JPWO2020036223A1 - Coated paper - Google Patents

Abstract

A coated paper having a pigment coating layer on a base paper, the coating amount is 5.0 g / m2 or more per side, the Oken type smoothness is 65 seconds or less, and the ISO whiteness is 70% or more. Provide coated paper that is.

Description

The present invention relates to a coated paper having good ink drying property.

In recent years, with the decrease in the number of newspapers sold in paper media, efforts have begun to utilize newspaper rotary presses for purposes other than newspapers. Generally, printing with a newspaper rotation (offset printing) machine using a penetration drying type cold set ink is good for paper because the ink is dried by penetrating the ink into the paper without a drying process. Ink absorbability is required. If the ink absorbency of the paper is poor, problems such as stains on the printing machine and the paper surface and a decrease in printing speed occur, which causes deterioration of print quality and operability. In such a printing method, uncoated paper without a pigment coating layer, particularly newspaper paper containing a large amount of used paper pulp has been generally used. However, although uncoated paper or newspaper has good ink drying properties, there are problems with insufficient ink inking property and printing gloss, and cold set type offset printing is used for printing information other than characters. It was a big obstacle when using. To solve this problem, news inks corresponding fine coated paper having a single side per 0.5 g / m ² or more 4.0 g / m ² less pigment coating layer has been proposed in Patent Document 1. With this finely coated paper, it is possible to achieve printability with excellent ink drying property and sharpness comparable to that of newspaper paper. Further, Patent Document 2 proposes a cold set offset printing paper coated with a surface treatment agent containing a plastic pigment and a synthetic adhesive at a rate of 4 g / m ^{2 or more per side.} This printing paper is said to have high printing gloss, color printability, and less drag stains.

Japanese Unexamined Patent Publication No. 2007-31927 Japanese Unexamined Patent Publication No. 2012-117174

An object of the present invention is to provide a coated paper having excellent ink drying property, ink inking, and printing gloss.

The problem is solved by the following invention.
[1] A coated paper having a pigment coating layer on a base paper.
The coating amount of the pigment coating layer is 5.0 g / m ² or more per side, and
Oken type smoothness is 65 seconds or less,
Coated paper with ISO whiteness of 70% or more.
[2] The coated paper according to [1], wherein the total amount of calcium carbonate and clay is 80 parts by weight or more per 100 parts by weight of the pigment in the pigment coating layer.
[3] The coating according to [1] or [2], wherein the 75 ° glossiness is 30% or more when solid printing is performed using cold set newspaper ink so that the printing density is 1.6. paper.
[4] The coated paper according to any one of [1] to [3], wherein the coating amount is 8.0 g / m ^{2 or less per side.}
[5] The coated paper according to any one of [1] to [4], wherein the coating paper has a basis weight of 45 to 75 g / m ^2.
[6] The coated paper according to any one of [1] to [5], wherein the density of the coated paper is 0.5 to 1.0 g / cm ^3.
[7] The method according to any one of [1] to [6], further comprising a step of providing a pigment coating layer of ^{5.0 g / m 2} or more per side on a base paper having a smoothness of 20 seconds or less. How to make coated paper.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a coated paper having excellent ink drying property, ink carving property, and printing gloss.

Hereinafter, the present invention will be described in detail. In the present invention, "X to Y" includes X and Y which are odd values.

1. 1. Coated paper In the present invention, the coated paper is a paper having a specific amount of pigment coating layer on the base paper. The coated paper of the present invention is particularly suitable for offset printing with cold set inks such as newspaper inks.

(1) Pigment coating layer The pigment coating layer is a layer containing a white pigment as a main component. The coated paper of the present invention includes a pigment coating layer of ^{5.0 g / m 2 or more per side.} The coating amount is preferably 5.5 to 8.0 g / m ² per side, and the upper limit thereof is more preferably ^{7.0 g / m 2 or less.} White pigments include commonly used pigments such as calcium carbonate, kaolin, clay, calcined kaolin, amorphous silica, zinc oxide, aluminum oxide, satin white, aluminum silicate, magnesium silicate, magnesium carbonate, titanium oxide, and plastic pigments. Can be mentioned.

When the pigment coating layer contains calcium carbonate or clay, the smoothness of the coated paper is improved, so that a fine printed image with good color development can be obtained. From this viewpoint, the total amount of calcium carbonate and clay is preferably 80 parts by weight or more, and more preferably 90 parts by weight or more per 100 parts by weight of the pigment in the pigment coating layer. The upper limit of the total amount is not limited and is 100 parts by weight or less.

