JP2705406B2 - Manufacturing method of coated paper for printing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing coated paper. More specifically, the present invention relates to a method for producing a coated paper for obtaining excellent printability without generating mottling.

[0002]

2. Description of the Related Art In recent years, in the field of coated paper for printing, quality requirements from the market have become increasingly strict, and excellent white paper gloss, smoothness and printability have been demanded. However, the conventional single-coating method using a metaling bar, a blade, an air knife, and the like, and the double coating method in which a metalling bar or a blade is applied to an undercoat and an air knife is applied to an overcoat can meet this demand. It's getting harder.

[0003] For this reason, recently, a double coating of a blade-on-blade using a blade capable of obtaining more excellent printing surface characteristics has been carried out for undercoating and overcoating of coated paper, and from the viewpoint of coating. Are being improved.

[0004] In general, paints applied by a coater are composed of pigments such as kaolin, calcium carbonate and organic pigment, water-soluble polymer adhesives such as latex and starch, and various auxiliary chemicals. The solid content is, for example, in a blade coater, the solid content is coated on the substrate in the range of 50 to 75% by weight, then sent to the drying step and dried, and the finished moisture is in the range of 3 to 8% by weight. It is adjusted to become.

During the drying, it is said that the printing quality of the coated paper, especially the mottling (ink unevenness of ink deposition) is most significantly affected. For example, 1986 Coating
Conference / TAPPI Proceedings, 73-78, in double coating by pilot blade coater,
Critical solids range (coating concentration)
It is disclosed that when the drying efficiency is increased, mottling occurs. In addition, Paper Technology, October,
In P26-34 (1989), during blade coating, if the third zone where the paint solidifies out of the four drying zones is strongly dried, mottling occurs, so that this area is formed so that gentle drying can be performed. Although it is described that it is important to predict where it will occur, no specific means is mentioned.

Also, “Paper Coating (Application of Polymer Latex)” (published by the Society of Polymer Publishing, September 1989), 193
No. 219, the structure of the surface of the coating layer and the structure of the internal voids were formed as the drying progressed.
A region up to the point where a pseudo-capillary tube is formed on the surface and the wet surface gloss begins to decrease (first critical concentration or immobilization point) from this point, drying proceeds, and air and water displacement occurs. The existence of the region up to the second critical concentration where it starts to occur and the region until the dry void structure is formed is explained based on an example in which a coating color is applied to a non-permeable base such as a glass or plastic film. ing.

However, there is no description of a specific means applied in order to predict which part corresponds to these areas, especially the immobilization point, in an actual operation in which continuous coating is performed. . As one means, it is conceivable to calculate the amount of evaporating water from the temperature, air flow and heat of the dryer and estimate the coating film concentration. It is extremely difficult to follow the drying conditions in response to changes in factors.

[0008]

In view of this situation, the present inventors have made intensive studies on the drying of paint when applied to base paper or base paper, and as a result, the paint was applied to the surface of base paper or base paper. In the drying process, when the moisture evaporates and dries, the reflectance of the coated surface due to light changes extremely sharply even when the coated paper is running at high speed when the coating film concentration exceeds a certain level. Focusing on doing, continuously measure the coating concentration on the coating surface using a non-contact laser type surface inspection meter that functions under a large amount of water evaporation atmosphere and high temperature, and Adjust the drying conditions in the previous drying step so that the coating concentration (coating concentration on the coating surface) reaches a specific level, and further adjust the coating concentration at the outlet of the dryer to another specific level. In the dryer By then changing the temperature and wind speed to adjust the evaporation rate, mottling of the coated paper it has been found to be able to effectively eliminate.

This technique has already been disclosed in Japanese Patent Application No. 2-33.
As disclosed in Japanese Patent No. 0226, the inventors of the present invention have conducted further intensive studies on the paint composition at this time, and as a result, a fixed ratio of a polyamide urea resin was contained in the paint to lower the immobilization point. By installing an instrument for measuring the coating concentration at the entrance and exit of each dryer to determine where the immobilization point exists in the dryer group, the ink drying property is further improved along with the elimination of mottling. The present inventors have found that an excellent coated paper for printing free from uneven printing due to water loss can be obtained, and the present invention has been completed.

