JP2008214782A - Coated paper for gravure printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide coated paper for gravure printing, which is improved in stiffness despite having a light weight and showing less missing dots. <P>SOLUTION: In the coated paper for gravure printing provided with a coated layer consisting of a pigment and an adhesive on at least one side surface of base paper, the adhesive contains a branched copoly(meth)acrylamide having a cationic group and/or an anionic group and also a weight-average molecular weight of 50,000 to 1,000,000, and 1.0 to 10.0 pts.wt. branched copoly(meth)acrylamide is contained based on 100 pts.wt. pigment. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a coated paper for gravure printing, and relates to a coated paper having improved rigidity and particularly excellent printing workability despite its light weight.

  In recent years, magazines and books have come to be preferred from heavy to light. Along with this, paper has also been required to be lighter. Gravure printing is an inevitable problem in reducing the weight of paper for effective use of paper pulp produced from forest resources due to increased transportation costs, postage costs, and increased environmental protection. The field of coated paper is no exception.

  Gravure printing is intaglio printing in which ink for the concave portion of a plate is transferred under pressure, and is excellent in gradation reproducibility, and is therefore used in commercial printing fields such as magazines, catalogs, and pamphlets.

  In gravure printing, missing dots with halftone dots are generated when the plate is a hard metal roll as compared to offset printing and the plate is difficult to adhere completely to the paper during printing. When there are many missing dots, the print quality is significantly reduced. Therefore, the base paper and the coating layer of the coated paper for gravure printing are required to have smoothness and cushioning properties.

  In order to improve the smoothness of the coating layer surface of the coated paper for gravure printing, it is generally effective to add pigments with high aspect ratio (delaminated clay, talc, etc.) to the coating layer composition It is said that. However, blending many pigments with a high aspect ratio in the coating layer composition increases the viscosity of the coating solution, making it difficult to handle during preparation and causing coating defects such as streak and scratch. Cheap. For this reason, it is the present condition that solid content concentration of a paint cannot be made very high, As a result, it becomes necessary to make drying conditions strong, and it leads to high cost. In addition, pigments such as delaminated clay and talc with high aspect ratios were used in large amounts, as can be seen from the fact that they are generally used in low-gloss applications such as matte coated paper. In some cases, the glossiness of the white paper is low, so that it is not suitable for applications that require high white paper glossiness.

In addition, for the purpose of preventing the occurrence of missing dots and improving opacity, a method of using calcined clay in combination with other pigments is also known. However, calcined clay is inferior in fluidity, so the viscosity of the coating liquid increases. This may cause coating defects such as streaks and scratches and may deteriorate the workability of the coater. For this reason, the solid content density | concentration of a coating material cannot be made very high. On the other hand, a method is known in which an organic pigment such as a plastic pigment is used to impart high white paper glossiness, a missing dot prevention effect, opacity, and the like (see Patent Document 1). However, since organic pigments are expensive compared to inorganic pigments, the cost is high, and the coating liquid added with organic pigments tends to increase in viscosity under high shearing force, resulting in poor coating such as streak and scratch. Prone to cause. For this reason, it is the present condition that solid content concentration of a paint cannot be made very high, As a result, it becomes necessary to strengthen drying conditions, and there is a problem that it leads to high cost.
JP-A 64-20396

  On the other hand, if the stiffness of the coated paper for printing is low at the time of gravure printing, the hand feeling of the printed matter is deteriorated or the printing workability is deteriorated because there is no strain at the time of printing. In this respect, stiffness is also a very important quality.

