JPH08199496A - Production of coated paper for mat gravure - Google Patents

Abstract

PURPOSE: To provide a method for producing coated paper for gravure printing, low in white luster and low mistaken dotting, namely, excellence in gravure printability, ink receptivity and excellence in face state of coated paper. CONSTITUTION: Base paper is coated with a coating composition containing >=50wt.% of kaolin having >=1.0μm and <=3.0μm average particle diameter based on the whole pigment, dried and is calendered at least once by using a rough surface roll having a roughness shape of <=90μm average interval S of local crests by ISO4287/1, 3-22μm average roughness of ten points Rz based on JIS B0601, 2-18μm crest height of central line Rp and >=0.55 ratio (Rp/Rz) of the crest height of central line Rp to the average roughness of ten points to provide a method for producing coated paper for mat gravure having <=40 white luster.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a matte gravure-coated paper which is suitable for gravure printing, particularly has few misdots, is excellent in ink acceptability and printing gloss.

[0002]

2. Description of the Related Art In recent years, visualization of printed matter has progressed, and quality requirements for coated paper for printing have become stronger and stronger. In particular,
Gravure printing is becoming more and more popular due to the development of color printing for magazines and the like. Although gravure printing is insufficient in gradation, a large amount of ink can be transferred, high printing density can be obtained, and image reproducibility is excellent, so that a printed product with a sense of volume can be obtained. However, in order to obtain gravure printing suitability, a surface with high smoothness is formed, so that the white paper gloss is high, and although it is good as a full-color image, there is a drawback that the character printed surface is difficult to read. From such a point, matte gravure coated paper has been developed.

Gravure-coated paper with reduced white paper gloss, that is, matte gravure-coated paper, is used in order to reduce white paper gloss.
When calendar processing such as super calendar and soft calendar is lightened, smoothness deteriorates and a mis-dot phenomenon occurs that print dots drop out during gravure printing.
The image quality is significantly impaired. Also, JP-A-55-152895
As disclosed in JP-A-59-199897 and JP-A-59-199897, in order to increase the cushioning property of the base paper and improve the gravure printing suitability, mechanical pulp such as GP or a high-yield pulp is added to the base paper pulp. Is often done. However, when mechanical pulp and high-yield pulp must be blended with the base paper, the hue of the paper is restricted, and high whiteness cannot be obtained. Further, the color fading property is deteriorated and it cannot withstand long-term storage.

Generally, as a pigment in a coating composition,
It is often practiced to add a large amount of calcium carbonate, especially dry ground heavy calcium carbonate. JP 59
As disclosed in Japanese Patent Publication No. 1998-1998, it is also practiced to use calcium carbonate having a specific particle size distribution. However, when a large amount of coarse-grained calcium carbonate is used, the smoothness is deteriorated. Therefore, it is necessary to reinforce the super calendering and calendering treatments in order to secure the gravure printing suitability. As a result, the glossiness of the white paper is increased, so that coarser-grained calcium carbonate is used, and the smoothness is further deteriorated, resulting in a vicious circle. When a large amount of coarse calcium carbonate is used in the coating liquid,
The water retention is reduced, and coating results such as streaks are likely to occur.

Regarding the method of calendaring,
Supercalenders are excellent in terms of improving gravure suitability such as preventing misdots, but supercalendering produces too much white paper gloss. On the other hand, the soft calendar consists of a combination of a metal roll and an elastic roll covered with a thin hard synthetic resin material layer, as shown in the article from Paper Pulp Technology Times, August 1987, page 31, It is a calender that processes with a small number of nips such as 1 to 4 nip, and although it is difficult for white paper gloss to appear, the smoothness improving effect is low and the gravure printing suitability improving effect is difficult to expect. Also, when trying to obtain a high smoothness by improving the linear pressure with a soft calender treatment, the elastic roll is hard, so it is affected by the thickness distribution according to the texture of the paper,
The glossiness of the white paper becomes uneven, remarkably impairing the appearance, and it becomes unusable as a matte gravure coated paper.

