JP2008088625A - Coated paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated paper having high glossiness of white paper, excellent in acceptance of ink in offset printing, free from occurrence of blister and capable of providing high-definition image. <P>SOLUTION: The coated paper is obtained by providing a paper base material and coated layers mainly each composed of a pigment and an adhesive on the both surfaces of the paper base material. In the coated paper, kaolin having an aspect ratio of 5-15 and an average particle diameter of 0.3-1.0 μm is included in an amount of ≥60 pts.wt. in 100 pts.wt. pigment in the coated layer, and white paper glossiness of the surfaces of the coated layers is 50-80% and air permeability is ≤7,000 sec and internal binding strength according to J. TAPPI No. 54-93 is 0.27-0.85 KJ/m<SP>2</SP>. The coated paper contains, preferably, 1-10 pts.wt. of hollow organic pigment having 0.5-1.5 μm average particle diameter in 100 pts.wt. pigment. In the coated paper, it is preferable that the Bekk smoothness of the paper base material is ≤50 sec and air permeability is ≤40 sec. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a coated paper that is excellent in acceptability of printing ink, has a particularly high gloss of white paper, and does not generate blisters.

  For printing paper used for offset printing, art paper, coated paper, etc. provided with a coating layer mainly composed of pigment and adhesive on the paper substrate in order to have a smooth surface and satisfy the feeling of printing after printing Coated paper is used. Such coated papers are classified into three types according to the glossiness of the white paper: low glossiness to matte (glossiness of 20% or less), dull (glossiness of 20 to 45%), and gloss (glossiness of 45% or more). . In particular, gloss with a high gloss of white paper is super calendered after the coating layer is applied, so the density of the base paper and the coating layer is high, and air permeability (for general coated paper, the air permeability is about 15000 seconds). ) Is markedly reduced. However, in the rotary method in which ink is dried instantly by high heat such as an oven, when gloss type coated paper is used, blistering of the image area (hereinafter referred to as blister) occurs when the ink is dried. Therefore, improvement is desired.

  As for blisters, (1) when water vapor in the coated paper expands and the paper base layer is destroyed and large blisters are formed in the image area, that is, macro blisters are generated. In some cases, water vapor between the layers expands and fine blisters, that is, microblisters, are generated in the image area.

  As a general measure, it is conceivable to increase the internal bond strength of the paper substrate for macro blisters and prevent the paper substrate layer from rupturing, and to improve the air permeability of the coating layer for micro blisters. As for the macroblister, JP-A-3-227491 proposes a method of adding a polyacrylamide-based paper strength enhancer. However, if the amount added is increased, flocs are generated. The amount of addition is limited from the viewpoint of formation, and even if a coating layer is provided using the obtained paper substrate, the blister is not sufficiently improved. Regarding microblisters, JP-A-4-241199 proposes an attempt to increase the porosity of the undercoat layer and improve the air permeability by cationizing the undercoat layer, but sufficient air permeability is obtained. It is not possible to completely suppress the microblister.

  An object of the present invention is to improve the above-described problems, and the glossiness of a blank paper is high, the ink acceptability in offset printing is excellent, no blister is generated, and a high-quality image is obtained. The coated paper obtained is provided.

  In order to achieve the above object, the present inventors have conducted intensive research on the relationship between the internal bond strength of the paper substrate and the air permeability of the coating layer and the occurrence of blisters. Coating paper with a coating layer mainly composed of an agent is coated with a coating liquid containing kaolin as the main pigment with an aspect ratio that is the ratio of the plane major axis to the thickness and an average particle size within a specific range. The present invention has been completed by finding that the coated paper obtained by drying and smoothing the coating paper has air permeability and has a specific range of internal bond strength.