  In the case of reducing the weight of the coated paper, there is a method of reducing the basis weight of the base paper or (and) reducing the coating weight. If the base paper has a low basis weight, the paper thickness decreases in proportion to the weight reduction, and the stiffness decreases. As a countermeasure, there is a method of improving the rigidity by adding a high amount of starch to the coating layer. However, in this case, the high coating content of starch makes the printed coated paper stiff and the rigidity is improved, but this is not preferable because cushioning properties are reduced and missing dots are increased. On the other hand, there are cases where an excessive calendar process is applied to the coated paper to mechanically smooth the surface of the coating layer to reduce missing dots. However, in this case, it is not preferable because the stiffness of the paper is lowered by the calendar process and the hand feeling is lowered. An object of the present invention is to provide a printing paper in which the base paper has a low basis weight and the rigidity is improved and missing dots are not generated even when the coating amount is low.

  As described above, it is difficult to obtain a coated paper for gravure printing that is light in weight and excellent in printing workability in the prior art.

  In view of the situation as described above, an object of the present invention is to provide a coated paper for gravure printing that is light in weight, has improved rigidity, and has fewer missing dots.

As a result of intensive investigations to achieve the above-mentioned objects, the inventors of the present invention have used cationic and / or anionic group-containing branched copolymer poly (meth) acrylamide having a specific molecular weight as an adhesive for coating layers. The inventors have found that the inclusion is extremely effective, and have reached the present invention.
That is, the present invention provides a coated paper in which a coating layer comprising a pigment and an adhesive is provided on at least one side of a base paper, wherein the adhesive has a cationic group and / or an anionic group and has a weight average molecular weight. A coated paper for gravure printing, comprising 50,000 to 1,000,000 branched copolymer poly (meth) acrylamide.
The content of the branched copoly (meth) acrylamide is preferably 1.0 to 10.0 parts by weight with respect to 100 parts by weight of the pigment.
The branched copolymer poly (meth) acrylamide has at least (meth) acrylamide monomers, a cationic group and / or an anionic group, a monomer having a polymerizable double bond, and a polymerizable double bond 4. Poly (meth) acrylamide obtained by copolymerizing at least one monomer selected from the group of quaternary ammonium salt monomers and a crosslinking agent is preferable.
Further, as an adhesive, 5 parts by weight or less of starch is preferable with respect to 100 parts by weight of the pigment.
In the present invention, from the viewpoint of making the ink inking property good and satisfying gravure printing suitability, 50 parts by weight or more of 100 parts by weight of the pigment has an average particle diameter of 0.2 to 3.0 μm. It is a pigment, and kaolin is particularly preferable. Moreover, it is preferable that the Clark stiffness of MD direction of the coated paper for gravure printing of this invention is 15 cm < ³ > / 100 or more.
The coated paper for gravure printing of the present invention has excellent printing workability and gravure suitability even at a low basis weight of 70 g / m ² .
In the present invention, “(meth) acryl” is a concept including “acryl” and “methacryl”.

  Although the coated paper for gravure printing of the present invention has a low basis weight and a low coated amount, the rigidity is improved and a coated paper for gravure printing with few missing dots can be obtained.

  In the present invention, the adhesive used for the coated layer of the coated paper has a cationic group and / or an anionic group, and has a weight average molecular weight of 50,000 to 1,000,000 branched copolymer poly (meth) acrylamide. It is necessary to contain. The branched copolymer poly (meth) acrylamide is produced by copolymerizing (meth) acrylamide monomers, cationic monomers and / or anionic monomers, and crosslinking agents.

As (meth) acrylamide monomers used as a raw material for the branched copolymer poly (meth) acrylamide, acrylamide and methacrylamide are most preferable. Other examples include N-ethylacrylamide, N, N-dimethylacrylamide, N-isopropylacrylamide, diacetone acrylamide and the like, and water-soluble N-substituted lower alkyl acrylamide.
In the present invention, as the (meth) acrylamide monomer, only one type may be used or two or more types may be used in combination.

  Examples of the cationic monomer used for copolymerization with (meth) acrylamide include N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, and N, N-dimethylaminopropyl. Tertiary amine monomers such as (meth) acrylate, N, N-diethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethylaminopropyl (meth) acrylamide, allylamine, diallylamine, etc. Or salts thereof with inorganic or organic acids such as hydrochloric acid, sulfuric acid, acetic acid, or quaternized ammonium obtained by reacting the tertiary amine monomer with methyl chloride, benzyl chloride, dimethyl sulfate, epichlorohydrin or the like. Salt-based monomers, etc. Cationic monomer having a bond can be exemplified. In the present invention, these cationic monomers can be used alone or in combination of two or more.

