JPH11247097A - Double-sided coated paper for printing - Google Patents

Abstract

(57) 【Abstract】PROBLEM TO BE SOLVED: High quality double-sided printing paper which is a coated paper with excellent white paper gloss, printing gloss and smoothness, and particularly high rigidity, and excellent printability such as absorbent skin swimsuit meatness and ink drying property. Provide coated paper. A double-sided coated paper for printing, in which a base paper is provided with a coating layer containing a pigment and an adhesive as main components, and the double-sided coated paper is measured in accordance with JIS P8143 A method. Mean value L of the projected length of the projected Clark
Satisfies the following formula (1), and the void volume at 0.03 to 0.3 μm when the double-sided coated paper is measured by a mercury porosimeter is 9.00 cc/m ^{2 to} 11.50 cc/
Double-sided coated paper for printing that is m ² . L> 1.28X + 40 (1) [where, L = average value (unit: mm) of Clarke protrusion length in grain and side grain of double-sided coated paper, X = product tsubo (g/m ² ). Is]

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated paper for printing, and more particularly to a double-sided coated paper for printing which is excellent in white paper gloss, printing gloss and smoothness, has high rigidity (paper stiffness), and is excellent in printing workability. ..

[0002]

2. Description of the Related Art Generally, coated paper for printing is required to have high gloss and smoothness and excellent printability. In recent years, with the need for high-speed printing coupled with improvements in printing technology, from the viewpoint of printing workability and printability, the printing coating material having not only the above-mentioned paper quality characteristics but also a strong stiffness (so-called rigidity) is used. Paper is required. Normally, if the paper stiffness is weak (stiffness is low), paper breakage etc. will occur during high-speed printing, etc., it will not be possible to perform satisfactory printing work, leading to a decrease in work efficiency,
It often causes user complaints. On the other hand, if the paper is strong (high), not only will it be possible to smoothly feed the paper during high-speed printing, but the high rigidity will give the product an extravagance (heavyness), resulting in a high-quality printed product. Cultivated. In addition, a printed matter with high rigidity (coated paper)
When used as a text sheet for bookbinding and finishing in magazines or catalogs, it naturally enhances luxury and weight, and the product value as a printing sheet is enhanced accordingly.

By the way, the stiffness of paper is closely related to its tsubo (weight) and its density. Generally, the larger the tsubo, the higher the stiffness. On the other hand, the higher the density of the paper, the stiffness becomes. It tends to decrease. Therefore, as the basis weight of the product is increased, the rigidity naturally increases. On the other hand, as the basis weight of paper increases,
Although a feeling of weight can be obtained, the weight of paper becomes unnecessarily heavy, and when it is used as a catalog or mail, etc. where the amount is limited, problems such as the limitation of the number of sheets and the weight limitation are caused and various inconveniences occur. is there. For this reason, there is a demand for coated paper products that are as light as possible and that have high rigidity.

[0004] Since coated papers for printing are usually required to have an excellent printing finish in addition to rigidity, as a result, further excellent gloss and smoothness are required for products. In order to impart desired high gloss and high smoothness to the coated paper, it is necessary to increase the density of the paper to some extent.
That is, in order to add high gloss and high smoothness to the coated paper, calendering is indispensable, and if calendering is performed, the density is inevitably increased and the rigidity is decreased. As described above, there is a contradictory relationship between the means for increasing the high gloss and the high smoothness and the increase in the rigidity, and it is extremely difficult to balance the both well.
In addition, if a large amount of an adhesive is mixed in the coating layer to finish it at a high density, printability, particularly ink setting and ink receptivity, deteriorates, which is likely to cause a problem.

By the way, various proposals have heretofore been made regarding techniques for improving the rigidity of coated paper for printing. For example, softwood pulp (NK
From the viewpoints of P), a high proportion of starch, and a high proportion of starch, as well as a copolymer having a high glass transition temperature (hereinafter referred to as Tg) as proposed in JP-A-6-287503. At present, it is attempted to achieve the intended purpose by proposing a method of blending the combined latex at a high rate.

However, when a high proportion of softwood pulp is blended with the base paper, or a high proportion of starch is blended in an aqueous composition containing pigments and adhesives as main components (hereinafter referred to as paint), paper stiffness (stiffness) is reduced. Although it becomes higher, there is a drawback that the smoothness and gloss of the coated paper surface are reduced. Therefore, in order to avoid such a defect, it is often the case that a copolymer latex having a high Tg is blended in the paint as an adhesive at a high rate to improve the rigidity (strengthen the paper stiffness). In addition, when a copolymer latex having a high Tg is used as an adhesive, in order to develop a more excellent gloss due to its properties, as disclosed in, for example, JP-A-53-7964, The coated paper is passed through a high temperature calender of 100° C. or higher called a gross calender or a soft calender, and pressure treatment is applied to finish.