That is, the coated paper according to the present invention comprises a paper base and a coating layer mainly composed of a pigment and an adhesive on both sides thereof, and in 100 parts by weight of the pigment in the coating layer, It contains 60 parts by weight or more of kaolin having an aspect ratio of 5 to 15 and an average particle size of 0.3 to 1.0 μm, and the coated paper has a blank sheet glossiness of 50 to 80% and an air permeability of 7000 seconds or less and J. Org. TAPPI No. The internal bond strength according to 54-93 is 0.27 to 0.85 KJ / m ² .

  Further, it is preferable that 1 to 10 parts by weight of a hollow organic pigment having an average particle size of 0.5 to 1.5 μm is contained in 100 parts by weight of the pigment. Furthermore, it is preferable that the paper substrate has a Beck smoothness of 50 seconds or less and an air permeability of 40 seconds or less.

  The present inventors consider that it is necessary to obtain a high gloss while maintaining a bulky structure of the coating layer by a mild smoothing treatment for imparting high gloss and low air permeability to the coated paper, As a result of intensive research, it was found that kaolin having an aspect ratio in the range of 5 to 15 and an average particle diameter of 0.3 to 1.0 μm was used as the main pigment of the coating layer, resulting in high gloss and high It was found that air permeability was obtained, and a coated paper in which generation of macro blisters and micro blisters did not occur was obtained.

  Compared to commonly used kaolin having an aspect ratio of 15 to 20 and delaminated kaolin having an aspect ratio of 40 or more, the kaolin used in the present invention has an aspect ratio in the range of 5 to 15, and has a large thickness. And since the average particle diameter is as small as 0.3 to 1.0 μm and the particle size distribution is a hexagonal plate shape, after the coating layer is smoothed, the gap between the pigments does not become a dense structure, Moreover, it is presumed that this is because of the high flatness characteristic of hexagonal plate kaolin.

  By the way, when the particle diameter is smaller than 0.3 μm, gloss is easily produced, but the air permeability is remarkably lowered. On the other hand, when it exceeds 1.0 μm, it becomes difficult to obtain gloss, and a desired gloss cannot be obtained. As for the particle size distribution, the particle size distribution with a particle size of 0.25 to 1.0 μm is preferably 65% or more.

  The kaolin used as the main pigment of the present invention is blended in the range of 60 parts by weight to 100 parts by weight with respect to 100 parts by weight of the total pigment in the coating layer. Incidentally, if it is less than 60 parts by weight, the air permeability is remarkably lowered.

Furthermore, the present inventors have conducted extensive research on suppressing the occurrence of macroblisters. TAPPI No. It was ascertained that by adjusting the internal bond strength according to 54-93 to 0.27 to 0.85 KJ / m ² , it is possible to prevent macroblisters generated by the rupture between layers of the paper substrate. Incidentally, when the internal bond strength is less than 0.27 KJ / m ^{2, the} occurrence of macroblisters cannot be completely prevented even if the air permeability of the coated paper is increased. On the other hand, when it exceeds 0.85 KJ / m ² , pulp flocs are generated, and the formation and appearance are remarkably deteriorated. Preferably, a 0.35~0.85KJ / m ^2.

  To improve the internal bond strength of the paper substrate, for example, the type of pulp produced from a highly rigid coniferous tree, increasing the bond between fibers by promoting beating, adding a paper strength enhancer, There are impregnation and coating, etc., which are appropriately selected according to the purpose.

  The paper substrate of the present invention preferably has a Beck smoothness of 50 seconds or less and an air permeability of 40 seconds or less. When the Beck smoothness exceeds 50 seconds, the operability may be deteriorated, for example, streak is generated or the adhesion of the paint is deteriorated. On the other hand, if the air permeability exceeds 40 seconds, the air permeability after the coating layer is provided and smoothed is deteriorated, and the generation of blisters cannot be completely prevented. Preferably, the Beck smoothness is 30 seconds or less and the air permeability is 30 seconds or less.