  As an anionic monomer used for copolymerization with (meth) acrylamide, a monomer containing a carboxyl group together with a polymerizable double bond, for example, monocarboxylic acid such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, And dicarboxylic acids such as fumaric acid, itaconic acid, citraconic acid and muconic acid. In the present invention, these anionic monomers can be used alone or in combination of two or more.

  In the present invention, the cationic monomer and the anionic monomer may be used in combination, or only the cationic monomer or only the anionic monomer may be used. The mixing ratio of the anionic monomer and / or the cationic monomer is preferably 0.01 to 15 parts by weight with respect to 100 parts by weight of the (meth) acrylamide monomer.

  In the present invention, a nonionic monomer may be contained as a copolymerization component of the branched copolymer poly (meth) acrylamide. As such nonionic monomers, alkyl esters of the anionic monomers (alkyl group having 1 to 8 carbon atoms), acrylonitrile, styrene, vinyl acetate, methyl vinyl ether, and derivatives thereof can be used as appropriate. In the present invention, these monomers can be used alone or in combination of two or more.

  In the present invention, a crosslinkable monomer is used to make poly (meth) acrylamide a crosslinkable type. Crosslinkable monomers include di (meth) acrylates such as ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, methylene bis (meth) acrylamide, and ethylene bis (meth) acrylamide. Bis (meth) acrylamides such as hexamethylenebis (meth) acrylamide, divinyl esters such as divinyl adipate and vinyl sebacate, bifunctional vinyl monomers such as allyl methacrylate, diallylamine, diallyldimethylammonium, diallyl phthalate, , 3,5-triacryloylhexahydro-S-triazine, and trifunctional vinyl monomers such as triallyl isocyanurate. In the present invention, these crosslinkable monomers can be used alone or in combination of two or more.

  Thus, by making the branched copolymer poly (meth) acrylamide into a crosslinked type, the coated paper of the present invention can have sufficient stiffness even at a low basis weight. However, if the degree of cross-linking is increased, spinnability is manifested. When coating is performed using a film transfer type coating method, boiling occurs during coating, mist is generated between coating rolls, or even coating is performed. This is not preferable because it causes problems in terms of process and quality. On the other hand, if the degree of cross-linking is lowered, a molecular structure close to a straight chain is formed and the spinnability is considered to be reduced. Therefore, it is necessary to adjust the blending amount of the cross-linking agent during the reaction.

  The branched copolymer poly (meth) acrylamide used in the present invention is produced by copolymerizing the above-mentioned (meth) acrylamide monomers, a cationic monomer and / or an anionic monomer, and a crosslinking agent by a known method. . The weight average molecular weight is required to be 50,000 to 1,000,000, preferably 50,000 to 800,000, and more preferably 10 to 650,000. When the weight average molecular weight is less than 50,000, sufficient stiffness cannot be imparted to the coated paper. When the weight average molecular weight exceeds 1,000,000, the effect is not improved, and the misdot rate is inferior.

  In the present invention, in order to facilitate coating, it is necessary to adjust the viscosity of the branched copolymer poly (meth) acrylamide. The B-type viscosity of the branched copolymer poly (meth) acrylamide 10% aqueous solution may be in the range of 20 to 150 mPa · s, and preferably 30 to 100 mPa · s.

  Further, the blending amount of the branched copolymer poly (meth) acrylamide in the present invention is preferably 1.0 to 10.0 parts by weight, and 2.0 to 8.0 parts by weight with respect to 100 parts by weight of the pigment. It is more preferable that When the blending amount is less than 1.0 part by weight, improvement in stiffness is hardly recognized. When the blending amount is more than 10.0 part by weight, problems such as coating viscosity increase tend to cause problems in coating stability.