[0010] Accordingly, an object of the present invention is to solve the disadvantages of the prior art, and particularly to provide excellent ink drying properties after printing.
An object of the present invention is to provide a method for producing a coated paper for printing having excellent printability without mottling and water loss.

[0011]

According to the present invention, an aqueous coating liquid containing a pigment and an adhesive as a main component is applied to a base paper or a base paper, and is continuously introduced into a drying process of a group of dryers. The coating and immobilizing point of the coating liquid by adding a polyamide urea resin in an amount of from 0.05 to 2.0% per solid weight of the coating liquid. When the coating liquid is applied to base paper or base paper and dried, the coating film concentration is continuously measured by a dryer group equipped with an instrument for measuring the coating film concentration. The position of the immobilization point is detected by the method, and the water evaporation rate in the dryer in which the immobilization point exists
A method for producing a coated paper for printing, characterized by maintaining the pressure at or below kg / m ² · h.

In a preferred embodiment of the present invention, a laser type surface inspection instrument is used as an instrument for measuring the coating film concentration, and is installed at the entrance and exit of each dryer.

FIG. 1 shows a state in which a paint is applied on a plastic film and then dried using a laser type surface inspection meter (SU-12 coaxial laser beam sensor manufactured by High Frequency Communication Industrial Co., Ltd.). In this example, the reflectance of the film is measured and displayed as a voltage. At the same time, the film is peeled off, and the film concentration is measured by a drying method. This voltage measurement was performed using the coating film concentration as a variable, and it was found that a graph with high accuracy could be obtained by repeating this voltage measurement.

As can be seen from this graph, the coating density can be detected as a change in the voltage of the beam meter by the laser type surface inspection meter, and both show a very good correlation. In the example of FIG. 1, when the coating film concentration is 76% by weight or less, the voltage is saturated at 11 V, but this can be followed by switching the sensor. According to the experiments by the present inventors, in the example of FIG. 1, the coating surface of the coating film was measured at the point where the voltage indication of the beam meter gradually decreased from 11 V to 1.80 V, that is, at the point where the solid content concentration was 79.6 wt%. This point was the immobilization point because of the loss of gloss.

If the composition of the coating liquid is different, the position of the inflection point in the graph of FIG. 1 changes, but as a result of the present inventors' research on a large number of coating liquids having different compositions, Even if the voltage indication of the beam meter is 1.80 ± 0.0
It was found that the time of 5 V corresponded to the immobilization point of the coating liquid. Therefore, even when the paper is running at high speed in an actual coating machine, the reading of the laser type surface inspection meter is 1.80.
By knowing where the ± 0.05 V point is, the position of the immobilization point of the coating film can be easily known.

In the present invention, this measuring device is installed between the dryer sections in the drying step, that is, on the paper rolls at the entrance and exit of the dryer, and irradiates a laser beam at right angles to the coating surface of the running coated paper. To receive the reflected light from the coated surface. Further, it is desirable to adjust the tension of the coated paper with a paper roll so that the vibration is minimized on the coated surface when the laser beam is irradiated. When installing a laser type surface inspection meter at the entrance and exit of each dryer, it is a matter of course to adjust the sensitivity of the sensor according to the coating concentration of the coated paper, but if the coating concentration is 90% or more, A known BM meter can be used together.

In the present invention, the reading of the laser type surface inspection meter at the entrance of a certain one-section dryer is 1.8.
When the laser type surface inspection meter reading at the outlet of the dryer is greater than 5V and less than 1.75V, there will be a coating immobilization point in the dryer. The dryer having an immobilization point has a water evaporation rate of 15 kg / m under drying conditions appropriately selected from a range of a normal temperature of 70 to 160 ° C. and a wind pressure of 10 to 220 mmAq.
² · h or less, preferably 5kg / m ² · h more than 13kg
/ M ² · h or less.

The dryer having an immobilization point to which the water evaporation rate according to the present invention is applied varies depending on the drying conditions applied in the drying composed of a group of dryers of 3 to 6 sections. In a group, it usually falls between any of the second to fifth dryers. These dryer systems are conventionally known as hot air drying, blast drying, steam heating, infrared burner heating, infrared heater heating, gas heater heating,
It is used by appropriately selecting from various methods such as electric heater heating, laser heating, high frequency heating, and electron beam heating.