  Adjustment of the Beck smoothness of the paper substrate is performed using a smoothing apparatus such as a machine calendar or a soft nip calendar. On the other hand, the air permeability is adjusted by adjusting the paper strength enhancer such as polyamide, acrylamide, amine compound, amide, epoxy or melamine compound, water repellent of natural wax, olefin, zirconium or fluorine wax, and polyvinyl alcohol. , Fluorine resin, acrylic resin, styrene resin, acrylic-styrene copolymer resin, amide resin, urethane resin, epoxy resin and other water-soluble resin or water-dispersible resin impregnated, size press coating It is performed by such processing.

  In the present invention, 1 to 10 parts by weight of a hollow organic pigment having an average particle size of 0.5 to 1.5 μm can be blended in the coating layer with respect to the total pigment weight.

  As a result of intensive studies on improving the acceptability of printing inks, the present inventors have determined that a hollow organic pigment having an average particle size of 0.5 to 1.5 μm is added to 100 parts by weight of the total pigment in the coating layer. Thus, when 1 to 10 parts by weight is blended, it has been found that the acceptability of the printing ink is improved, and the present invention has been completed. Although it is not clear about this phenomenon, the softness and high cushioning hollow organic pigment are blended in the coating layer, the cushioning property of the coating layer surface is improved, and the hollow organic pigment and the ink It is estimated that the affinity is good.

  Incidentally, if the average particle size of the hollow organic pigment is less than 0.5 μm, the air permeability of the coating layer may be lowered. On the other hand, if the average particle size is larger than 1.5 μm, the desired gloss may not be obtained. On the other hand, if the blending amount exceeds 10 parts by weight, the operability such as streak may be remarkably lowered. On the other hand, if the blending amount of the hollow organic pigment exceeds 10 parts by weight, the strength of the coating layer is lowered, and the blanket may be smeared during printing. A more preferable blending amount is 1 to 4 parts by weight.

  Examples of the hollow organic pigment used in the present invention include polystyrene resins, styrene-acrylic copolymer resins, urea resins, melamine resins, acrylic resins, vinylidene chloride resins, and benzoguanamine resins. One type or two or more types are appropriately selected and used.

  The pulp of the paper substrate is not particularly limited with respect to the production method and type, etc., and is not limited to chemical pulp such as KP, mechanical pulp such as SGP, RGP, BCTMP, CTMP, waste paper pulp such as deinked pulp, or Non-wood pulp such as kefna, bamboo, straw and hemp, organic synthetic fibers such as polyamide fiber, polyester fiber and polynosic fiber, and inorganic fibers such as glass fiber, ceramic fiber and carbon fiber can also be used.

  Moreover, a filler can be mix | blended with a paper base 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 fine particles Examples thereof include organic pigments such as hollow particles.

  In addition to pulp fibers and fillers in the paper stock, various anionic, nonionic, cationic or amphoteric yield improvers that have been conventionally used, as long as the desired effects of the present invention are not impaired. Various paper-making internal additives such as a drainage improver, a paper strength enhancer, and an internal additive sizing agent 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 papermaking method is not particularly limited. For example, an acidic papermaking method in which the papermaking pH is around 4.5, a weakly acidic papermaking pH of about 6 containing an alkaline filler such as calcium carbonate as a main component, and a papermaking pH of about 9 is weak. The present invention can be applied to all paper making methods such as an alkaline neutral paper making method. As the paper machine, a long paper machine, a twin wire paper machine, a round paper machine, and a Yankee paper machine can be used as appropriate.

  Examples of the pigment used for the coated paper of the present invention include, in addition to the kaolin and hollow organic pigment of the present invention, for example, heavy calcium carbonate, light calcium carbonate, kaolin, calcined kaolin, structural kaolin, deramikaolin, talc, sulfuric acid Calcium, barium sulfate, titanium dioxide, zinc oxide, alumina, magnesium carbonate, magnesium oxide, silica, magnesium aluminosilicate, particulate calcium silicate, particulate magnesium carbonate, particulate light calcium carbonate, white carbon, bentonite, zeolite, sericite Solid type or through-hole type such as mineral pigments such as smectite, polystyrene resin, styrene-acrylic copolymer resin, urea resin, melamine resin, acrylic resin, vinylidene chloride resin, benzoguanamine resin Organic pigments such as resins It is possible to have, one or more kinds among these are appropriately selected and used.

