment slurry was prepared. Get in this way
Of non-associative acrylic synthetic water retention agent
Gravity with 0.2 parts and a glass transition temperature of -40 ° C
6 parts of styrene-butadiene copolymer latex A for
In addition, water was added to obtain a coating liquid with a solid content of 61%.
It was [Base paper] 30% by weight of mechanical pulp as pulp for papermaking
Having a basis weight of 42 g / m^TwoUse medium quality paper as coated base paper
It was [Manufacture of coated paper] The above-mentioned coating liquid was applied to one side of the above base paper.
Coating amount of 12g / m ^TwoTo 500 m / min
Both sides were coated with a blade coater having a coating speed of. [Calendar] Roll temperature 65 ℃, 2 nip, calendar
Under a linear pressure of 150 kg / cm and a sheet passing speed of 10 m / min
Super calendar processing is applied to produce coated paper for gravure printing.
Obtained. [Example 2] In the preparation of the coating liquid of Example 1, the firing
Same as Example 1 except that the addition amount of Oline was 5 parts.
A coated paper for gravure printing was obtained by the method. [Example 3] In the preparation of the coating liquid of Example 1,
Neared Kaolin CAPIM DG made by Rio Capim,
Volume distribution particle size 0.40 to 4.20 μm: changed to 68%
Coating method for gravure printing is the same as in Example 1 except that
Got the paper. Example 4 Engineered Kaolin (Engelhard
ECLIPS 650, volume distribution particle size 0.40
4.20 μm: 66%) 60 parts, calcined kaolin (imery
Alphatex, volume distribution particle size 0.40-4.
20 μm: 64%) 10 parts, fine kaolin (Engelha)
Made MIRASHEEN, volume distribution particle size 0.40
˜4.20 μm: 51%) 30 parts of pigment
Outside, the coated paper for gravure printing was prepared in the same manner as in Example 1.
Obtained. [Comparative Example 1] Engineered Kaolin (Engelhard
ECLIPS 650, volume distribution particle size 0.40
4.20 μm: 66%) 100 parts of pigment
Outside, the coated paper for gravure printing was prepared in the same manner as in Example 1.
Obtained. [Comparative Example 2] Second-class kaolin (manufactured by Imerys KCS, body
Product distribution particle size 0.40 to 4.20 μm: 54%) 90 parts,
Calcined Kaolin (Imeris Alphatex, volume
Distribution particle size 0.40 to 4.20 μm: 64%) 10 parts
A coated paper was obtained in the same manner as in Example 1 except for the above. [Comparative Example 3] Engineered Kaolin (Engelhard
ECLIPS 650, volume distribution particle size 0.40
4.20 μm: 66%) 30 parts, calcined kaolin (imery
Alphatex, volume distribution particle size 0.40-4.
20 μm: 64%) 10 parts, secondary kaolin (Imeris company)
Manufactured by KCS, volume distribution particle size 0.40 to 4.20 μm: 5
4%) The same as Example 1 except that the pigment was composed of 60 parts.
A coated paper was obtained by the same method. [Comparative Example 4] Engineered Kaolin (Engelhard
ECLIPS 650, volume distribution particle size 0.40
4.20 μm: 66%) 70 parts, fine kaolin (Enge
MIRASHEEN manufactured by Ruhard Co., volume distribution particle size 0.
40 to 4.20 μm: 51%) as 30 parts of pigment
A coated paper was obtained in the same manner as in Example 1 except for the above. [Comparative Example 5] Engineered Kaolin (Engelhard
ECLIPS 650, volume distribution particle size 0.40
4.20 μm: 66%) 70 parts, fine grain heavy calcium carbonate
(FMT-90 made by Phimatech, volume distribution particle size
0.40 to 4.20 μm: 66%) 30 parts pigment
A coated paper was obtained in the same manner as in Example 1 except that [Comparative Example 6] Engineered Kaolin (Engelhard
ECLIPS 650, volume distribution particle size 0.40
4.20 μm: 66%) 100 parts of pigment
-Percalender treatment Linear pressure from 150 kg / cm to 30
The same method as in Example 1 except that the pressure was changed to 0 kg / cm.
Thus, a coated paper for gravure printing was obtained.

The above results are shown in Tables 1 and 2.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

According to the present invention, it is possible to obtain a coated paper for gravure printing having a low density, a high white paper gloss and rigidity, and a high opacity and speckle remarkably improved gravure printing suitability. You can

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Seiki Yoneshige             5-21-1 Oji, Kita-ku, Tokyo Nippon Paper Industries             Technical Research Institute Co., Ltd. (72) Inventor Hirokazu Morii             5-21-1 Oji, Kita-ku, Tokyo Nippon Paper Industries             Technical Research Institute Co., Ltd. F-term (reference) 4L055 AC01 AG27 AG63 AG76 AG89                       AH02 AH37 AJ04 BE02 BE08                       EA16 EA32 FA11 FA15 GA19

Claims (2)

[Claims] 1. A coated paper for gravure printing, wherein a coating layer having a pigment and an adhesive is provided on a base paper, and as the pigment, 65% or more of particles are contained in a range of 0.4 to 4.2 μm on a volume basis. A coated paper for gravure printing, comprising a coating layer containing kaolin having a diameter distribution of 50 parts by weight or more per 100 parts by weight of pigment and containing calcined kaolin. 2. The coated paper for gravure printing according to claim 1, wherein the content of the calcined kaolin is 3 to 20 parts by weight per 100 parts by weight of the pigment.