JP2009293159A - Coated paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coated paper with a glossy white paper which is excellent in paper feeding and transportability in post-processing steps such as a paper folding machine and an encapsulating sealer for printed matter of offset printing and digital printing machines.
A hexagonal plate is provided for 100 parts by mass of a pigment having a paper base material and one or more coating layers mainly comprising a pigment and an adhesive on at least one surface thereof, and contained in the outermost coating layer. 5 to 40 parts by mass of a thermoplastic organic particle having a glass transition temperature (Tg) of 30 to 130 ° C. having an average particle diameter of 30 to 500 nm, and the outermost coating layer The surface has a blank paper glossiness of 60% or more and a smoothness of 3000 seconds or less. It is preferable to blend calcium carbonate at 30 parts by mass or less with respect to 100 parts by mass of the pigment contained in the outermost coating layer.
[Selection figure] None

Description

  The present invention relates to a coated paper with high glossy white paper, which is a printed matter by offset printing or digital printing, and is excellent in paper feeding and transporting in post-processing steps such as a paper folding machine and encapsulating sealing.

  As the post-processing of the printing unit, there are a paper folding machine, an enclosing seal, and the like. For example, there is a paper folding machine used when folding a direct mail advertisement or the like into a size to be put in an envelope. In this type of paper folding machine, there is provided a folding plate having a slit into which a sheet-like paper can enter and a stopper that is disposed at a predetermined position in the slit and prevents the paper from proceeding. When the paper enters the slit and the leading edge of the paper comes into contact with the stopper and the slit entrance is bent, the bent portion is sandwiched between a pair of rotating rollers with the peripheral surfaces in contact with each other. Fold. At this time, since it is necessary to insert the sheets into the folding plate one by one, a sheet feeding device that separates and feeds the sheets of the sheet bundle one by one by a friction method is usually provided.

  Generally, a friction type paper feeding device rotates while contacting a sheet feeding plate on which a sheet bundle is placed and a front edge of the sheet bundle on the paper feeding plate, and separates and conveys the sheet from the sheet bundle. A paper feed roller, and a straw plate disposed so as to be in contact with the peripheral surface of the paper feed roller. The sheet separated from the sheet bundle on the sheet feeding plate is conveyed by the sheet feeding roller and enters between the sheet feeding roller and the separating plate. The material of the paper feed roller and the paper board is determined in consideration of the frictional force against the paper, and the frictional force between the paper feed roller and the paper and the frictional force between the paper board and the paper are either Is set to be larger than the frictional force between the sheets. Therefore, when a plurality of sheets overlap each other and enter between the paper feed roller and the separating plate, the sheet that directly contacts the sheet feeding roller is conveyed by the sheet feeding roller, and the sheet that directly contacts the separation plate is not conveyed. It is stopped by the frictional force of the rolling board. As a result, the sheets can be separated one by one and fed to the next stage. The folded paper passes between the transport rollers and the belt or is transferred to the sealing process by synchronization and sealed.

  However, this type of paper folding machine has the following problems. When papers with high surface smoothness, such as commonly used high white gloss art paper and coated paper, are stacked, the adhesion between the papers increases. For this reason, in the case of art paper, coated paper, and the like with high white paper gloss, the contact pressure between the sheet bundle and the paper feed roller (hereinafter referred to as paper feed pressure) as compared with paper having a rough surface such as PPC paper. ) Is not set high, the paper feed will occur, so in the case of art paper and coated paper with high white paper gloss, the paper feed pressure is about twice that of ordinary paper (high quality paper, medium quality paper, rough paper, stencil paper, etc.) (Patent Document 1).

  As described above, when the paper feeding pressure is increased, the consumption and deterioration of the paper feeding roller are promoted, and the friction coefficient with the paper is remarkably reduced, so that paper jam (hereinafter also referred to as jam) and idle feeding occur. . Therefore, it was necessary to frequently replace the feed roller. Even in the process of transporting folded paper, in the case of art paper or coated paper with high white gloss, the friction coefficient between the paper and the paper is extremely fast due to the adhesion of paper powder from the pigment to the transport roller and belt. Since it suddenly drops and skew and paper breakage occur, frequent roll and belt replacement has been required. For this reason, coated paper with a high gloss of white paper, which is excellent in paper feeding and transportability in post-processing steps such as a paper folding machine and encapsulating sealing, is desired for printed matter of offset printing and digital printing machines.

JP-A-6-87544

  The coated paper according to the present invention has high white paper gloss, less adhesion of paper dust to the paper feed roller, transport roller and belt, and is excellent in paper feed and transport performance. The present invention provides a coated paper that can greatly reduce the consumption and deterioration, and can reduce the cost.

  The coated paper according to the present invention has a paper substrate, and at least one surface thereof having one or more coating layers mainly composed of a pigment and an adhesive, and 100 parts by mass of the pigment contained in the outermost coating layer. On the other hand, 50 to 95 parts by mass of a hexagonal plate pigment, 5 to 40 parts by mass of thermoplastic organic particles having a glass transition temperature (Tg) of 30 to 130 ° C. having an average particle diameter of 30 to 500 nm, and The outermost coating layer surface has a blank paper glossiness of 60% or more and a smoothness of 3000 seconds or less. It is preferable to blend calcium carbonate at 30 parts by mass or less with respect to 100 parts by mass of the pigment contained in the outermost coating layer, and non-film-forming with respect to 100 parts by mass of the pigment contained in the outermost coating layer. It is preferable to blend the functional hollow organic pigment at 20 parts by mass or less.