On the other hand, when a copolymer latex having a high Tg is used, the adhesive strength tends to decrease, and as a result,
Problems such as partial peeling of the coating layer occur. Therefore, in order to improve such a defect, for example, Japanese Patent Laid-Open No. 56-
In Japanese Patent No. 68188, it is proposed to use a copolymer latex having a Tg of 38°C or higher and a copolymer latex having a Tg of 5 to 25°C in combination. However, even with the method according to such a proposal, in order to make the copolymer latex having a high Tg exhibit sufficient adhesive strength,
It is necessary to strengthen the processing conditions of the high temperature calender. As a result, there is a problem in that the printability and calender operability of the resulting coated paper are reduced.

The operation of the high temperature calender will be additionally described. In this calendering treatment, a paper web provided with a coating layer containing a thermoplastic substance such as the above-mentioned copolymer latex is prepared from a high temperature metal roll and an elastic roll. It is processed by passing through the calender nip part. That is, the copolymer latex is plasticized by the high temperature and high pressure applied to the web and the pigment in the coating layer is effectively oriented, or the surface of the metal roll is copied to obtain a coating having high gloss. This is a work to obtain the paper. On the other hand, when such a high temperature and pressure means are taken, a coating layer is stuck on the surface of a high temperature metal roll or elastic roll, or a part of the coating layer is peeled off on the roll surface, resulting in a product value. In many cases, operability was deteriorated by lowering the quality or inducing roll dirt.

As a method for preventing the above-mentioned roll stains and sticking to the roll surface, a release agent such as waxes, fatty acids, fatty acid salts and silicone resins may be added to the paint, or the above-mentioned release agent may be added. It is also practiced to apply the mold agent directly to the roll surface. However, if such a measure is taken, excess release agent accumulates on the roll surface,
Difficulties such as causing stains and reducing the gloss of the coated paper are accompanied. For the above reasons, commercially available so-called super art papers and art papers for high gloss printing coated papers are excellent in gloss and smoothness, but on the other hand, the high rigidity desired by the present invention. The product having the is not yet obtained.

Next, supplementing the stiffness, the A method of JISP8143 is defined as one of the indices showing the stiffness of the paper. This method is also called Clark's method, and is known as an evaluation method that matches the feel (heavyness) of hand when the paper is lifted by a hand (finger). In the Clark method, the protrusion length L (unit: cm) when the paper is measured is cubed and divided by 100.
L ³ /100). Incidentally, in the present invention,
The rigidity is defined as the average value (unit: mm display) of the protrusion length L in the vertical and horizontal stitches of the product.

Further, the glossiness is usually expressed by a numerical value measured according to JIS P8142, and the present invention is intended for a product having a high glossiness of 75% or more. is there. That is, the double-sided coated paper exhibiting such a glossiness is usually subjected to a considerable pressure treatment to add gloss. On the other hand, the rigidity of such a double-sided coated paper is sensuously low, and in many cases, the hand feeling (heavyness) is poor. For example, it is generally commercially available,
As a result of measuring the rigidity L specified in the present invention as described above for a product called so-called super art paper or art paper, the result of the measurement is 100-110 g of tsubo.
The rigidity L (mm) of about /m ² is approximately 150 to 17
2 mm, about 125-135 g/m ² , 162
To 200 mm, more of the order of 155~165g / m ^2, values such 210～238Mm (Note: The larger the value, stiffness is high) indicating the. Of course, the glossiness of all of these products exceeds 75% as measured in accordance with JIS P8142. And, although all products have high gloss and high smoothness, many of them have a poor hand feeling (heavyness).

[0012]

As described above, conventional double-sided coated papers for high-gloss printing are subject to calendering treatment under strong conditions (high temperature, high pressure), and thus the surface gloss It has excellent smoothness and smoothness, but on the other hand, it lacks a profound feeling. There is a strong contradictory relationship between improving the gloss and smoothness of the paper surface and the solid feeling of the coated paper, so-called stiffness (paper stiffness), and a method to balance and improve both is still found. The reality is that there is none. The inventors of the present invention have conducted extensive studies in order to solve the drawbacks of the coated paper for high-gloss printing. as a result,
The present invention relates to a double-sided coated paper for printing, and in particular, has a specific rigidity, and when the coating layer surface is measured by a mercury porosimeter, the volume of the void volume in a specified range of specific voids (micropores). It is intended to provide a coated paper having high rigidity, excellent gloss and smoothness, and further excellent printability (such as meat absorption property, ink drying property).

[0013]

[Where, L = average value of Clark protrusion length (unit: mm) in grain and side grain of double-sided coated paper, X = product tsubo (g/m ² ).

