JP2645575B2 - Coated paper for printing - Google Patents

Description

The present invention relates to coated paper for printing, in particular, opacity, whiteness,
The present invention relates to a coated paper for printing which has excellent rigidity and excellent white paper gloss and print gloss.

B) Conventional Techniques and Problems In recent years, there has been an increasing demand for coated paper for printing to reduce the weight of coated paper and visualize printed matter. In printing, the speed has been increased, and coated papers that can withstand the speed have been required.

On the other hand, how to increase production efficiency is the most important issue from the standpoint of coated paper production. Under these circumstances, opacity and rigidity are particularly noteworthy qualities in response to weight reduction of coated paper. Rigidity is important from the viewpoint of high-speed printing.

From the viewpoint of visualization of printed matter, it is important to have whiteness, smoothness and high gloss in addition to opacity. There are several known techniques for obtaining high opacity. For example, mechanical pulp is selected as the pulp to be used, or a high filling factor is added to the base paper. For example, a gloss calendar is used.

Further, from the viewpoint of whiteness, it is necessary to use a large amount of raw materials having high whiteness, and with regard to rigidity, measures other than high ash base paper and measures common to opacity are effective.

However, if such measures are to be taken when actually producing coated paper, the accompanying drawbacks also appear at the same time, making it difficult to make the intended coated paper a reality.

For example, the quality, opacity, stiffness, gloss, and smoothness of the coated paper obtained by the finishing method differ greatly, but in the case of machine calendering, the web is usually placed between two unheated steel rolls under a high linear pressure. Because of the passage, smoothness is produced but little gloss can be obtained.

The super calender is composed of multiple rolls of steel and elastic material alternately, with a linear pressure of 180-450 kg / cm and a nip pressure of 1
The roll temperature is usually 40 to 300 kg / cm ² and the roll temperature is usually 30 to 80 ° C.

For this reason, the coated paper obtained has high gloss and smoothness, but is inevitably crushed and disadvantageous for obtaining high opacity and stiffness. Another finishing method is gloss calendering, which uses heated finishing rolls to increase the nip transit time without finishing at high linear pressures as in super calendering, which results in higher coating paper or coated paperboard. Causes gloss.

The linear pressure of the device is 90-180kg / cm, nip pressure 70-140kg / c
m ² , a temperature of 100 to 150 ° C. is particularly high, and about 230 ° C. is a usual production condition. This relatively low linear pressure finish results in relatively good opacity because it does not significantly densify the paper, while the relatively high temperature softens the coating and allows for gloss enhancement. However, this finishing effect is limited to the top surface of the web.

Therefore, the surface of this coated paper does not have the smoothness obtained by a speed calender, and it is generally difficult to obtain high quality.

Also, as can be seen in Publication No. 63-500188, nip pressure, roll linear pressure, residence time at the nip of the web, etc. are regulated to obtain a quality comparable to a super calender, but even in this case, The preferred nip width is 1.27 to 2.
It is 54 cm, which is much wider than the nip width of the super calender of 0.6 to 1.2 cm, and does not improve the durability of the roll and the contamination of the drum, which are operational problems of using the gloss calender. Another recent finishing method uses a soft calendar. In the soft calender method, a metal roll and an elastic roll are combined and calendering is performed with a small number of nips.

The elastic roll uses a special synthetic resin-coated roll having hardness equal to or higher than that of the super calender, but the key point lies in the material of the roll.
That is, it is necessary to select a special material which is excellent in heat resistance and abrasion resistance under a high nip pressure and is not easily damaged. For this reason, the application of this finishing method is such that a relatively low load is not applied to the roll such as a mat finish.

On the other hand, in order to obtain high opacity in the formulation, for example, when mechanical pulp is used as the pulp, the whiteness is low, and when trying to cope with high ash differentiation of the base paper,
Its stiffness decreases. For this reason, coated paper with excellent opacity, whiteness, rigidity, white gloss, and printed gloss can be realized at low cost and with good operability, and in particular, it cannot be obtained as a lightweight coated paper. That reality has become a major challenge for those who manufacture coated paper.

