JP6867750B2 - Manufacturing method of coated paper for printing and coated paper for printing - Google Patents

Description

The present invention relates to a coated paper for printing that can be used as a coated paper for offset printing and the like, and a method for producing the same.

From the viewpoint of printability, the coated paper for printing is required to have high whiteness, high opacity, and the like. Therefore, Patent Document 1 proposes that the coated paper for offset printing has a high content of deinked pulp of 50% or more, and the coating layer contains a purple pigment, a blue pigment, and heavy calcium carbonate. .. The document states that this makes it possible to obtain printing paper having both high white and high opacity physical characteristics.

However, when the deinked pulp has a high content of 50% by mass or more, there arises a problem that the brightness, which is one of the printability, becomes low.

The document also proposes that the base paper contains a blue dye, a purple dye, or a red dye as a more preferable printing paper. However, the dye is chemically unstable. Therefore, according to this proposal, there arises a problem of fading due to deterioration over time, that is, a problem of fluctuation in brightness and the like.

Japanese Patent No. 5686984

A main problem to be solved by the present invention is to provide a printing coated paper and a method for producing a printing coated paper, which have high whiteness and high opacity but do not have a risk of low brightness.

The present inventors have made diligent studies to solve the above problems. As a result, even if the base paper has a natural color, the coating layer is brewed (colored) by containing both a purple pigment and a blue pigment and a fluorescent whitening agent to achieve high whiteness and high opacity. However, it has been found that a coated paper for printing can be obtained, which does not have a possibility of lowering the lightness and preferably does not cause a problem of fading. The mode for solving the above-mentioned problems based on this finding is as follows.

(Aspect described in claim 1)
It is a coated paper having a base paper and a coating layer.
The hue of JIS P 8150 of the base paper is a ^* value of 0.1 or more and less than 0.7, and b ^* value of −0.2 or more and less than 0.6 in the measurement including ultraviolet rays.
The coating layer contains both a purple pigment and a blue pigment, as well as a fluorescent whitening agent.
The opacity of JIS P 8149 of the coated paper is 85% or more, and the brightness of JIS P 8150 is 85% or more in the measurement including ultraviolet rays.
The hue of JIS P 8150 of coated paper, less than a ^* value of 0.5 to 2.5 in the measurement containing the ultraviolet, b ^* values -5 or less than -2 der is,
Deinked pulp is used as the raw material pulp of the base paper in an amount of 30 to 45% by mass of the total raw material pulp on an absolute dry basis, and the ash content measured in accordance with JIS P 8251 (525 ° C.) of the base paper is 3.0. By setting it to ~ 9.5%, the opacity of the coated paper is set to 85% or more.
Coated paper for printing, which is characterized by this.

(Aspect according to claim 2)
The coating layer contains a white pigment and
The total content of the purple pigment and the blue pigment in the coating layer with respect to 100 parts by mass of the white pigment is 0.001 to 0.005 parts by mass in terms of solid content.
More than 70% by mass of the white pigment is calcium carbonate.
The coated paper for printing according to claim 1.
(Aspect according to claim 3)
The calcium carbonate is a light calcium carbonate,
The coated paper for printing according to claim 2.

(Aspect according to claim 4)
The content of the fluorescent whitening agent is 10 to 80 mg / m ² .
The amount of the fluorescent whitening agent in the coating layer is 0.05 to 0.8 parts by mass with respect to 100 parts by mass of the white pigment.
The coated paper for printing according to claim 2 or 3.

(Aspect according to claim 5)
The brightness of JIS P 8150 of the base paper is 75% or more in the measurement including ultraviolet rays, and the brightness of the coated paper is 85% or more.
The coated paper for printing according to any one of claims 1 to 4.

(Aspects according to claim 6)
An inorganic pigment having a particle size of 0.2 to 0.4 μm is used as the purple pigment and the blue pigment, and the total content of the purple pigment and the blue pigment is 0.1 to 1.4 mg / m ² . ,
The coated paper for printing according to any one of claims 1 to 5.

