JPH06158591A - Pigment-coated paper for printing and its production - Google Patents

Abstract

PURPOSE:To provide pigment-coated paper used for printing. excellent in luster and smoothness and free from coating failures generated on the coating, from printing irregularity generated on the printing, and from coating irregularity generated in the coating. CONSTITUTION:The pigment-coated paper used for printing and produced by disposing a coating layer consisting mainly of the pigment on a substrate is characterized in that 3-20wt.% of the whole amount of the pigment is satin white, that all of the coating solution for the coating layer can pass through intervals of <=120mum, and that the coating solution is coated with a curtain coating device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pigment-coated paper for printing and a method for producing the same, in which a coating solution containing a pigment is applied to a continuously running strip-shaped substrate (hereinafter referred to as "web"). TECHNICAL FIELD The present invention relates to a pigment-coated paper and a manufacturing method thereof. In particular, the present invention relates to printing paper such as art and coated paper, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, pigment-coated paper has been used as a printing paper because it has higher smoothness and gloss than that of uncoated high-quality paper and has uniform ink absorption. Particularly in recent years, the visualization of printed matter has advanced, and the demand for printing paper has also diversified. Furthermore, there are various printing methods such as gravure, rotary offset, sheet-fed offset, etc., and printing paper with characteristics suitable for each printing method. Is being developed. Under such circumstances, a demand for a coating technique for printing paper on which a pigment is coated is to obtain a product having excellent gloss, high surface smoothness, and no coating defects under high productivity.

There are various coating methods for printing paper for pigment coating, and specific examples thereof include a blade coating method, an air knife coating method and a roll coating method. However, in these coating methods, the type and shape of the pigment contained in the coating liquid must be restricted in consideration of the quality of the coated product and the stability of the process, and the pigment having a great effect on the quality improvement. However, it is difficult to obtain high quality printing paper.

That is, satin white is used as a pigment that constitutes the coating layer of the coated paper for printing, because the gloss of the coated paper is improved by adding a relatively small amount to the coating liquid.
However, Satin White has elements that are obstacles to the coating operation, such as high viscosity of the coating liquid with which it is blended, high cohesiveness, and high response to pH.

For example, in the blade coating method and the rod coating method, coating defects such as streaks and scratches are likely to occur in the coating operation, but in particular, the coating liquid containing satin white has a high viscosity at a high shear rate. The fluidity of the liquid is reduced in the field where a high shear rate is applied just under the blade tip or directly under the rod, and the probability of streak or scratch increases. Further, since the coating liquid containing Satin White has a high cohesive property, the generated soft agglomerates hinder the flow of the liquid, so that streaks and scratches are likely to occur.

As described above, when streaks or scratches are generated, the generated portions are all wasted paper, which causes a large loss in terms of production efficiency and cost. Further, the occurrence of these coating defects becomes more remarkable as the coating speed becomes higher and the coating concentration becomes higher, and the efficiency of production and the improvement of quality are not compatible with each other.

Further, in such a coating method, the water or binder component in the coating liquid infiltrates into the web more than necessary during the period from the supply of the excess liquid to the measurement, so that the liquid scraped off as the excess liquid is The composition of the liquid before supply differs. Therefore, the composition of the coating solution changes with the passage of time, and a product of stable quality cannot be obtained.

The air knife coating method tends to generate a pattern peculiar to the air knife in the coating layer, and is particularly remarkable when a coating liquid containing satin white is used. By this,
The gloss and smoothness of the surface of the coating layer are significantly lowered, not only the quality is lowered, but also a serious obstacle during printing.
This tendency becomes remarkable when the coating speed is increased or when the concentration of the liquid is increased, and it is not possible to improve the production efficiency and the quality at the same time.

There are various types of roll coating methods depending on the combination of rolls and the like. Basically, a plurality of rolls are combined and the coating liquid is transferred between the rolls to measure the liquid and transfer it to the web. It is a coating method. Such a coating method easily generates a pattern peculiar to the roll, and
When a coating liquid containing Satin White is used, peeling unevenness called a split pattern is likely to occur at the time of peeling after the transfer of the coating roll surface and the web, and the gloss and smoothness of the coating surface are deteriorated. Not only will the quality deteriorate, but it will also become a serious obstacle during printing. This tendency becomes remarkable when the liquid concentration or the coating speed is increased.