  According to the present invention, it is possible to obtain a coated paper having a high blank paper gloss, which is excellent in paper feeding and transportability in post-processing steps such as a paper folding machine and an encapsulating seal.

  In the post-processing steps of the printed matter such as a paper folding machine or an encapsulating seal, the present inventors have applied a coated paper such as a high-white gloss art paper or a coated paper, a paper feed roller of the paper folding machine, and a transport roller for the enclosing seal. As a result of intensive studies on a phenomenon in which the frictional force drop between the belt and the belt occurs significantly faster than in the case of PPC paper, a paper base material and at least one surface of which is a coating layer mainly composed of a pigment and an adhesive In the coated paper having a glass transition temperature (Tg) of 50 to 95 parts by weight of a hexagonal plate-like pigment and an average particle diameter of 30 to 500 nm with respect to 100 parts by weight of the pigment contained in the outermost coating layer. It has been found that it is important that 5 to 40 parts by mass of thermoplastic organic particles of 30 to 130 ° C. are blended, and that the surface of the outermost coating layer has a blank paper glossiness of 60% or more and a smoothness of 3000 seconds or less. It was.

  When paper is fed by a paper folding machine, when the paper is transported by the paper feed roller and enters between the paper feed roller and the paper board, the frictional force between the paper feed roller and the paper, between the paper board and the paper. The frictional force is set to be larger than the frictional force between sheets. However, since art paper and coated paper are much smoother than PPC paper, the frictional force between the papers is higher than the frictional force between the scooping plate and the paper, and two or more sheets overlap to the folding part. Be fed. For this reason, it is necessary to increase the paper feed pressure with the paper feed roller as compared with paper having a rough surface such as PPC paper. The surface of the paper feed roller has countless fine pores to increase the frictional force with the paper, but when the paper feed pressure is increased, pigment on the surface of the coating layer forms on the surface of the paper feed roller. If the fine pores that are filled are filled and the paper is transported by the paper feed roller in this state, the pigment peels off from the surface of the coating layer, the surface of the paper feed roller becomes smooth (consumable / deteriorated), It was found that there was a significant decrease in the frictional force between the paper and the paper, leading to paper jam and idle feeding. Also, the pigment that peels off from the coating layer surface and is embedded in the pores on the surface of the paper feed roller is calcium carbonate based on the analysis results, and in particular, amorphous heavy calcium carbonate is easily peeled off from the coating layer. I found. Furthermore, it was also found that the hexagonal plate-like pigment does not peel off from the coating layer at all and does not fill the pores of the paper feed roller. As described above, 50 parts by mass or more of hexagonal plate pigment is added to 100 parts by mass of pigment in the outermost coating layer constituting the coating layer surface, and the average particle size is 30 to 500 nm. If 5 to 40 parts by mass of thermoplastic organic particles having a transition temperature (Tg) of 30 to 130 ° C. are blended, and preferably 30 parts by mass or less of calcium carbonate, pigment peeling from the surface of the coating layer is prevented. It was possible to suppress the pores on the surface of the paper feed roller from being filled with the peeled pigment. By containing calcium carbonate in a composition of 30 parts by mass or less, the coating property can be improved, and the ink setting property in printing can be appropriately controlled. When the hexagonal plate-like pigment is less than 50 parts by mass or when the calcium carbonate exceeds 30 parts by mass, the pores on the surface of the paper feed roller may be filled, and jams and misfeeds may occur. May be required. Similarly, the enveloping roll and belt are filled with pores, and the frictional force between the roller and belt and the paper decreases sharply, causing jams, misfeeds and paper breaks. Must be done frequently.

  The hexagonal plate-like pigment used in the present invention preferably has an average particle size of 2.0 μm or less. If it exceeds 2.0 μm, the glossiness of the white paper may be significantly reduced. Specifically, one type or two or more types are appropriately selected from kaolin, structural kaolin, and deramikaolin.

  The coated paper according to the present invention has a blank paper glossiness of 60% or more, preferably 60 to 80%, and a smoothness of 3000 seconds or less, preferably 300 to 3000 seconds. If the gloss is less than 60%, the desired white paper appearance and gloss may not be obtained. In general, art paper or coated paper with high white paper glossiness is inevitably high in surface smoothness because the layer coated on the base paper formed from pulp fibers is smoothed. In a highly smooth coating layer, if any pigment is embedded in the pores on the surface of the paper feed roller, the frictional force between the paper and the paper tends to decrease significantly. For this reason, in the case of high white paper gloss with glossiness exceeding 80%, or when the smoothness exceeds 3000 seconds, for the above reasons, paper feeding in a post-processing step such as a paper folding machine or an encapsulating seal, Trouble may be caused by transportability. If the smoothness is less than 300 seconds, it may be difficult to set the glossiness of blank paper to 60% or more.

