JP3257745B2 - Coated paper for lightweight printing and method for producing the same - Google Patents

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 light-weight printing and a method for producing the same, and more particularly to a light-weight printing which is mainly used for mail-order catalogs and flyers, and is desired to have both printability and light basis weight. And a method for producing the same.

[0002]

2. Description of the Related Art Coated papers have been widely used as printing papers because of their excellent smoothness and uniform ink absorption as compared with uncoated fine papers. In particular, in recent years, visualization of printed matter has progressed, and the ratio of color printing in which multicolor printing is performed has increased, and the ratio of coated paper to printing paper has been increasing.

However, when a coating solution containing a pigment and an adhesive as main components is applied on a support, the basis weight naturally increases. Such an increase will lead to an increase in transportation or mailing costs, especially in mail-order catalogs and product flyer applications where the ratio of mailing costs is high. Coated amount of lightly coated paper was welcomed as printing paper.

[0004] The lightly coated finely coated paper is a coated paper whose absolute dry amount per one side is generally in the range of ^{3 to} 6 g / m2. the coated paper less than 6 g / m ² on a dry, said blade, rod, air knife, a transfer roll, conventionally, when applied by a coating method used, the coating layer completely covers the substrate Not work, and some problems arise.

In other words, when the coverage of the base material is low at the time of printing, the amount of ink deposited differs between the uncovered portion and the covered portion, and printing unevenness is likely to occur. Such printing unevenness is particularly likely to occur in multicolor printing, which has become mainstream in recent years. Further, since the ink transferred to the uncoated portion penetrates directly into the base material, it tends to cause troubles such as show-through, and such troubles are likely to occur in multicolor printing in which the amount of transferred ink is large.

[0006] As described above, when the lightly coated fine coated paper having a low basis weight, which is excellent in terms of the amount of information per weight in terms of the transportation cost, especially the mailing cost, is applied by the conventional coating method, it is difficult to apply the method. In quality represented by printability in color printing, it cannot be said that the quality is always satisfactory, and it is not possible to achieve both a reduction in basis weight and printability.

[0007] If the problem in the printability of the finely coated paper is caused by the low coating amount of the coating layer, the basis weight of the substrate is reduced, and the reduced amount is reduced by the increased coating amount. There is also a way to use it. That is, as the basis weight of the base material is smaller, the ratio of the amount of the coating layer applied to the basis weight of the coated paper can be increased, so that high printability can be obtained.

However, the basis weight of the substrate is small, that is,
When a thin base material is coated on both sides of such a base material to produce a coated paper for lightweight printing, it is essential to increase the opacity to avoid interference between the front and back surfaces of the printed surface. As a means for improving opacity, it is common to employ a means for increasing the filler addition rate.However, if the filler addition ratio is increased, the strength of the base material is reduced, and fine holes, that is, pins I can not escape the occurrence of holes.

[0009] When the strength of the base material is reduced, a problem occurs at the time of coating in the conventional coating methods such as a blade, a rod, an air knife, and a transfer roll. In other words, in a post-metering coating method such as a blade, a rod, and an air knife,
Since there is a distance from the supply of the coating liquid to the substrate to the measurement, the substrate is exposed to the shearing field in the measuring section after the coating liquid has sufficiently penetrated into the substrate. In other words, when the substrate with low strength swells with water in the coating solution and further decreases in strength, it is exposed to the shearing field, so the probability of cutting the substrate becomes extremely high,
In effect, a problem arises in that it cannot be applied.

The transfer roll is a pre-measurement type coating method in which a pre-measured liquid is transferred, and the strength of the base material does not decrease due to the difference in distance between the liquid supply part and the measurement part. If it is low, at the exit of the roll after application and the roll where the substrate is peeled off, by tacking with the coating liquid interposed,
The probability of cutting the substrate becomes very high, which causes a problem that it cannot practically be applied.

Due to this fact, it can be determined that it is practically impossible to use a coating method that has been generally used in the past when coating a substrate having a small basis weight.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to provide a low-basis-weight base material capable of achieving both information amount per unit weight and high printability with a coating amount that can be satisfied in printability. The purpose of the present invention is to provide a light-weight printing coated paper applied in a state in which the base material has high coatability. Is to get under stable operating conditions.