As described above, a coating solution containing satin white, which can improve the gloss by adding a relatively small amount and can obtain a high-quality pigment-coated paper, is used to reduce gloss and surface quality.
In addition, the present situation is that there is no coating method that can be applied without causing coating defects.

[0011]

The object of the present invention is to solve the problems of deterioration in gloss and smoothness that occur when a coating solution containing satin white is applied, and to prevent the occurrence of coating defects. It is to obtain a high-quality pigment-coated paper for printing in which printing unevenness due to coating unevenness does not occur.

[0012]

The pigment-coated paper for printing of the present invention is a pigment-coated paper for printing in which a coating layer containing a pigment as a main component is provided on a substrate. 20% by weight
Is satin white, and all the coating liquids of the coating layer are 12
It has a feature that it can pass through a gap of 0 μm or less, that the coating layer is coated by a curtain coating device, that coating defects do not occur, gloss and smoothness are high, and printing unevenness does not occur.

The method for producing a pigment-coated paper for printing of the present invention is a method for producing a pigment-coated paper for printing in which a coating layer containing a pigment as a main component is provided on a substrate. 3-
A coating liquid containing 20% by weight of satin white is prepared, all of the coating liquid is passed through a gap of 120 μm or less, and the coating liquid is coated on the substrate by a curtain coating device.

Satin White has a chemical formula of 3CaO.Al.
A pigment represented by ₂ O ₃ · 3CaSO ₄ · 31H ₂ O, which has a needle-like crystal shape when wet paste, and an amorphous powder shape after drying, and a high gloss with a relatively small amount of addition. Is known to be obtained.

Specifically, when Satin White is added in the range of 3 to 20 parts by weight, the effect of improving the gloss of coated paper is most excellent. If the mixing amount is less than 3% by weight, the effect of the addition is small and the improvement in gloss cannot be expected, and if the mixing amount is more than 20% by weight, the thixotropy of the coating solution sharply rises, and any coating method was used. Also in this case, the quality of the coated surface deteriorates, the smoothness and gloss deteriorate, and as a result, uneven printing occurs.

When the curtain coating device is applied to the coating liquid containing 3 to 20% by weight of satin white, the surface quality of the blade coating device, the rod coating device, the air knife coating device, and the roll coating device described above is applied. It is possible to avoid deterioration of gloss and smoothness due to deterioration. In other words, the curtain coating method is a pre-metering type coating device, and since there is no scraping of the coating liquid during coating, the coating liquid forms a very uniform, so-called contour coating layer along the surface shape of the web, giving a glossy finish. In addition, it is possible to obtain a pigment-coated paper for printing, which is excellent in smoothness and uniformity of coating amount, and as a result, print unevenness does not occur.

The coating liquid containing 3 to 20 parts by weight of satin white has a high cohesive property, and in particular, it has a high probability of generating a soft agglomerate which is not solidified and has an indefinite shape. Although it is difficult to specify the size of the soft agglomerates, most of the pigments contained in the coating liquid have a particle size of 10 μm or less, and therefore the size of the soft agglomerates is several tens of μm to several mm. It is a range. Here, the size of the flow path through which the coating liquid passes during the coating operation is
The stagnation of such soft agglomerates has a very dominant influence on the occurrence of coating defects.

That is, as a characteristic of the curtain coating method, as can be seen from FIG. 1, the only place where the liquid flows in a restricted flow path is the slit 2. This slit has a wide selection range, but normally 0.2 m
It is between m and 1 mm. In curtain coating, the liquid flowing out from the lip 3 forms a free surface until it comes into contact with the web 5, so the flow path is not regulated. On the other hand, in the rod or blade coating method, the minimum gap between the web or the rod or blade where the liquid is measured is usually
It is 0.05 mm or less. Therefore, when soft agglomerates are present in the liquid, the probability of appearing as streaks is lower in the curtain coating method than in the rod or blade coating method.