In view of this situation, the present inventors have conducted intensive studies to develop coated papers having unprecedented high opacity and rigidity, as well as high blank glossiness and print glossiness. Contains certain light calcium carbonate as
Moreover, by applying a special finishing to the coated paper provided with a pigment coating layer on the base paper in which the amount of ash contained is a specific amount, an effect not seen before was found, and the present invention was completed. .

The purpose of the coated paper produced in this way is to obtain an excellent coated paper that is compatible with unconventional coated paper properties.

C) Means for Solving the Problems The present invention relates to calcite-based light calcium carbonate having a filler content in the range of 0.3 to 2.0 μm in terms of the weight of the base paper.
Contains at least 4% by weight and the total ash content of the base paper is 10% by weight
It is the above, more preferably a coated paper for printing characterized in that a pigment coated layer is provided on base paper whose base paper has not been subjected to size press treatment, and after coating, the coated surface is pressed against a soft calender.

Further, the treatment with the soft calender desirably satisfies the following three conditions as pressure bonding conditions to the soft calender having a coating surface nip number of 6 or less.

a: The hardness of the soft calender single roll is 75 or more (Shore D hardness).

b: The index L defined by the following equation satisfies the following condition.

L ≦ 0.002 * However, D _O : Elastic roll outer diameter cm D _B : Rigid roll outer diameter cm D _i : Elastic roll iron core outer diameter cm P _L : Nip linear pressure kg / cm S _D : Elastic roll hardness (Shore D) V: Line processing speed cm / sec K = 3 (D _O −D _i ) · (D _O / D _i ) ^0.5 c: Nip linear pressure must satisfy the following conditions.

100 ≦ P _L ≦ 550 In the present invention, as described above, a specific light calcium carbonate is used, and the light calcium carbonate referred to in the present invention is purified lime and carbon dioxide obtained by calcining limestone. Then, quick lime is dissolved in water to make lime milk, and carbon dioxide gas is blown into the lime milk compounding method, or lime milk or a carbonate solution made by reacting calcium chloride solution with sodium carbonate is synthesized. It refers to precipitated calcium carbonate, and its crystal form (such as calcite or argonite) and size and shape can be adjusted depending on conditions such as a synthesis reaction.

In the case of calcite-based crystals, there are usually spindle-shaped and iga-like and cubic (cubic and dumpling) shapes in which they are cohesively bonded. The aragonite has a shape usually called a rod shape or a needle shape.

The internal filler used in the present invention is light calcium carbonate, and its shape has an average particle size of 0.3 μm or more and 2.0 μm or more.
It is a calcite crystal having the following range. In particular, those having a relatively rounded shape are preferable. Compared with those having the particle shape of the present invention, for example, aragonite-based ones, the rate of inhibiting the inter-fiber bonding is particularly small, so that the strength is less reduced. However, although the improvement rate of opacity is small, the present invention assumes that soft calendering is performed on a coating machine, and the opacity reduction rate due to calendering affects the final opacity. I do.

The light calcium carbonate having the particle shape according to the present invention has a lower opacity reduction ratio due to calender finishing than the other shapes, and the opacity of the final product is high. The reason for this is not clear, but if the reduction in opacity due to calendering is considered to be a reduction in optically effective voids, the optical shape depends on the particle shape of light calcium carbonate, that is, the average particle size, crystal shape, outer shape, etc. This is considered to affect the rate of effective void reduction.

When the average particle size is smaller than 0.3 μm, the paper strength is greatly reduced with respect to the internal addition ratio, and when the average particle size is 2.0 μm or more, the improvement rate of the opacity decreases, which is not preferable.