A technique for producing a matte coated paper by treating the coated paper with a metal roll roughened by a sandblasting method or the like to finish the matte coated paper for offset printing is known. It is disclosed in Japanese Patent Publication No. Sho 55-1359. Surface roughening roll treatment (mat calendar treatment)
Independently of the composition of the coating layer, the surface smoothness is deteriorated, so that when it is used for producing matte gravure coated paper, gravure printing suitability is impaired.

[0007]

From the above, the glossiness of the white paper is sufficiently low, the suitability for gravure printing is excellent, especially the occurrence rate of misdots is low, and the ink acceptability, the print glossiness and the surface condition of the coated paper are excellent. At present, it is difficult to manufacture matte gravure coated paper with high productivity, and the realization thereof is a major issue for those who manufacture coated paper.

[0008]

In view of the present situation, the present inventors have developed a matte gravure coated paper having unprecedented excellent gravure printing suitability, ink acceptability, printing gloss, and coated paper surface state. As a result of intensive research aimed at producing with high productivity, the present invention has been completed.

That is, the method for producing a matte gravure coated paper according to the present invention comprises coating a base paper with a coating composition containing kaolin having an average particle size of 1.0 to 3.0 μm in an amount of 50% by weight or more in all pigments. After covering and drying, the coated surface is brought into contact with the rough surface roll side at least once through a calender nip provided with a rough surface roll having a roughness shape satisfying the following conditions, It is characterized by having a gloss of 40 or less. The average spacing S of local peaks of ISO4287 / 1 is 90
μm or less 10-point average roughness Rz according to JIS B0601 is 3
-22 μm Center line mountain height Rp is 2-18 μm Ratio of center line mountain height Rp and ten-point average roughness Rz (Rp / R
z) is 0.55 or more

In the method for producing a matte gravure coated paper according to the present invention, before passing through the calender nip provided with the rough surface roll, the smooth metal roll and the filling roll or the elasticity of Shore D hardness of 80 ° or more are used. It is preferable to pass between the calender nips made of rolls at least twice.

Further, by using the rough roll having the surface of ceramic or cermet sprayed thereon, it is possible to obtain better production efficiency and suitability for gravure printing.

The method for producing the matte gravure coated paper of the present invention will be described in detail below. In the matte gravure coated paper, the use of kaolin as the coating layer pigment makes it less likely that misdots will occur due to the effect of increasing local smoothness. In particular, it is well known that the suitability for gravure printing can be improved by using a large flat plate kaolin such as delaminated kaolin. It is also known that when fine kaolin is used, the void diameter of the coating layer becomes small, and the absorption rate of the gravure ink increases due to the capillary phenomenon. However, when a large amount of kaolin is blended, the glossiness of the white paper is inevitably increased, and it is difficult to manufacture a matte gravure coated paper.

Therefore, when the surface is treated with the rough surface roll of the present invention in a coating layer containing kaolin having an average particle diameter of 3.0 μm or less in an amount of 50% or more of all pigments, a considerable linear pressure is applied to carry out calender treatment. Even if you go, you can prevent the glossiness of the blank sheet from rising. However, if kaolin having an average particle diameter of 1.0 μm or less is used, low white paper gloss cannot be realized. If the content of kaolin is less than 50% of the total pigment,
Miss dots cannot be reduced.

In gravure printing, ink is filled in the recesses of the cells forming the image area of the plate and pressed against the printing paper to transfer the ink to form an image. Therefore, if a concave portion larger than the distance between the cells is formed on the surface of the printing paper, the chance of contact between the ink and the printing paper is lost, causing misdots. Particularly, in the halftone dot gravure printing, which is the mainstream of multicolor gravure printing, the halftone dot area is small in a region where the print density is low, so that extra dots are likely to occur. Under normal printing conditions, the halftone dot area ratio that is most likely to cause misdots is around 10%, but in this case the shortest distance between cell edges is about 90 μm for a 150-line plate.
The rough surface roll used in the present invention is made so that the average distance between the peaks of the rough surface is shorter than the distance between the edges of this cell, and there is no large concave portion extending between the cells, so that misdots are generated. Greatly reduce.