  In the present invention, the above-mentioned branched copolymer poly (meth) acrylamide is blended with a conventionally used ordinary adhesive for coated paper to obtain an adhesive for a coating layer. Examples of the usual adhesive for coated paper include styrene / butadiene, styrene / acryl, ethylene / vinyl acetate, butadiene / methyl methacrylate, vinyl acetate / butyl acrylate, and the like, and polyvinyl Synthetic resin adhesives such as alcohol / maleic anhydride copolymer, acrylic acid / methyl methacrylate copolymer, casein, soy protein, synthetic protein, oxidized starch, positive starch, urea phosphated starch , Etherified starch such as hydroxyethyl etherified starch, starches such as dextrin, cellulose derivatives such as carboxyethyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, and the like. In the present invention, at least one of these adhesives can be appropriately selected and used.

  These adhesives for coated paper preferably contain 5 parts by weight or less of starch with respect to 100 parts by weight of pigment from the viewpoint of printability. By blending starch, the strength of the coating layer is increased, but when blending 5 parts by weight or more with respect to 100 parts by weight of the pigment, the coating layer becomes stiff and the gravure printing suitability is poor. Various adhesives such as styrene / butadiene, styrene / acrylic, ethylene / vinyl acetate, butadiene / methyl methacrylate, and vinyl acetate / butyl acrylate, which are conventionally used for coated paper, are used as adhesives. Synthetic adhesives such as coalesced or maleic anhydride copolymer, acrylic acid / methyl methacrylate copolymer; proteins such as casein, soy protein, synthetic protein; oxidized starch, positive starch, urea phosphated starch, hydroxy One or more ordinary adhesives for coated paper such as etherified starch such as ethyl etherified starch are appropriately selected and used. Further, the use ratio (A: B) of the branched copolymer poly (meth) acrylamide (A) and the coated paper adhesive (B) is preferably 5:95 to 50:50, particularly 10:90. It is preferably ˜40: 60. The total amount of these adhesives is preferably 3 to 15 parts by weight, more preferably 3 to 10 parts by weight, based on 100 parts by weight of the pigment, from the viewpoints of printability and coating suitability. As the adhesive, it is preferable to use a copolymer latex having a glass transition temperature of −50 ° C. to 0 ° C. By using the thing of this range, it becomes a coating layer which has cushioning properties suitable for gravure printing.

  As the pigment used for the coating layer in the present invention, a pigment conventionally used for coated paper can be used as long as the object of the invention is not impaired. For example, heavy calcium carbonate, light calcium carbonate, kaolin, clay, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicate, colloidal silica, satin white and other inorganic pigments, plastic pigments, etc. These are organic pigments, and these pigments can be used alone or in combination of two or more as required. In the present invention, in order to improve the smoothness and gravure printability of the coated paper, the average particle diameter is 0.2 to 3.0 μm of pigment, and contains 50 parts by weight or more per 100 parts by weight of the pigment. More preferably, it is 65 parts by weight or more, and still more preferably 80 parts by weight or more. When the amount is less than 50 parts by weight, the smoothness tends to be low, and the number of missing dots during gravure printing tends to increase. Moreover, as an average particle diameter, More preferably, it is 0.4-2.5 micrometers. When it is smaller than 0.2 μm, the specific surface area of the pigment is increased, so that the viscosity of the coating is increased, and the coating suitability is inferior, which is not preferable from an operational viewpoint. If it is larger than 3.0 μm, the glossiness of white paper and the printability tend to be low, which is not preferable. Further, in the present invention, kaolin is preferably used, and particularly by using engineered kaolin, the printability and the effect of suppressing gloss unevenness are improved. In addition, the average particle diameter of this invention is calculated | required by measuring the value of the 50% part of a volume cumulative distribution by measuring with the laser method (Malvern Mastersizer S type).