Further, the blending ratio of the filler containing light calcium carbonate to the base paper must be 10% by weight or more as ash, more preferably in the range of 12 to 20% by weight. When the filler content is less than 10% by weight, sufficient physical properties of the coated paper cannot be obtained by the soft calendering treatment described later, and when the filler content is 20% by weight or more, the strength of the base paper is insufficient for offset printing. The required content of light calcium carbonate in the filler is 40 to 100% of the total ash content, and if it is less than 40%, sufficient opacity cannot be obtained.

In the present invention, the average particle size is defined as an aqueous dispersion of the filler of 5%.
After dispersing with an ultrasonic disperser for one minute, measure with a light transmission type particle size distribution analyzer (SKN type, manufactured by Seishin Enterprise Co., Ltd.)
Is the particle diameter when the particle size reaches 50%, that is, the so-called weight average particle diameter.

The ash value of the present invention is obtained by collecting an arbitrary amount of a sample from 1 to 10 g, drying at 105 ° C. for 1 hour, and measuring the dry weight. Thereafter, the residue was ashed at 500 ° C. for 3 hours, and the absolute dry weight of the residue is a percentage by weight based on the absolute dry weight of the sample.

In the present invention, fillers usually used in papermaking, such as kaolin, clay, heavy calcium carbonate, titanium dioxide, calcined kaolin, and talc for papermaking, can be used in combination.

Also, sizing agents, defoamers, slime control agents, dyes, coloring pigments, optical brighteners, dry paper strength agents, wet paper strength agents,
Additives commonly used in papermaking, such as drainage improvers and retention improvers, can also be included as needed.

Furthermore, it is possible to apply starch, polyvinyl alcohol, paint, and various surface sizing agents to the surface of the base paper by a size press, gate roll or bill blade device. However, when the size press treatment is performed, the base paper becomes hard, and the finishing described below is performed. In order to sufficiently exhibit the processing effect, base paper that has not been subjected to size processing is preferable.

The base paper used in the present invention is a general pulp (NBK
P, LBKP), high yield pulp (GP, TMP, CTMP, CMP, etc.),
It is made of waste paper pulp.

In the present invention, a pigment coating layer is provided on the above-described base paper,
The coating layer is size-pressed on one or both sides of the base paper,
Gate rolls, on-machine coating equipment such as building blades or a blade coater usually used, refers to those provided with off-machine coaters such as air knife coaters, the coating amount is 3 to 25 g / m ² more preferably 5 to 15 g /
a m ^2.

As the coating liquid that can be used in the present invention, generally known pigments, binders, dispersants, thickeners, and the like can be used.

As the pigment, kaolin, calcium carbonate, clay, satin white, talc, titanium oxide, aluminum hydroxide, silica, zinc oxide, activated clay, silicon earth, lake, plastic pigment, or the like, or a sand-milled product of these pigments can be used as appropriate. . Examples of the dispersant include polycarboxylic acids such as acrylic acid aggregates, copolymers of acrylic acid and maleic acid, or their soda salts, ammonium salts, phosphoric acids such as sodium hexametaphosphate and sodium pyrophosphate, lignosulfonates, and naphthyl. Anionic surfactant systems such as sulfonates, citric acid, malic acid or one or more of these salts can be used as appropriate.

Examples of the binder include various copolymers such as styrene / butadiene, styrene / acrylic, vinyl acetate, acrylic, ethylene / vinyl acetate, butadiene / methyl methacrylic, vinyl acetate / butyl acrylate, polyvinyl alcohol, and maleic anhydride. Acid-styrene copolymer, isobutene
Synthetic binders such as maleic anhydride copolymers, acrylic acid / methyl methacrylate copolymers, oxidized starch, enzyme-modified starch, and cold water-soluble starch obtained by flash-drying them, and natural systems such as casein and soybean protein Examples of the binder include generally known binders and the like.