Gravure printing is intaglio printing, in which the printing paper directly contacts the printing plate, the printing paper is pushed into the cells of the printing plate to some extent at the nip between the impression cylinder and the printing plate, and the ink is transferred in a form that absorbs the ink. . Therefore, the depth of the unevenness of the printing paper is important.

In the rough surface roll of the present invention, if Rp exceeds 18 μm and Rz exceeds 22 μm, misdots are likely to occur. If Rp is less than 2 μm and Rz is less than 3 μm, the glossiness of white paper cannot be less than 40%, and the matte effect cannot be obtained. In gravure printing, the printing paper is in direct contact with the hard plate, so that the contact area of the printing paper with the plate is secured as much as possible to avoid misdots and to obtain the quality of the printed matter such as high printing gloss. Will be needed. For that purpose, it is necessary that the uneven surface of the coated paper has a very flat surface with a suitable number of deep pores. Therefore, the surface of the patterning roll should not be uneven, but should be carved with protrusions. In order to satisfy this condition, the surface shape of the rough surface roll has a ratio (Rp / Rp) of the center line mountain height Rp and the ten-point average roughness Rz.
Rz) needs to be 0.55 or more.

In gravure printing, since adhesion to the plate is required, smoothness over a wide range is required.
For this reason, before performing treatment with a rough surface roll, a nip in which a filling roll such as a cotton roll or a wool roll and a smooth metal roll such as a chilled roll or a forged steel roll are combined, or a smooth metal roll and a Shore D hardness of 80 ° or more. If it is treated with a nip in combination with a roll such as an elastic roll having the plastic cover material layer and sufficiently smoothed, the gravure suitability after the rough surface roll treatment can be further improved. The material of the elastic body is plastic such as polyether resin, urethane resin, epoxy resin, and aramid resin. The calender treatment prior to the rough surface roll treatment may be performed by a calender installed immediately after the dryer in the coating apparatus.

The roll forming a nip with the rough surface roll during the rough surface roll treatment may be a filling roll such as a cotton roll, a wool roll or an asbestos roll.
In order to obtain higher gravure printing suitability, the distribution of pressure in the nip tends to be uniform in the width direction, and abrasion is excellent when operating in a nip combined with a rough surface roll. Shore D hardness of 80 ° or more It is desirable to form the nip with an elastic roll having a plastic cover material layer such as polyether resin, urethane resin, epoxy resin, or aramid resin. On the other hand, if it is too hard, the surface of the coated paper may have irregular unevenness. Therefore, the Shore D hardness of 80 ° to 90 ° is a more preferable range.

Further, the material of the rough surface roll is not particularly limited, and a steel or alloy roll provided with a desired roughness on the roll surface by a sand blast method, a corrosion method, an engraving method, a thermal spraying method, or the like. The surface of which is subjected to chrome plating is appropriately used. However, in order to control the average spacing (S) of local peaks to 90 μm or less, the sandblast method is not sufficient, and the distance between the peaks can be reduced by using a rough surface roll having ceramic or cermet sprayed on the surface. You can easily control.

Further, when the rough surface roll used in the present invention is manufactured by the thermal spraying method, the rod spray method and the plasma powder spray method are mentioned, and Al ₂ O ₃ , TiO ₂ , SiO ₂ , Fe
₂ O ₃ , MgO, CaO, Cr ₂ O ₃ , ZrO ₂ , Y ₂ O ₃ ,
_{C, MnO 2, K 2 O} , and the like Na ₂ O.

Here, the center line peak height Rp is obtained by extracting a portion of the reference length from the roughness curve in the direction of the center line and passing through the center line of the roughness curve and the maximum peak height parallel thereto. It represents the distance from the straight line. The ten-point average roughness Rz in accordance with JIS B0601 is the highest to fifth peaks measured from a straight line that does not cross the roughness curve and is parallel to the average line of the part where the reference length is extracted from the roughness curve. The difference between the average value of 1 and the average value of the elevations of the valley bottom from the deepest to the fifth is expressed in μm. The average spacing S of local peaks of ISO4287 / 1 is an average value of the spacing of local peaks of a portion obtained by extracting the reference length from the roughness curve.