The average particle size of calcium carbonate is preferably 0.5 to 1.0 μm. The average particle size can be measured with a laser diffraction type particle size distribution measuring device such as Mastersizer manufactured by Malvern, and D50 can be used as the average particle size. The content of particles having a particle size of 2.0 μm or less of calcium carbonate is preferably 90% by volume or more, more preferably 93% by volume or more, and further preferably 95% by volume or more. Examples of calcium carbonate include heavy calcium carbonate and light calcium carbonate. Further, as the light calcium carbonate, the light calcium carbonate (causable light calcium carbonate) described in Japanese Patent No. 5274077 or the like may be used.

The average particle size of the clay is preferably 6.0 μm or less. When the particle size of the clay is small, fine voids can be formed in the coating layer, and the ink drying property can be improved. The average particle size of the clay can also be measured with a laser diffraction type particle size distribution measuring device or the like, and D50 can be used as the average particle size. The lower limit of the average particle size is not limited, but is preferably 1.0 μm or more. From the viewpoint of whiteness, the clay content in the total amount of calcium carbonate and clay is preferably 50 parts by weight or less, more preferably 40 parts by weight or less.

The pigment coating layer contains an adhesive. Examples of the adhesive include etherified starch such as oxidized starch, positive starch, urea phosphate esterified starch and hydroxyethyl etherified starch, various starches such as dextrin, proteins such as casein, soybean protein and synthetic protein, and polyvinyl. Alcohol, cellulose derivatives such as carboxymethyl cellulose and methyl cellulose, styrene-butadiene copolymer, conjugated diene polymer latex of methyl methacrylate-butadiene copolymer, acrylic polymer latex, vinyl such as ethylene-vinyl acetate copolymer Examples include polymer latex. These can be used alone or in combination of two or more. It is preferable to use a mixture of a starch-based adhesive and a latex-based adhesive because the balance between the coating suitability of the pigment coating liquid and the printing suitability such as surface strength is excellent. The total amount of the adhesive in the pigment coating layer is preferably 1 to 15 parts by weight, more preferably 2 to 14 parts by weight, still more preferably 3 to 13 parts by weight with respect to 100 parts by weight of the pigment. If the amount of the adhesive is less than 1 part by weight, the adhesive is insufficient and the strength of the coating layer is weakened, so that there is a possibility that many defects such as white spots may occur during printing. On the other hand, if the amount is more than 15 parts by weight, the voids in the pigment coating layer are insufficient, so that the penetrating cold set ink is difficult to penetrate into the paper, and the drying property may be inferior.

The pigment coating layer may contain various auxiliaries such as dispersants, thickeners, defoamers, colorants, antistatic agents, and preservatives used in the general paper manufacturing field.

The pigment coating layer can be provided by applying a coating liquid to one side or both sides of the base paper by a known method. The solid content concentration in the coating liquid is preferably about 30 to 70% by weight from the viewpoint of coating suitability. The pigment coating layer may be one or more layers, but it is preferably one layer because it is a finely coated paper. The total amount of the pigment coating layer applied is 5.0 g / m ² or more per side, and preferably 5.5 g / m ² or more. The upper limit of the coating amount ^{is preferably 8.0 g / m 2} or less, and more preferably less than 7.0 g / m ^2. If the coating amount is ^{less than 5 g / m 2} , the coating layer cannot sufficiently cover the base paper, so that the ink color development property is lowered. Further, if the coating amount is excessively high, the ink penetration becomes poor and the ink drying property deteriorates.

(2) Base paper The pulp raw material of the base paper used in the present invention is not particularly limited, and mechanical pulp such as ground pulp (GP), thermomechanical pulp (TMP), and chemithermomechanical pulp (CTMP), and waste paper pulp (deinked pulp (deinked pulp). DIP)), chemical pulp such as coniferous kraft pulp (NKP) and coniferous kraft pulp (LKP) can be used. As the used paper pulp, selected used paper such as high-quality paper, medium-quality paper, low-grade paper, newspaper, leaflets, and magazines, and unsorted used paper in which these are mixed can be used, but medium-quality paper containing mechanical pulp can be used. It is preferably used paper pulp containing low-grade paper or newspaper as a raw material. The printing paper of the present invention contains 30 parts by weight or more of chemical pulp in 100 parts by weight of pulp. By containing a large amount of chemical pulp, the density of the printing paper can be improved and the ink can be prevented from being excessively penetrated into the deep part of the base paper, so that the ink color development property can be improved. From this viewpoint, the lower limit of the chemical pulp content is preferably 40 parts by weight or more, and more preferably 50 parts by weight or more. On the other hand, since paper is required to have an appropriate degree of stiffness in a printing process, a processing process, or when it is made into a book, it is preferable to contain a certain amount of mechanical pulp or used paper pulp containing mechanical pulp as a raw material. Therefore, the upper limit of the chemical pulp content is preferably 90 parts by weight or less, and more preferably 80 parts by weight or less.