As described above, when the curtain coating method is applied to the coating of such a coating liquid, the occurrence of coating defects due to soft agglomerates is extremely reduced. Before applying to
It was found that the soft agglomerates can be redispersed by passing through a gap of m or less, and the occurrence of such coating defects can be avoided.

Furthermore, since the curtain coating method is a pre-metering type coating method, the amount of the liquid flowing out from the head is collected and used in a small amount. On the other hand, blade coating method,
The rod coating method and the air knife coating method are post-measurement type coating methods in which the liquid is once excessively supplied to the web and then scraped off for measurement, so the amount of collected liquid is smaller than that of curtain coating. Many. Moreover, in such a coating method,
When excess liquid is supplied to the web, the water and binder in the liquid are selectively absorbed by the web, and the concentration of the recovered liquid becomes high and the concentration of the coating liquid becomes high. Accompany the collected liquid and cause streaks. With the curtain coating method, stable coating can be performed without changing the concentration of the coating liquid even during long-term operation.
The operation of passing through a gap of 20 μm or less has a secondary effect of removing solidified substances and foreign matters of the coating liquid mixed in the coating liquid.

As a means for passing the coating liquid through a gap of 120 μm or less, a means for passing a filter is generally used. Any filter can be used as long as it has an opening of 120 μm or less, and specifically, a wire filter, a W-CELL filter, a helical mesh filter, a wire mesh filter, a serie filter, a Roningen filter, a screen filter, Examples thereof include a resin mesh filter and a resin multilayer mesh filter.

As another means for passing the gap of 120 μm or less, a contact type pump can be used for feeding the coating liquid. Specifically, a snake pump, a Moino pump, a gear pump, a Tathill pump, etc. can be mentioned.

As described above, the present invention is characterized in that the coating layer which comes into contact with the web is coated by the curtain coating method.
20% by weight is satin white, and all the coating solutions are 12
A method for obtaining a pigment-coated paper for printing, which has high gloss and smoothness and does not cause printing unevenness by applying a curtain coating device after passing through a gap of 0 μm or less and without causing coating defects. However, there is no disclosure of such a method yet.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a schematic view of a coating apparatus for coating a pigment coated paper for printing showing an embodiment of the present invention. The coating liquid prepared in advance is sent from the coating liquid storage tank 11 to the coater head 1 through the filter 13 by the liquid supply pump 12.

The interior of the coater head 1 is composed of a manifold 6 and slits 2, each of which is finished with high precision. The supplied coating liquid is filled in the manifold 6, and the influence of the dynamic pressure due to the liquid feeding of the pump 12 is reduced in the narrow gap that passes when being sent to the slit 2, and the pressure distribution in the width direction is made uniform, Lip 3
Further outflow, a vertical curtain film 4 is formed.

The vertical curtain film 4 having a uniform profile in the width direction comes into contact with the continuously running web 5,
It is applied to the web 5. Here, the edge guides 10a, 1
0b is provided not to exceed the width of the coater head 1 and further to the width of the web 5, and the vertical curtain film is formed to exceed the width of the web 5. The vertical curtain film 4 is formed so as to exceed the width of the web 5 in order to prevent thick coating of the coating layer on both ends of the vertical curtain film 4. Web 5
The coating liquid that flows down beyond the width of is collected in the liquid receiving tank 9,
After being returned to the coating liquid storage tank 11, the coating liquid is applied again. Further, even when the coating is interrupted such as when the web 5 is cut, the coating liquid is collected in the liquid receiving tank 9.

The air flow entrained in the web 5 is shielded at the contact portion (hereinafter referred to as the "coating portion") between the continuously running web 5 and the vertical curtain film 4 by the circulation of air around the curtain. Web 5 without vertical curtain film 4 being disturbed
A wind shield 8 is provided to reach the position. Further, the web 5 is configured so that the conveying direction of the web 5 is changed immediately before the coating section by the roll 7, so that the influence of air entrained in the web 5 on the coating section is minimized.