(Aspect according to claim 7)
JIS P 8150 is coated on one or both sides of the base paper with ^{a *} value of 0.1 or more and less than 0.7 and b ^* value of -0.2 or more and less than 0.6 in the measurement including ultraviolet rays by the film transfer method. It is a method of forming a working layer to manufacture coated paper.
The coating layer contains both a purple pigment and a blue pigment, and a fluorescent whitening agent.
The opacity of JIS P 8149 of the coated paper was set to 85% or more, and the brightness of JIS P 8150 was set to 85% or more in the measurement including ultraviolet rays.
Wherein the hue of JIS P 8150 of coated paper, and the measurements including ultraviolet a ^* value of 0.5 to 2.5, less less than b ^* values -5 to -2,
Deinked pulp is used as the raw material pulp of the base paper in an amount of 30 to 45% by mass of the total raw material pulp on an absolute dry basis, and the ash content measured in accordance with JIS P 8251 (525 ° C.) of the base paper is 3.0. By setting it to ~ 9.5%, the opacity of the coated paper is set to 85% or more.
A method for manufacturing coated paper for printing, which is characterized in that.

According to the present invention, it is a method for producing a coated coated paper for printing and a coated coated paper for printing, which have high whiteness and high opacity but do not have a possibility of lowering the brightness.

It is sectional drawing of the coated paper for printing of this embodiment. It is a figure which shows the change of the hue when the violet pigment and the blue pigment are contained.

Next, a mode for carrying out the present invention will be described. The present invention is not limited to the following embodiments. Various modifications can be made without departing from the gist of the present invention.
As shown in FIG. 1, the printing coated paper 1 of this embodiment is formed on the base paper 2 and one side ((1)) or both sides ((2) of FIG. 1) of the base paper 2. It has a coating layer 4. However, this is an example, and for example, another layer such as an undercoat coating layer may exist under the coating layer 4, that is, between the coating layer 4 and the base paper 2. For reference, the form in which the undercoat coating layer 3 is formed on one side of the base paper 2 in (3) of FIG. 1 and the undercoat coating layer 3 is formed on both sides of the base paper 2 in (4) of FIG. Shows the form.

The coating layer 4 contains a purple pigment, a blue pigment, and a fluorescent whitening agent. Hereinafter, a detailed description will be given.

(Base paper)
The base paper 2 is mainly composed of raw material pulp and filler.

The base paper 2 may have a single layer or a plurality of layers.

(Raw material pulp)
Examples of raw material pulp include broadleaf kraft pulp (LBKP), coniferous kraft pulp (NBKP), chemical pulp such as sulfite pulp, crushed wood pulp (GP), refiner crushed wood pulp (RGP), thermomechanical pulp (TMP), and chemithermo. Mechanical pulp (CTMP), chemigrand pulp (CGP), semi-chemical pulp (SCP), and the like can be used.

Chemical pulp has high whiteness because lignin is removed. On the other hand, there is a problem that the opacity of the produced paper becomes low. This problem is particularly noticeable in the case of low basis weight coated paper.

Therefore, in this embodiment, it is essential to use deinked pulp (DIP) as the raw material pulp of the base paper 2. The blending amount of the deinked pulp is preferably 30% by mass or more and 45% by mass or less, more preferably 32% by mass or more and 43% by mass or less, and particularly preferably 35% by mass or more and 40% by mass or less, based on absolute dryness. It is as follows. If the amount of deinked pulp is less than the above range, the opacity may not be sufficiently high. On the other hand, if the blending amount of the deinked pulp exceeds the above range, the whiteness and lightness may not be sufficiently increased even by adjusting with a coloring material or the like.

The coloring material refers to a colored pigment or dye other than white. Further, the mass of the deinked pulp includes not only the mass of the deinked pulp itself but also the mass of an inseparable filler or the like adhering to the deinked pulp.

Examples of the raw material for the deinked pulp include selected recycled paper made of high-quality paper, medium-quality paper, low-grade paper, newspaper, leaflets, magazines, and the like, unsorted used paper made by mixing these used papers, and the like.

(Filling fee)
Examples of the filler include heavy calcium carbonate, light calcium carbonate, clay, silica, light calcium carbonate-silica complex, kaolin, calcined kaolin, derami kaolin, white carbon, talc, magnesium carbonate, barium carbonate, barium sulfate, and water. Inorganic fillers such as aluminum oxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, zinc oxide, titanium oxide, and amorphous silica, and organic fillers such as urea-formalin resin, melamine resin, polystyrene resin, and phenol resin. Etc. can be used.