  Therefore, in the present invention, as a result of earnestly studying to achieve a high white paper glossiness by suppressing an excessive increase in smoothness, 5 thermoplastic organic particles are added to 100 parts by mass of the pigment contained in the outermost coating layer. It has been found that by blending ˜40 parts by mass, high white paper gloss can be achieved with lower smoothness.

  Hereinafter, a mechanism for improving the gloss of blank paper by adding thermoplastic organic particles to the coating layer will be described. As a general rule, in the coating layer mainly composed of pigment and adhesive, the adhesive enters between the pigments of the coating layer and has a role of adhering between the pigments. A decrease in gloss of blank paper occurs. Therefore, it is desired that the amount is as small as possible. The thermoplastic organic particles used in the present invention have a feature that the particle surface layer exhibits adhesiveness by heat in the production drying step, so that the amount of the adhesive can be reduced and the decrease in gloss of the white paper can be suppressed. Furthermore, if the spherical organic organic particles having a small particle diameter are selected, the effect of improving the glossiness of the white paper is obtained, so that it is preferably used.

  Examples of the thermoplastic organic particles used in the present invention include polystyrene resins, styrene-butadiene copolymer resins, styrene-acryl copolymer resins, styrene-methacryl copolymer resins, acrylic resins, vinylidene chloride resins, and the like. Is mentioned. The thermoplastic organic particles preferably have a Tg of 30 to 130 ° C, more preferably 50 to 130 ° C. When Tg is lower than 30 ° C., the pigment is thermally deformed in the drying process during the production of the coated paper, and the gloss of the white paper may be remarkably lowered. If the Tg exceeds 130 ° C., the particle surface layer may not be able to bring out the effect of adhesion due to heat in the drying step of the production described above. The particle diameter of the thermoplastic organic particles is preferably 30 to 500 nm. If it exceeds 500 nm, the glossiness of the white paper may be lowered.

  In this invention, it is more preferable to mix | blend 5-40 mass parts with respect to 100 mass parts of pigments which contain the above-mentioned thermoplastic organic particle in an outermost coating layer, and 10-30 mass parts. If it is less than 5 parts by mass, the effect of improving the glossiness of the white paper may be low. On the other hand, if it exceeds 40 parts by mass, the cost will be high, which is economically disadvantageous.

  In the present invention, in order to achieve high white paper glossiness and desired smoothness, it is preferable to blend non-film-forming hollow particles with respect to 100 parts by mass of the pigment contained in the outermost coating layer. The non-film-forming hollow particles are deformed when the surface of the coating layer is smoothed (supercalender) by passing paper between the nip between the chilled roll and the elastic roll, and the surface of the chilled roll is copied (replica). Contributes to improved white paper gloss. Therefore, the particle diameter of the non-film-forming hollow particles is preferably 3.0 μm or less. More preferably, it is 1.5 μm or less. When the particle size is larger than 3.0 μm, the particle size is too large, and the replica effect of chilled roll may not be observed. The hollow ratio is preferably 30% or more. Non-film-forming hollow particles used in the present invention include, for example, polystyrene resin, styrene-butadiene copolymer resin, styrene-acryl copolymer resin, styrene-methacryl copolymer resin, acrylic resin, vinylidene chloride Resins, urea resins, melamine resins, benzoguanamine resins, and the like can be used, which are appropriately selected from these and used in combination of one or more. The blending amount is preferably 1 to 20 parts by mass of the non-film-forming hollow organic pigment with respect to 100 parts by mass of the total pigment. If it is less than 1 part by mass, the desired effect may not be obtained. On the other hand, if it exceeds 20 parts by mass, the cost is high and it is economically disadvantageous.

  The pulp forming the paper base is not particularly limited in terms of production method, type, etc., chemical pulp such as KP, SP, mechanical pulp such as SGP, RGP, BCTMP, CTMP, ECF pulp, TCF pulp, etc. Waste paper pulp such as chlorine-free pulp, deinked pulp, non-wood pulp such as kenaf, bagasse, bamboo, straw, hemp, etc., organic synthetic fibers such as polyamide fiber, polyester fiber, polynosic fiber, and glass fiber Inorganic fibers such as ceramic fibers and carbon fibers can be used.

  Moreover, a filler can be mix | blended with a paper base material as needed. The filler in this case is not particularly limited, but various pigments generally used for fine paper, such as kaolin, calcined kaolin, calcium carbonate, calcium sulfate, barium sulfate, titanium dioxide, talc, zinc oxide, alumina, Mineral pigments such as magnesium carbonate, magnesium oxide, silica, white carbon, bentonite, zeolite, sericite, smectite, polystyrene resin, urea resin, melamine resin, acrylic resin, vinylidene chloride resin and their dense materials Examples thereof include organic pigments that are actual, fine hollow, and through-hole type particles.

  In addition to pulp fibers and fillers, various anionic, nonionic, cationic or amphoteric yield improvers, drainage improvers, paper strength enhancers, fixing agents are used in the stock. Various paper-making internal additives such as sizing agent and internal additive can be appropriately selected and used as necessary. Furthermore, internal additives for papermaking such as dyes, fluorescent brighteners, pH adjusters, antifoaming agents, pitch control agents, slime control agents and the like can be appropriately added depending on the use of the paper.

