JP2003293289A - Method for producing cast coated paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing cast coated paper with which the size of curls is suppressed and the surface properties of the cast coated surface are excellent when environmental humidity is changed. <P>SOLUTION: The method for producing the cast coated paper comprises coating one surface of base paper with a coating liquid consisting essentially of a pigment and an adhesive, bringing the coated layer in a wet state into pressure contact with a cast drum mirror finished surface and drying the coated layer. In the method, after the pressure contact of the coated layer and drying of the coated layer, the surface opposite to the cast coated surface is further coated with water or an aqueous solution of starch, etc., or an aqueous dispersion of the pigment, etc., and drying accompanied by restraining in the cross direction (CD) (direction vertical to the threading direction) is then carried out. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing cast coated paper, and in particular, it is possible to effectively prevent curling in a wide range of environments and curling that occurs when recording is performed using an aqueous ink. The present invention relates to a method for producing cast coated paper for inkjet recording.

[0002]

2. Description of the Related Art Cast coated paper is characterized in that it has a higher white paper gloss and superior surface properties than general coated paper because the surface state of the mirror surface of the cast drum is transferred. Conventionally,
General printing applications such as magazine covers and posters, bags used for high-end shopping bags, cosmetic packaging boxes, adhesive labels used as adhesive label top paper, inkjet recording applications used for inkjet printer paper, etc. Widely used in. Particularly, in recent years, in ink jet recording applications, by improving the suitability for ink jet recording such as ink absorbency and image reproducibility, it has become possible to perform very high quality full color printing close to the silver salt photographic method.

Generally, the method for producing cast-coated paper includes a direct method in which the surface of the base paper is coated with the coating liquid, and then the coating layer is immediately pressed with a forming roll in a wet state, and a coating liquid is coated. After coating, the coating layer is passed through a coagulation bath to coagulate into a gel state with deformable plasticity, and then the coagulation method is performed by pressing on a cast drum, and the coating liquid is applied and then dried once to dry coating. After obtaining the coated surface, the coated surface is then roughly re-wet plasticized with water or an appropriate re-wetting liquid, and re-wetting method in which it is pressed onto a cast drum.

In all of these methods, a coating liquid having a pigment and an adhesive is coated on a base paper, and a coating layer in a plastic state with water is formed on a surface of a cast drum having a mirror surface and heated by a forming roll ( It is common in that it is pressed with a press roll), dried and released to give a strong gloss finish. In general, cast coated paper has a large difference in coating amount between the front and back, and when the environmental humidity is changed, for example, curling tends to occur more easily than general coated paper. Especially for cast-coated paper with inkjet recording suitability as the coating layer, it is thought that the main reason is that it has good affinity with water, but it causes a large curl when the environmental humidity is changed. There is a strong tendency.

The ink jet recording system ejects small ink droplets by various mechanisms and deposits them on recording paper to form dots for recording, which facilitates full-color printing and enables high-speed printing. There are advantages such as On the other hand, in the case of water-based ink, the fibers of the base paper are swollen and then dried to be contracted, so that there is a disadvantage that a large curl is generated after printing depending on the properties of the paper.

Japanese Unexamined Patent Publication No. 60-94692 discloses a method in which steam is applied to a cast coated surface to prevent curling. However, when steam is applied to the cast coated surface, the curl preventing effect is not sufficient, and the gloss or surface property of the cast coated surface is adversely affected. Further, Japanese Patent Laid-Open No. 9-228296 discloses that
It is disclosed that curling is prevented by producing a cast coated paper in which polyethylene glycol is coated on the back surface of the base paper after the base paper is coated with the coating liquid and after the drying step or after the drying. However, there is no description of a drying method after the back surface application, and therefore, there is a problem that when an aqueous coating material other than polyethylene glycol is applied, there is almost no curl suppressing effect.