A more preferable specific means (embodiment) for obtaining a high-gloss double-sided coated paper satisfying the physical properties specified as above and having excellent printability is mainly a pigment and an adhesive on the base paper. The undercoating aqueous composition and the overcoating aqueous composition as components are coated, dried to provide a multilayer coating layer, and after the overcoat coating layer is provided, pass through a high temperature calender of 100°C or higher. Which is a double-sided coated paper for printing, which is subjected to pressure treatment, particularly as an adhesive of the aqueous composition for undercoating,
The copolymer latex having a glass transition temperature of 30° C. or higher is 1 in terms of solid content relative to all pigments of the aqueous undercoating composition.
5 wt% or more, further, as a pigment of the aqueous composition for topcoating, satin white is contained in an amount of 5 to 20% by weight with respect to all the pigments of the aqueous composition for topcoating, and as an adhesive, the glass transition temperature is The vinyl acetate copolymer at 25 to 60° C. is based on all pigments of the aqueous topcoating composition,
A double-sided coated paper for printing which contains 8 to 20% by weight.

[0015]

[Where, L = average value of Clark protrusion length (unit: mm) in grain and side grain of double-sided coated paper, X = product tsubo (g/m ² ).

In the present invention, when the protruding length L of the coated paper product at the longitudinal and lateral directions is measured and the average value is taken as the stiffness L of the coated paper (unit: mm), It was confirmed that a sufficient correlation between strength (stiffness) and feel (heavyness) was obtained, and as described above, the grain length of the coated paper,
The average value (L: mm) of the protruding lengths in the cross stitch is defined as the rigidity.

As described above, the method for obtaining a coated paper satisfying the specific rigidity (L) and void volume, which are the features of the present invention, and having excellent printability is not particularly limited. However, particularly preferable embodiments are as follows. That is, the coated paper exhibiting the excellent effect desired by the present invention is a multilayer paper obtained by coating a base paper with an aqueous undercoating composition and a topcoating aqueous composition having a pigment and an adhesive as main components, and drying. A double-sided coated paper for printing, which comprises a coating layer, an upper coating layer, and a paper which is passed through a thermal calender at 100° C. or higher for pressure treatment. As an adhesive, a copolymer latex having a Tg of 30° C. or higher is contained in an amount of 15% by weight or more based on the total solid content of all pigments of the aqueous undercoating composition, and as a pigment of the overcoating aqueous composition, satin is used. White pigment is contained in an amount of 5 to 20% by weight based on all pigments of the aqueous topcoating composition, and a vinyl acetate copolymer having an Tg of 25 to 60° C. is used as an adhesive in all pigments of the aqueous topcoating composition. On the other hand, the double-sided coated paper for printing is characterized by containing 8 to 20% by weight.

In the present invention, as described above, after providing a base coat having a specific material constitution and a coating layer which becomes a multi-layer coat of an aqueous composition for top coat (hereinafter, simply referred to as a paint), 1
The desired double-sided coated paper for printing is obtained particularly effectively by passing the paper through a thermal calender at 00° C. or higher and finishing the pressurization. In order to obtain a high-quality double-sided coated paper for printing, Tg is used as an adhesive for the undercoat paint.
The content of the copolymer latex having a temperature of 30° C. or higher is 15% by weight or more based on the solid content of the pigment in the undercoat paint, and satin white is used as a pigment in the overcoat paint for all pigments in the overcoat paint. It is contained in an amount of 5 to 20% by weight relative to the solid content, and has an Tg of 25 to 25 as an adhesive.
It is important that the vinyl acetate-based copolymer at 60° C. is contained in an amount of 8 to 20% by weight based on the solid content based on all pigments of the topcoat paint. In the present invention, the physical property value of the double-sided coated paper after passing through a high temperature calender and finishing, that is, the density measured according to JIS P8118 is 1.15 to 1.35 g/cm ³ , JIS of layered surface
The glossiness measured according to P8142 is 75% or more, and J.P. TAPPI paper pulp test method No. When the finishing is performed so that the physical property value is 15 mmHg or less as measured by a smoother smoothness meter of the 5A method, a desired high-quality double-sided coated paper for printing can be easily obtained.

According to the present invention, the average value (L) of the protrusion lengths in the longitudinal and transverse directions of the coated paper measured by the Clark method satisfies the formula (1), and the value measured by the mercury porosimeter on the surface of the coated layer is 0. by void volume in .03~0.3μm it is finished so as to satisfy the ^{9.00cc / m 2 ~11.50cc / m 2} , exhibited high smoothness, high gloss,
For the first time, they have found that a double-sided coated paper not only exhibiting high rigidity and a so-called weight feeling (luxury feeling), but also excellent printability (meat absorbing swimwear, ink drying property), and completed the present invention. It was

The rigidity (L value) defined by the above formula (1) naturally increases as the product tsubo becomes larger. Particularly, in the case of the coated paper according to the present invention, the conventional product (equivalent tsubo product). Compared to
It shows a large value and is an extremely profound product. One of the preferred embodiments for obtaining a product having such a high L value is a specific high Tg copolymer compounded in the above-mentioned multilayer coating layer, that is, the undercoating layer and the overcoating layer. It is in the action and effect of latex.