  The paper making method of the paper base is not particularly limited, and includes, for example, an acidic paper making method in which the paper making pH is around 4.5, and a neutral sizing agent and / or an alkaline filler such as calcium carbonate as a main component. It can be applied to all papermaking methods such as a weakly acidic pH of about 6 to a weakly alkaline neutral papermaking method of about 9 in papermaking. The paper machine can also be a long paper machine, a twin wire paper machine, a round paper machine, Commonly used paper machines such as inclined wire paper machines can be used as appropriate.

  In the coated paper of the present invention, a hexagonal plate-like pigment (kaolin, structural kaolin, deramikaolin, etc.) of 50 parts by mass or more of the total pigment is used as the pigment for forming the outermost coating layer, and 30 masses. It is preferably used for calcium carbonate (heavy calcium carbonate, light calcium carbonate) within a range of not more than parts, but other commonly used pigments can also be used. For example, minerals such as calcined kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, alumina, magnesium carbonate, magnesium oxide, silica, magnesium aluminosilicate, calcium silicate, white carbon, bentonite, zeolite, sericite, smectite One or two or more pigments are appropriately selected from these.

  As the adhesive, generally used water-soluble and / or water-dispersible polymer compounds can be used. For example, cationic starch, amphoteric starch, oxidized starch, enzyme-modified starch, thermochemically-modified starch, esterification Starches, starches such as etherified starch, cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose, natural or semi-synthetic polymer compounds such as gelatin, casein, soy protein and natural rubber, polydienes such as polyvinyl alcohol, isoprene, neoprene and polybutadiene , Polyalkenes such as polybutene, polyisobutylene, polypropylene, and polyethylene, vinyl polymers such as vinyl halide, vinyl acetate, styrene, (meth) acrylic acid, (meth) acrylic acid ester, (meth) acrylamide, and methyl vinyl ether Synthetic polymer compounds such as copolymers, synthetic rubber latex such as styrene-butadiene, methyl methacrylate-butadiene, polyurethane resin, polyester resin, polyamide resin, olefin-maleic anhydride resin, melamine resin, etc. Etc. can be illustrated. One or more of the above can be appropriately selected and used according to the purpose.

  In the coating liquid used in the present invention, in addition to the pigments and adhesives described above, various auxiliary agents such as surfactants, pH adjusters, viscosity adjusters, water retention agents, softeners, gloss imparting agents, waxes, Dispersant, flow modifier, antistatic agent, stabilizer, antistatic agent, cross-linking agent, sizing agent, fluorescent brightener, colorant, ultraviolet absorber, antifoaming agent, water resistant agent, plasticizer, preservative A fragrance or the like can be appropriately used as necessary within the range having the desired effect of the present invention.

  As described above, various types of starch can be used as the adhesive in the coating layer, and various types of starch may be used for imparting water retention to the paint. If the amount of starch used is large, the resulting coating is obtained. The air permeability of the paper may be inferior. For this reason, the usage-amount of starch is 5 mass parts or less with respect to 100 mass parts of pigments, Preferably it is 2 mass parts or less. As a method for imparting paint water retention without using starch, use of cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, or synthetic water retention agents such as alkali swelling acrylic thickeners is preferred.

Although the coating amount after drying of the coating layer of this invention is not specifically limited, It is 2-25 g / m < ² > with respect to the single side | surface of a paper base material, Preferably it is 5-20 g / m < ² >. When the coating amount is less than ² g / m ^2, it is difficult to form the coating layer uniformly on the base paper, and when the coating amount exceeds 25 g / m ² , the coating layer thickness increases and the coating layer shrinks. Therefore, the coating amount in the range specified above is preferable.

  As a coating method for forming a coating layer, generally known coating apparatuses such as blade coaters, air knife coaters, roll coaters, reverse roll coaters, bar coaters, curtain coaters, slot die coaters, gravure coaters, Champlex coaters, brushes Devices such as a coater, a slide bead coater, a two-roll or metering blade type size press coater, a bill blade coater, a short dwell coater, and a gate roll coater are appropriately used.

  The coating layer is formed on one side or both sides of the paper substrate, and can have a multilayer structure of two or more layers as necessary. In addition, when making it double-sided coating or a multilayer structure, each coating liquid does not need to be the same or the same coating amount, and should just adjust and mix | blend suitably according to desired quality. However, from the viewpoint of suppressing the generation of blisters, at least one layer of at least one side of the paper substrate needs to have a coating layer defined in the present invention. When forming multiple layers, it is preferable that the coating layer prescribed | regulated by this invention turns into an outermost coating layer. In addition, when a coating layer is provided on one side of a paper base material, a synthetic resin layer, a coating layer made of pigment and adhesive, etc., an antistatic layer, etc. are provided on the back side to prevent curling, impart printability, and supply / discharge It is also possible to impart aptitude and the like. Furthermore, it is of course possible to use the back side of the paper base material with application suitability by applying various processes such as adhesion, heat sensitivity, magnetism, flame resistance, heat resistance, water resistance, oil resistance, and slip resistance. is there.

  As the moisture of the coated paper, after providing a coating liquid layer on a paper substrate, after a normal drying step, or after smoothing treatment in a surface treatment step or the like as necessary, the moisture is 3 to 10 %, Preferably adjusted to about 4 to 8%.