In order to apply the formed vertical curtain film 4 in a stable state, the web 5 is moved to the coater head 1.
The height to the lower outflow portion is required to some extent, but in the present embodiment, the height can be controlled, and the height suitable for stabilizing the vertical curtain film 4 is 60 to 30.
It is 0 mm, preferably 100 to 250 mm, more preferably 120 to 180 mm.

Needless to say, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made. In the above-described embodiment, the width of the formed curtain film is larger than the width of the web 5, but this is to prevent the increase of the coating amount at both ends of the coating layer. If it is not a problem, or if it can be solved by adopting the method disclosed in Japanese Examined Patent Publication No. 49-14130, etc., or other method for preventing increase in coating amount, the vertical curtain film is used as the web 5 The width may be equal to or slightly smaller than this.

It is also possible to attach a profile adjusting mechanism or a control mechanism to the curtain head. When an opening degree profile adjusting mechanism is attached to the slit 2 shown in FIG. 1, a more uniform coating amount profile in the width direction can be obtained.

In the present invention, the coating liquid containing a pigment as a main component is a liquid in which the pigment, the binder and other additives are dissolved or dispersed in water, and the concentration of the pigment, the binder and the other additives is 10%. ~ 70% by weight. The blending ratio of the pigment and the binder is generally 5% by weight or more, preferably 10% by weight of the total amount of the pigment.
It is desirable to be 70% by weight.

As pigments for coated paper used in the present invention, in addition to satin white, kaolin, clay, calcium carbonate, titanium oxide, aluminum hydroxide, zinc oxide, barium sulfate, calcium sulfate, silica, mica, activated clay, Examples include rakes and plastic pigments.

As the binder used in the present invention,
Various copolymers of styrene / butadiene, vinyl acetate / acrylic, ethylene / vinyl acetate, butadiene / methylmethacrylate, vinyl acetate / butyl acrylate, polyvinyl alcohol, maleic anhydride copolymer, isobutene / maleic anhydride Acid-based copolymers, synthetic adhesives such as acrylic acid / methyl methacrylate-based copolymers, oxidized starch, etherified starch, esterified starch, enzyme-modified starch and cold water-soluble starch obtained by flash-drying them, casein, Examples include commonly known adhesives such as natural adhesives such as soybean protein. Further, if necessary, various auxiliaries such as a thickener, a water retention agent, a water resistance agent, a colorant and the like, which are mixed with a usual pigment for coated paper, can be appropriately used.

The coating composition of the present invention thus obtained is
A single-layer or multi-layer coating is applied on both sides or one side of the web. A coating device other than the curtain coating device can be used for coating the lower layer portion in the multilayer coating, and wet-on-wet coating may be performed in which the upper layer coating is performed without drying the lower layer coating portion.

The web used in the present invention includes generally used high-quality paper, medium-quality paper, waste paper, machine-coated paper,
Includes art paper, cast coated paper, synthetic paper, resin coated paper, plastic film, etc.

[0036] In the present invention, the coating amount of the coating solution mainly composed of pigment on a dry weight standards, 1 g / m ² or more, preferably, suitably 3 to 30 g / m ^2.

[0037]

The pigment-coated paper for printing of the present invention is a pigment-coated paper for printing provided with a coating layer containing a pigment as a main component, and 3 to 20% by weight of the total amount of the pigment is satin white. A coating layer was provided by a curtain coating device using the coating liquid in which all of the layer coating liquid was passed through a gap of 120 μm or less. The thus obtained pigment-coated paper for printing has excellent properties, with no coating defects, high gloss and smoothness, and no uneven printing.

[0038]

EXAMPLES The present invention will now be described in more detail by way of examples, which should not be construed as limiting the invention thereto. The parts and% shown below are based on weight.

Example 1 60 g / m ² basis weight (absolutely dry) high-quality paper was coated with a blade coating device so that the absolutely dry application amount was 8 g / m ² .
An undercoat coating liquid having a solid content concentration of 61% having the following composition was prepared and coated at a coating speed of 800 m / min to prepare an undercoat base paper.