The present invention is characterized in that coated paper is processed under special conditions in a soft calender. As described above, the soft calender has 2 to 6 nips and a smaller number of nips than the super calender, and the elastic roll is made of a hard iron core made of synthetic resin (75-97 in Shore D hardness).
It is covered thinly. For this reason, the nip width becomes narrow.
The rigid roll is composed of a chilled roll and a forged steel roll, has a heating mechanism, and can process paper web even at a high temperature exceeding 100 ° C.

In the super calender, the density of the paper is rapidly increased by passing through a wider nip width and a larger number of nips (8 to 14 nips) than the soft calender, and the opacity and rigidity are reduced. Both are spoiled. It is the nip transit time that characterizes the calendering process.

However, in order to grasp the nip passing time during the paper passing process, it is necessary to clarify the nip width. Also in the above-mentioned publication No. 63-500188, an equation for calculating the nip width formed by deforming the elastic roll in a static state from the elastic modulus (E), Poisson's ratio (σ), etc. of the elastic roll is shown. (TAPPI October 1978, pp. 115-118), and are shown below.

* However, D _O : Outer diameter of elastic roll cm D _B : Outer diameter of rigid roll cm P _L : Nip linear pressure kg / cm However, when paper exists between nips, that is, when processing web, The elastic modulus of the web must be taken into account. The elastic modulus of the web varies depending not only on the composition of the raw materials of the web and the production conditions but also on the basis weight.

Therefore, the inventor of the present invention has applied a base paper having a basis weight of 25
With to 100 g / m ² coating amount 3 to 30 g / m ² of coated paper, the result of examining the relationship between the nip passing time and calendar conditions, the above factors in the region of the base paper basis weight and coating weight of above (L) corresponds to the nip transit time, and when the factor of L satisfies the following relationship as described above, it is found that low density, high opacity, rigidity, high smoothness, and gloss can be obtained. Was.

L ≦ 0.002 When the value of L exceeds 0.002, the density increases, and the rigidity and opacity are remarkably reduced. Therefore, the value of L must be suppressed to a range not exceeding 0.002.

As described above, since the value of L in the soft calendar is suppressed to a small value, as a result, at the same linear pressure,
High nip surface pressure can be obtained. For this reason, if too high a linear pressure is applied, the density of the paper web will increase.
It is not desirable to apply a linear pressure exceeding cm). In order to obtain gloss and smoothness of the coating layer surface, it is desirable to apply a linear pressure of at least 100 (kg / cm).

If the elastic roll hardness is too low as described above, it is necessary to apply a remarkably high linear pressure, so that a Shore D hardness of less than 75 is not desirable.

Naturally, an increase in the number of nips leads to an increase in the density, so it is desirable to keep the number of nips within six.

The processing conditions of the soft calender in the present invention increase the nip surface pressure, but keep the nip passage time short, so that if the coated paper to be processed, especially the base paper layer, is not flexible, the smoothness and gloss of the coated layer surface will be high. Can not be obtained. Increasing the filler content can significantly increase the flexibility of the coated base paper, but the most effective filler is light calcium carbonate. The necessary smoothness and gloss cannot be obtained with an L value of 0.002 or less in a papermaking clay or the like.

In the present invention, a specific amount of spindle-shaped filler having a specific particle size and calcite-based light calcium carbonate in the form of burrs and cubes in which agglomerates are bonded are mixed in a base paper as a filler. Provided and subjected to soft calendering under specific conditions, the characteristic value of the coated paper, density: 1.20 or less, opacity:
84% or more, smoothness: 29 mmHg or less, stiffness: 25 cm ^3/100 or more, dry pick: 3 or more, the white paper gloss: 36% or more, print gloss: by 50% or more, a relatively low density, i.e.,
A coated paper for printing of the present invention having high rigidity, high opacity, high gloss of white paper, and high gloss of print is obtained.

D) Examples Hereinafter, the effects of the present invention will be described in more detail using examples.

Example 1 Commercially available LBKP (freeness 350 ml csf): 70 parts Commercially available NBKP (freeness 420 ml csf): 30 parts Unless otherwise specified in the following Examples and Comparative Examples,
It is prepared with the above pulp composition.