  The smoothing process is performed on-machine or off-machine using a normal smoothing device such as a super calender, gloss calender, or soft calender. The number, heating, etc. are also adjusted as appropriate according to a normal smoothing apparatus.

  When the coated paper that has been subjected to the smoothing treatment needs to have a texture of the coated paper, the blank paper glossiness at an incident / light receiving angle of 75 degrees based on JIS Z8741 is 60 to 80%, preferably 70 to 80%.

  The coated paper according to the present invention can be used as an image recording paper for non-impact printing methods such as electrophotographic method, thermal transfer method, ink jet method as well as offset printing.

  In particular, in an electrophotographic system in which an image is formed with toner particles of about 5 to 7 μm, an extremely high quality image can be obtained by using the above-mentioned coated paper. For example, when an image is formed and evaluated using an electrophotographic printer based on a method compliant with ISO-13660 draft standard QEA (Quality Engineering Associates, Inc.), a mottle at a tile size of 40 μm is 10 GSV (Grey Scale Value). ) In the following, the line ragedness (jaggedness) was 10 μm or less and the brilliance (blurring degree) was 11 μm or less, so that a remarkably good image could be obtained. Similarly, good images could be obtained even in the ink jet type and thermal transfer type images.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these ranges. In the examples, “parts” and “%” indicate “parts by mass (solid component)” and “mass%” unless otherwise specified. The glass transition temperature (Tg) indicates the main peak temperature of Tg measured by a measuring instrument of thermoplastic organic particles, or Tg calculated from the monomer composition.

Example 1
(Preparation of paper substrate)
To a pulp slurry of 90 parts of LBKP (freeness (CSF) = 450 ml) and 10 parts of NBKP (freeness (CSF) = 450 ml), light calcium carbonate (PC: manufactured by Shiroishi Calcium Co., Ltd.) was added to 5 parts. Paper is made on a long paper machine using a stock containing 1.5 parts of starch, 0.1 part of alkenyl succinic anhydride and 0.6 part of sulfuric acid band per 100 parts of pulp, and starch is applied during the paper making process. Paper with a basis weight of 80 g / m ² , coated and dried with a size press so that the work weight is 1 g / m ^{2 in} dry weight, and smoothed with a machine calendar to a smoothness of 30 seconds. A substrate (hereinafter referred to as a paper substrate) was obtained.
[Preparation of coating solution]
Water and a dispersing agent (trade name: Aron A-9, manufactured by Toagosei Co., Ltd.) 0.01 part are added to 80 parts of Miragloss 91 (component: kaolin, manufactured by Engelhard), and dispersed with a Coreless disperser. A kaolin dispersion with a content of 72% was obtained. To this dispersion, 20 parts of S2577 (component: styrene-butadiene resin, Tg 75 ° C., particle size 250 nm, manufactured by JSR) having a solid content of 50% as a solid content was added as thermoplastic organic particles to prepare a pigment slurry. . To this pigment slurry, 2 parts of oxidized starch (trade name; Ace A, manufactured by Oji Cornstarch Co., Ltd.) and 6 parts of SBR latex (T-2550K (Tg; −14 ° C., particle size 120 nm) manufactured by JSR) were added and stirred. Further, water was added to prepare a coating solution having a solid content concentration of 55%.

[Formation of coating layer on paper substrate surface]
The coating solution obtained as described above was coated on both sides at 500 m / min using a blade coater so that the dry weight per side of the paper substrate was 10 g / m ^2, and then dried with hot air at 160 ° C. Paper was passed through a pressure nip composed of a roll and an elastic roll so that the gloss of white paper was 70%, and a coated paper having a basis weight of 100 g / m ² was obtained.

Example 2
A coated paper was prepared in the same manner as in Example 1 except that the base material obtained in the same manner as in Example 1 was used and the coating liquid was changed as described below.

[Preparation of coating solution]
Water and a dispersant (trade name: Aron A-9, manufactured by Toagosei Co., Ltd.) 0.01 part are added to 65 parts of Milagros 91 (component: Kaolin, manufactured by Engelhard), and dispersed with a Coreless disperser. A kaolin dispersion with a content of 72% was obtained. To this dispersion, 35 parts of S2577 (component: styrene-butadiene resin, Tg 75 ° C., particle size 250 nm, manufactured by JSR) having a solid content of 50% as a solid content was added as thermoplastic organic particles to prepare a pigment slurry. To this pigment slurry, 2 parts of oxidized starch (trade name; Ace A, manufactured by Oji Cornstarch Co., Ltd.) and 4 parts of SBR latex (T-2550K (Tg; −14 ° C., particle size 120 nm) manufactured by JSR) were added and stirred. Further, water was added to prepare a coating solution having a solid content concentration of 55%.

[Formation of coating layer on paper substrate surface]
The coating solution obtained as described above was coated on both sides at 500 m / min using a blade coater so that the dry weight per side of the paper substrate was 10 g / m ^2, and then dried with hot air at 160 ° C. Paper was passed through a pressure nip composed of a roll and an elastic roll so that the gloss of white paper was 70%, and a coated paper having a basis weight of 100 g / m ² was obtained.