The coating speed is usually 300 to 1500.
m / min, and desirably the speed is increased as much as possible from the viewpoint of productivity. However, the speed is appropriately determined in consideration of constraints such as ease of operation and drying load.

Another feature of the present invention is that a polyamide urea resin is added to a coating liquid containing a pigment and an adhesive as a main component in an amount of 0.05 to 2.0% (solid content weight ratio), and the immobilization point is increased. Is applied to base paper or base paper.

It is already known that a weakly cationic polyamide urea resin is incorporated into a coating material in order to finish the coating film in a porous manner. For example, the latest paper processing handbook (Tech Times, published in 1988, P586
587), the polyamide urea resin is referred to as a waterproofing agent or a printability improving agent. The mechanism of action is that the weak cationic polyamide urea resin is adsorbed on the anionic pigment particles, and as a result, the interaction between the pigment particles acts to lower the solidification point (so-called immobilization point). ing.

The decrease in the passivation point means that the coating film solidifies when the solid content of the coating is still low during the drying process, in other words, when the coating film on the base paper or the base paper still has a large amount of water. It is described that the water content in the coating film evaporates as the drying process is continued, and the water content in the coating film evaporates.
Such a porous coating leads to improved ink drying properties.

As the cationic substance, for example, JP-A-51
JP-A-123304 also exemplifies a cationic activator or a cationic starch, but the effect on the immobilization point is not specified and is unknown.

In order to know the immobilization point, the coating liquid is applied to a calcined plate, and when the coating liquid loses fluidity, the solid content concentration is measured, or the coating liquid is applied to a plastic film. Various test methods have been known, for example, when the surface of the coating film has lost its glossiness, the coating film is peeled off and the solid content concentration at that time is measured.

However, each of these methods is a static method and cannot be applied to an actual coater. As mentioned earlier, Paper Technology, October,
P26-34 (1989) describes the third of the four drying zones where the paint solidifies during blade coating.
It is stated that it is important to predict where this area will occur so that mild drying can be performed, since mottle occurs when the second zone is strongly dried, but there is no specific means for this. Not mentioned.

Although the immobilization point has an important meaning as described above, the immobilization point exists in any dryer while the paper is continuously running in the actual operation of the coater. There was no suitable way to detect drying and control drying conditions.

For example, JP-A-3-51393 discloses that a weak cationic modified polyamine resin is blended to adjust the immobilization point. No method is described for detecting during the operation of the machine and correspondingly controlling the drying conditions. However, as in the present invention, the use of a laser-type surface inspection meter makes it possible to easily detect in which dryer the immobilization point exists even during the running of the paper, and it is possible to set appropriate drying conditions.

The polyamide urea resin used in the present invention is an amide polyurea or a polyalkylene obtained by subjecting a urea and a polyalkylene polyamine to a deammonification reaction, followed by a dehydration condensation with a dibasic carboxylic acid and a deammonia reaction with the urea. Polyamide and polybasic carboxylic acid are dehydrated and condensed and then deammonia-reacted with urea. A polyamide polyurea (see Japanese Patent Publication No. 3-16438) or the obtained polyamide polyurea is reacted with formaldehyde in an aqueous solution, Next, a reaction with epihalohydrin (see Japanese Patent Publication No. 3-23679).
Etc. are preferably used.

The amount of the polyamide urea resin added in the present invention is 0.05% based on the weight of the solid content (dry residue) of the paint.
To 2.0%, more preferably 0.1% to 1.0%.
Used in the range of%. When the addition amount of the polyamide urea resin is less than 0.05%, the effect of making the coating film porous is insufficient, and when it exceeds 2.0%, the coating viscosity becomes high, and coating unevenness occurs. Problems such as streak-like defects on the coated surface occur.

The lowering of the immobilization point due to the addition of the polyamide urea resin depends on the composition of the coating solution, the type of the polyamide urea resin and the amount of addition. 1.0 ~ than immobilization point
A decrease of about 3.0% by weight was observed. On the other hand, as described above, the polyamide urea-based resin also has an effect of making the coating film water-resistant, so that the coating film picking during offset printing,
It also has the effect of preventing printing unevenness due to water loss.

The pigment used in the coating liquid of the present invention includes kaolin, clay, calcium carbonate, titanium oxide, aluminum hydroxide, zinc oxide, barium sulfate, calcium sulfate, talc, silica, plastic pigment, satin white and the like. Is appropriately selected.