<Undercoating liquid formulation> Commercial heavy calcium carbonate (carbital 90) 70 parts Commercial secondary kaolin (caobrite) 30 parts Commercial phosphate esterified starch 9 parts Commercial styrene-butadiene latex 8 parts Commercial polyacrylic acid dispersion Agent 0.1 part Sodium hydroxide 0.1 part

A topcoat coating solution having a solid content concentration of 52% was prepared by the following formulation, and the basecoat paper obtained above was coated with a curtain coater so that the absolute dry coating amount was 14 g / m ^2. The coating liquid was coated at a coating speed of 700 m / min to prepare a pigment coated paper for printing. The filter for passing the overcoat coating liquid was a helical mesh filter (W-CELL filter manufactured by Arai Iron Works Co., Ltd.) in which a wire having a triangular cross section was spirally wound around a cylindrical cell, and the aperture was 110 μm.

<Composition of Topcoat Liquid> Commercial Sachin White 3.5 parts Commercial Heavy Calcium Carbonate (Carbital 90) 8 parts Commercial Cubic Light Calcium Carbonate (Brilliant 15) 12 parts Commercial First Grade Kaolin (Ultra White 90) 46.5 Part commercially available secondary clay (hydrasperth) 30 parts commercially available polyacrylic acid-based dispersant 0.1 part commercially available phosphate esterified starch 2 parts commercially available styrene-butadiene latex 14 parts

Example 2 A pigment-coated paper for printing was prepared in the same manner as in Example 1 except that the coating solution for topcoat was prepared as follows.

<Composition of Topcoat Liquid> Commercial Sachin White 12 parts Commercial Heavy Calcium Carbonate (Carbital 90) 8 parts Commercial Cubic Light Calcium Carbonate (Brilliant 15) 12 parts Commercial First Grade Kaolin (Ultra White 90) 38 parts Commercial Second Class Clay (Hydrasperse) 30 parts Commercial polyacrylic acid-based dispersant 0.1 parts Commercial phosphoric esterified starch 2 parts Commercial styrene-butadiene latex 14 parts

Example 3 A pigment-coated paper for printing was prepared in the same manner as in Example 1 except that the coating solution for topcoat was prepared as follows.

<Topcoat liquid formulation> Commercial satin white 19 parts Commercial heavy calcium carbonate (carbital 90) 8 parts Commercial cubic light calcium carbonate (Brilliant 15) 12 parts Commercial first grade kaolin (Ultra White 90) 31 parts Commercial second grade Clay (Hydrasperse) 30 parts Commercial polyacrylic acid-based dispersant 0.1 parts Commercial phosphoric esterified starch 2 parts Commercial styrene-butadiene latex 14 parts

Example 4 As the base paper for applying the overcoat liquid, a high-quality paper having a basis weight of 60 g / m ² (absolutely dry) having no undercoat layer was used, except that
A pigment-coated paper for printing was prepared in the same manner as in Example 2.

Example 5 Example 2 was repeated except that the filter for passing the overcoat coating liquid was a wire mesh filter obtained by processing a stainless mesh into a cylindrical shape and having a mesh opening of 110 μm.
A pigment-coated paper for printing was prepared in the same manner as in.

Comparative Example 1 A pigment-coated paper for printing was prepared in the same manner as in Example 1 except that the filter opening was 130 μm.

Comparative Example 2 A pigment-coated paper for printing was prepared in the same manner as in Example 2 except that the filter openings were 130 μm.

Comparative Example 3 A pigment-coated paper for printing was prepared in the same manner as in Example 3 except that the filter opening was 130 μm.

Comparative Example 4 A pigment-coated paper for printing was prepared in the same manner as in Example 4, except that the aperture of the filter was 130 μm.

Comparative Example 5 As a base paper for applying the topcoat liquid, a high-quality paper having a basis weight of 60 g / m ² (absolutely dry) without an undercoat layer was used.
A pigment coated paper for printing was prepared in the same manner as in Comparative Example 2.