The coated paper of the present invention preferably contains mechanical pulp or used paper pulp containing mechanical pulp in a total of 10 parts by weight or more, and more preferably 20 parts by weight or more in 100 parts by weight of the pulp. .. The upper limit of the total amount is preferably 50 parts by weight or less. If the total amount exceeds this value, the density may decrease and the ink color development property may decrease, and further, the whiteness may decrease and the image appearance may decrease.

A known filler can be added to the base paper. As fillers, heavy calcium carbonate, light calcium carbonate, clay, silica, light calcium carbonate-silica complex, kaolin, calcined kaolin, deramikaolin, magnesium carbonate, barium carbonate, barium sulfate, aluminum hydroxide, calcium hydroxide, Inorganic fillers such as amorphous silica produced by neutralizing magnesium hydroxide, zinc hydroxide, zinc oxide, titanium oxide, and sodium silicate with mineral acid, urea-formalin resin, melamine resin, polystyrene resin, phenol Examples include organic fillers such as resin. These may be used alone or in combination. Among these, calcium carbonate and light calcium carbonate-silica composites, which are typical fillers for neutral papermaking and alkaline papermaking and can obtain high opacity, are preferable.

As the internal chemicals, bulking agents, dry paper strength improvers, wet paper strength improvers, drainage improvers, dyes, neutral sizing agents and the like may be used as necessary. Examples of the dry paper strength improver include polyacrylamide and cationized starch, and examples of the wet paper strength improver include polyamideamine epichlorohydrin. These chemicals are added within a range that does not affect the formation or operability. Examples of the neutral sizing agent include alkyl ketene dimer, alkenyl succinic anhydride, and neutral rosin sizing agent. Although the bulking agent may be used, it may become too bulky, so it is preferable that the amount used is small, and it is more preferable not to use it. When a bulking agent is used, it is preferable to adjust the paper thickness by calendar processing or the like so that the density of the paper is within the range of the present invention. These internal chemicals can be used together with pulp and filler as a paper charge, if necessary.

The base paper is preferably a single-layer paper, and is produced by a known papermaking method. For example, it can be performed using a long net paper machine, a gap former type paper machine, a hybrid former type paper machine, an on-top former type paper machine, a round net paper machine, and the like, but the present invention is not limited thereto. The offset printing paper for cold set of the present invention may be manufactured by an on-machine method in which a papermaking process and a pigment coating process are continuous, or by an off-machine method in which coating is performed in a pigment coating process after the papermaking process. You may. The papermaking and coating speed is preferably 400 to 2000 m / min.

The Oken-type smoothness of the base paper is preferably 20 seconds or less. When the smoothness is 20 seconds or less, the smoothness of the surface of the base paper becomes a relatively low level, but when the smoothness of the base paper is about this level, the ink is applied even if the amount of the pigment coating layer applied is large. The drying property can be improved. The reason for this is not clear, but if the smoothness of the base paper is within the above range, the specific surface area of the coated paper after the pigment coating layer is provided becomes high, and the smoothness is low, so that at the time of coating. It is presumed that the ink absorbability is improved because the base paper coverage is low and the ink is easily absorbed by the exposed base paper. The lower limit of the Oken-type smoothness is not limited, but is preferably 5 seconds or longer, and more preferably 10 seconds or longer. Further, since the coated paper of the present invention has ^{a pigment coating layer of 5 g / m 2} or more, the ink onset property and the print glossiness are also good, and the ink dryness, the ink onset property and the high print glossiness are combined. ..

(3) Other Treatments The coated paper of the present invention may further have a clear coating layer containing an adhesive as a main component on one side or both sides of the base paper. The clear coating layer is preferably adjacent to the base paper layer, but may be provided on the outermost layer farthest from the base paper. The adhesive used for the clear coating layer is as described above. When a clear coating layer is provided adjacent to the base paper, it is possible to suppress the penetration of the pigment coating liquid into the base paper, and the base paper coverage of the pigment coating layer is improved, which is preferable. Starch is preferred. In addition, the strength of the base paper is improved by permeating the clear coating liquid into the base paper. From the above, the coating amount of the clear coating layer is preferably 0.5 to 5.0 g / m ² , more preferably ^{1.0 to 4.5 g / m 2, and 2.0 to 4.0 g / m 2 on both sides.} m ² is more preferred.