Example 3
A coated paper was prepared in the same manner as in Example 1 except that the base material obtained in the same manner as in Example 1 was used and the coating liquid was changed as described below.

[Preparation of coating solution]
Water and a dispersing agent (trade name: Aron A-9, manufactured by Toagosei Co., Ltd.) 0.01 part are added to 80 parts of Miragloss 91 (component: kaolin, manufactured by Engelhard), and dispersed with a Coreless disperser. A kaolin dispersion with a content of 72% was obtained. To this dispersion was added 10 parts of FMT-97 (component; heavy calcium carbonate, manufactured by Phimatech Co., Ltd.) having a solid content of 75% as a solid, and S2577 (component; styrene) having a solid content of 50% as thermoplastic organic particles. -Butadiene resin, Tg 75 ° C., particle size 250 nm, manufactured by JSR Co., 6 parts as solid content, and solid content 28% AE851 (component: styrene-acrylic, particle size 1 μm, as non-film-forming hollow particles, A pigment slurry was prepared by adding 4 parts of a hollow ratio of 55% (manufactured by JSR). To this pigment slurry, 2 parts of oxidized starch (trade name; Ace A, manufactured by Oji Cornstarch Co., Ltd.) and 9 parts of SBR latex (T-2550K (Tg; −14 ° C., particle system 120 nm) manufactured by JSR Co.) were added and stirred. Further, water was added to prepare a coating solution having a solid content concentration of 55%.

[Formation of coating layer on paper substrate surface]
The coating solution obtained as described above was coated on both sides at 500 m / min using a blade coater so that the dry weight per side of the paper substrate was 10 g / m ^2, and then dried with hot air at 160 ° C. Paper was passed through a pressure nip composed of a roll and an elastic roll so that the gloss of white paper was 70%, and a coated paper having a basis weight of 100 g / m ² was obtained.

Example 4
Using the base material obtained in the same manner as in Example 1, the following lower layer coating solution and upper layer coating solution were used to form a two-layer coating.

[Preparation of lower layer coating solution]
FMT-97 having a solid content of 75% (component: heavy calcium carbonate, manufactured by Phimatech Co., Ltd.) as a solid content in 100 parts of slurry, oxidized starch (trade name; Ace A, manufactured by Oji Cornstarch Co., Ltd.), 4 parts, SBR latex 10 parts of T-2550K (Tg; −14 ° C., particle size 120 nm, manufactured by JSR) was added and stirred, and water was further added to prepare a coating solution having a solid concentration of 60%.

[Formation of coating layer on paper substrate surface]
The lower layer coating solution obtained above was coated on both sides at 500 m / min using a blade coater so that the dry weight per side of the paper substrate was 7 g / m ^2, and then dried with hot air at 160 ° C.

[Preparation of upper layer coating solution]
Water and a dispersing agent (trade name: Aron A-9, manufactured by Toagosei Co., Ltd.) 0.01 part are added to 80 parts of Miragloss 91 (component: kaolin, manufactured by Engelhard), and dispersed with a Coreless disperser. A kaolin dispersion with a content of 72% was obtained. To this dispersion was added 10 parts of FMT-97 (component; heavy calcium carbonate, manufactured by Phimatech Co., Ltd.) having a solid content of 75% as a solid, and S2577 (component; styrene) having a solid content of 50% as thermoplastic organic particles. -Butadiene resin, Tg 75 ° C., particle size 250 nm, manufactured by JSR Co., 6 parts as solid content, and solid content 28% AE851 (component: styrene-acrylic, particle size 1 μm, as non-film-forming hollow particles, A pigment slurry was prepared by adding 4 parts of a hollow ratio of 55% (manufactured by JSR). To this pigment slurry, 2 parts of oxidized starch (trade name; Ace A, manufactured by Oji Cornstarch Co., Ltd.) and 9 parts of SBR latex (T-2550K (Tg; −14 ° C., particle size 120 nm) manufactured by JSR) were added and stirred. Further, water was added to prepare a coating solution having a solid content concentration of 55%.

[Formation of coating layer on paper substrate surface]
The coating solution obtained above was coated on both sides at 500 m / min using a blade coater so that the dry weight per side of the paper substrate was 8 g / m ^2, and then dried with hot air at 160 ° C. Paper was passed through a pressure nip composed of a roll and an elastic roll so that the gloss of white paper was 70%, and a coated paper having a basis weight of 100 g / m ² was obtained.

Example 5
Using the base material obtained in the same manner as in Example 1, S2577 (component: styrene-butadiene resin, Tg 75 ° C., manufactured by JSR) having a solid content of 50% as thermoplastic organic particles was prepared as a coating liquid. A coated paper was prepared in the same manner as in Example 3, except that POT7102 (component; styrene-butadiene resin, Tg 124 ° C., particle size 60 nm, manufactured by Nippon Zeon Co., Ltd.) having a solid content of 50% was used.

Example 6
Using the base material obtained in the same manner as in Example 1, S2577 (component: styrene-butadiene resin, Tg 75 ° C., manufactured by JSR) having a solid content of 50% as thermoplastic organic particles was prepared as a coating liquid. A coated paper was prepared in the same manner as in Example 3 except that the solid content was changed to POT7104 (component: styrene-butadiene resin, Tg 35 ° C., particle size 200 nm, manufactured by Nippon Zeon Co., Ltd.).