[0013]

The light-weight printing coated paper of the present invention has a base material having a basis weight of 20 to 30 g / m ² , and a pigment and an adhesive are mainly contained on one or both sides of the base material. Solid
Curtain coating equipment using a coating solution with a partial concentration of 40% by weight or more
Location by per surface 6~14g / m ² (absolute dry coating amount) applied
The coating layer is characterized by having a low basis weight and excellent printability.

Further, the method for producing a coated paper for light-weight printing according to the present invention is characterized in that a base material having a basis weight of 20 to 30 g / m ^{2 is} coated on one or both sides with a solid concentration of 40% mainly containing a pigment and an adhesive.
With wt% or more of the coating solution by a curtain coating apparatus which is characterized in that per surface bone dry coating weight 6~14g / m ² applied to provide a coating layer, the coating operation for the low basis weight substrate In this case, there is no obstacle such as cutting of the base material, the stable operation state, a low basis weight, and a coated paper for lightweight printing excellent in printability can be obtained.

The smaller the basis weight of the substrate, the higher the ratio of the amount of the coating layer applied to the basis weight of the coated paper, so that high printability can be obtained. However, in consideration of producing the base material under stable operating conditions and considering the uniformity of the mass distribution which is an important property as the base material of the coated paper, the preferred minimum base weight of the base material is 20 g / m2 in absolute dryness. ² Of course, with respect to the upper limit of the basis weight of the base material, in a papermaking apparatus which usually forms a base material of a coated paper for printing, the basis weight of the absolutely dry basis is 10%.
Although it can be up to 0 g / m ² or more, in consideration of increasing the information amount per unit weight, which is the original purpose of the lightweight printing coated paper in the present invention, and further considering the mailing cost and the like. For example, it is preferable that the absolute basis weight is 30 g / m ² . In other words, taking into account both printability and the original significance of lightweight printing paper, the basis weight range of the base material is 20 to
It is preferably 30 g / m ² .

As in the case of such a base material, it has a low basis weight and is weak in strength, and in order to secure printing paper and necessary opacity,
The filler content must be increased, and the substrate becomes increasingly weaker in strength. In addition, since the frequency of pinholes increases due to an increase in the filler, the strength is partially further reduced.

On the other hand, the curtain coating method is suitable for coating a substrate having a small basis weight and a low strength for the following reason. In other words, since the curtain coating device is a pre-metering type coating device, the measurement is completed before the transfer of the coating solution to the base material, so that the strength of the base material decreases due to the penetration of water in the coating solution. Does not occur, even when the coating solution is transferred,
Since no external pressure is applied to the substrate, the substrate is not cut. Further, since the coating is performed by the transfer of the liquid film on the curtain, the pinhole can be covered with the coating liquid without any obstacle even when the substrate has a pinhole.

Furthermore, since the pressure involved in the liquid permeation at the time of coating is only the capillary pressure, the permeation of the coating liquid can be minimized, so that the strength of the substrate is reduced even in the drying step after coating. Instead, the probability of cutting the substrate can be reduced.

The coating layer applied by the curtain coating device is a coating film in which a curtain film having a uniform thickness in the width direction is stretched by a continuously running base material. Therefore, since a coating layer having a uniform thickness is formed irrespective of the unevenness of the base material, the coatability of the base material is high and the printability is high even with a relatively low application amount.

According to further studies by the present inventors, the preferred range of the coating amount for the lightweight printing coated paper in the present invention is 6% per side on a completely dry coating amount.
１４14 g / m ² . If it is less than 6 g / m ² , the coating layer cannot completely cover the substrate, and high printability cannot be obtained. If it is more than 14 g / m ² , the stiffness is too low, especially in sheet-fed printing. In addition, the transportability of the light-weight printing coated paper is deteriorated, and trouble occurs in the printing process.

The solid content concentration of the coating liquid affects the permeability of the coating liquid to the substrate. When applying to a substrate having a small basis weight using a curtain coating apparatus as in the lightweight printing coated paper of the present invention, the solid content concentration is 40% by weight.
Due to the above, the strength of the substrate does not decrease even in the drying step after application, and the probability of cutting the substrate can be reduced.

The curtain coating apparatus according to the present invention refers to an apparatus which forms a curtain film having a uniform thickness in a width direction from a coating head and transfers the curtain film as a coating layer to a continuously running support.

In the present invention, the coating liquid containing a pigment and an adhesive as main components is a liquid dissolved or dispersed in water together with a pigment, an adhesive and other additives. The mixing ratio of the pigment and the adhesive is generally 5 parts by weight or more, preferably 10 to 70 parts by weight, based on 100 parts by weight of the pigment.