However, from the viewpoint of improving opacity, it is preferable to use heavy calcium carbonate or light calcium carbonate. Further, from the viewpoint of improving whiteness, lightness and opacity, it is preferable to use light calcium carbonate. Further, as the light calcium carbonate, it is preferable to use a light calcium carbonate coated with an inorganic substance such as silica or aluminum, or an agglomerate in which light calcium carbonate is aggregated. Of course, these light calcium carbonates can also be used in combination as appropriate.

(Color material)
A purple pigment or a blue pigment may be internally added to the base paper 2 as a filler.

The base paper 2 may contain a purple dye, a blue dye, a yellow dye, a green dye, a red dye, and the like. Since the dye is dyed on the fiber, the coloring efficiency is good. The dye may be discolored, but if it is contained in the base paper 2, at least the coating layer 4 is present on the base paper 2, so that the effect on the appearance is small.

It is preferable that the purple pigment and the blue pigment are internally added so that the base paper 2 has a natural color. Specifically, in the measurement in which the hue of JIS P 8150 of the base paper 2 contains ultraviolet rays, the a ^* value is preferably 0.1 or more and less than 0.7, and the b ^* value is −0.2 or more and less than 0.6, more preferably. a ^* value 0.2 or more and less than 0.6, b ^* value -0.1 or more and less than 0.5, particularly preferably a ^* value 0.25 or more and less than 0.55, b ^* value -0.05 or more 0 It is less than .45. By adjusting in this way, the whiteness and lightness of the base paper 2 itself can be improved, and the whiteness and lightness after the coating layer 4 is formed can be improved.

The brightness of JIS P 8150 of the base paper 2 is preferably 75% or more, more preferably 78% or more, and particularly preferably 80% or more in the measurement including ultraviolet rays.

(Additive)
Additives can be added to the base paper 2 if necessary.

Examples of the additive include a coagulant, a defoaming agent, a fluorescent whitening agent, a sulfate band, a yield improver, a drainage improver, a paper strength enhancer, a sizing agent, and a dye.

(Undercoat coating layer)
As described above, the undercoat coating layer (clear coating layer) 3 can be provided on one side or both sides of the base paper 2.

As the raw material of the undercoat coating layer 3, for example, a natural polymer type, a synthetic polymer type, or the like can be used.

Examples of natural polymer systems include enzymatically decomposed starch, oxidized starch, hydroxyethylated starch, cationized starch, urea phosphorylated starch, and modified starch obtained by modifying raw starch such as corn, wheat, tapioca, and potato by various manufacturing methods. One or more of them can be selected and used from oxidized starch, carboxymethylated cellulose (CMC), carboxyethylated cellulose (CEC), and the like.

As the synthetic polymer system, for example, one or more of polyacrylamide (PAM), polyethylene glycol (PEG), and the like can be selected and used.

Additives such as a defoaming agent, a fluorescent whitening agent, a water resistant agent, and a sizing agent can be internally added to the undercoat coating layer 3.

The coating amount of the undercoat coating layer 3 is preferably 0.1 to 1.0 g / m ² , more preferably 0.2 to 0.8 g / m ² , and particularly preferably 0.3 to 0. Per surface. It is 6 g / m ² .

The coating amount of the undercoat coating layer 3 can be formed by using, for example, a coater such as a size press coater, a gate roll coater, a rod metering coater, a billed coater, or a blade coater.

It is also conceivable that the undercoat coating layer 3 is colored by blending a pigment or a dye. However, since the whiteness and lightness of the base paper 2 are lowered when the undercoat coating layer 3 is colored, it is preferable not to color the undercoat coating layer 3.

(Coating layer)
The coating layer 4 mainly contains a purple pigment and a blue pigment as a coloring material, a fluorescent whitening agent, and an adhesive.

The coating layer 4 may be a single layer or a plurality of layers.