The coated paper of the present invention may be surface-treated. Examples of the surface treatment include soft calendar, super calendar, gloss calendar, thermal calendar, and shoe calendar.

(4) Characteristics of the coated paper of the present invention 1) Wangken-type smoothness The coated paper of the present invention has a Wangken-type smoothness (JIS P8155) of 65 seconds or less, preferably 60 seconds or less. If this value exceeds the upper limit, the penetration rate of the ink slows down and the drying property deteriorates. The lower limit is not limited, but it is preferably 30 seconds or more from the viewpoint of surface properties such as print gloss.

2) ISO whiteness The coated paper of the present invention has an ISO whiteness (JIS P8148) of 70% or more, preferably 75% or more, and more preferably 80% or more. If the whiteness is less than 75%, the whiteness of the blank portion is lowered, and the appearance of the printed image is also lowered.

3) Print Gloss The coated paper of the present invention preferably has a 75 ° gloss of 30% or more when solid printing is performed using cold set newspaper ink so that the print density is 1.6. , 35% or more is more preferable. If the glossiness is less than 30%, the glossiness of the printed matter is insufficient, and the appearance of the printed image may be deteriorated.

4) Basis weight and density The basis weight of the coated paper of the present invention is preferably 45 g / m ² or more, more preferably 50 g / m ² or more, and further preferably 55 g / m ² or more. The upper limit of the basis weight is preferably 75 g / m ² or less, more preferably 70 g / m ² or less, still more preferably 65 g / m ² or less, and from the viewpoint of ease of turning when made into a book. Most preferably, it is 63 g / m _{2 or less.} If the basis weight is less than 45 g / m ^2, such as insufficient stiffness of the paper upon the book, there is a possibility that the hand Nikkan poor, if it is 75 g / m ^2, greater than a monolayer from the viewpoint of drainage It may be difficult to make paper with. The density of the paper is preferably 0.5 to 1.0 g / cm ³ , and more preferably 0.6 to 0.9 g / cm ³ .

2. Method for Producing Coated Paper of the Present Invention The coated paper of the present invention is preferably produced through a step of providing a pigment coating layer of the coating amount on one or both sides of the base paper by blade coating. The pigment coating layer can also be provided by roll coating, but since blade coating is a coating method in which the coating liquid is scraped off with a blade after coating, a highly smooth coating surface can be obtained. It is possible to obtain a printing paper having good ink color development.

3. 3. Applications The coated paper of the present invention exhibits excellent ink drying property, ink inking, and printing gloss in offset printing for cold setting, and is therefore suitable for offset printing for cold setting. In particular, by using it for offset printing for cold sets using a rotary press, it is possible to efficiently produce a large amount of high-quality printed matter at high speed. Therefore, the coated paper of the present invention is suitable for applications in which printing with cold set ink is used, and is useful as, for example, newspaper paper, book paper, comic paper, textbook paper, and the like. Further, since the coated paper of the present invention has good ink drying property, it can also be used in an on-demand printing method such as inkjet, which requires ink drying property and color development property.

[Example 1]
As base paper, NBKP30 wt%, LBKP23 wt%, 27 wt% deinked pulp, and paper making to prepare a paper stock containing 12 wt% precipitated calcium carbonate as GP20 wt% filler, density of 0.56 g / cm ^3, a basis A base paper 2 having an amount of 54 g / m ^{2 was prepared.} Heavy calcium carbonate as a pigment (manufactured by Fimatec Limited, trade name: FMT97, proportion of particles having a particle size of 2 μm or less by the precipitation method: 97%, D50 = 0.64 μm) 82 parts by weight (solid content) and second grade 18 parts by weight (solid content) of clay (manufactured by IMERYS, trade name: KCS, D50 = 4.9 μm) was used, and 5 parts by weight of styrene-butadiene copolymer latex and 7.5 parts by weight of oxidized starch were used as an adhesive. Parts were blended, and water was further added to obtain a coating liquid 1 having a solid content concentration of 55% by weight. The pigment coating liquid was applied to one side of the base paper with a blade coater so that the dry coating amount was 5.5 g / m ² (target coating amount), and then dried to obtain a coated paper. .. The coated paper was evaluated by the method described later.