  In the present invention, various auxiliary agents blended in a normal coating paper coating solution, such as a dispersant, a thickener, a water retention agent, an antifoaming agent, a colorant, and a printability improver, are appropriately used. Can do. As the auxiliary used in the present invention, an acrylic synthetic water retention agent and hydroxyethyl cellulose are preferably used, and an associative acrylic synthetic water retention agent is more preferably used. The associative acrylic synthetic water retention agent functions to improve the water retention of the coating solution and to reduce the high shear viscosity of the coating solution. Therefore, it is suitable for high-speed coating, the paint is not pushed into the coating base paper during coating, the coating layer on the base paper is bulky, and the cushioning property of the coating layer is improved. The rate tends to be low. Hydroxyethyl cellulose has the same effect. In addition, when using an acrylic synthetic water retention agent and / or hydroxyethyl cellulose, the blending amount is preferably 0.1 to 1.0 part by weight with respect to 100 parts by weight of the inorganic pigment.

  As the base paper used in the present invention, general paper such as acidic and neutral high-quality paper, medium-quality paper, and recycled paper can be used. The pulp used for the base paper is not particularly limited. For example, LBKP (hardwood bleached kraft pulp), NBKP (softwood bleached kraft pulp), LBSP (hardwood bleached sulfite pulp), NBSP (coniferous bleached sulfite pulp), etc. Chemical pulp, mechanical pulp such as GP (ground pulp), TMP (thermomechanical pulp), CTMP (chemothermomechanical pulp), and waste paper pulp can be used alone or in combination.

  In the present invention, in order not to deteriorate the printing workability, the content of mechanical pulp in the total pulp is preferably 10% by weight or more. Since mechanical pulp has more rigid fibers than chemical pulp, the base paper blended with mechanical pulp is less likely to be crushed by various pressures applied in the paper making process. Accordingly, the use of mechanical pulp increases the overall bulkiness, so that the amount of voids inside the base paper increases, opacity increases, and at the same time rigidity increases. Among mechanical pulps, ground pulp can be preferably used in the present invention because it contributes greatly to reducing the density. The ratio of the mechanical pulp is preferably 70% by weight or less, particularly preferably 50% by weight or less of the total pulp from the viewpoints of whiteness and coating suitability.

  In the present invention, the filler used for the production of the base paper includes heavy calcium carbonate, light calcium carbonate, calcium carbonate such as chalk, kaolin, clay, calcined clay, amorphous silicate, light calcium carbonate-silica composite, and pyrolo. Silicates such as phyllite, sericite, and talc and inorganic fillers such as titanium dioxide can be used alone or in combination. As a compounding quantity of a filler, it is preferable to contain 2-20 weight% per base paper total weight, More preferably, it is 3-15 weight%.

In the present invention, a sizing agent such as a rosin sizing agent, a synthetic sizing agent, a petroleum resin sizing agent, or a neutral sizing agent can be used as an internal sizing agent used for producing a base paper. Further, it is preferable to use a fixing agent for fibers such as sulfate band and cationized starch in combination with an appropriate sizing agent.
Furthermore, paper-made internal additives such as paper strength enhancers, dyes, pH control agents, antifoaming agents, pitch control agents, and the like can be appropriately added depending on the purpose.

The papermaking method is not particularly limited, and any of acidic papermaking, neutral papermaking, and alkaline papermaking using a long web paper machine or a twin wire paper machine may be used. Moreover, the base paper etc. which pre-coated starch, polyvinyl alcohol, etc. using a size press, a gate roll coater, and a pre metering size press can also be used. The basis weight of base paper is preferably from 25~200g / ^{m 2,} it is particularly preferably 30 to 50 g / ^{m 2.}

  On the base paper thus obtained, a coating liquid containing the pigment and adhesive described above is applied to provide a coating layer. In the present invention, a film transfer type roll coater such as a two-roll size press coater, a gate roll coater, a blade metering size press coater, a rod metering size press coater, and a shim sizer, a fladet nip / blade coater, a jet fountain / blade. Coating using a coater and short dwell time applicate type coater, or a known coater such as a rod metering coater, curtain coater, or die coater using a grooved rod, plain rod, etc. instead of a blade. Can do.