When the coating layer 4 is a plurality of layers, the purple pigment, the blue pigment, and the fluorescent whitening agent may be contained in at least one of the layers. However, from the viewpoint of enhancing whiteness, brightness, opacity, and printability (strikeout, sharpness, etc.), it is preferable to contain a purple pigment, a blue pigment, and a fluorescent whitening agent in at least the outermost layer. ..

(Purple pigment and blue pigment)
Hereinafter, the reasons for using the purple pigment, the blue pigment, and the fluorescent whitening agent will be described.
In order to make the coated paper look white, there is a technique called brewing (coloring) in which purple pigment and blue pigment are added to balance the reflected light of the coated paper as a whole. Since the purple pigment and the blue pigment absorb the light of the long wavelength portion (about 500 to 700 nm) in the visible light, that is, the light of the yellow portion, the bluish tint which is the residual color is conspicuous. However, since the amount of reflected light is reduced by the amount of the absorbed light, the brightness of the coated paper is lowered, and the lightness becomes gray or close to black.

Therefore, in this embodiment, a purple pigment, a blue pigment, and a fluorescent whitening agent are used. According to this form, it is considered that the fluorescent whitening agent changes ultraviolet rays (wavelength is about 300 to 400 nm) into blue light (wavelength is about 450 nm) which is visible light. Therefore, even when the purple pigment and the blue pigment are used, a high visual brightness can be obtained.

Further, by containing the purple pigment and the blue pigment as the coloring materials, the opacity of the coated paper 1 is improved and the strike-through of the ink is prevented.

As the purple pigment and the blue pigment, either an inorganic pigment or an organic pigment can be used. However, since the obtained coated paper 1 has excellent hiding power and has excellent physicochemical stability such as light resistance, it is recommended to use an inorganic pigment as the purple pigment and the blue pigment. preferable.

Further, as the inorganic pigment, it is more preferable to use a pigment having a particle size of 0.2 to 0.4 μm. Basically, it is considered that the smaller the particle size, the higher the hiding property, but if the particle size becomes too small, the hiding property is considered to be lower.

The particle size means the volume average particle size measured by the laser analysis method. The laser analysis method is a particle size distribution measuring device (laser type microtrack particle size analyzer) for a dispersion solution in which 10 mg of a sample is added to 8 ml of a methanol solution and dispersed with an ultrasonic disperser (output: 80 W) for 3 minutes. , Manufactured by Nikkiso Co., Ltd.).

Examples of the purple pigment include cobalt violet such as cobalt arsenate, cobalt phosphate, cobalt / lithium / phosphor oxide, hydrous ammonium cobalt phosphate, and cobalt borate, and inorganic pigments such as purple ultramarine, iron oxide purple, manganese violet, and mineral violet. Indigoid-based, quinacridone-based, oxazine-based, anthraquinone-based, carbonium-based, xanthene-based organic pigments and the like can be used. As the commercially available purple pigment, for example, SA Violet C12896 (Mikuni Color Co., Ltd.) or the like can be used.

Examples of blue pigments include ultramarine, azurite, prussian blue (dark blue), ultramarine, smalto, cobalt blue (cobalt aluminate), cerulean blue (cobalt tinate), cobalt chromium blue, cobalt-aluminum-silicon oxide, etc. Cobalt / zinc / silicon oxide, manganese blue, phthalocyanine, etc. can be used. As the commercially available blue pigment, for example, EMT-Blue DS-18 (Toyo Ink Mfg. Co., Ltd.) and the like can be used.

The total content of the purple pigment and the blue pigment in the coating layer 4 is preferably 0.1 to 1.4 mg / m ² , more preferably 0.2 to 0.6 mg / m ² , and particularly preferably 0.3 to 0.3. It is 0.45 mg / m ² . If the total content is less than the above range, the light absorption by the pigment may be insufficient and the opacity may not be high. On the other hand, if the total content exceeds the above range, the hue may deviate significantly from the origin (see FIG. 2), and the apparent whiteness may be lost.

The total content of the purple pigment and the blue pigment in the coating layer 3 is preferably 0.001 to 0.005 parts by mass, more preferably 0.0015, with respect to 100 parts by mass of the white pigment described later in terms of solid content. It is ~ 0.0035 parts by mass, particularly preferably 0.002 to 0.003 parts by mass. If the total content is less than the above range, the opacity of the coated paper 1 becomes insufficient, and the desired hue may not be obtained. On the other hand, if the total content exceeds the above range, the brightness of the coated paper 1 may be insufficient.