[0007]

In view of the above situation, the object of the present invention is to reduce the size of curl when the environmental humidity is changed, and to obtain a cast coating having excellent surface properties on the cast coating surface. It is an object of the present invention to provide a method for producing a cast coated paper for ink jet recording, which is a paper, in which the size of curl generated especially when printing is suppressed as much as possible.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention applied a coating liquid containing a pigment and an adhesive as a main component to one surface of a base paper and wet it. In a method for producing a cast coated paper, which comprises pressing a coating layer in a state onto a mirror surface of a cast drum and drying it, after pressure bonding and drying of the cast drum, water or an aqueous solution of starch or the like is further applied to the opposite surface of the cast coating surface. An aqueous dispersion such as a pigment is applied and dried with restraint in the CD direction (perpendicular to the paper passing direction), preferably with a cylinder dryer having a large restraining force in the CD direction during drying, and more preferably Has reached the present invention by carrying out pressure contact of the cast coated surface with the cylinder surface. As a result, the difference in the dimensional change rate between the front and back can be significantly reduced, and as a result, when the environmental humidity is changed, the curl generated after offset printing and inkjet printing can be significantly reduced, and cast coating can be performed. It was possible to obtain a cast coated paper having excellent surface properties on the coated surface.

The reason why the curl is improved by the method of the present invention is that water or an aqueous dispersion such as an aqueous solution or a pigment is applied to the surface opposite to the cast surface formed after pressure bonding and drying of the cast drum, and then dried again. By doing so, the opposite side of the cast surface is stretched, then it shrinks moderately, and even for fibers close to the cast surface side, curling can be prevented because the shrinkage stress accumulated during drying on the cast drum is released. it can. At this time, the cast coated surface can be dried without impairing the surface property of the cast surface by pressing the cast coated surface against the surface of the cylinder dryer. At this time, it is desirable that the surface of the cylinder dryer be mirror-finished. When drying with a cylinder dryer, it is better to press the cast surface against the cylinder dryer in order to maintain good surface properties.The point is that when water is applied to the opposite surface of the cast coating surface and it is dried, steam is cast. It is considered that since the surface property formed by the casting process is maintained as it is because the material is dried without passing through the surface to be covered, excellent surface property is obtained.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The cast coated base paper of the present invention includes, for example, pulp fibers disintegrated into a slurry, and if necessary, fillers, sizing agents and other additives are added, and papermaking is carried out by a paper machine. It can be obtained by applying a machine calender after size-pressing an aqueous solution of starch or a polymer substance, and drying after papermaking or drying. The pulp to be used may be appropriately selected from the pulps used in ordinary papermaking such as L (hardwood) and N (softwood) chemical pulp, mechanical pulp, waste paper pulp, etc. As the filler, for example, talc, kaolin, clay, calcium carbonate, titanium dioxide, silica and the like can be appropriately selected and used from the commonly used fillers. The base paper for casting used in the present invention has a basis weight of 5 which is used for general printing coated paper and cast coated paper.
It is a base paper of 0 to 400 g / m ² , and it is a high-quality paper depending on the purpose,
Select and use medium-quality paper or recycled paper. As the base paper for cast coated paper in the present invention, a base paper coated with an undercoat of a paint containing a pigment and an adhesive may be used. As the coating method at the time of undercoating, coating using a known coating machine such as a blade coater, an air knife coater, a roll coater, a spray coater, a kiss coater, a squeeze coater, a curtain coater, a bar coater, a gravure coater, and a comma coater. The method can be appropriately selected and used from the methods.

Examples of pigments used in the coating layer when the cast coated paper of the present invention is cast are amorphous silica, kaolin, clay, calcium carbonate, talc, alumina, aluminum hydroxide, magnesium carbonate and satin. Pigments such as white, titanium dioxide, aluminum silicate, colloidal silica, montmorillonite and plastic pigments can be used alone or in combination of two or more kinds.

Examples of the adhesive used in the coating layer of the present invention include casein, soybean protein, synthetic protein, oxidized starch,
Use one or more adhesives selected from starches such as esterified starch, polyvinyl alcohol, carboxymethyl cellulose, hydroxycellulose, styrene / butadiene latex, acrylic emulsion, vinyl acetate emulsion, polyurethane, etc. can do. Furthermore, the coating liquid of the present invention includes a dispersant, a fluidity modifier, a defoaming agent, a dye, which is used in general paints.
Lubricants, water retention agents, dye fixing agents, pigment dispersants, thickeners, fluidity improvers, defoamers, foam suppressors, release agents, foaming agents, penetrants,
Add various auxiliaries such as coloring dyes, coloring pigments, optical brighteners, UV absorbers, antioxidants, preservatives, antifungal agents, water resistance agents, wet paper strength enhancers, dry paper strength enhancers. You can also do it.