The pigments used in the present invention include kaolin, clay, calcium carbonate, satin white, titanium oxide, aluminum hydroxide, zinc oxide, barium sulfate,
Examples include calcium sulfate, silica, activated clay, lake, plastic pigment, binder pigment and the like.

Examples of the adhesive used in the present invention include various copolymers such as styrene / butadiene, vinyl acetate / acrylic, ethylene / vinyl acetate, butadiene / methyl methacrylic, and vinyl acetate / butyl acrylate. Synthetic adhesives such as alcohol, maleic anhydride copolymer, isobutene / maleic anhydride copolymer, acrylic acid / methyl methacrylate copolymer, oxidized starch, etherified starch,
Commonly known adhesives such as esterified starch, enzyme-modified starch, cold-water-soluble starch obtained by flash-drying them, and natural adhesives such as casein and soybean protein are included. In addition, if necessary, various auxiliaries such as a thickener, a water retention agent, a water resistance agent, and a coloring agent, which are blended in a general pigment coating solution for coated paper, can be used.

Examples of the base material used in the present invention include generally used high-quality paper, medium-quality paper, waste paper, and pigment-coated paper.

[0027]

The present invention is characterized in that the absolute basis weight of the substrate is 20 to 30 g /
m ² , wherein the coating layer provided on one or both sides of the base material is a coating liquid having a solid content concentration of 40% by weight or more applied by using a curtain coating apparatus. When the coating amount per side of the above is in the range of 6 to 14 g / m ^{2 on} a dry basis, a coated paper for lightweight printing excellent in printability and operation stability during coating can be obtained.

[0028]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The parts and percentages shown below are based on weight, and the parts are based on 100 parts of the total amount of the pigment. Further, the basis weight and the application amount are absolutely dry values.

Example 1 <Substrate> Softwood pulp (Canada standard freeness 150 ml) and hardwood pulp (Canada standard freeness 350 ml) 60% were prepared as pulp formulations. In addition, talc is used as a filler, and as a weight in paper,
4%. The sizing agent uses a rosin sizing agent,
A base material having a basis weight of 22 g / m ² was prepared by internally adding 0.4% per pulp weight and using a sulfuric acid band as a fixing agent and adding 2% per pulp weight.

<Coating> With the following composition, the solid content concentration is 44
% Of the coating solution was applied to both surfaces of the obtained base material using a curtain coating device at an application amount of 8 g / m ² per one surface to produce a coated paper for lightweight printing. -Coating liquid formulation Commercially available primary kaolin (Ultra White 90) 40 parts Commercially available secondary kaolin (Caobrite) 30 parts Commercial heavy calcium carbonate (Carbital 90) 20 parts Commercially available anatase type titanium oxide (A-110) 10 parts Commercially available styrene・ Butadiene latex 12 parts Commercially available phosphorylated starch 5 parts Commercially available polyacrylic acid dispersant 0.1 part

Example 2 A coated paper for lightweight printing was produced in the same manner as in Example 1 except that the concentration of the coating solution was changed to 56%.

Example 3 A coated paper for lightweight printing was produced in the same manner as in Example 1 except that the basis weight of the base material was changed to 28 g / m ² .

Example 4 A coated paper for light-weight printing was produced in the same manner as in Example 1 except that the coating amount per side of the coating solution was 12 g / m ² .

Example 5 A coated paper for lightweight printing was produced in the same manner as in Example 4 except that the concentration of the coating solution was changed to 56%.

Example 6 A coated paper for lightweight printing was produced in the same manner as in Example 4 except that the basis weight of the substrate was changed to 28 g / m ² .

Comparative Example 1 A coated paper for lightweight printing was produced in the same manner as in Example 1, except that the basis weight of the base material was changed to 18 g / m ² .

Comparative Example 2 A coated paper for lightweight printing was produced in the same manner as in Example 4 except that the basis weight of the base material was changed to 18 g / m ² .

Comparative Example 3 A coated paper for lightweight printing was produced in the same manner as in Example 1 except that the concentration of the coating solution was 37%.

Comparative Example 4 A coated paper for lightweight printing was produced in the same manner as in Example 4 except that the concentration of the coating solution was changed to 37%.

COMPARATIVE EXAMPLE 5 Except that the coating amount per side of the coating solution was set to 5 g / m ² ,
A coated paper for lightweight printing was produced in the same manner as in Example 1.