As the adhesive, casein, soy protein,
Modified starch such as yeast protein, starch, oxidized starch and esterified starch, etherified starch, cationized starch, enzyme-modified starch, natural adhesives such as cellulose derivatives, styrene-butadiene copolymer, methyl methacrylate-butadiene Conjugated diene-based polymer latex such as copolymer,
Acrylic polymer latex such as acrylate or methacrylate polymer or copolymer, acetic acid polymer latex such as ethylene / vinyl acetate copolymer, and synthetic adhesive such as polyvinyl alcohol are appropriately selected. One or more types are used for the present invention. The adhesive is used in an amount of 8 to 30 parts by weight, preferably 10 to 20 parts by weight, based on 100 parts by weight of the pigment.
If the amount of the adhesive used is 8 parts by weight or less, the strength of the coated surface becomes weak, and if the amount is 30 parts by weight or more, the cost becomes high, which is not suitable for the present invention.

In preparing the coating liquid, various auxiliaries such as a dispersant, a flow modifier, an antifoaming agent, and a coloring agent, which are blended in a general coating liquid for coated paper, are used to obtain desired characteristics. It is appropriately selected and used as needed. The solid content concentration of the coating solution is generally adjusted to about 45 to 75% by weight, but in consideration of the drying load and operability affected by the viscosity of the coating solution, the solid content is preferably set to about 55 to 70% by weight. Will be constructed.

The immobilization point of this coating solution is usually 75 to 85% by weight of solid content, and 74 to 82% by weight in the present invention.
However, this depends on the composition of the paint, additives, etc., so it cannot be said unconditionally. As described above, the method of applying the paint to the unglazed plate or the plastic film, or the laser type as in the present invention, Measure each time by using a surface inspection meter.

The aqueous coating solution thus prepared was formed on a conventional paper machine using pulp selected from softwood bleached kraft pulp, hardwood bleached kraft pulp, recycled pulp from used paper, mechanical pulp and the like. One or both sides of the acidic base paper or the neutral base paper are coated with 10 to 30 g / m ² , more preferably 15 to 25 g / m ² .

The base paper used in the present invention has a basis weight of 50 to 400.
g / m ² can be used, and it may be a single-layered or multi-layered one. That is, 80 to 150 g / m ² is used for sheet-like materials such as catalogs and pamphlets, and 200 to 150 g / m ² is used for box making, postcards, cards and the like.
Base paper having a basis weight of about 300 g / m ² is considered to be preferable.

The aqueous coating liquid may be applied directly to the base paper,
Alternatively, the base paper may be coated on a base paper having a base coat of about 3 to 15 g / m ² per side (this is referred to as “base paper” in the present invention). In recent years, since a clear finish of printing has been increasingly required, so-called two-layer coating (or two-step coating) for coating on a base paper has been more preferred.

In the present invention, the coating and drying methods are not particularly limited, and a blade coater, an air knife coater, a bar coater, a roll coater, a champlex coater, a size press used in general coated paper production. One or both sides of the paper are coated in a single layer or a multilayer by a coater, a gravure coater, or the like, and usually dried in a dryer zone of 3 to 6 sections.

When the coating is a multilayer coating (for example, when an undercoat layer is provided and an overcoat layer is further provided thereon), the undercoat layer other than the uppermost layer coating is not directly printed. In applying the undercoat layer, the installation of the laser type surface inspection meter may be omitted.

In the case of double-side coating or multilayer coating,
The whole coating may be performed continuously by one coater having two or more coating equipments, or a part of the whole coating may be coated and wound once, and then the same coater or another coater may be used. The remaining coating may be performed. The final coated paper product is dried to a paper moisture in the range of approximately 3-8% by weight and wound on a reel.

The coated paper thus obtained is subjected to surface finishing using a super calender, a mat calender or the like in an on-machine or off-machine state as required, and is obtained as a product.

In the present invention, the addition of the polyamide urea resin lowers the immobilization point and performs mild water evaporation with the coating film surface being porous, so that the ink absorption and drying properties are excellent, and the mottling of the mottling is improved. A coated paper having improved water resistance can be obtained.

[0043]

The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. In addition, all the parts or% shown in the Examples and Comparative Examples represent absolute dry parts or absolute dry weight%. All coating amounts are indicated by absolute dry weight.