The total content is a value calculated by the following formula.
Total content of purple pigment and blue pigment (mg / m ² ) = (total coating amount (g / m ² ) x total mass part (mass part) of purple pigment and blue pigment / total solid content in coating liquid Mass part (mass part)) x 1000
The mass part is a value when converted to solid content.

(Other pigments)
If necessary, the coloring material may contain pigments other than purple pigments and blue pigments, for example, pigments such as red pigments, yellow pigments, and green pigments. It is not preferable to include a black pigment as a coloring material. When the black pigment is contained, the brightness of the coating layer 4 is lowered, and the coated paper 1 may not have the desired brightness and the sharpness after printing.

(Optical brightener)
By including the fluorescent whitening agent in the coating layer 4, the coating layer 4 can be colored and the brightness can be improved.

As the fluorescent whitening agent, for example, a stillbenzene-based, benzimidazole-based, imidazole-based, imidazolone-based, virazolin-based, coumarin-based, naphthalimide-based fluorescent whitening agent and the like can be used. As the commercially available fluorescent whitening agent, for example, Kayahole SIM (L) (manufactured by Nippon Kayaku Co., Ltd.) can be used.

However, as the fluorescent whitening agent, a stillbenzene-based stillbenzylsulfonic acid derivative is preferably used, and more preferably, a tetra-type one in which four sulfo groups are derived is used. At the time of papermaking of coated paper 1, usually, waste paper or the like at the time of papermaking is blended as a circulating raw material. Therefore, by using a tetra-type fluorescent whitening agent, it is possible to suppress excessive coloring of the base paper 2 and fading of lightness.

The total content of the fluorescent whitening agent in the coating layer 4 is preferably 10 to 80 mg / m ² , more preferably 15 to 70 mg / m ² , and particularly preferably 20 to 45 mg / m ² . If the total content is less than the above range, the desired brightness and hue of the coated paper may not be obtained. On the other hand, if the total content exceeds the above range, the color of the fluorescent whitening agent itself may appear, the brightness may decrease, and the effect of fading may become stronger.

The total content of the fluorescent whitening agent in the coating layer 4 is preferably 0.05 to 0.8 parts by mass, more preferably 0.15 to 0.6 parts by mass with respect to 100 parts by mass of the white pigment described later. , Particularly preferably 0.2 to 0.4 parts by mass.

The total content is a value calculated by the following formula.
Total content of fluorescent whitening agent (mg / m ² ) = (total coating amount (g / m ² ) x total mass part (mass part) of fluorescent whitening agent / total solid content mass part in coating liquid (Mass part)) x 1000
The mass part is a value when converted to solid content.

(White pigment)
The coating layer 4 contains a white pigment, if necessary.

The white pigment may be an inorganic pigment or an organic pigment.

Examples of white pigments include kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, light calcium carbonate, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicate, colloidal silica. , Satin white, etc. can be used.

However, from the viewpoint of improving whiteness, it is preferable to use heavy calcium carbonate or light calcium carbonate, and it is particularly preferable to use light calcium carbonate.

The content of the light calcium carbonate is preferably 70% by mass or more, more preferably 72% by mass or more, and particularly preferably 75% by mass or more of the total amount of the white pigment.

(adhesive)
Examples of the adhesive (binder) include styrene / butadiene adhesive, styrene / acrylic adhesive, ethylene / vinyl acetate adhesive, butadiene / methyl methacrylate adhesive, vinyl acetate / butyl acrylate adhesive, and polyvinyl. Alcohol, casein, soybean protein, synthetic protein, oxidized starch, positive starch, urea phosphate esterified starch, carbamate esterified starch, hydroxyethyl etherified starch, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, etc. can be used. ..

The blending amount of the adhesive is preferably 2 to 15 parts by mass, more preferably 3 to 12 parts by mass, and particularly preferably 5 to 11 parts by mass with respect to 100 parts by mass of the white pigment described above in terms of solid content. ..