The method of applying the coating liquid on the base paper for casting is the same as the method for applying the undercoat layer, as in the case of the blade coater, air knife coater, roll coater, comma coater, brush coater, kiss coater, squeeze coater, curtain. It can be appropriately selected from coating methods using known coating machines such as coaters, bar coaters, gravure coaters, and spray coaters. The coating amount of the coating layer can be arbitrarily adjusted within a range that covers the surface of the base paper and obtains sufficient ink absorbency, but is 5 to 30 g / m ² in terms of solid content per one side. It is desirable that the amount is 10 to 25 g / m ² .

The coating layer thus formed on the base paper is manufactured by being pressed and dried on a cast drum having a mirror surface heated in a wet state. The wet coating layer can be pressed and dried on the mirror surface drum by pressing directly on the cast drum in the undried state after coating. Or a rewetting method in which the coating layer once dried after coating is plasticized with a rewetting liquid and pressure-bonded.

In the present invention, a coagulation method in which a coating layer in a wet state is coagulated with a coagulating liquid containing an organic acid, an oxo acid, or a metal salt of these acids, and pressed and dried on a mirror surface drum is a direct method. The surface properties of the cast coating layer are superior to those of the wet coating method and the rewetting method.

A uniform coating method may be used in which a cast coating surface is formed by pressure bonding to a cast drum and drying to form a cast coating surface, and then an aqueous solution such as water or starch or an aqueous dispersion liquid such as a pigment is applied to the surface opposite to the cast coating surface. There is no particular limitation as long as it can be applied to, and any device may be used. Generally, blade coater, air knife coater, roll coater, spray coater,
Kiss coater, squeeze coater, curtain coater,
The coating method is appropriately selected from coating methods using known coating machines such as a bar coater, a gravure coater and a comma coater. In addition, the coating speed during cast coating is generally slower than that during coating of general coated paper, and it is difficult to obtain a uniform coating profile. Therefore, in order to obtain an appropriate coating amount, a plurality of coating devices according to a known coating method may be arranged in the coating direction. Depending on the purpose and quality characteristics, the water content when applying water to the opposite surface is 0.1 to 20 g / m ²
From among these, it is desirably selected arbitrarily from the range of 1 to 10 g / m ² .

Further, as a method of drying with restraint in the CD direction, a cylinder dryer for drying in a state of being pressed against a rotating heated cylinder, or a type in which hot air is blown while a paper is pressed against a cylinder, etc. , A dryer of a type that heats and dries while sandwiching the paper between two belts and a canvas. Generally, the drying method using a cast drum is the same as the drying mechanism of a cylinder dryer, and since the binding force in the CD direction at the time of drying is strong, the drying method after coating on the opposite surface is also the same as that of a cylinder dryer. By drying in the condition that the direction is restricted,
The front and back surfaces are well-balanced in drying and curling can be further suppressed. The water content of the cast coated paper after drying is preferably 1 to 10% by weight, and more preferably 3 to 8% by weight from the viewpoint of the surface properties of the cast surface and curl suppression.

The cast coated paper of the present invention is a magazine cover,
It can be used for general printing applications such as posters, high-end shopping bags, bag applications used for cosmetic packaging boxes, adhesive labels used as the top paper of adhesive labels, inkjet recording applications used for inkjet printer paper, etc. In particular, it is particularly effective as an inkjet recording application in which curling easily occurs.

[0019]

The present invention will be described in more detail below with reference to examples of the present invention and comparative examples, but the present invention is not limited to these examples. In addition, "part" shown in the embodiment
And "%" are parts by weight and% by weight, unless otherwise specified.
Indicates. The evaluation method of each evaluation item is as follows. <Evaluation method> (1) Evaluation of curl Each of the cast coated papers manufactured according to each of the examples and comparative examples was cut into a size of 100 x 100 mm, and first, 2
The curl is measured by standing still for 4 hours or more with the surface having the cast coating facing upward in an environment of 3 ° C. and 50% RH. Then increase the humidity to 85% while maintaining the temperature at 23 ° C,
In this state, the surface coated with the cast material is faced up in the same manner, and a static value is obtained for 4 hours or more, and then the curl is measured. Further, while maintaining the temperature at 23 ° C., the humidity is returned to 50%, and in this state, the surface coated with the cast coating is faced up for 4 hours or more and then the curl is measured.