That is, the Tg as an adhesive compounded in the undercoat paint is 30° C. or higher, preferably 30° C. or higher, 45° C.
15% by weight or more, preferably 15 to 30% by weight, based on the solid content, of the following copolymer latex with respect to the pigment in the paint.
Is compounded in. By the way, if Tg is less than 30° C. or the blending amount is less than 15% by weight, the desired rigidity may not be obtained. On the other hand, if the blending amount exceeds 30% by weight,
Alternatively, when a copolymer latex having a Tg of more than 45° C. is blended, the void volume of the coating layer tends to be small, and the ink drying property and the absorbent swimwear fleshness may be deteriorated and the printability may be deteriorated. is there. The high Tg copolymer latex itself has a hard property and shows plasticity due to high heat, but after cooling, it maintains the coating shape and at the same time hardens the coating layer, resulting in an increase in rigidity. is there.

Further, in the present invention, T is also contained in the top coating composition.
The vinyl acetate copolymer having a g of 25 to 60° C. is added to the pigment in an amount of 8 to 20% by weight to further enhance the rigidity. In short, by blending a high Tg copolymer latex as an adhesive for the undercoat layer and the overcoat layer, it is possible to obtain extremely high rigidity, which has not been obtained by conventional products. The purpose of the high Tg vinyl acetate-based copolymer to be blended in the top coat is to improve the printability (particularly, the fleshness of the swimsuit) in addition to increasing the rigidity. By the way, T of vinyl acetate copolymer
When g is less than 25° C., the effect of increasing the rigidity is reduced, while when it exceeds 60° C., there is a risk of poor water absorption and a decrease in adhesive strength during offset printing, which is not preferable. The Tg of the copolymer latex can be adjusted by
It can be carried out by appropriately controlling the type and blending ratio of the monomer components constituting the copolymer latex. As described above, in the present invention, by adding a high Tg copolymer latex to each coating layer of a coating layer having a two-layer structure, the rigidity is increased, and vinyl acetate having a high Tg is formed in the top coating layer. By blending the copolymer, not only the rigidity but also the printability can be improved more effectively.

Next, as another important factor in the present invention, the void volume in the fine pores 0.03 to 0.3 μm on the surface of the coating layer measured by a mercury porosimeter is 9.00 cc/m ^{2 to} 11.50 cc. /M ² is satisfied. That is, in general, a coated paper for printing is finished by providing a coated layer containing a pigment and an adhesive as main components on a base paper containing pulp fibers as a main component. In that case, the base paper layer has a network structure of pulp fiber, and the pigment coating layer has a dense layer structure by covering the network structure of the base paper, thereby producing an effect of improving the appearance of blank paper and printability as a final product. Is working for In addition, the usual coated paper for printing is finished by smoothing the surface or adding high gloss by a pressure treatment machine such as a super calender or a soft calender at the final finishing stage. When the network structure of these fibers and the coating layer are observed microscopically, fine pores (for example, several tens of μm for large ones, several hundreds of μm in some cases are observed in the fiber layer.
The pigment coating layer serves to coat the mesh layer of the fiber with an aqueous composition containing a pigment and an adhesive having a very small particle size as a main component, and to correct irregularities of the fiber. Therefore, the micropores on the surface of the coating layer are extremely small as compared with the micropores in the fiber network structure, and the size thereof is 0.5 μm or less even at the largest size. What has an influence on the print finish, so-called printing effect, is the fine pores existing on the surface of the coating layer, in addition to the pigment and the adhesive itself that form the coating layer.

The fine pores present on the surface of the coating layer are subjected to multicolor printing by appropriately absorbing the printing ink. by the way,
If the surface of the coated layer is a film-like layer with no fine pores at all, it takes too long for the ink to penetrate into the layer and satisfactory printing cannot be performed. Therefore, the presence of appropriately fine pores effectively balances the penetration of the printing ink into the coating layer. On the other hand,
If there are too many fine holes, the penetration of the ink will proceed too far and there will be no problem in the printing time etc., but since the ink will penetrate too much into the layer, the printing gloss will decrease over time, and the printing effect Is unfavorable. From the above viewpoints, as a result of various studies, in the present invention, the void volume of the micropores 0.03 to 0.3 μm on the coating layer surface measured by a mercury porosimeter is 9.00 cc/m ^{2 to} 11.50 cc/m. ²
It has been found that when the coating layer is finished so that the product has an extremely excellent printing effect and printability.