(Other)
The coating layer 4 can contain various auxiliary agents such as a dispersant, a thickener, a water retention agent, a defoaming agent, and a water resistant agent, if necessary.

The coating layer 4 can be formed by using, for example, a coater such as a size press coater, a gate roll coater, a rod metering coater, a billed coater, or a blade coater. However, when the coating layer 4 is a single layer, especially when the ^{coating paper 1 is a finely coated paper having a basis weight of 60 g / m 2} or less, a film transfer using a gate roll coater, a rod metering coater, or the like is used. It is preferable to form the coating layer 4 by the method. In the case of finely coated paper, if it is formed by the film transfer method, it can be applied efficiently even with a low coating amount such that ^{the coating amount is 5.0 to 8.0 g / m 2 per side.} Can be done (improvement of operability). Further, when light calcium carbonate is used as the white pigment in the coating layer 4, the particle size distribution of the particle size is sharper than that of heavy calcium carbonate, so that the viscosity of the high share of the coating liquid becomes high and the fluidity becomes high. Tends to get worse. However, with the film transfer coating method, coating can be performed even with a coating amount of ^{5.0 to 8.0 g / m 2.}

The coating amount of the coating layer 4 is preferably 5.0 to 8.0 g / m ² , more preferably 5.2 to 7.5 g / m ² , and particularly preferably 5.5 to 7.0 g per one side. / M ² . If the amount of coating is less than the above range, the ratio of the coating layer 4 to the entire coating paper 1 is small, and there is a possibility that the desired brightness and hue cannot be obtained. On the other hand, if the coating amount exceeds the above range, the ratio of the base paper 2 to the entire coated paper 1 is small, and the desired opacity may not be obtained.

(Coated paper for printing)
(Basis weight)
The basis weight of the coated paper 1 is preferably 40 to 60 g / m ^2, more preferably 42~59g / m ^2, particularly preferably 45~58g / m ^2. In the case of finely coated paper, especially when the basis weight is 60 g / m ² or less, the effect of the present invention is fully exhibited. However, if the basis weight is less ^{than 40 g / m 2} , the opacity may be insufficient.

(Opacity)
The opacity of the coated paper 1 is a value measured in accordance with JIS P 8149.

The opacity is preferably 85% or more, more preferably 86% or more, and particularly preferably 87% or more. In order to set the opacity within the above range, for example, the amount of deinked pulp (DIP) and ash content of the base paper 2 can be adjusted, the coloring of the coating layer 4 can be adjusted, and the like.

The ash content of the base paper 2 is preferably a value measured in accordance with JIS P 8251 (525 ° C.) in consideration of opacity, lightness, stiffness of coated paper, and the like. It is 3.0 to 9.5%, more preferably 4.0 to 9.3%, and particularly preferably 5.0 to 9.0%.

(brightness)
The brightness of the coated paper 1 is a value measured in accordance with JIS P 8150 so as to include ultraviolet rays.

The brightness of the coated paper 1 is preferably 85% or more, more preferably 86% or more, and particularly preferably 87% or more. In order to set the brightness within the above range, for example, the amount of deinked pulp (DIP) and ash content of the base paper 2 can be adjusted, the coloring of the coating layer 4 can be adjusted, and the like.

(Hue)
The hue of the coated paper 1 is a value measured so as to include ultraviolet rays in accordance with JIS P 8150.

In this hue, the a ^* value is preferably 0.5 or more and less than 2.5, more preferably 0.6 or more and less than 2.0, and particularly preferably 0.7 or more and less than 1.8. The b ^* value is preferably −5 or more and less than -2, more preferably -4.8 or more and less than -2.5, and particularly preferably -4.6 or more and less than -2.8. When the hue (a ^* value and b ^* value) is in the above range, the surface of the printing coated paper 1 becomes pale and the whiteness of appearance stands out.

The hue (a ^* value and b ^* value) can be controlled by adding a violet pigment and a blue pigment.
FIG. 2 shows the L ^* a ^* b ^* system chromaticity coordinates. ^{L * in} the figure represents the degree of black and white in terms of brightness. a ^* increases the degree of redness when + (plus) and the degree of greenness when- (minus). b ^* increases the degree of yellowness when + (plus) and the degree of bluishness when-(minus). When the purple pigment and the blue pigment are not added at the origin, when the blue pigment is added, the hue of b * changes toward − (minus) and a * also changes toward − (minus). When a purple pigment is added, the hue of b * changes toward − (minus) and a * changes toward + (plus).