Comparative Example 6 A pigment-coated paper for printing was prepared in the same manner as in Example 1 except that the composition of the top coating liquid was as follows.

<Topcoat Liquid Blend> Commercial Sachin White 22 parts Commercial Heavy Calcium Carbonate (Carbital 90) 8 parts Commercial Cubic Light Calcium Carbonate (Brilliant 15) 12 parts Commercial First Grade Kaolin (Ultra White 90) 28 parts Commercial Second Class Clay (Hydrasperse) 30 parts Commercial polyacrylic acid-based dispersant 0.1 parts Commercial phosphoric esterified starch 2 parts Commercial styrene-butadiene latex 14 parts

Comparative Example 7 A pigment-coated paper for printing was prepared in the same manner as in Example 1 except that the composition of the top coating liquid was as follows.

<Composition of Topcoat Liquid> Commercial Satin White 2.5 parts Commercial Heavy Calcium Carbonate (Carbital 90) 8 parts Commercial Cubic Light Calcium Carbonate (Brilliant 15) 12 parts Commercial First Grade Kaolin (Ultra White 90) 47.5 Part commercially available secondary clay (hydrasperth) 30 parts commercially available polyacrylic acid-based dispersant 0.1 part commercially available phosphate esterified starch 2 parts commercially available styrene-butadiene latex 14 parts

Comparative Example 8 A pigment-coated paper for printing was prepared in the same manner as in Example 1 except that no filter for passing the top coating liquid was used.

Comparative Example 9 A pigment-coated paper for printing was prepared in the same manner as in Example 2 except that no filter for passing the top coating liquid was used.

Comparative Example 10 A pigment-coated paper for printing was prepared in the same manner as in Example 3, except that a filter for passing the overcoat coating liquid was not used.

Comparative Example 11 The topcoat coating solution used in Example 1 was applied to the undercoat base paper obtained above with a blade coating device to give an absolute dry coating amount of 14 g.
/ M ² so that the top coating solution is applied at a coating speed of 700
It was applied at m / min to prepare a pigment coated paper for printing. No filter was used to pass the topcoat coating liquid.

COMPARATIVE EXAMPLE 12 The topcoat coating liquid used in Example 1 was applied to the undercoat base paper obtained above by a rod coating device to give an absolute dry coating amount of 14 g /
As will be m ^2, the overcoat coating solution, coating speed 700m
/ Min to prepare a pigment-coated paper for printing. No filter was used to pass the topcoat coating liquid.

Comparative Example 13 The topcoat coating liquid used in Example 1 was diluted to 45%, and the undercoat base paper obtained above was coated with an air knife coating device so that the absolute dry coating amount was 14 g / m ² . The topcoat coating liquid was applied at a coating speed of 250 m / min to prepare a pigment coated paper for printing. No filter was used to pass the topcoat coating liquid.

Comparative Example 14 The topcoat coating solution used in Example 1 was diluted to 48%, and the undercoat base paper obtained above was diluted with a reverse roll coater.
The top coating liquid was applied at a coating speed of 180 m / min so that the absolute dry coating amount was 14 g / m ² , to prepare a pigment coated paper for printing. No filter was used to pass the topcoat coating liquid.

Comparative Example 15 Opening 1 as a filter for passing the top coating liquid
A pigment coated paper for printing was prepared in the same manner as in Comparative Example 10 except that a 10 μm helical mesh filter was used.

Comparative Example 16 Example 1 was used as a filter for passing the top coating liquid.
A pigment coated paper for printing was prepared in the same manner as in Comparative Example 11 except that the same filter as that used in 1. was used.

Comparative Example 17 Example 1 was used as a filter for passing the top coating liquid.
A pigment-coated paper for printing was produced in the same manner as in Comparative Example 12 except that the same filter as that used in 1. was used.

Comparative Example 18 Example 1 was used as a filter for passing the top coating liquid.
A pigment-coated paper for printing was produced in the same manner as in Comparative Example 13 except that the same filter as that used in 1. was used.