By the way, for extremely small voids of less than 0.03 μm, micropores have little effect on ink penetration during printing, while voids of more than 0.3 μm are present in a normally finished coating layer. Almost no voids and larger voids are fine pores present in the base paper, and have little relation to the coating layer that has a strong influence on the printing effect. Further, it can be said that most of the fine pores existing in the coating layer are 0.3 μm or less. Further, in the present invention, as described above, the void volume of the micropores 0.03 μm to 0.3 μm is 9.00 cc/m ^{2 to} 11.50 cc/m ^2.
When it is set so as to obtain an extremely excellent printing effect. By the way, if it is less than 9.00 cc/m ² , the ink absorbency is lowered, and as a result, the ink drying property is deteriorated. On the other hand, if it exceeds 11.50 cc/m ² , the ink easily penetrates, and as a result, Ink gloss disappears,
In any case, the printability is deteriorated, which is not preferable.
Therefore, by adjusting the coating layer surface so as to have the specific void volume as described above, the excellent effects desired by the present invention can be obtained.

The method of adjusting the void volume of the specific fine pores of the coating layer to the above range is not particularly limited, but for example, satin white is blended in the coating material constituting the coating layer, A desired value can be obtained by combining calendar conditions (operations) and the like. The amount of satin white is adjusted as a pigment in the overcoat layer and is adjusted to 5 to 20% by weight based on the total pigment in the overcoat layer.
By the way, if it is less than 5% by weight, it is difficult to obtain a desired void volume, and if it exceeds 20% by weight, the ink gloss is lowered,
Adhesion to the heat calender roll, and further problems such as paint preparation are unfavorable. Furthermore, the void volume changes depending on the type of pigment or adhesive, the combination of pigment and adhesive, heating calender conditions, etc., so the desired void volume can be adjusted appropriately while adjusting the balance of quality. You will get it.

In the present invention, further, the physical properties of the obtained product, that is, the density measured according to JIS P8118 is 1.15 to 1.35 g/cm ³ , and JIS P8142 is used.
The glossiness measured according to J. No. is 75% or more, and J. T
APPI Paper Pulp Test Method No. By finishing the smoothness measured according to 5A (smoother smoothness) to 15 mmHg or less, high rigidity, high gloss, which is the object of the present invention,
It is possible to efficiently obtain a double-sided coated paper for printing having high smoothness and extremely excellent printability and workability. The method for obtaining the above-mentioned specific density, smoothness, and glossiness is set under the high-temperature calender or under
It is possible to achieve balance by selecting the material forming the overcoat layer and adjusting the compounding amount appropriately, and there is no particular limitation.

In the present invention, the pigment of the undercoat paint is not particularly limited, but for example, kaolin,
One or more of inorganic pigments such as calcined clay, aluminum hydroxide, calcium carbonate and talc, and organic pigments such as plastic pigments are appropriately used in combination. Kaolin, calcined clay, aluminum hydroxide and the like are particularly effective in providing voids in the coating layer. Examples of the adhesive include copolymer latexes having a Tg of 30° C. or higher, such as styrene-butadiene copolymer latex, methyl methacrylate-butadiene copolymer latex, and acrylic copolymers. .. Further, the above-mentioned copolymer latex having a Tg of less than 30° C., proteins such as casein and synthetic proteins, polyvinyl alcohol, olefin-maleic anhydride resins, synthetic resin adhesives such as melamine resins, oxidized starch, and thermochemistry. Adhesives that are commonly known and used such as starches such as modified starch and cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose can be appropriately used in combination.

Next, as the pigment for the top coat, in addition to the above-mentioned satin white, for example, inorganic pigments such as kaolin, calcium carbonate, talc, aluminum hydroxide, polystyrene, epoxy resin, styrene-acrylic copolymer resin, etc. It is possible to select and use one or more pigments used in the general coated paper manufacturing field such as organic pigments. As the adhesive for the overcoat layer, other than the specific vinyl acetate-based copolymer as described above, a copolymer latex conventionally used, for example, styrene-butadiene, to the extent that the effects of the present invention are not impaired. Copolymer latex, conjugated methacrylate copolymer latex such as methyl methacrylate-butadiene copolymer latex, further casein, proteins such as soybean protein, polyvinyl alcohol, synthetic resin adhesives such as melamine resin, oxidized starch, Ordinary adhesives such as starches such as thermochemically modified starch are appropriately selected and used.

The total amount of the adhesive compounded in the lower and upper coating materials is adjusted to be 15 to 25% by weight based on the solid content of the pigment in the lower coating material. On the other hand, in the top coating composition, the pigment content is adjusted to 8 to 25% by weight based on the solid content. In addition, in the paint for forming the undercoat paint and the topcoat paint, if necessary, a defoaming agent, a coloring agent, a release agent,
Various auxiliaries such as a flow modifier and an antiseptic can also be added appropriately.

There is no particular limitation on the method of applying the undercoating layer coating material prepared on the above conditions to the base paper. For example, a blade coater, an air knife coater, a roll coater, a bar coater, etc. It is applied by an on-machine or off-machine coater provided with a coating device.