Next, examples of the present invention will be described. The present invention is not limited to the following examples. Various modifications can be made without departing from the gist of the present invention.
(Example 1)
Hardwood kraft pulp (LBKP), softwood kraft pulp (NBKP), and deinked pulp (DIP) were used as raw material pulps to obtain pulp slurries. The blending ratio of each raw material pulp was as shown in the table below. Light calcium carbonate (Tamapearl TP121-6S (manufactured by Okutama Kogyo Co., Ltd.) and Tamapearl \ TAMAPEARL are registered trademarks), a coagulant, a retention agent, and a paper strength enhancer were added to the pulp slurry.

The obtained pulp slurry was paper-made with a gap former to obtain a base paper.

Oxidized starch was primed on the obtained base paper. The coating amount was 0.8 g / m ^{2 on} both sides.

On the other hand, an adhesive, a coloring material, a white pigment, and a fluorescent whitening agent were mixed to obtain a coating liquid.

As the adhesive, SB latex (PB2901 (manufactured by Nippon A & L Inc.)) and starch (RC # 20 (manufactured by Nippon A & L Inc.)) were used. As the coloring material, a purple pigment (SA Violet BOX (manufactured by Mikuni Color Co., Ltd.)) and a blue pigment (SA Blue 12422 (manufactured by Mikuni Color Co., Ltd.)) were used. As the white pigment, heavy calcium carbonate (Carbital 90 (manufactured by Imerys Minerals Japan), CARBITAL is a registered trademark) and clay (KAOFINE (manufactured by Shiraishi Calcium)) were used. As the fluorescent whitening agent, (ZDMV (L) (manufactured by Blancophore)) was used. The mixing ratios of these various materials are as shown in the table below.

Using the obtained coating liquid, coating layers were formed on both sides of the base paper (undercoat coating layer). This formation was carried out by a film transfer method. The coating amount of the coating layer was as shown in the table below.

The basis weight, opacity, lightness, and hue of the obtained coated paper were examined. The results are shown in the table below.

Subsequently, indigo, red, and yellow solid printing was performed on the obtained coated paper with an offset rotary printing machine, and the three-color crossing portion was printed with a Macbeth reflection densitometer RD-918 (manufactured by Colmogen Corporation, USA). , The three-color crossing portion was measured. Printing was performed so that the ink density was 2.0. The coated paper (printed matter) after printing was sensory evaluated for strike-through and sharpness. The results are shown in the table below. The evaluation criteria for sensory evaluation were as follows.

(Breakthrough)
The printed matter was viewed through the back side of the printed surface under an indoor fluorescent lamp, and evaluated in the following four stages.
◎: When there is no set-off (set-through) 〇: When there is a slight set-off, but it is hardly noticeable and there is no problem in practical use △: There is some set-off, and it is somewhat difficult to put it into practical use. Case ×: When the set-off is severe and it is not practical at all

(Clarity)
An arbitrary number of 30 people observes the boundary between the printed part and the blank part of the printed matter under an indoor fluorescent lamp and evaluates it on a 5-point scale (5: The boundary between the printed part and the blank part of the printed matter is clearly visible, and the blank part Clear bright white> 1: The boundary between the printed part and the blank part of the printed matter looked blurry, and the blank part was stagnant and dark white). The obtained evaluation values were averaged and classified into the following four stages.
⊚: When the average value is 4.0 or more. It can be said that it is suitable as printing paper.
〇: When the average value is 3.5 or more. It can be said that there is no problem in using it as printing paper.
Δ: When the average value is 3.0 or more. It can be said that there is some difficulty in putting it to practical use as printing paper.
X: When the average value is less than 3.0. It can be said that it is not suitable as printing paper.

(Other Examples and Comparative Examples)
The same test as in Example 1 was carried out by changing the raw material and the mixing ratio of the coated paper as shown in the table below. The results are shown in the table below.