・ Light calcium carbonate (average particle size: 1 μm, calcite type): 13 parts (*) * Indicated by ash content in base paper.

<Internal chemicals>-Commercially available alkyl ketene dimer-based internal sizing agent {AKD}:
0.03 parts ・ Commercialized cationized starch: 0.2 parts ・ Commercially available cationic polyacrylamide retention aid: 0.0
3 parts Unless otherwise specified in the following Examples and Comparative Examples,
The internal chemicals are prepared with the above composition.

With the above composition, base paper of 37g / cm ² basis weight (absolutely dry) is made,
A coating solution having the following composition was coated on both sides with a blade coater at a coating amount of 7 g / cm ² per side.

-Commercial primary kaolin: 50 parts-Commercial secondary kaolin: 50 parts-Commercial polyacrylic acid-based dispersant: 0.05 parts-Commercial phosphorylated starch: 4 parts-Commercial styrene / butadiene latex: 12 parts-Calcium stearate: 0.3 Parts ・ Sodium hydroxide: 0.15 parts Unless otherwise specified in the following Examples and Comparative Examples,
The coating liquid is prepared with the above-mentioned composition.

 Further, the basis weight of the base paper and the coating amount are also adjusted to the above values.

Smear paper processed under the above conditions, smear under the following conditions,
Soft calendering was performed immediately after drying.

<Soft calender specifications>-Number of nips: 2 ニ Form a nip so that the rigid roll surface hits each side of the coated paper once.-Rigid roll: diameter 80cmφ, forged steel roll-Elastic roll: diameter 70cmφ, synthetic Resin coating, Shore D
Hardness: 80 ・ Elastic roll iron core outer diameter: 67cmφ in diameter <Soft calendering condition> ・ Processing speed: 1000m / min ・ Rigid roll surface temperature: 120 ° C ・ Line pressure: 150kg / cm ・ L value: 0.001 Example 1 The characteristics of the products are summarized in Table 1, and satisfactory characteristic values are obtained.

Example 2 A base paper having the same composition as in Example 1 was coated under the same coating conditions as in Example 1 except that the blending amount of light calcium carbonate was changed to 11 parts (by base paper ash). Processing was performed under the same soft calendar conditions as in Example 1.

The characteristics of the product of Example 2 are summarized in Table 1. As compared with Example 1, the opacity is slightly lower, but satisfactory characteristics are obtained.

Example 3 A base paper having the same composition as in Example 1 was coated under the same coating conditions as in Example 1, except that the blending amount of light calcium carbonate was changed to 16 parts (by base paper ash). Processing was performed under the same soft calendar conditions as in Example 1.

The properties of the product of Example 3 are summarized in Table 1. As compared with Example 1, the properties are all improved except that the density is slightly higher and the pick strength is slightly reduced.

Example 4 The filler to be blended was light calcium carbonate (crystal system: calcite, average grain system: 1 μm), and the blending amount was 5 parts.
Except for the base paper having the same composition as in Example 1, except that the other fillers were made into clay (the average particle size was 1 μm 8 parts (by base paper ash))
Coating was performed under the same coating conditions as in Example 1, and processing was performed under the same soft calender conditions as in Example 1.

The characteristics of the product of Example 4 are summarized in Table 1. As compared with Example 1, all the other characteristics are reduced except that the density is slightly lower and the pick strength is slightly improved, but not to a problematic level. .

Example 5 A base paper having the same composition as in Example 1 was coated under the same coating conditions as in Example 1 except that the average particle diameter of the blended light calcium carbonate was 0.5 μm. The processing was performed under the same soft calender conditions.

The properties of the product of Example 5 are summarized in Table 1. As compared with Example 1, the density is slightly higher and the other properties are all improved except that the pick strength is slightly reduced.

Example 6 A base paper having the same composition as in Example 1 was coated under the same coating conditions as in Example 1 except that the average particle size of the blended light calcium carbonate was changed to 2 μm. Processing was performed under the same soft calendar conditions.