As the base paper, a base paper having a basis weight of about 30 to 300 g/m ² which is used for a general coated paper for printing is used. In the present invention, the basis weight of the base paper is not more than 140 g/m ² , preferably not more than 140 g/m ² . When 110 g/m ^{2 to} 30 g/m ² of base paper is used, the extremely excellent action and effect desired by the present invention can be obtained. It should be noted that with a thin base paper having a weight of less than 30 g/m ^2, the paper strength of the base paper is inevitably weakened, and there is a possibility that satisfactory production cannot be achieved. On the other hand, in the case of a thick base paper having a weight of more than 140 g/m ² , the paper has a strong stiffness from the beginning, and there is no need to further increase the rigidity.

The coating amount of the undercoat paint on the base paper is determined by the void volume of the product, the stiffness of paper (stiffness) or the quality of white paper, the printing quality,
It is desirable to adjust at which the 5g / m ² ~20g / m ² about considering coating suitability. Next, the coating amount of the top coat is determined by the printability of the product (absorbent swimsuit flesh and ink dryness).
And considering the quality (ink gloss and smoothness),
It is regulated by 12g / m ² ~25g / m ² approximately. In addition,
For drying the coated layer after coating, various drying methods conventionally used in the coated paper manufacturing field such as steam drying, hot air drying, gas heater heating, electric heater heating, and infrared heater heating are appropriately used. It

In the present invention, the coated paper obtained by applying the undercoating coating composition and drying as described above is subjected to a paper-passing treatment using a high temperature calender of 100° C. or higher to obtain a high quality double-sided coating. It is intended for finishing on paper. The calender in this case is not particularly limited, but for example, a metal roll such as a super calender, a gross calender, a soft calender, etc., or various calenders composed of a drum and an elastic roll are in an online, in-line or offline state. Used as appropriate. In this case, the surface temperature of the metal roll is 100 to 300°C, and the temperature range of 100 to 200°C is more preferable in consideration of product quality, calender operability and the like. Further, it is important that the elastic roll can endure durability under high temperature and high pressure and heat resistance, and can impart high gloss and high smoothness, and has a Shore D hardness of 85 to 95 degrees, The surface roughness Rmax is 5 μm or less, preferably 3 μm.
Hereinafter, a resin roll polished to a size of 1 μm or less is more preferably used.

In order to obtain the desired product of the present invention more efficiently, the density of the double-sided coated paper after finishing is 1.15.
A high temperature calendering treatment is performed so that the weight becomes 1.35 g/cm ³ . Incidentally, if the density is less than 1.15 g/cm ³ , desired gloss and smoothness may not be obtained, and further, the adhesive strength of the coating layer may be lowered. On the other hand, 1.3
If it exceeds 5 g/cm ³ , the coating layer becomes too dense and the voids between the pigments are greatly reduced, and the desired porosity cannot be obtained, and the printability such as deterioration of the fleshness of the absorbent swimwear and poor ink drying properties is achieved. There is concern about adverse effects on printing workability.

[0036]

EXAMPLES The present invention will be specifically described below with reference to examples. Of course, the present invention is not limited to those ranges. Unless otherwise specified, "parts" and "%" in the examples mean "parts by weight" and "% by weight", respectively.
The evaluation items and evaluation criteria are as follows.
The obtained results are shown in Table 1.

[Glass Transition Point of Copolymer Latex] The copolymer latex is dried at room temperature to form a film,
It was measured using a differential thermal scanning calorimeter (DSC-8230D/Rigaku: temperature rising rate 10° C./min).

[Density] The density was measured according to JIS P8118.

[Glossiness of White Paper] It was measured according to JIS P8142.

[Smoothness] JAPAN TAPPI Paper Pulp Test Method No. It measured based on 5A.

[Stiffness] In accordance with the method A of JIS P8143, the projecting lengths of the longitudinal and lateral lines of the sample were measured, and the average value thereof was shown as the projecting length L (stiffness: mm).

[Void Volume] PMI (POROUS MA
TERIALS INC. ) A mercury porosimeter manufactured by Seika Sangyo Co., Ltd. is used to collect 1 gram of a piece of paper, and after measurement, the void volume at 0.03 to 0.3 μm is integrated to obtain a void volume per 1 m ^{2 of} product. The value is converted to.

[Ink Drying Property] A black ink for offset sheet-fed printing 0.5
cc was developed and printed, and after 60 seconds of printing, a high-quality paper was adhered to the printing surface with a constant pressure, and the ink transfer (set-off) condition to the high-quality paper was evaluated according to the following criteria (5-point method). 5: The set is very fast, it can be used for high-speed offset sheet-fed printing, there is no need to increase the amount of spray powder, and there is no problem of set-off. 4; The set is fast and there is no need to increase the amount of spray powder in normal printing, and there is no problem of set-off. 3; standard level. 2; Set is a little slow, and it is necessary to use a large amount of spray powder, but printing is possible by adjusting the printing conditions. 1; Level that is slow to set and cannot be used for offset printing.