Of course, when transferring the surface shape of the rough surface roll to the coated paper, the transfer efficiency varies depending on the line speed, the calender linear pressure, the roll surface temperature, the use of the steam shower, the composition of the coating solution, and the calendering order. As a result, it is fully conceivable that the white paper gloss and print gloss will be affected. However, in order to provide a coated paper that has low white paper gloss, high printing gloss with respect to various quality requirements, is rich in homogeneity, and has a high-class feeling, the surface shape conditions described in the present invention are used. It is a necessary condition to carry out the imprinting treatment with a rough surface roll that satisfies the conditions, and these operating conditions may be changed in order to obtain the desired matting effect.

In the coating liquid used for the matte coated paper of the present invention, a material for paper processing can be generally used in addition to the material constituting the present invention.

Examples of the pigment include heavy calcium carbonate, light calcium carbonate, satin white, talc, titanium oxide, aluminum hydroxide, zinc oxide, zeolite, barium sulfate, amorphous silica, plastic pigment and the like. As the adhesive, for example, starch such as acetylated starch, phosphoric acid esterified starch, oxidized starch, etherified starch, starch having a reduced viscosity by self-denaturation, dextrin, casein, natural adhesive such as soybean protein, Acrylic-based, styrene-acrylic-based, styrene-butadiene-based, vinyl acetate-acrylic-based, ethylene-vinyl acetate-based, butadiene-methylmethacrylic-based, vinyl acetate-butyl acrylate-based copolymer adhesives, synthesis of polyvinyl alcohol, etc. Examples include adhesives.

For these coating liquids, various commonly used auxiliaries such as a dispersant, a thickener, a water retention agent, a defoaming agent, a water resistant agent, and a coloring agent can be appropriately used, if necessary. .

In the present invention, as a device for applying the coating liquid, a flooded nip type, a jet fountain type,
One-layer or two- or three-layer coating applied by various ordinary coating equipment such as various blade coaters such as short dwell type, rod blade coaters, roll coaters, air knife coaters, bar coaters, die coaters and curtain coaters. The coated paper is dried after each layer coating, and in some cases, it is coated with an on-machine coater installed on a paper machine for making a base paper. Further, the rough surface roll treatment of the present invention may be installed immediately after leaving the dryer in the coating apparatus and may be subjected to treatment immediately after drying. In addition, prior to the rough surface roll treatment of the present invention, or steam on the coated paper during the treatment,
In some cases, a process of spraying minute water droplets is performed.

The base paper used for the matte gravure coated paper of the present invention is a chemical pulp such as LBKP or NBKP, G
Including various pulps such as P, PGW, TMP, CTMP, CMP, CGP and other mechanical pulps, DIP and other waste paper pulps, various fillers such as light calcium carbonate, heavy calcium carbonate, talc, clay and kaolin, sizing agents, It contains various additives such as fixing agents, retention agents, cationizing agents, paper strength enhancers, etc., and is made into acid, neutral, and alkaline papers for medium-quality coated base paper, high-quality coated base paper, recycled coated paper base paper, etc. Can be mentioned. As the base paper of the present invention, there can be used a non-size press base paper, a base paper size-pressed with starch, polyvinyl alcohol or the like, or a base paper coated with an undercoat pigment by a gate roll coater or various blade coaters.

[0028]

EXAMPLES The present invention will be described in more detail below with reference to examples, but of course the present invention is not limited to these examples. The parts and% used in the examples mean parts by weight and% by weight, respectively. The various measured values in the examples or comparative examples are obtained by the following method.

[Average Particle Size] The volume-weighted average particle size (MV μm) was determined by measuring with a Microtrac 7995-30SPA model manufactured by Leads & Northrop.