  As the adhesive, a water-soluble and / or water-dispersible polymer compound can be used. For example, cationic starch, amphoteric starch, oxidized starch, enzyme-modified starch, thermochemically-modified starch, esterified starch, Starch such as tellurized starch, cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, natural or semi-synthetic polymer compounds such as gelatin, casein, soybean protein, natural rubber, polydienes such as polyvinyl alcohol, isoprene, neoprene, polybutadiene, Polyalkenes such as polybutene, polyisobutylene, polypropylene and polyethylene, vinyl halides, vinyl acetate, styrene, (meth) acrylic acid, (meth) acrylic acid esters, (meth) acrylamide, methyl vinyl ether and other vinyl polymers and copolymer Coalesce, styling - butadiene, methyl methacrylate - synthetic rubber latex butadiene etc., polyurethane resins, polyester resins, polyamide resins, olefin - maleic anhydride resins, synthetic polymer compounds such as melamine resins and the like. Among these, one or more kinds are appropriately selected and used according to the purpose.

  The blending ratio of the adhesive is in the range of 5 to 50 parts by weight (solid part) with respect to 100 parts by weight of pigment (solid part). Incidentally, if it is less than 5 parts by weight, the strength of the coating layer of the coating layer is weak, and the coating layer peels off and accumulates on the printing plate of the rotary press, which may cause damage to the printing plate. On the other hand, if it exceeds 50 parts by weight, the coating layer becomes dense and the air permeability may be significantly reduced.

  In this coating solution, in addition to these pigments and adhesives, various auxiliary agents such as surfactants, pH adjusters, viscosity adjusters, softeners, gloss imparting agents, waxes, dispersants, flow modifiers, Anti-conductive agent, stabilizer, antistatic agent, cross-linking agent, sizing agent, fluorescent brightening agent, colorant, UV absorber, antifoaming agent, water-resistant agent, plasticizer, lubricant, preservative, fragrance, etc. are required It is also possible to use it appropriately according to.

The coating amount of the coating layer of the present invention is 8 to 20 g / m ² , preferably 10 to 20 g / m ² . When the coating amount is less than 8 g / m ² , the unevenness on the surface of the paper substrate cannot be sufficiently covered, and the acceptability of the printing ink may be significantly reduced. On the other hand, if it exceeds 20 g / m ² , the operability such as poor drying at the time of coating deteriorates and the production cost increases.

  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, die slot coaters, gravure coaters, Champlex coaters, Apparatuses such as a brush 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 both sides of the paper substrate, and it is possible to provide a multilayer structure by providing one layer or two or more intermediate layers as necessary. In the case of double-sided coating or multi-layer structure, each coating solution need not be the same or the same coating amount, and may be appropriately adjusted according to the required quality level and is particularly limited. is not. In addition, when a coating layer is provided on one side of the paper substrate, a synthetic resin layer, a coating layer composed of pigment and adhesive, etc., an antistatic layer, etc. are provided on the back side to prevent curling, impart printability, and supply / discharge properties Etc. can also be given. Further, it is of course possible to use the back surface of the paper substrate with application suitability by applying various processes such as adhesion, magnetism, flame retardancy, heat resistance, water resistance, oil resistance, and slip resistance.

  In the present invention, after a coating layer is provided on a paper substrate, it is smoothed by a normal drying step, surface treatment step or the like, so that the water content is about 3 to 10%, preferably about 4 to 8%. Adjust and finish.

  Further, when the smoothing process is performed, it is carried out by a smoothing apparatus such as a normal super calendar, gloss calendar, soft calendar, etc., and is used appropriately in on-machine or off-machine. The number, the heating, etc. are appropriately adjusted according to a normal smoothing apparatus.