Example 7
Using the base material obtained in the same manner as in Example 1, S2577 (component: styrene-butadiene resin, Tg 75 ° C., manufactured by JSR) having a solid content of 50% as thermoplastic organic particles was prepared as a coating liquid. A coated paper was prepared in the same manner as in Example 1 except that the solid content was changed to 2600B (component: styrene-butadiene resin, Tg 13 ° C., particle size 130 nm, manufactured by JSR).

Comparative Example 1
A coated paper was prepared in the same manner as in Example 1 except that the base material obtained in the same manner as in Example 1 was used and the coating liquid was changed as described below.

[Preparation of coating solution]
Water and a dispersing agent (trade name: Aron A-9, manufactured by Toagosei Co., Ltd.) 0.01 part are added to 100 parts of Milagros 91 (component: Kaolin, manufactured by Engelhard), and dispersed with a Coreless disperser. A kaolin dispersion with a content of 72% was obtained. In this dispersion, 2 parts of oxidized starch (trade name; Ace A, manufactured by Oji Cornstarch Co., Ltd.), styrene-butadiene copolymer latex (hereinafter referred to as SBR latex, T2550K (Tg; −14 ° C., particle system 120 nm) JSR 10 parts) was added and stirred, and water was further added to prepare a coating solution having a solid concentration of 55%.

Comparative Example 2
A coated paper was prepared in the same manner as in Example 1 except that the base material obtained in the same manner as in Example 1 was used and the coating liquid was changed as described below.

[Preparation of coating solution]
Water and a dispersing agent (trade name: Aron A-9, manufactured by Toagosei Co., Ltd.) 0.01 part are added to 80 parts of Miragloss 91 (component: kaolin, manufactured by Engelhard), and dispersed with a Coreless disperser. A kaolin dispersion with a content of 72% was obtained. A pigment slurry was prepared by adding 20 parts of FMT-97 having a solid content of 75% (component: heavy calcium carbonate, manufactured by Pimatech) to this dispersion. Furthermore, in this dispersion, 2 parts of oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.), styrene-butadiene copolymer latex (hereinafter referred to as SBR latex, T2550K (Tg; -14 ° C., particle system 120 nm). (Made by JSR) 10 parts were added and stirred, and water was further added to prepare a coating solution having a solid concentration of 55%.

Comparative Example 3
A coated paper was prepared in the same manner as in Example 1 except that the base material obtained in the same manner as in Example 1 was used and the coating liquid was changed as described below.

[Preparation of coating solution]
Water and a dispersing agent (trade name; Aron A-9, manufactured by Toagosei Co., Ltd.) 0.01 part are added to 40 parts of Miragloss 91 (component: kaolin, manufactured by Engelhard), and dispersed with a Coreless disperser. A kaolin dispersion with a content of 72% was obtained. A pigment slurry was prepared by adding 60 parts of FMT-97 having a solid content of 75% (component: heavy calcium carbonate, manufactured by Pimatech) to this dispersion. Furthermore, in this dispersion, 2 parts of oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.), styrene-butadiene copolymer latex (hereinafter referred to as SBR latex, T2550K (Tg; -14 ° C., particle system 120 nm). (Made by JSR) 10 parts were added and stirred, and water was further added to prepare a coating solution having a solid concentration of 55%.

Comparative Example 4
A coated paper was prepared in the same manner as in Example 1 except that the base material obtained in the same manner as in Example 1 was used and the coating liquid was changed as described below.

[Preparation of coating solution]
Water and a dispersant (trade name; Aron A-9, manufactured by Toagosei Co., Ltd.) 0.01 part are added to 60 parts of Milagros 91 (component: Kaolin, manufactured by Engelhard), and dispersed with a Coreless disperser. A kaolin dispersion with a content of 72% was obtained. A pigment slurry was prepared by adding 40 parts of FMT-97 having a solid content of 75% (component; heavy calcium carbonate, manufactured by PMMA Tech) to this dispersion. Furthermore, in this dispersion, 2 parts of oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.), styrene-butadiene copolymer latex (hereinafter referred to as SBR latex, T2550K (Tg; -14 ° C., particle system 120 nm). (Made by JSR) 10 parts were added and stirred, and water was further added to prepare a coating solution having a solid concentration of 55%.

Comparative Example 5
A coated paper was obtained in the same manner as in Example 5 except that in Example 5, the sheet was passed through a pressure nip composed of a metal roll and an elastic roll so that the gloss of the blank paper was 85%.

[Blank Gloss Evaluation]
The white paper glossiness of the coated paper obtained in each Example and Comparative Example was measured based on JIS Z8741 under conditions where the incident angle and the light receiving angle were 75 degrees. The measuring instrument used was GLOSS METER MODEL GM-26D manufactured by Murakami Color Research Laboratory.

[Oken smoothness evaluation]
The smoothness of the coated paper obtained in each Example and Comparative Example was measured using the JAPAN TAPPI Paper Pulp Test Method No. Based on 5-2: 2000, measurement was performed using a fully automatic digital type Oken air permeability and smoothness tester EYO manufactured by Asahi Seiko Co., Ltd. The larger the smoothness value (seconds), the better the smoothness.