[Meat absorbency in swimsuit] Using an RI printing suitability evaluation machine (Ming Seisakusho), 0.5 c of ink for offset sheet-fed printing
After c was color-developed and printed, and after 60 seconds of printing, a high-quality paper was adhered to the printing surface with a constant pressure, and the ink transfer (set-off) condition to the high-quality paper was evaluated according to the following criteria. 5: With offset sheet-fed printing, high-speed printing and high-definition printing can be endured, and even if the dampening water increases, the flesh-absorbing swimsuit has a very good level. 4; High-speed printing is possible with offset sheet-fed printing, and the level of flesh-absorbing swimwear is also good. 3; standard level. 2; The flesh-absorbing swimsuit is slightly inferior, but at a level that can be printed by limiting the amount of dampening water and printing speed in offset printing. 1; The level of the absorbent swimsuit is inferior and difficult to use as offset printing.

Example 1 [Undercoating step] (Preparation of undercoating paint) Kaolin (trade name: as a pigment)
UW-90/Engelhard Co., Ltd. 90 parts and calcium (trade name: FMT-90/Pharmatech Co., Ltd.) 10 parts are used, 0.2 parts of sodium polyacrylate is added to the pigment as a dispersant, and choles dispersion is performed. A pigment slurry having a solid content of 70% was prepared using a machine. The slurry thus obtained had a Tg of 35° C. as a high Tg latex and was a styrene-butadiene copolymer latex (trade name: P-
5980/Sumika A&L) was prepared with a solid content of 18 parts, and phosphoric acid esterified starch (trade name: Ace P260/Oji Corn Starch) was prepared at a concentration of 30% (solid name: Ace). 1.5 parts of P260/Oji Corn Starch Co., Ltd., and water were further added to prepare a paint having a solid content concentration of 60%.

(Coating) Next, the above-prepared coating material was applied onto a high-quality base paper having a weight of 76 g/m ² of tsubo made by neutral papermaking,
Use a blade coater equipped with a hot air dryer with a hot air temperature of 150°C to apply a dry coating amount of 10 g/m ^{2 on} each side, and apply a dry coating to both sides to obtain a weight of 96 g/m 2.
² undercoat papers were obtained.

[Topcoat Process] (Preparation of Topcoat Paint) As a pigment, 10 parts of satin white (trade name: SW-BL/Shiraishi Industry Co., Ltd.), 60 parts of kaolin (trade name: Miracleps PG/Engelhard Co., Ltd.),
Aragonite-based light calcium carbonate (trade name: TP-1
23CS/Okutama Kogyo Co., Ltd.), and 5 parts of an organic pigment (trade name: Rhopaque HP-91/Rohm & Haas Co., Ltd.) are used, and sodium polyacrylate is used as a dispersant for the pigment in a solid content ratio of 0. 2 parts, sodium hydroxide 0.2
Part was added, and the solid content concentration was adjusted to 65 using a Choles disperser.
% Pigment slurry was prepared.

To the thus obtained pigment slurry, 12 vinyl acetate copolymer latex (Tg: 30° C., trade name: Resin 225-5099/Nippon NSC) was added.
Parts, styrene-butadiene copolymer latex having a Tg of 0° C. (trade name: 0632/Nippon Synthetic Rubber Co., Ltd.), and phosphate esterified starch (trade name: Ace P260/Oji Corn Starch Co., Ltd.) 1.5 parts ( (Respectively calculated as solid content),
Further, water was added to prepare a paint having a solid content concentration of 53%.

(Coating) Next, the coating material obtained above is
Both sides of the above-mentioned undercoated paper (96 g/m ² ) using a blade coater equipped with a hot air dryer having a hot air temperature of 170° C. so that the coated amount after drying is 16 g/m ² per side. It was coated and dried.

[Soft Calender Finishing] The thus-obtained double-sided coated paper with one side coated twice has a surface temperature of 13
0°C chrome plated metal roll and Shore D
Paper is passed (line pressure 250 KN/m, speed 500 m/min) so that the front side and the back side contact the metal surface twice each at the nip portion of the elastic roll made of resin with the hardness of 91°. A double-sided coated paper for high gloss printing was obtained. The quality of the obtained double-sided coated paper was evaluated, and the results are shown in Table 1.

Example 2 Double-sided coating was carried out in the same manner as in Example 1 except that the content of satin white was changed to 5 parts and kaolin (trade name; Miraclips PG/Engelhard) was changed to 65 parts. I got the paper. Table 1 shows the quality evaluation results of the double-coated paper thus obtained.

Example 3 A double-sided coated paper was obtained in the same manner as in Example 1 except that the compounding ratio of the vinyl acetate copolymer was changed to 18 parts in the preparation of the top coating composition of Example 1. Table 1 shows the quality evaluation results of the double-coated paper thus obtained.