Smoother Smoothness Smoother smoothness (mmHg) of base paper and matte coated paper was measured using a smoother smoothness tester manufactured by Toei Denshi KK.

[White paper glossiness] The white paper glossiness (%) is JI
The measurement was carried out at an angle of 75 ° according to S P8142.

[Miss dot ratio] The miss dot ratio is measured by a printing station type gravure printing suitability tester manufactured by Toyo Ink Industry Co., Ltd.
G91 (Black) ink with toluene 1 with Zahn cup # 3
According to the viscosity of 5 seconds, printing was carried out at a printing speed of 60 m / min. And a line pressure of 15 kg / cm with a plate having a screen area ratio of 150 lines of 10%.
Image analysis device P for 25 mm x 25 mm field of view of printed matter
The image is captured by the IAS-LA500 type, the darkest part and the brightest part are divided into 256 gradations, the 63 gradations are binarized from the darkest part as a threshold value, the number of blank areas is calculated, and the ratio to the total number of halftone dots % Was calculated as the misdot rate. Generally, if the misdot rate is 1.5% or more, the image quality is poor and it is difficult to accept.

Examples 1 to 7 [Production of base paper] To a pulp consisting of 80 parts of LBKP and 20 parts of NBKP, 5 parts of light calcium carbonate, 0.1 part of a commercially available alkylketene dimer internal sizing agent, and 0.2 parts of a commercially available cationic starch. Part, a pulp slurry to which 0.03 part of a commercial cationic polyacrylamide part retention improver was added, was made into a paper having a basis weight of 70 g / m ^2, and an aqueous starch solution was applied with a size press at 2 g / m ² per side. Then, the linear pressure was adjusted by an on-machine calendar so that the smoother smoothness was 550 mmHg, and calendering was performed to produce a base paper.

[Preparation of coating liquid] According to the following blending amounts,
A coating liquid having a solid content concentration of 60% was prepared. (Coating liquid formulation) Commercially available secondary kaolin (Enkerhardt Co., Ultracoat) Average particle size 2.9 μm 80 parts Commercially available heavy calcium carbonate (ECC JAPAN, Carvital 90) 10 parts Commercially light carbonate Calcium (TP222H manufactured by Okutama Kogyo Co., Ltd.) 10 parts Commercial polyacrylic acid-based dispersant (Toa Gosei Chemical Co., Aron T-40) 0.1 part Commercially available styrene-butadiene-based latex (Nihon ZEON Co., Ltd., Nipol LX407F) 9 Part Commercial carboxymethyl cellulose 1.0 part Calcium stearate 0.4 part Calcium hydroxide: adjusted to pH 9.5

[Manufacture of Coated Paper] The above coating liquid was applied to the above-mentioned base paper for coating using a flooded nip type blade coater (manufactured by Mitsubishi Heavy Industries KK) with a bevel blade system at a coating speed of 500 m / min. A coated paper was prepared by coating so that the coating amount on one side would be 14 g / m ² and drying.

[Matte treatment of coated paper] A part of the coated paper was treated with a super calendar or a soft calendar under the following conditions. <Super calender conditions> -Number of steps: 6-Rigid roll: chilled roll, outer diameter 400 mm-Filling roll: cotton roll, outer diameter 420 mm-Processing speed: 300 m / min.-Line pressure: 205 kg / cm

<Soft calendar specifications> • Nip number: 2 (nip is formed so that the rigid roll surface contacts the front and back surfaces of the coated paper once) • Rigid roll: Forged steel roll (with heating mechanism), diameter 8
00mm-Elastic roll: synthetic resin (polyether resin) coated roll, Shore D 89 ° diameter 700mm

<Soft calender treatment conditions> -Treatment speed: 400 m / min-Rigid roll surface temperature: 100 ° C-Linear pressure: 160 kg / cm

Coated paper that had been subjected to the above-mentioned super calender or soft calender treatment, or the coated paper was subjected to rough surface roll treatment.