  Since the coated paper subjected to the smoothing process needs to have a texture of printing paper, the blank paper glossiness at an incident / light receiving angle of 75 degrees based on JIS Z8741 is preferably 50 to 80%, more preferably 60 ~ 80%. Further, the air permeability is preferably adjusted to 7000 seconds or less, more preferably 5000 seconds or less, and still more preferably 3000 seconds or less.

If the glossiness is less than 50%, the appearance of white paper and the desired gloss may not be obtained. On the other hand, if the glossiness is higher than 80%, the air permeability can be reduced even if the pigment used in the present invention is used. It cannot be adjusted to 7000 seconds or less, and macro blisters or micro blisters may occur. Incidentally, when the air permeability exceeds 7000 seconds, microblisters may be generated even when the internal bond strength of the coated paper is 0.27 to 0.85 KJ / m ² . On the other hand, even if the air permeability is 5000 seconds or less, if the internal bond strength is less than 0.27 KJ / m ² , macro blistering may occur.

  The coated paper obtained by the above method should be used as image recording paper for non-impact printing methods such as electrophotographic methods and thermal transfer methods due to its high surface smoothness and high air permeability as well as suitability for rotary offset printing. You can also.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these ranges. In the examples, “parts” and “%” represent “parts by weight (solid content)” and “% by weight” unless otherwise specified.

Example 1
(Preparation of substrate)
A pulp slurry of 70 parts of LBKP (freeness (CSF) = 500 ml) and 30 parts of NBKP (freeness (CSF) = 500 ml) and a polyacrylamide resin (trade name: PS117, manufactured by Arakawa Chemical Industries) as a paper strength enhancer 0 0.1%, polyacrylamide resin (trade name: PS460, manufactured by Arakawa Chemical Co., Ltd.) 0.3%, 1 part of sulfuric acid band was added, and the mixture was diluted with white water to pH 5.3, solid content concentration A 1.1% stock was prepared. This stock is made using a long paper machine, and then a size press solution of a polyacrylamide resin (trade name; Polymer Set 531, manufactured by Arakawa Chemical Industries Co., Ltd.) with a concentration of 2% is applied to a dry weight. The base paper having a basis weight of 80 g / m ² was obtained by applying with a size press device so as to be 1 g / m ² , drying, and smoothing with a machine calendar so that the Beck smoothness was 30 seconds ( Paper substrate 1). Table 1 shows the Beck smoothness, air permeability, and internal bond strength of the paper substrate.

[Adjustment and application of coating solution]
To 100 parts of Astra Plus (component: Kaolin, manufactured by Huber), 0.2 parts of polyacrylic acid soda (trade name Aron A-9, manufactured by Toa Gosei Co., Ltd.) is added as a dispersant, and water is added using a Coreless disperser. A pigment slurry was prepared by dispersing. To this pigment slurry, 3.0 parts of oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.) and 10 parts of styrene-butadiene copolymer latex (trade name: OX1060, manufactured by Nippon Zeon Co., Ltd.) were added and stirred. Water was added to prepare a coating solution having a solid content concentration of 50%. Table 2 shows the composition, shape, aspect ratio, average particle size, and particle size distribution of the inorganic pigment used.

[Formation of coating layer on paper substrate]
The obtained coating solution was coated on both sides using a blade coater so that the dry weight per side of the paper substrate was 12 g / m ^2, and passed through a pressure nip composed of a metal roll and an elastic roll. The coated paper having a basis weight of 104 g / m ² was obtained by adjusting the white paper glossiness at an incident / light receiving angle of 75 degrees based on JIS Z8741 to 65%.

Example 2
Coating was performed in the same manner except that 100 parts of Astraplus (component: Kaolin, manufactured by Huber) used in Example 1 were changed to 70 parts of Astraplus and 30 parts of brilliant (component: light calcium carbonate, manufactured by Shiraishi Calcium). Paper was created and evaluated.