Comparative Example 6 A coated paper for light-weight printing was produced in the same manner as in Example 1, except that the coating amount per side of the coating solution was 17 g / m ² .

Comparative Example 7 A coated paper for lightweight printing was produced in the same manner as in Example 1, except that a blade coating device was used as the coating device.

Comparative Example 8 A coated paper for lightweight printing was produced in the same manner as in Example 1 except that a rod coating device was used as the coating device.

Comparative Example 9 An air knife coating device was used as a coating device.
A coated paper for lightweight printing was produced in the same manner as in Example 1.

Comparative Example 10 A coated paper for lightweight printing was produced in the same manner as in Example 1 except that a transfer roll coating device was used as a coating device.

The obtained light-weight printing coated papers were subjected to super calender finishing under the same conditions, and then evaluated.

Evaluation of print unevenness was carried out by using a four-color printing Roland offset printing machine under the condition of excess dampening water, and allowed to stand at room temperature for 24 hours. The area ratio of the cyan monochromatic halftone dots of the sample was 50%. The printing was performed visually.
(Unit: 5 out of 5)

The gloss was measured using a Murakami gloss meter.
The measurement was performed at an incident angle of 75 ° and a reflection angle of 75 °.

The evaluation of the show-through of the ink was carried out by printing on one side of a sample using a four-color printing Roland offset printing machine, leaving it to stand at room temperature for 24 hours, and measuring the area ratio of the four-color multicolor halftone dots of the sample to 100%. The back side of the solid printing section was visually observed. The evaluation unit was a five-level evaluation. The evaluation criterion was 5 if no show-through was observed, 4 was a case where slight show-through was observed, and 3 was a degree where show-through was observed but there was no practical problem, and the show-through was clearly observed Then, 2 was determined to be able to determine that it interfered with the image on the back surface, and 1 was determined to be significant to show off the image and to significantly interfere with the image on the back surface.

[0050]

[Table 1]

According to Examples 1 to 6, the absolute dry basis weight of the substrate was in the range of ²⁰ to 30 g / m ² , and a coating solution having a concentration of 40% by weight or more was applied to one side using a curtain coating apparatus. By applying the applied amount per absolute dryness in the range of 6 to 14 g / m ² , by applying, there is no obstacle such as print unevenness or ink show-through, and a light-weight printing coated paper excellent in the appearance of gloss, It is clear that it can be obtained under high operability.

According to Comparative Examples 1 and 2, the basis weight of the substrate was 20
If it is less than g / m ² , the strength of the substrate is too low, and the substrate is likely to be cut, and the operability is not stable. Show-through also easily occurs. According to Comparative Examples 3 and 4, when the liquid concentration is less than 40%, the penetration of the coating liquid into the base material significantly occurs, so that the strength of the base material is reduced after coating, and the base material is easily cut. And operability is not stable. According to Comparative Example 5, when the coating amount is less than 8 g / m ² , the coating property of the base material of the coating layer is deteriorated, so that printing unevenness and show-through occur. According to Comparative Example 6, when the application amount exceeds 14 g / m ² , the rigidity of the coated paper for lightweight printing is insufficient, and the transportability during printing deteriorates. According to Comparative Examples 7 to 9, cutting of the base material occurs due to penetration of the liquid occurring between the liquid supply unit and the measuring unit and the shearing force during the measurement. According to Comparative Example 10, at the roll outlet after application, the substrate adheres to the roll due to the adhesive force of the application liquid, and the substrate is cut.

[0053]

According to the present invention, it is possible to obtain a light-weight coated printing paper which is excellent in the appearance of gloss without obstruction such as printing unevenness and ink show-through and has high operability.

Claims (2)

(57) [Claims] 1. A coated paper for lightweight printing, wherein the substrate has a basis weight of 2
Consists 0~30g / m ^2, on one side or both sides of the substrate,
Solid content concentration of 40% by weight or less containing pigment and adhesive as main components
A coated paper for lightweight printing, characterized in that a coating layer is provided by applying 6 to 14 g / m ² (absolutely dry coating amount) per side using a curtain coating apparatus using the above coating liquid . 2. A method for producing a coated paper for lightweight printing, comprising:
On one or both sides of a substrate having a basis weight of 20 to 30 g / m ^2, a coating solution containing a pigment and an adhesive as a main component and having a solid content concentration of 40% by weight or more is used. A method for producing a coated paper for lightweight printing, characterized in that a coating layer is provided by applying 6 to 14 g / m ² .