[Example 2]
A coated paper was obtained and evaluated by the same method as in Example 1 except that the coating amount was changed as shown in Table 3.

[Example 3]
A coating liquid 2 was obtained in the same manner as the coating liquid 1 except that 100 parts by weight (solid content) of a secondary clay (manufactured by IMERYS, trade name: KCS, D50 = 4.9 μm) was used as the pigment. A coated paper was obtained and evaluated by the same method as in Example 1 except that the coating liquid 1 was changed to the coating liquid 2.

[Comparative Examples 1 and 2]
A coated paper was obtained and evaluated by the same method as in Example 1 except that the target coating amount was changed to 4.0 g / m ² and 3.0 g / m ^{2, respectively.}

[Comparative Examples 3 and 4]
The base paper 2 was subjected to calendar processing at a linear pressure of 20 kg to obtain a base paper 1, and coated paper was obtained and evaluated by the same methods as in Example 2 and Comparative Example 1 except that this was used.

[Comparative Example 5]
The coated paper obtained in Comparative Example 3 was subjected to calendar treatment at a linear pressure of 60 kg, and the coated paper was obtained and evaluated by the same method as in Comparative Example 3.

As shown in Table 3, it is clear that the coated paper of the present invention has excellent ink drying property, ink inking and printing gloss in offset printing for cold setting.

The details of the evaluation method will be described below.
(1) Blank paper glossiness Measured based on JIS P8142.
(2) Basis weight The measurement was performed in accordance with the "basis weight measuring method" described in JIS P8124.
(3) Paper Thickness and Density Measured in accordance with "Paper and Paperboard-Thickness and Density Test Method" described in JIS 8118.
(4) Oken type smoothness Measured based on JIS P8155.
(5) Whiteness ISO whiteness measurement method: Measured with a color difference meter CMS-35SPX manufactured by Murakami Color Co., Ltd. using a light source containing ultraviolet light in accordance with JIS P8148.
(6) Ink drying property Offset printing for cold set (Media Shine ink manufactured by DIC Graphics Co., Ltd.) is performed with a manual RI printing machine (manufactured by Ming Seisakusho Co., Ltd.), and the printed matter one minute after printing is coated. It was transferred to paper, and the degree of stain on the coated paper was evaluated visually and numerically. For the numerical evaluation, X-Rite (manufactured by X-Rite Co., Ltd.) was used, and the Y value difference (blank paper-ink transfer part) was evaluated.
A: There is little ink transfer and excellent drying properties.
B: There is some ink transfer, but there is no problem in use.
C: The ink is not dry and cannot be used.
(7) Ink Ink Density With respect to the sample printed in (6) above, the print density 1 hour after printing was measured using X-Rite (manufactured by X-Rite).
A: It is over 1.50 and the ink penetration is good.
B: 1.40 to 1.50, and ink inking is slightly good.
C: Less than 1.40 and poor ink inking.
(8) Print Gloss The print gloss of the sample printed in (6) above was measured based on JIS P-8142 after being left for one day in an environment of 23 ° C. and 50% relative humidity after printing. The print glossiness corresponds to 75 ° glossiness when solid printing is performed using cold set newspaper ink so that the print density is 1.6.
A: It is over 35% and the print gloss is quite good.
B: 30 to 35%, and the print gloss is slightly good.
C: Less than 30% and poor print gloss.

Claims (7)

A coated paper with a pigment coating layer on the base paper.
The coating amount of the pigment coating layer is 5.0 g / m ² or more per side, and
Oken type smoothness is 65 seconds or less,
Coated paper with ISO whiteness of 70% or more. The coated paper according to claim 1, wherein the total amount of calcium carbonate and clay is 80 parts by weight or more per 100 parts by weight of the pigment in the pigment coating layer. The coated paper according to claim 1 or 2, wherein the 75 ° glossiness when solid printing is performed using cold set newspaper ink so that the printing density is 1.6 is 30% or more. The coated paper according to any one of claims 1 to 3, wherein the coating amount is 8.0 g / m ^{2 or less per side.} The coated paper according to any one of claims 1 to 4, wherein the coated paper has a basis weight of 45 to 75 g / m ^2. The coated paper according to any one of claims 1 to 5, wherein the density of the coated paper is 0.5 to 1.0 g / cm ^3. The production of the coated paper according to any one of claims 1 to 6, further comprising a step of providing a pigment coating layer of ^{5.0 g / m 2} or more per side on a base paper having a smoothness of 20 seconds or less. Method.