The curl was measured by placing each sample on a flat plate so that the inner surface of the curl faced up, and measuring the heights of the four corners of each sample. The values shown in the table are average values of the heights of the four corners. A positive value was obtained when the surface was coated with the cast coating on the inside, and a negative value was obtained when the surface was coated with the opposite surface. Therefore, the smaller the absolute value of the curl, the better the curl. (2) Surface property of cast coated surface The surface property of the cast coated surface was visually evaluated. ◯: Mirror surface pattern is well reproduced and has a smooth surface. Δ: Mirror surface pattern is not sufficiently reproduced and slight gloss unevenness occurs. X: The reproduction of the mirror surface pattern is insufficient and uneven gloss occurs. (3) White paper glossiness Measured at 75 ° C. glossiness according to JIS P 8142. (4) Inkjet recording suitability test A predetermined solid and image pattern were recorded using an inkjet printer (PM-800C: product name of Seiko Epson Corporation), and evaluated according to the following criteria. Curling evaluation after recording After recording, make a recording under the environment of 23 ° C and 50% RH.
Curl evaluation after standing for a time was visually performed. A: No curl occurs. ◯: Almost no curl occurs. Δ: A little curl occurs. X: Severe curling occurs. [Example 1] A high-quality paper having a basis weight of 107 g / m ² was used as a base paper,
Using a roll coater, 121 parts of synthetic silica as a pigment, 35 parts of urethane as a binder, 10 parts of casein, and 4.7 parts of a mold release agent were applied to a coating liquid of 25 g / m ² To one side of the base paper, and then coagulation treatment with a coagulation liquid prepared by mainly mixing ammonium formate.
It was pressed onto a mirror surface (cast drum) heated to, and dried to obtain a cast coating layer. After that, water was further added to the surface opposite to the cast coated surface by using a roll coater at 6.1 g / m ²
It was applied and dried using a cylinder dryer to obtain a cast coated paper having a water content of 3.5%. At the time of drying, the cast coated surface was brought into contact with the cylinder dryer to perform drying (FIG. 1). [Example 2] After a cast coated surface was obtained in the same manner as in Example 1, 6.4 g / m ^{2 of} water was applied to the surface opposite to the cast coated surface using a roll coater, and a cylinder dryer was used. Upon drying, a cast coated paper was obtained in the same manner as in Example 1 except that the surface opposite to the cast coated surface was in contact with the cylinder dryer (FIG. 2). [Example 3] A cast coated surface was obtained in the same manner as in Example 1, and then 6.2 g / m ² of a 6% aqueous solution of oxidized starch was coated on the surface opposite to the cast coated surface using a roll coater. In the same manner as in Example 1, a cast coated paper was obtained. [Example 4] After obtaining a cast coated surface in the same manner as in Example 1, 40 parts of secondary kaolin, 20 parts of finely divided kaolin and heavy carbonic acid were applied to the surface opposite to the cast coated surface using a roll coater. Cast coating was performed in the same manner as in Example 1 except that 40 parts of calcium, 10 parts of styrene-butadiene latex as a binder, 10 parts of oxidized starch and a coating solution prepared at a concentration of 60% were applied at 7.2 g / m ^2. Got the paper. [Example 5] A high-quality paper having a basis weight of 190 g / m ² as a base paper,
7 g / m ^{2 of a} coating liquid prepared by blending 100 parts of synthetic silica with 5 parts of SB latex, 20 parts of polyvinyl alcohol, and 5 parts of a sizing agent to prepare a coating liquid having a solid content of 20% by a blade method. Worked to obtain an undercoat product. Using a roll coater, high-purity alumina 9
After applying 0 part and 10 parts of synthetic silica, 13 parts of polyvinyl alcohol as a binder, and 0.2 parts of an antifoaming agent to one side of the base paper so as to have a coating amount of 25 g / m ² , 1.7% anhydrous borax and 5% boric acid
%, Magnesium nitrate hexahydrate (3% by weight of anhydrous component) and a release agent (0.2%) were mixed to prepare a coagulation solution, which was heated to 105 ° C. while the coating layer was in a wet state. It was pressed onto a mirror surface (cast drum) and dried to form a cast coating layer. After that, on the opposite side of the cast coated surface,
Water was applied at 6.1 g / m ² using a roll coater and dried using a cylinder dryer to obtain cast coated paper. At the time of drying, the cast coated surface was brought into contact with the cylinder dryer to perform drying. [Comparative Example 1] A cast coated paper was obtained in the same manner as in Example 1 except that after the cast coated surface was obtained in the same manner as in Example 1, water was not applied to the opposite side of the cast coated surface and drying was not performed. Got [Comparative Example 2] A cast coated paper was obtained in the same manner as in Example 5 except that after the cast coated surface was obtained in the same manner as in Example 5, water was not applied to the opposite side of the cast coated surface and drying was not performed. Got [Comparative Example 3] Except that a cast coated surface was obtained in the same manner as in Example 1, water was further applied to the opposite side of the cast coated surface, and then drying was performed using an air dryer instead of a cylinder dryer. A cast coated paper was obtained in the same manner as in Example 1. [Comparative Example 4] After obtaining a cast coated surface in the same manner as in Example 1, without applying water and drying, steam humidification was used from the opposite side of the cast coated surface to obtain 1.4% of water content. By applying, a cast coated paper was obtained.