As the black pigment, SA Black 5207 (manufactured by Mikuni Color Co., Ltd.) was used. As the light calcium carbonate, Tamapearl TP-121-7C (manufactured by Okutama Kogyo Co., Ltd., Tamapearl \ TAMAPEARL is a registered trademark) was used.

(Discussion)
From the comparison between Examples and Comparative Examples 1 to 3, it was found that the lack of even one of the blue pigment, the purple pigment, and the fluorescent whitening agent results in insufficient opacity, lightness, or sensory evaluation.

Further, from the comparison between Examples and Comparative Examples 4 and 5, even if a blue pigment, a purple pigment, and a fluorescent whitening agent are used, the sensory evaluation is insufficient unless the opacity, lightness, and hue are controlled. It turned out to be.

The present invention is applicable as a printing coated paper that can be used as an offset printing coated paper and the like, and a method for producing the same.

1 ... Coated paper, 2 ... Base paper, 3 ... Undercoat coating layer, 4 ... Coating layer.

Claims (7)

It is a coated paper having a base paper and a coating layer.
The hue of JIS P 8150 of the base paper is a ^* value of 0.1 or more and less than 0.7, and b ^* value of −0.2 or more and less than 0.6 in the measurement including ultraviolet rays.
The coating layer contains both a purple pigment and a blue pigment, as well as a fluorescent whitening agent.
The opacity of JIS P 8149 of the coated paper is 85% or more, and the brightness of JIS P 8150 is 85% or more in the measurement including ultraviolet rays.
The hue of JIS P 8150 of coated paper, less than a ^* value of 0.5 to 2.5 in the measurement containing the ultraviolet, b ^* values -5 or less than -2 der is,
Deinked pulp is used as the raw material pulp of the base paper in an amount of 30 to 45% by mass of the total raw material pulp on an absolute dry basis, and the ash content measured in accordance with JIS P 8251 (525 ° C.) of the base paper is 3.0. By setting it to ~ 9.5%, the opacity of the coated paper is set to 85% or more.
Coated paper for printing, which is characterized by this. The coating layer contains a white pigment and
The total content of the purple pigment and the blue pigment in the coating layer with respect to 100 parts by mass of the white pigment is 0.001 to 0.005 parts by mass in terms of solid content.
More than 70% by mass of the white pigment is calcium carbonate.
The coated paper for printing according to claim 1. The calcium carbonate is a light calcium carbonate,
The coated paper for printing according to claim 2. The content of the fluorescent whitening agent is 10 to 80 mg / m ² .
The amount of the fluorescent whitening agent in the coating layer is 0.05 to 0.8 parts by mass with respect to 100 parts by mass of the white pigment.
The coated paper for printing according to claim 2 or 3. The brightness of JIS P 8150 of the base paper is 75% or more in the measurement including ultraviolet rays, and the brightness of the coated paper is 85% or more.
The coated paper for printing according to any one of claims 1 to 4. An inorganic pigment having a particle size of 0.2 to 0.4 μm is used as the purple pigment and the blue pigment, and the total content of the purple pigment and the blue pigment is 0.1 to 1.4 mg / m ² . ,
The coated paper for printing according to any one of claims 1 to 5. JIS P 8150 is coated on one or both sides of the base paper with ^{a *} value of 0.1 or more and less than 0.7 and b ^* value of -0.2 or more and less than 0.6 in the measurement including ultraviolet rays by the film transfer method. It is a method of forming a working layer to manufacture coated paper.
The coating layer contains both a purple pigment and a blue pigment, and a fluorescent whitening agent.
The opacity of JIS P 8149 of the coated paper was set to 85% or more, and the brightness of JIS P 8150 was set to 85% or more in the measurement including ultraviolet rays.
Wherein the hue of JIS P 8150 of coated paper, and the measurements including ultraviolet a ^* value of 0.5 to 2.5, less less than b ^* values -5 to -2,
Deinked pulp is used as the raw material pulp of the base paper in an amount of 30 to 45% by mass of the total raw material pulp on an absolute dry basis, and the ash content measured in accordance with JIS P 8251 (525 ° C.) of the base paper is 3.0. By setting it to ~ 9.5%, the opacity of the coated paper is set to 85% or more.
A method for manufacturing coated paper for printing, which is characterized in that.

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