Example 1 40 parts of kaolin (Ultra White 90, manufactured by Engel Hard Minerals and Chemicals (EMC), USA) and heavy calcium carbonate having a particle diameter of 1 to 4 μm (manufactured by the company, ground calcium carbonate) were used as pigments. 60 parts were placed in a mixer, and 3 parts of oxidized starch (manufactured by Oji Constarch, trade name Oji Ace A 10% solution) and 50% latex (manufactured by Asahi Kasei Corporation, trade name L-1) were stirred therein.
537) 12 parts, 1.0 part of a polyamide urea resin (Sumitomo Chemical's Sumirez 703, solid content concentration: 50%), 0.3% of sodium polyacrylate as a dispersant per pigment, and 0.5% of calcium stearate as a lubricant % And a fluorescent dye 0.2% were sequentially added and thoroughly mixed and dispersed, and the pH was adjusted to alkaline with a 25% aqueous ammonia solution to prepare a coating solution having a solid content of 60%.

This coating liquid was applied onto a plastic film, and the data of the coating concentration and the corresponding reading value (voltage) of a laser type surface inspection meter when the coating liquid was dried are shown in the same manner as in FIG. The coating concentrations corresponding to the voltages of 1.75 V and 1.85 V, respectively, were averaged to give the immobilization point. The immobilization point of this coating solution was 79.2%.

This coating solution was applied to one side of a base paper having a basis weight of 80 g / m ^{2 formed} by using a hardwood bleached kraft pulp with a known paper machine using a blade coater (manufactured by Mitsubishi Heavy Industries, Ltd.).
g / m ² .

The coated paper was dried using a hot-air drier consisting of four sections (manufactured by Ishikawajima-Harima Heavy Industries Co., Ltd., arched hot-air drier, drying length: 6 m each). The outlets of the first, second and third dryers of this dryer are equipped with a laser type surface meter (manufactured by K.F.
12, coaxial laser beam sensor)
A BM meter was installed at the dryer outlet so that the coating film concentration, coating amount, and moisture of the coated paper could be monitored. The coating speed and the temperature and air pressure in the first and second dryers were adjusted so that the laser type surface inspection meter at the inlet of the third dryer (the outlet of the second dryer) showed 2.50 V, and the third dryer was also adjusted. Water evaporation rate at 7.8
kg / m ² · h. At this time, the laser type surface inspection meter at the outlet of the third dryer showed 1.51 V. Finally, the drying conditions in the drying zone of the fourth dryer were adjusted to make the finished moisture of the coated paper 6.7%.

The coated paper thus obtained was subjected to a super calender treatment at a nip pressure of 250 kg / cm. After that, the quality was evaluated as follows.

(1) Ink drying property The degree of ink set-off when printed at a speed of 6,000 sheets / hour by a Mitsubishi Diamond four-color printing machine was visually determined and expressed as follows. ○ Good without any set-off △ Slight set-off □ Many set-offs are impractical Note that ○-△ and △-□ indicate the middle of each.

(2) Printing unevenness due to mottling and water loss The printed matter of the above (1) was visually judged and expressed in five stages as follows. □ □ to △ △ △ to ○ ○ Poor ← → Excellent The results are shown in Table 2 together with the results of other examples and comparative examples.

Example 2 In Example 1, the laser type surface inspection meter at the entrance of the third dryer (the exit of the second dryer) was 3.00.
The coating speed, the temperature and the air pressure in the first and second dryers were adjusted to indicate V, and the water evaporation rate in the third dryer was 14.1 kg / m ² · h. At this time, the laser type surface inspection meter at the outlet of the third dryer showed 1.42V. Otherwise, the quality was evaluated in the same manner as in Example 1.

Example 3 The coated paper (before the super calender treatment) once wound up in Example 1 was applied to the same coater again, and applied to the uncoated surface in the same manner as in Example 1. A double coated paper was obtained. Thereafter, a super calender treatment was performed in the same manner as in Example 1 to evaluate the quality.

Example 4 A base paint (undercoat) having the following composition was prepared. Kaolin (Ultra White 90) 30 parts Heavy calcium carbonate (manufactured by our company, particle diameter 1-4 μm) 70 parts Oxidized starch (Oji Ace A 10% solution) 2 parts Latex (L-1537) 50% 14 parts Pigment with the above composition 0.3% sodium polyacrylate as a dispersant and 0.5% calcium stearate as a lubricant
%, And the mixture was sufficiently mixed and dispersed, and then the pH was adjusted to alkaline with a 25% aqueous ammonia solution. The solid concentration was 60%.