Evaluation method 1) Glossiness The glossiness of the sample after calendering was measured using a Murakami glossmeter with an incident angle of 75 ° -reflection angle of 75 °.

2) Smoothness Smoothness was measured by a smoother smoothness tester (model SM-6A, manufactured by Toei Denshi Kogyo Co., Ltd.).

3) Printing unevenness The sample was printed on a Roland offset printing machine under the conditions of excessive water supply of dampening water and appropriate conditions, and allowed to stand overnight at room temperature. The printed area having a halftone dot area ratio of 50% was visually evaluated.
As for the evaluation unit, 5 out of the 5 evaluations is the best, and 5 is judged to have no printing unevenness over the front surface of the sample even if the dampening water is excessively supplied. 4 that causes a small print unevenness
If the amount of dampening water is excessively supplied and uneven printing having a relatively large area is generated, it is determined to be 3, and if dampening water is properly supplied, weak printing unevenness is determined. When the occurrence of the above is determined to be 2, and when the supply of the dampening water is appropriate and the occurrence of clear print unevenness is determined to be 1.

4) Coating Defects The coating defects were detected by an optical defect detection device installed in the coating device, and the defect length relative to the coating length was taken as the defect rate. The coating defects that can be detected by the defect detection device are defects with uncoated portions such as streaks and scratches, and excessive coating portions such as stains.
If it is m or more and the length is 1 mm or more, it can be detected. The length of the defect is, for example, a length obtained by adding 1 m before and after the defect in consideration of a margin when deleting the defect portion, for example,
Even if the actual length of the defect is 0.1 m, the length of the defect is 2.1 m.

[0073]

[Table 1]

[0074]

[Table 2]

The evaluation results are shown in Tables 1 and 2. The top coating liquid contains 3 to 20 parts of Satin White, and 12
Coated paper for pigments for printing, which is excellent in glossiness and smoothness and is free from coating defects and printing unevenness by passing the overcoating coating solution through a filter having a gap of 0 μm or less and then applying it with a curtain coating device. Can be obtained. In Comparative Examples 1 to 5, the openings of the filter were too large, so that the soft agglomerates were removed or the dispersion was incomplete and coating defects occurred. In Comparative Example 6, the amount of satin white blended was too large, the gloss and smoothness were lowered, and printing unevenness occurred. In Comparative Example 7, the amount of sachin white is too small and the gloss is low. In Comparative Examples 8 to 10,
Since no filter was used, coating defects occurred. In Comparative Examples 11 to 18, since a coating method other than the curtain coating method was used, deterioration of gloss and smoothness, uneven printing, or defective coating was observed.

[0076]

According to the present invention, it is possible to obtain a pigment-coated paper for printing which is free from coating defects, is excellent in gloss and smoothness, and is free from uneven printing.

[Brief description of drawings]

FIG. 1 is a schematic view of a curtain coating apparatus showing an embodiment of the present invention.

[Explanation of symbols]

 1 Coater head 2 Slit 3 Lip 4 Curtain film 5 Web 6 Manifold 7 Roll 8 Wind shield 9 Liquid receiving tank 10a, 10b Edge guide 11 Storage tank 12 Liquid feed pump 13 Filter

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location B05D 7/24 303 B 8720-4D D21H 23/48

Claims (2)

[Claims] 1. A pigment-coated paper for printing, comprising a base material and a coating layer containing a pigment as a main component, wherein the total amount of the pigment is 3 to 2.
Pigment coated paper for printing wherein 0% by weight is satin white, all the coating liquid of the coating layer can pass through a gap of 120 μm or less, and the coating layer is coated by a curtain coating device. 2. A method for producing a pigment-coated paper for printing, wherein a coating layer containing a pigment as a main component is provided on a substrate, and a coating solution in which 3 to 20% by weight of the total amount of the pigment is satin white is prepared. Then, all of the coating liquid is passed through a gap of 120 μm or less, and the coating liquid is coated on the substrate by a curtain coating device.