In the present invention, the coating layer can be provided as a single layer or two or more layers on one side or both sides of the base paper. The coating amount of the coating layer, from the viewpoint of workability on the recording suitability and manufacturing, preferably a per side 2~35g / ^{m 2,} more preferably 3 to 20 g / ^{m 2.} Moreover, in this invention, even if it is 3-10 g / m < ² > per single side | surface, it has the advantage that a thing with favorable paper threading property and ink ink landing property is obtained.

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

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

Gravure coated printing paper of the present invention, by a Clark stiffness in the MD direction 15cm ^3/100 or more, the sheet passing property and sheet passing property and the seal face quality in particular gravure printing machine the better. In particular, as excellent low basis weight in a even printing workability, it is preferable that the Clark stiffness in the MD direction and 20 cm ^3/100.
Coating type gravure coated printing paper of the present invention is stamp surface quality and printability range basis weight of ^35g / ^{m 2 ~200g} / m 2 is good, preferably 35~100g / ^{m 2} , particularly preferably a 35~70g / ^{m 2,} more preferably even at low basis weight referred 35~50g / ^{m 2,} there is present invention a special effect printing workability not only gravure suitability is sufficient.

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples. In addition, parts by weight and% by weight indicate parts by weight of solid content and% by weight of solid content. Moreover, about the physical property of the material for coating materials, and the performance of the obtained coated paper, the test was implemented based on the evaluation method as shown below.
(1) Weight average molecular weight of polyacrylamide It measured by GPC using 0.3M sodium chloride aqueous solution as a solvent using column TSK-GEL P6000PW and P3000PW (all are Tosoh Corporation make).
(2) Basis weight Measured according to JIS P 8124.
(3) Clark stiffness Measured according to JIS P 8143.
(4) Blank Paper Glossiness The 75 degree glossiness of the blank paper portion was measured using a gloss meter GM26D manufactured by Murakami Color Co., Ltd.
(5) Number of missing dots Using a Ministry of Finance gravure printing machine (manufactured by Kumagai Riki Kogyo), printing was performed at a printing speed of 400 m / min and a printing pressure of 10 kgf / cm. Visual evaluation was made.
◎: Very good ○: Good △: Slightly inferior ×: Inferior (6) Ink setting property The occurrence of uneven ink setting after printing was visually evaluated with the gravure printing machine.
◎: Very good ○: Good △: Slightly inferior ×: Inferior

The physical properties of the tested polyacrylamide (PAM) are shown in Table 1.

<Coating base paper>
The coated base paper contains 3% of light calcium carbonate as a filler per weight of the base paper, and the basis weight contains 36% by weight of LBKP, 32% by weight of NBKP, 22% by weight of mechanical pulp and 10% by weight of DIP as paper pulp. A medium quality paper of 35 g / m ² was used.

<Preparation of coating solution>
Engineered kaolin (Capime DG manufactured by IMERYS, average particle size 1.19 μm) 70 parts, Engineered kaolin (Contour 1500 manufactured by IMERYS, average particle size 1.95 μm), secondary clay (manufactured by Huber: KCS: average) An inorganic pigment slurry was prepared by dispersing 15 parts by weight of a pigment having a particle diameter of 1.18 μm using a serie mixer. 7.0 parts of styrene / butadiene copolymer latex (glass transition temperature −40 ° C.) and 3.0 parts by weight of polyacrylamide (PAM-01) are added to the prepared slurry, and 0.4 parts of acrylic synthetic water retention agent is further added. Water was added to obtain a coating solution having a solid concentration of 65%.