The characteristics of the product of Example 6 are summarized in Table 1. As compared with Example 1, except that the density is lower and the pick strength is improved, all the other characteristics are slightly reduced, but the characteristic values have no practical problem. Has been obtained.

Example 7 Inclined size press (ISP: a base paper is passed between two rubber rolls, a reservoir of a water-soluble binder solution is formed at the nip inlet side, and immersed in the base paper. The water-soluble binder here is a 4% aqueous starch oxide solution. Except that the treatment was applied, a base paper having the same composition as in Example 1 was coated under the same coating conditions as in Example 1, and the same soft calender conditions as in Example 1 were used. Was performed.

Table 1 summarizes the product characteristics of Example 7;
, While the pick strength is improved, but the other properties are considerably reduced and barely remain problem-free.

COMPARATIVE EXAMPLE 1 The filler to be blended was commercially available and the clay (average particle size was 1 μm)
m) A base paper prepared under the same manufacturing conditions as in Example 1 was coated under the same coating conditions as in Example 1 except that the amount was changed to 13 parts (with base paper ash). Was performed.

Table 1 summarizes the product characteristics of Comparative Example 1.
As compared with the above, the density is lowered and the pick strength is improved, but all other characteristics are significantly reduced, and satisfactory characteristic values cannot be obtained.

Comparative Example 2 The filler to be blended was light calcium carbonate (crystal system was calcite, average particle size 1 μm), and the blending amount was 3 parts.
A base paper having the same composition as in Example 1 was coated under the same coating conditions as in Example 1, except that 7 parts of clay (average particle size was 1 μm) and 7 parts of other fillers were used. Again, processing was performed under the same soft calender conditions as in Example 1.

Table 1 summarizes the product characteristics of Comparative Example 2, while Example 1
As compared with the above, the density is lowered and the pick strength is improved, but all other characteristics are significantly reduced, and satisfactory characteristic values cannot be obtained.

Comparative Example 3 The filler to be blended was light calcium carbonate (crystal system was calcite, average particle size 1 μm), and the blending amount was 4 parts.
A base paper having the same composition as in Example 1 was coated under the same coating conditions as in Example 1 except that 4 parts of clay (average particle size was 1 μm) and 4 parts of clay were added (with base paper ash). Again, processing was performed under the same soft calender conditions as in Example 1.

Table 1 summarizes the product characteristics of Comparative Example 3, while Example 1
As compared with the above, the density is lowered and the pick strength is improved, but all other characteristics are significantly reduced, and satisfactory characteristic values cannot be obtained.

Comparative Example 4 A base paper having the same composition as in Example 1 was prepared except that the crystal system of light calcium carbonate to be blended was aragonite (average particle size: 1 μm) and the blending amount was 13 parts (by base paper ash). Coating was performed under the same coating conditions, and processing was performed under the same soft calender conditions as in Example 1.

Table 1 summarizes the product characteristics of Comparative Example 4, while Example 1
, The pick strength is remarkably reduced, and satisfactory characteristic values cannot be obtained.

Comparative Example 5 Light calcium carbonate to be blended (calcite is calcite)
Was applied under the same coating conditions as in Example 1, except that the average particle size of was 0.2 μm and the blending amount was 13 parts (with base paper ash). Processing was performed under the same soft calender conditions as in Example 1.

Table 1 summarizes the product characteristics of Comparative Example 5, while Example 1
, The pick strength is remarkably reduced, and satisfactory characteristic values cannot be obtained.

Comparative Example 6 Light calcium carbonate to be blended (the crystal system is calcite)
The base paper having the same composition as in Example 1 was coated under the same coating conditions as in Example 1 except that the average particle size of the base material was 2.5 μm and the blending amount was 13 parts (by base paper ash). Processing was performed under the same soft calender conditions as in Example 1.