Comparative Example 1
Coating is performed in the same manner except that 100 parts of Astraplus (component: Kaolin, manufactured by Huber) used in Example 1 is changed to 50 parts of Astraplus and 50 parts of brilliant (component: light calcium carbonate, manufactured by Shiraishi Calcium). Paper was created and evaluated.

Comparative Examples 2-4
100 parts of Astraplus (component: kaolin, manufactured by Huber) used in Example 1 was added to kao gloss (component: kaolin, manufactured by Huber) (Comparative Example 2), Astra plate (component: deramikaolin, manufactured by Huber) ( A coated paper was prepared and evaluated in the same manner except that it was changed to Comparative Example 3), Brilliant (component; light calcium carbonate, manufactured by Shiraishi Calcium Co.) (Comparative Example 4).
Here, in Comparative Examples 3 and 4, although the calender treatment conditions were strengthened, the glossiness did not increase.

Examples 3-5
100 parts of Astraplus (component; Kaolin, manufactured by Huber) used in Example 1 were combined with 97.5 parts of Astraplus (component: Kaolin, manufactured by Huber) and HP91 (component; hollow organic pigment, manufactured by Rohm & Haas) ) 2.5 parts (Example 3), 95 parts of Astraplus (component; kaolin, manufactured by Huber) and HP91 (component: hollow organic pigment, manufactured by Rohm & Haas), 5 parts (Example 4), Astraplus ( Coated paper was prepared and evaluated in the same manner except that the components were changed to 90 parts (Kaolin, manufactured by Huber) and 10 parts HP91 (component; hollow organic pigment, manufactured by Rohm & Haas) (Example 5).

Comparative Example 5
100 parts of Astra Plus (component; Kaolin, manufactured by Huber) used in Example 1 were changed to 50 parts of Astra Plus (Component: manufactured by Kaolin, Huber) and 50 parts of Kao Gloss (component: Kaolin, manufactured by Huber). A coated paper was similarly prepared and evaluated.

Examples 6-7
A coated paper was similarly prepared and evaluated except that Example 4 was changed to a coating amount of 8 g / m ² (absolute dry solid amount) (Example 6) and 18 g / m ² (Example 7). .

Comparative Example 6
A coated paper was prepared and evaluated in the same manner as in Example 4 except that the coating amount was changed to 6 g / m ² (absolute dry solid amount).

Examples 8-9
A coated paper was prepared and evaluated in the same manner as in Example 4, except that the glossiness after the smoothing treatment was changed to 55% (Example 8) and 75% (Example 9).

Example 10
In the preparation of the paper substrate of Example 4, the amount of polyacrylamide resin (trade name: PS117, manufactured by Arakawa Chemical Industries, Ltd.) was 0.4%, and the polyacrylamide resin (trade name: PS460, Arakawa Chemical Industries, Ltd.). Coated paper was prepared and evaluated in the same manner except that the amount of addition was changed to 0.6% (paper substrate 2).

Comparative Example 7
A coated paper was prepared and evaluated in the same manner as in the preparation of the paper substrate of Example 4 except that the polyacrylamide resin was not added and the size press was changed to water (paper substrate 3).

Comparative Example 8
In the preparation of the paper substrate of Example 4, the addition amount of polyacrylamide resin (trade name: PS117 Arakawa Chemical Industries) is 0.7%, and the polyacrylamide resin (trade name: PS460, Arakawa Chemical Industries, Ltd.). The coated paper was prepared and evaluated in the same manner except that the amount of addition was changed to 0.8% (paper substrate 4).

Evaluation method [Measurement of average particle size and particle size distribution of pigment]
As a measuring instrument, Cedygraph 5100 V3.07 was used. The results are shown in Table 2.

[Measurement of pigment aspect ratio and shape observation]
The image was magnified 15000 times with an electron microscope, and the aspect ratio was measured and the shape was observed. The results are shown in Table 2.