<Preparation of coated paper>
The above-mentioned coating solution is applied to both sides of the above-mentioned base paper using a blade coater at a coating speed of 500 m / min so that the coating amount per side becomes 7 g / m ² , and a scuff dryer After passing, the paper was dried with a cylinder dryer so that the water content in the paper was 5.5%.

<Calendar processing>
Next, soft nip calendering was performed under the conditions of a metal roll temperature of 160 ° C., an elastic roll with a Shore hardness of 85, a paper passing speed of 600 m / min, a linear pressure of 40 kg / cm and a calender nip number of 4 nips. Coated paper for gravure printing was obtained.

  A gravure coated coated paper was obtained in the same manner as in Example 1 except that PAM-01 used in the coating liquid of Example 1 was changed to PAM-02.

  A gravure coated coated paper was obtained in the same manner as in Example 1 except that PAM-01 used in the coating liquid of Example 1 was changed to PAM-03.

  A gravure coated coated paper was obtained in the same manner as in Example 1 except that PAM-01 used in the coating liquid of Example 1 was changed to PAM-04.

  A gravure coated coated paper was obtained in the same manner as in Example 1 except that PAM-01 used in the coating liquid of Example 1 was changed to PAM-05.

[Comparative Example 1]
A gravure coating as in Example 1 except that 3.0 parts by weight of hydroxyether starch (PG295) was added instead of using no polyacrylamide (PAM-1) used in Example 1. I got paper.

[Comparative Example 2]
A gravure coated paper was prepared in the same manner as in Example 1 except that the polyacrylamide (PAM-1) used in Example 1 was not used at all, and instead 3.0 parts by weight of ST-481H was used. Obtained.

[Comparative Example 3]
Except that the polyacrylamide (PAM-1) used in Example 1 was not used at all, and 3.0 parts by weight of Polystron 851 was used instead, a coated paper for gravure printing was used in the same manner as in Example 1. Obtained.
However, the viscosity of the obtained coating liquid was 4000 mPa · S or more (B-type viscosity · 20 ° C.), and it was not suitable for coating.

Table 2 shows the test results of the coated paper obtained in each example and comparative example.

As is clear from Table 2, the coated paper of the present invention was confirmed to be suitable for gravure printing because it maintained high rigidity despite its light weight, had good ink depositing properties and suppression of missing dots. .
On the other hand, in the case of Comparative Example 1, since many missing dots were generated during printing, it was confirmed that the cushioning property was not sufficient and the printing quality was inferior. Further, in the case of Comparative Example 2, it was confirmed that the printing workability was inferior due to insufficient paper stiffness. Comparative Example 3 was inferior in coating suitability.

Claims (6)

  In a coated paper in which a coating layer comprising a pigment and an adhesive is provided on at least one side of a base paper, the adhesive has a cationic group and / or an anionic group and has a weight average molecular weight of 50,000 to 1,000,000. A coated paper for gravure printing, characterized by containing a branched copolymer poly (meth) acrylamide.   The coated paper for gravure printing according to claim 1, wherein the content of the branched copolymer poly (meth) acrylamide is 1.0 to 10.0 parts by weight with respect to 100 parts by weight of the pigment.   The branched copolymer poly (meth) acrylamide is at least a (meth) acrylamide monomer, a monomer having a cationic group and / or an anionic group and a polymerizable double bond, and a quaternary ammonium having a polymerizable double bond. The coated paper for gravure printing according to claim 1 or 2, which is poly (meth) acrylamide obtained by copolymerizing at least one monomer selected from the group of salt monomers and a crosslinking agent. The coated paper for gravure printing described in any one of Claims 1-3 which contains 5 weight part or less of starch as said adhesive agent with respect to 100 weight part of pigments.   The coated paper for gravure printing according to any one of claims 1 to 4, wherein 50 parts by weight or more of 100 parts by weight of the pigment is a pigment having an average particle diameter of 0.2 to 3.0 µm. The gravure-coated coated paper according to claim 1, wherein the coated paper has a basis weight of 70 g / m ² or less.