"Evaluation of adhesion of pigment to paper feed roller"
A sample obtained by cutting the coated paper obtained in each Example and Comparative Example into A4 size is folded with a paper folding machine (trade name; manufactured by EF-35 Horizon), and the powder adhered to the paper feed roller is observed. The number of sheets passed is 2000.
<Evaluation criteria>
5: Powder is not seen on the roller surface.
4: Some powder is seen on the roller surface.
3: Some powder is seen on the roller surface.
2: Powder is seen on the roller surface, which is problematic in practice.
1: Remarkably much powder is seen on the roller surface.

“Evaluation of frequency of double feed and non-feed in the paper feeder”
Samples obtained by cutting the coated paper obtained in each Example and Comparative Example into A4 size were fed into a paper folding machine (trade name; manufactured by EF-35 Horizon Co., Ltd.), 20,000 sheets, The situation of occurrence of skew in which feeding and paper advance in an oblique direction was evaluated.
<Evaluation criteria>
5: Good with zero occurrence of non-feed, double feed and skew.
4: Number of occurrences of non-feed, double feed and skew is 10 times or less.
3: Number of occurrences of non-feed, double feed and skew is 50 times or less.
2: The number of occurrences of non-feed, double feed and skew is 50 to 100 times, which is a practical problem.
1: The number of occurrences of non-feed, double feed and skew is 100 times or more.

[Offset printing of coated paper, ink set evaluation]
The coated paper obtained in each of the examples and comparative examples is cut into strips, and a sheet is prepared which is attached side by side on a sample board. Newspaper printing ink (NEWS WEBMASTER / process ink G2: Sakata Inx Co., Ltd) Manufactured) 0.5 cc kneaded, moved the ink kneading rubber roll to the second cylinder, and newly installed a rubber roll wrapped with relatively smooth one-side coated paper for ink transfer on the fourth cylinder, Printing is performed on the second cylinder. When the fourth roll was touched, the rotation was temporarily stopped, and then ink was transferred to the fourth roll by 2 cm every 20 seconds, and the transfer density change was visually evaluated. The evaluation is performed visually, and those having an evaluation of 2 or less have practical problems. In the following, as a reference product, an OK special art post (256 g / m ² product), which is a standard ink-set printing coated paper in an actual printer, was used.
<Evaluation criteria>
5: Compared with the reference product, the ink density of the single-side coated paper to which the surface of the coated paper after printing is transferred is clearly low.
4: Compared with the reference product, the ink concentration of the single-side coated paper to which the surface of the coated paper after printing is transferred is slightly low.
3: Ink density equivalent to the standard product.
2: Compared with the reference product, the ink density of the single-side coated paper to which the surface of the coated paper after printing is transferred is slightly high.
1: Compared with the reference product, the ink density of the single-side coated paper obtained by transferring the surface of the fine coated paper for offset printing after the printing is clearly high.

"Inkjet evaluation of coated paper"
Winding the coated paper obtained in each example and comparative example, using Kodak DS6240, and performing a printing test under the following conditions, ink setback due to poor ink absorption in the winding of the printed matter Was visually evaluated.
<Conditions>
Ink used: # 1040 ink, printing speed: 100 m / min, resolution: 240 dpi (4 drops), image: monochrome image, drying temperature: 100 ° C., printing surface: single side <evaluation criteria>
5: Good without ink back-off.
4: Some ink set-off is observed.
3: The ink is slightly offset, but there is no practical problem.
2: There is a problem in practical use due to the see-through of the ink.
1: Remarkable setback of ink is observed.

[Color laser printer printing evaluation of coated paper]
The coated paper obtained in each Example and Comparative Example was wound up, and a printing test was performed under the following conditions using SR3000 manufactured by Showa Information Equipment Co., Ltd. The occurrence of toner blisters was visually evaluated.
<Conditions>
Printing speed: 30 m / min, printing surface: double-sided, resolution: 600 dpi, image: full-color image <Evaluation criteria>
5: Generation | occurrence | production of a blister is not seen at all.
4: Some blisters are generated.
3: Blister is slightly generated, but it is not visually recognized and has no practical problem.
2: Blister is generated and is visually recognized, which is a practical problem.
1: Blister which can be seen visually is generated remarkably.

Claims (3)

  In a coated paper having a paper base material and one or more coating layers mainly composed of a pigment and an adhesive on at least one surface thereof, a hexagonal plate shape with respect to 100 parts by mass of the pigment contained in the outermost coating layer 5 to 40 parts by weight of a thermoplastic organic particle having a glass transition temperature (Tg) of 30 to 130 ° C. having an average particle diameter of 30 to 500 nm, and the surface of the outermost coating layer The coated paper is characterized by having a gloss of 60% or more and a smoothness of 3000 seconds or less.   The coated paper of Claim 1 which mix | blends calcium carbonate with 30 mass parts or less with respect to 100 mass parts of pigments contained in the said outermost coating layer.   The coated paper of Claim 1 or Claim 2 which mix | blends a non-film-forming hollow organic pigment with 20 mass parts or less with respect to 100 mass parts of pigments contained in the said outermost coating layer.