<Rough surface roll treatment> A 1-nip test calender composed of an elastic roll and a hard roll and having a roll diameter of 500 mm. As the elastic roll, a cotton roll having a Shore D hardness of 85 ° and a resin-coated soft roll having a Shore D hardness of 89 ° were appropriately selected and used. The hard roll is a rough roll having the surface shape shown in Table 1 below, the processing linear pressure is 160 kg / cm, and the processing speed is 1
It was 50 m / min.

A matte gravure coated paper was obtained by processing under the above-mentioned conditions. About the obtained matte gravure coated paper,
After controlling the humidity for 24 hours or more in a constant temperature and humidity room at 20 ° C. and 65% RH, the gravure printing suitability and paper physical properties were measured. The finishing conditions and the quality of the matte gravure coated paper are shown in Table 1 below.

Example 8 A matte gravure coated paper was obtained in the same manner as in Example 1 except that the coating liquid pigment composition was changed as follows. Commercially available secondary kaolin (Enkerhardt Co., Ultracoat) average particle size 2.9 μm 50 parts Commercially available heavy calcium carbonate (ECC Japan, Carvita 90) 10 parts Commercially available light calcium carbonate (TP222H manufactured by Okutama Industry Co., Ltd.) ) 40 copies

Example 9 A matte gravure coated paper was obtained in the same manner as in Example 1 except that the coating liquid pigment composition was changed as follows. Commercially available secondary kaolin (Engelhard Co., Ultra White 90) average particle size 1.8 μm 50 parts Commercial heavy calcium carbonate (ECC Japan, Cavital 90) 10 parts Commercial light calcium carbonate (Okutama Industrial Co., Ltd.) TP222H) 40 parts

Comparative Examples 1 to 3 Matte gravure coated papers were obtained by treating under the same conditions as in Example 1 except for the rough surface roll treatment conditions shown in Table 2 below.

Comparative Example 4 A matte gravure coated paper was obtained in the same manner as in Example 1 except that the coating liquid pigment composition was changed as follows. Commercially available fine kaolin (manufactured by Kadam, Amazon 88) Average particle size 0.8 μm 50 parts Commercially available heavy calcium carbonate (ECC Japan, Caratal 90) 10 parts Commercially available light calcium carbonate (TP222H by Okutama Kogyo) 40 Department

[0046]

[Table 1]

[0047]

[Table 2]

From the results of Tables 1 and 2 above, Example 1
In the case of ~ 9, matte gravure coated paper having excellent gravure suitability could be obtained. On the other hand, in Comparative Examples 1 to 4, the properties required for the matte gravure coated paper could not be satisfied.

[0049]

As described above, according to the method for producing a matte gravure coated paper of the present invention, a gravure matte coated paper having excellent gravure printing suitability with sufficiently low white paper gloss and few misdots. Can be obtained.

Claims (3)

[Claims] 1. A coating composition containing kaolin having an average particle diameter of 1.0 to 3.0 μm in an amount of 50% by weight or more in all pigments is coated on a base paper, dried, and then the following conditions are satisfied. A matte gravure coating characterized in that the coated surface is brought into contact with the rough surface roll side at least once through a calender nip provided with a rough surface roll having a roughness shape so as to have a white paper gloss of 40 or less. Manufacturing method of paper. The average spacing S of local peaks of ISO4287 / 1 is 90
μm or less 10-point average roughness Rz according to JIS B0601 is 3
-22 μm Center line mountain height Rp is 2-18 μm Ratio of center line mountain height Rp and ten-point average roughness Rz (Rp / R
z) is 0.55 or more 2. Before passing through the calender nip provided with the rough surface roll according to claim 1, at least the calender nip composed of a smooth metal roll and a filling roll or an elastic roll having a Shore D hardness of 80 ° or more. The method for producing a matte gravure-coated paper according to claim 1, wherein the matte gravure-coated paper is passed twice. 3. The production of the matte gravure coated paper according to claim 1, wherein the rough surface roll according to claim 1 is a rough surface roll having a surface of ceramic or cermet sprayed thereon. Method.