[0021]

[Table 1] With respect to Examples 1 to 5 and Comparative Examples 1 to 4, the curl behavior when the environmental humidity was changed, the surface property of the cast surface, the glossiness of the white paper, and the curl when the IJ printing was performed were evaluated. Shown in. As is clear from the results of Table 1, the cast coated paper obtained by the method of the present invention has a very small curl even when there is a change in humidity and is excellent in the surface property of the cast surface as compared with the comparative example. Inkjet recording suitability is also good.

[0022]

According to the present invention, when the environmental humidity is changed, the size of curl is suppressed, and a cast coated paper having excellent surface properties of the cast coated surface can be obtained. It is possible to obtain a cast coated paper for inkjet recording in which the amount of curl generated at that time is suppressed as much as possible.

[Brief description of drawings]

FIG. 1 is an explanatory view of a manufacturing method of the present invention.

FIG. 2 is an explanatory diagram of a manufacturing method of the present invention.

[Explanation of symbols]

1 cast drum 2 coater head (coating department) 3 Coagulation liquid coating device 4 Backside watering device 5 cylinder dryer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tsuyoshi Yasuda             5-21-1 Oji, Kita-ku, Tokyo Nippon Paper Industries             Product Research Institute Co., Ltd. (72) Inventor Yuji Abe             5-21-1 Oji, Kita-ku, Tokyo Nippon Paper Industries             Technical Research Institute Co., Ltd. F-term (reference) 2H086 BA15 BA21 BA24                 4L055 AG11 AG17 AG18 AG27 AG47                       AG54 AG63 AG64 AG76 AG85                       AG89 AG97 AH02 AH13 AH37                       AJ04 BE09 FA18 FA30 GA09                       GA20

Claims (4)

[Claims] 1. A cast coated paper obtained by coating one side of a base paper with a coating liquid containing a pigment and an adhesive as a main component, pressing a coating layer in a wet state onto a mirror surface of a cast drum, and drying. In the manufacturing method, after pressure bonding and drying of the cast drum, water or an aqueous dispersion liquid such as an aqueous solution or a pigment is further applied to the surface opposite to the cast coating surface, and drying is performed with restraint in the CD direction (direction perpendicular to the paper passing direction). Method for producing cast coated paper characterized by carrying out 2. The method for producing cast coated paper according to claim 1, wherein the drying with restraint is performed by a cylinder dryer. 3. The method for producing cast coated paper according to claim 2, wherein the cast coated surface is pressed against the surface of the cylinder dryer. 4. The method for producing cast coated paper according to claim 1, wherein the cast coated paper is for inkjet recording.