Table 1 summarizes the product characteristics of Comparative Example 6, while Example 1
As compared with the above, the density is lowered and the pick strength is improved, but all other characteristics are significantly reduced, and satisfactory characteristic values cannot be obtained.

Comparative Example 7 A base paper having the same composition as in Example 1 was coated under the same coating conditions as in Example 1 and a supercalender treatment was performed under the following conditions.

<Super calender specifications>-Number of stages: 10-Rigid roll: chilled roll, outer diameter 400mφ-Elastic roll: Cotton roll, outer diameter 420mmφ <Super calender processing conditions>-Processing speed: 600m / min-Linear pressure: 200kg / cm Hollow roll temperature: 65 ° C. The product characteristics of Comparative Example 7 are summarized in Table 1, but Example 1
, The density is remarkably increased, and satisfactory characteristic values cannot be obtained.

Example 8 Base paper prepared under the same manufacturing conditions as in Example 1
The coating was performed under the same coating conditions as in Example 1, and the treatment was performed under the same conditions as in Example 1 except that the nip linear pressure of the soft calender was changed to 250 kg / cm.

The characteristics of the product of Example 8 are summarized in Table 1. As compared with Example 1, all the other characteristics were improved except that the density was slightly higher, and satisfactory characteristic values were obtained.

Example 9 Example 1 was prepared by adding base paper prepared under the same manufacturing conditions as in Example 1.
The coating was performed under the same coating conditions as in Example 1 except that the nip linear pressure of the soft calender was changed to 500 kg / cm.

The characteristics of the product of Example 9 are summarized in Table 1. As compared with Example 1, all the other characteristics were improved except that the density was slightly higher, and satisfactory characteristic values were obtained.

Example 10 Example 1 was prepared by adding base paper prepared under the same manufacturing conditions as in Example 1.
The coating was performed under the same coating conditions as in Example 1, and the treatment was performed under the same conditions as in Example 1 except that the nip linear pressure of the soft calender was set to 100 kg / cm.

The properties of the product of Example 9 are summarized in Table 1. As compared with Example 1, except that the density is slightly higher, all the other properties are slightly reduced, but the property values which are practically acceptable are obtained. ing.

Example 11 Example 1 was prepared by adding base paper prepared under the same manufacturing conditions as in Example 1.
Coating is performed under the same coating conditions as above, and the nip linear pressure of the soft calender is set to 150 kg / cm, the same conditions as in Example 1, but two soft calenders having the specifications shown in Example 1 are passed in series. The treatment was carried out under the same conditions as in Example 1 except that the nip was formed such that the rigid roll surface was applied twice to each side of the smeared paper front and back (number of nips: 4).

The characteristics of the product of Example 11 are summarized in Table 1. As compared with Example 1, all the other characteristics were improved except that the density was slightly higher, and satisfactory characteristic values were obtained.

Example 12 A base paper prepared under the same manufacturing conditions as in Example 1 was added to Example 1
The coating was performed under the same coating conditions as in Example 1, and the treatment was performed under the same conditions as in Example 1 except that the elastic roll hardness of the soft calender was set to 89.

The characteristics of the product of Example 12 are summarized in Table 1. As compared with Example 1, the density did not change and the other characteristics did not differ much, and satisfactory characteristic values were obtained.

Example 13 Example 1 was prepared by adding base paper prepared under the same manufacturing conditions as in Example 1.
The coating was performed under the same coating conditions as in Example 1, and the treatment was performed under the same conditions as in Example 1 except that the elastic roll hardness of the soft calender was set to 96.

The properties of the product of Example 13 are summarized in Table 1. As compared with Example 1, the density is not changed, the smoothness is improved, but the gloss is slightly reduced. However, satisfactory characteristic values are obtained as a whole.