[Measurement of internal bond strength of paper substrate and coated paper]
The measurement method is described in J. Org. TAPPI No. It measured according to 54-93. The measuring instrument used was an internal bond tester MODEL-B manufactured by SCOTT.

[Measurement of air permeability of paper substrate and coated paper]
Measured with a Oken air permeability meter.

[Measurement of Beck smoothness of paper substrate]
Measured by Beck smoothness measuring instrument

[Measurement of glossiness of coated paper]
The glossiness was measured 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.

[Printing coated paper]
The printing machine was Komori System C-20 manufactured by Komori Corporation and printed under the following conditions. Environment: 20 ° C., 65% RH
Printing speed: 200 to 250 m / min
Printing length: 6000m
Drying conditions: Adjust the paper surface temperature to 150 ° C using a gas heater

(Evaluation of printing ink acceptance of coated paper)
Evaluation was performed according to the following evaluation criteria.
A: No missing or missing halftone dots are observed. There are no practical problems and the quality is excellent.
○: Some missing or missing dots are observed. There is no problem in practical use.
Δ: Missing or missing halftone dots are frequently observed. There are practical problems.
X: The omission and missing of a halftone dot are remarkably observed. There is a problem in practical use and the quality is remarkably inferior.

(Blanket dirt evaluation)
The stain on the blanket after printing 6000 m was evaluated according to the following evaluation criteria.
(Double-circle): Dirt is not seen. There are no practical problems and the quality is excellent.
○: Some dirt is seen. There is no problem in practical use.
Δ: Dirt is frequently observed. There are practical problems.
X: Dirt was noticeable. There is a problem in practical use and the quality is remarkably inferior.

(Macro blister evaluation)
The state of occurrence of macro blisters was confirmed with an enlarged magnifying glass (30 times) and evaluated according to the following evaluation criteria.
A: Macro blister is not observed. There are no practical problems and the quality is excellent.
○: Some macro blisters can be seen. There is no problem in practical use.
Δ: Macro blisters are frequently observed. There are practical problems.
X: Macro blister was remarkably observed. There is a problem in practical use and the quality is remarkably inferior.

(Micro blister evaluation)
The generation state of the microblister was confirmed with an magnifying loupe (30 times) and evaluated according to the following evaluation criteria.
A: Micro-blister is not observed. There are no practical problems and the quality is excellent.
○: Some microblisters can be seen. There is no problem in practical use.
Δ: Micro blisters are frequently observed. There are practical problems.
X: Micro-blister was remarkably observed. There is a problem in practical use and the quality is remarkably inferior.

[Evaluation of paper substrate and coated paper]
From the above, Tables 1 and 3 show the results of the air permeability, the glossiness, and the internal bond strength of the paper substrate and the coated paper obtained. Moreover, the acceptability of the printing ink of the obtained coated paper, blanket dirt, and blisters were evaluated. The results are shown in Table 4.

  The coated paper according to the present invention is a coated paper that has a high gloss of white paper, is excellent in acceptability of ink in offset printing, does not generate blisters, and provides a high-quality image, and is extremely useful in practice. It is.

Claims (3)

In a coated paper in which a paper base and a coating layer mainly composed of a pigment and an adhesive are provided on both sides thereof, in 100 parts by weight of the pigment in the coating layer, an aspect ratio of 5 to 15, 60% by weight or more of kaolin having an average particle size of 0.3 to 1.0 μm, and the coated paper has a blank paper glossiness of 50 to 80%, an air permeability of 7000 seconds or less, and J.P. TAPPI No. Coated paper having an internal bond strength according to 54-93 of 0.27 to 0.85 KJ / m ² .   The coated paper according to claim 1, wherein 1 to 10 parts by weight of a hollow organic pigment having an average particle size of 0.5 to 1.5 µm is contained in 100 parts by weight of the pigment.   The coated paper according to claim 1, wherein the paper substrate has a Beck smoothness of 50 seconds or less and an air permeability of 40 seconds or less.