Example 4 Instead of the vinyl acetate copolymer used in the preparation of the top coating composition of Example 1, a vinyl acetate copolymer having a Tg of 44° C. (trade name; Primal P-310/Rohm and A double-sided coated paper was obtained in the same manner as in Example 1 except that it was changed to Haas Co.). Table 1 shows the quality evaluation results of the double-coated paper thus obtained.

Example 5 A double-sided coated paper was obtained in the same manner as in Example 1 except that the heating roll temperature was changed from 130° C. to 150° C. in the soft calender finish of Example 1. Table 1 shows the quality evaluation results of the double-coated paper thus obtained.

Comparative Example 1 In the preparation of the undercoat paint of Example 1, a styrene-butadiene copolymer latex having a Tg of 35° C. (trade name: P
-5980/Sumika A&L) styrene with Tg of 0°C
A double-sided coated paper was obtained in the same manner as in Example 1 except that the butadiene copolymer latex (trade name: 0632/Nippon Synthetic Rubber Co., Ltd.) was used. Table 1 shows the quality evaluation results of the double-coated paper thus obtained.

Comparative Example 2 In the same manner as in Example 1, except that 10 parts of satin white (pigment) was transferred to kaolin (Miracrypt PG) and 75 parts of Miracrypt PG was used in the preparation of the top coating composition of Example 1. A double-sided coated paper was obtained. Table 1 shows the quality evaluation results of the double-coated paper thus obtained.

Comparative Example 3 Example 1 was repeated except that the vinyl acetate copolymer was changed to a styrene-butadiene copolymer latex (trade name: 0632/Nippon Synthetic Rubber Co., Ltd.) in the preparation of the top coating composition of Example 1. A double-sided coated paper was obtained in the same manner as. Table 1 shows the quality evaluation results of the double-coated paper thus obtained.

Comparative Example 4 The vinyl acetate copolymer used in the preparation of the top coating composition of Example 1 was changed to a vinyl acetate copolymer having a glass transition point of 20° C. (trade name: Movinyl 630/Hoechst Synthetic Co., Ltd.). A double-sided coated paper was obtained in the same manner as in Example 1 except that it was changed. Table 1 shows the quality evaluation results of the double-coated paper thus obtained.

Comparative Example 5 A double-sided coated paper was obtained in the same manner as in Example 1 except that the undercoat layer was not provided in Example 1 and the top coating layer was 28 g/m ² per side. Table 1 shows the quality evaluation results of the double-coated paper thus obtained.

Comparative Example 6 A double-sided coated paper was obtained in the same manner as in Example 1 except that the temperature of the metal roll was 50° C. in the paper passing finish with the soft calender. Table 1 shows the quality evaluation results of the double-coated paper thus obtained.

[0061]

[Table 1]

[0062]

As is clear from Table 1, the coated papers according to the examples of the present invention have a coating layer surface with high gloss and high smoothness, and have extremely high rigidity (excellent in solid feeling). The double-sided coated paper for printing was excellent in printability such as ink drying property and absorbent swimsuit flesh property.

Claims (3)

[Claims] 1. A double-sided coated paper for printing, which comprises a base paper and a coating layer containing a pigment and an adhesive as main components, said Clark being measured according to the method A of JIS P8143 of the double-sided coated paper. The average value L of the protrusion length in the longitudinal and lateral directions satisfies the following formula (1), and the void volume at 0.03 to 0.3 μm when the double-sided coated paper is measured with a mercury porosimeter is 9.00 cc. /M ^{2 to} 11.50 cc/m ²
A double-sided coated paper for printing, characterized in that L> 1.28X + 40 (1) [where, L = average value (unit: mm) of Clarke protrusion length in grain and side grain of double-sided coated paper, X = product tsubo (g/m ² ). Is] 2. A base paper is coated with an aqueous undercoating composition and an aqueous overcoating composition containing a pigment and an adhesive as main components and dried to form a multilayer coating layer, and further an overcoat coating layer is provided. Then, in a double-sided coated paper for printing, which is passed through a thermal calender at 100°C or higher and subjected to pressure treatment, an adhesive for the aqueous composition for undercoating having a glass transition temperature of 30°C or higher is used. The polymer latex is contained in an amount of 15% by weight or more based on the total solid content of all pigments of the aqueous undercoating composition, and as a pigment of the overcoating aqueous composition, Satin White is all pigments of the overcoating aqueous composition. Against 5 to 20
The vinyl acetate copolymer having a glass transition temperature of 25 to 60° C. is contained as an adhesive in an amount of 8 to 20% by weight based on all pigments of the aqueous topcoating composition. The double-sided coated paper for printing according to claim 1. 3. The double-sided coated paper for printing has a density of 1.15 to 1.35 g/c measured according to JIS P8118.
m ^3, the gloss measured in accordance with JIS P8142 75% or more, further J. TAPPI Paper Pulp Test Method No.
The smoothness based on the 5A method (smoothness smoothness meter) is 15
The double-sided coated paper for printing according to claim 1 or 2, which has a viscosity of not more than mmHg.