Example 14 Example 1 was prepared by adding base paper prepared under the same manufacturing conditions as in Example 1.
Coating is performed under the same coating conditions as above, and the nip linear pressure of the soft calender is 100 kg / cm, the same conditions as in Example 1. However, three soft calenders having the specifications shown in Example 1 are passed in series. The treatment was carried out under the same conditions as in Example 1 except that the nip was formed such that the rigid roll surface hit the front and back surfaces of the smear three times three times each (the number of nips: 6).

The characteristics of the product of Example 14 are summarized in Table 1. The density is considerably higher than that of Example 1, but at an acceptable level, and the characteristics such as smoothness and gloss are improved, and satisfactory characteristics are obtained. Values have been obtained.

Comparative Example 8 Example 1 was added to base paper prepared under the same manufacturing conditions as in Example 1.
The coating was performed under the same coating conditions as in Example 1, and the treatment was performed under the same conditions as in Example 1 except that the nip linear pressure of the soft calender was set to 50 kg / cm.

The properties of the product of Example 15 are summarized in Table 1, except that the density is slightly lower than that of Example 1, but the other properties are slightly lower.

Comparative Example 9 Example 1 was prepared by adding base paper prepared under the same manufacturing conditions as in Example 1.
Coating was performed under the same coating conditions as in Example 1, and the treatment was performed under the same conditions as in Example 1 except that the nip linear pressure of the soft calender was set to 600 kg / cm.

The properties of the product of Example 16 are summarized in Table 1. As compared with Example 1, the density is remarkably higher, but both the glossiness of white paper and the glossiness of printing are increased.

Comparative Example 10 Example 1 was added to base paper prepared under the same manufacturing conditions as in Example 1.
The coating was performed under the same conditions as in Example 1 except that the nip linear pressure of the soft calender was 550 kg / cm and the elastic roll hardness was 60.

The characteristics of the product of Example 17 are summarized in Table 1. As compared with Example 1, the density is higher, but both the glossiness of white paper and the glossiness of printing are increased.

E) Effects of the Invention By carrying out the present invention, it is possible to produce coated paper having high opacity and high rigidity, and at the same time, high smoothness, white gloss, and print gloss.

 ────────────────────────────────────────────────── (5) References JP-A-62-199898 (JP, A) JP-A-62-282099 (JP, A) JP-A-61-168524 (JP, A) US Patent 3,304,154 (US , A) "Paper and Pulp Technology Times", May 1988, pp. 10-14 "Paper and Pulp Technology Times", August 1987, pp. 31-36, "Paper Coating I", Polymer by Soichi Muroi Latex Application, pp. 80-82 September 20, 1986 Published by Polymer Publishing Association

Claims (2)

(57) [Claims] 1. A fusiform or cubic calcite-based light calcium carbonate having a filler content of 0.3 to 2 .mu.m in average particle size and an agglomerate bond thereof, containing at least 4% by weight based on the weight of the base paper. A pigment coating layer is provided on a base paper having a total ash content of the base paper of 10% by weight to 20% by weight, and after drying, the coated surface is pressure-bonded to a soft calender having a nip number of 6 or less. Satisfies the conditions, and the characteristic value of the coated paper is: density: 1.20 or less, opacity: 84% or more, smoothness: 2
Coated paper for printing characterized in that the paper gloss is 9 mmHg or less, the glossiness of blank paper is 36% or more, and the printing glossiness is 50% or more. a: The hardness of the soft calender elastic roll is 75 or more (Shore D hardness). b: The index L defined by the following equation must satisfy the following conditions. L ≦ 0.002 * However, D _O : Elastic roll outer diameter cm D _B : Rigid roll outer diameter cm D _i : Elastic roll iron core outer diameter cm P _L : Nip linear pressure kg / cm S _D : Elastic roll hardness (Shore D) V: Line processing speed cm / sec K = 3 (D _O −D _i ) · (D _O / D _i ) ^0.5 c: Nip linear pressure must satisfy the following conditions. 100 ≦ P _L ≦ 550 2. The coated paper for printing according to claim 1, wherein the base paper has not been subjected to size press treatment.