Separately from this, a top coating (top coating)
The same paint as in Example 1 was prepared. In order to apply this, a coater (manufactured by Mitsubishi Heavy Industries) having four blade coater heads and capable of continuously applying two layers (undercoat and overcoat) on both sides of the base paper in one pass of paper was used. The coating order was as shown in Table 1.

[0055]

Each dryer used a hot-air drying method. The coating speed and the temperature and air pressure in the first, second, and third dryers so that the laser type surface inspection meter at the entrance of the fourth dryer (the exit of the third dryer) shows 3.00 V in the coating order 2 and 4. And the water evaporation rate of the fourth dryer was adjusted to 9.3 kg / m ^2.
H. At this time, the laser type surface inspection meter at the outlet of the fourth dryer showed 1.55 V. Thereafter, a super calender treatment was performed in the same manner as in Example 1 to evaluate the quality.

[0057] Example 5 a basis weight of middle layer of the base paper of Example 4 and 10 g / m ^2, O and paper making three layers on each side of the middle layer basis weight 100 g / m ² of paper making combined total 210g / m ² Other than using the base paper
The quality was evaluated in exactly the same manner as in Example 4.

Example 6 Instead of 1.0 part of the polyamide urea resin (Smiretz 703) in the coating liquid composition used in Example 1, another polyamide urea resin (Epinox P-593 manufactured by Dick Hercules, solid content) The quality was evaluated in exactly the same manner as in Example 1 except that 0.3 part (concentration: 60%) was used. The laser type surface inspection meter measured 2.50 V at the entrance of the third dryer and 1.58 V at the exit. The immobilization point of this coating solution was 81.3%.

Example 7 The heavy calcium carbonate in the coating liquid composition used in Example 1 was replaced with 50 parts of heavy calcium carbonate and 10 parts of Sachin White (manufactured in-house, average major axis 2.5 μm, minor axis 0.1 μm). Instead, 12 parts of latex (L-1537) was further replaced with another latex 48% solution (trade name: JS, manufactured by Nippon Synthetic Rubber Co., Ltd.).
R-0870) The quality was evaluated in exactly the same manner as in Example 1, except that 12 parts were used. The laser type surface inspection meter measured 2.50 V at the entrance of the third dryer and 1.49 V at the exit. The immobilization point of this coating solution was 77.1%.

Comparative Example 1 The quality was evaluated in the same manner as in Example 1 except that the polyamide urea resin was not used in the composition of the coating liquid used in Example 1. The immobilization point of this coating solution was 82.5%.

Comparative Example 2 In Example 1, the water evaporation rate of the third dryer was set to 18.
It was 5 kg / m ² · h. At this time, the reading of the laser type surface inspection meter at the outlet of the third dryer was 1.13 V.
Thereafter, the quality was evaluated in the same manner as in Example 1.

[0062]

[0063]

According to the present invention, it is possible to produce a coated paper having excellent ink drying properties and excellent printability without causing printing unevenness such as mottling and water loss.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the coating film concentration (%) when the coating film is dried and the reading (V) of a laser type surface inspection meter.

Claims (2)

(57) [Claims] 1. A printing method comprising applying an aqueous coating liquid containing a pigment and an adhesive as a main component to a base paper or a base paper, and continuously introducing the base paper or the base paper into a drying process of a dryer group having a plurality of sections. In the method for producing a coated paper, a polyamide urea-based resin is added in an amount of 0.05 to 2.0% based on the weight of the solid content of the coating liquid so that the immobilization point of the coating liquid is in the range of 74 to 82% by weight. When the coating liquid is applied to the base paper or the base paper and dried, the position of the immobilization point is determined by continuously measuring the coating film concentration with a dryer group equipped with an instrument for measuring the coating film concentration. Wherein the water evaporation rate in the dryer in which the immobilization point exists is maintained at 15 kg / m ² · h or less. 2. The method for producing coated paper for printing according to claim 1, wherein a laser type surface inspection meter is used as an instrument for measuring the coating film concentration, and is installed at the entrance and exit of each dryer.