JP2005299006A - Coated paper for label-printing on single side - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly lustrous coated paper for label-printing, having few pits on the coated surface. <P>SOLUTION: The coated paper for label-printing on single side has a coated layer composed mainly of pigments and adhesives on a paper substrate, wherein an organic pigment, precipitated calcium carbonate and kaoline are contained as the pigments, the coated layer is coated at a rate of ≥200 m/min by a blade coater and the coated surface treated by smoothing with a calender has ≥85% glossiness following JIS P8142 (75° specular gloss). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a single-sided printing coated paper for labels, and particularly relates to a single-sided printing coated paper for labels having particularly high gloss and good surface properties and surface smoothness.

  For the production of single-sided coated paper, a method of coating and drying a coating agent mainly composed of a pigment and an adhesive on one side of a base paper (paper substrate) and then smoothing and finishing by a calendar process is generally used. It's being used.

  One of the uses of this single-sided coated paper is a label. The label is printed on the coated surface (front surface), and the release paper is attached to the non-coated surface (back surface) via an adhesive.

  Recently, with the visualization, coloration, and upgrading of labels, the glossiness and the gorgeousness of printing are emphasized on the surface.

  For this reason, cast coated paper is usually used as coated paper for high gloss label printing. However, cast-coated paper is obtained by applying a coating agent mainly composed of a pigment and an adhesive on the surface of a base paper, and then pressing and drying the coating layer on a heated metallic mirror drum. However, in this manufacturing method, the coating layer in a wet state is directly pressed against a heating drum and dried, so the moisture in the coating layer must pass through the base paper layer and evaporate to the opposite side, It is necessary to improve the vapor permeability by making the coating layer porous, and as a result, pits (minute pits on the coating surface) are likely to occur, causing white spots in printed materials. There was a problem. In addition, even a fast cast coater has a speed of 200 m / min or less, and there is a problem that productivity is inferior.

  On the other hand, several methods for producing coated paper having high glossiness have been proposed. For example, (a) 5 to 20 parts by weight of 100 parts by weight of a hollow organic pigment having a particle diameter of 0.8 to 1.3 μm and a glass transition temperature (Tg) of 100 ° C. or more is blended in the coating agent. The base paper is coated and dried, and then finished with a super calender (see Patent Document 1). (B) The base paper is coated and dried with a coating agent containing an organic pigment, and then the surface temperature of the metal roll is 50 to 50. For example, gloss calendar treatment is performed under conditions of 250 ° C. and linear pressure of 30 to 200 kg / cm (see Patent Document 2).

The coated papers obtained by these proposed production methods still have problems in use as coated paper for label printing in terms of glossiness and surface coverage.
JP-A-6-192996 JP-A-9-119090

  An object of the present invention is to provide a coated paper for high-gloss label printing in which a coating layer is coated at a high speed of 200 m / min or more and no pits are generated on the coated surface.

As a result of intensive studies to obtain a highly glossy coated paper having suitability as a high-definition label printing paper, the present inventor formulated an organic pigment, light calcium carbonate and kaolin as pigments in the coating agent. By coating this coating agent on a base paper (paper base material) with a blade coater, drying and calendering, a glossy coated paper with no gloss unevenness or pits and comparable to cast-coated paper can be obtained. As a result, the inventors have found that the present invention can be obtained and have made the present invention.
This invention is made | formed based on this knowledge, and the said subject is achieved by following (1)-(5).
(1) In the single-sided printing coated paper which provides the coating layer which has a pigment and an adhesive as a main component on a paper base material, the said coating layer contains an organic pigment, light calcium carbonate, and kaolin as said pigment, It is coated at a speed of 200 m / min or more by a blade coater, and the glossiness according to JIS P8142 (75 ° specular glossiness) of the coated surface after the smoothing treatment by a calendar is 85% or more. Single-sided printed coated paper for labels.
(2) The pigment content in terms of solid content in the coating layer is 5 to 40 parts by weight of light calcium carbonate and 3 to 30 parts by weight of organic pigment with respect to 100 parts by weight of the total pigment, and further, light calcium carbonate and organic The total amount of the pigment and kaolin is 80 parts by weight or more, The single-sided printing coated paper for labels as described in (1) above.
(3) The above-mentioned (1) or (2), wherein the organic pigment is a hollow styrene / acrylic copolymer particle having an average particle diameter of 0.5 to 3.0 μm and a porosity of 40% or more. ) Single-sided printed coated paper for labels.
(4) The above-mentioned (1) to (3), wherein the light calcium carbonate is an aragonite type light calcium carbonate having a major axis of 3.0 to 5.0 μm and a minor axis of 0.1 to 0.6 μm. ) Single-sided printed coated paper for labeling according to any of the above.
(5) As an adhesive for the coating layer, 5 to 20 parts by weight of a polymer latex having a glass transition temperature of 0 ° C. or higher with respect to 100 parts by weight of the pigment is applied, and smoothing is performed with a thermal calendar of 100 ° C. or higher after coating and drying. The single-sided printing coated paper for labels according to any one of the above (1) to (4), wherein

According to the first aspect of the present invention, since the pigment contained in the coating layer is a mixed system of an organic pigment, light calcium carbonate, and kaolin, glossiness and surface coverage are good. Since the coating agent is coated on the base paper at a speed of 200 m / min or more by a blade coater, the operation surface is effective. In addition, since the coating agent is coated on the base paper and smoothed with a calendar after drying to obtain a glossiness of 85% or more, it is effectively used as a printing medium for labels that have been visualized, colored, and upgraded. can do.
According to invention of Claim 2, the said effect is further improved by having prescribed | regulated each ratio of the organic pigment, light calcium carbonate, and kaolin which occupy for a pigment.

According to the invention described in claim 3, by using hollow styrene / acrylic copolymer particles having an average particle diameter of 0.5 to 3.0 μm and a porosity of 40% or more as the organic pigment, Glossiness and surface coverage are further improved.
According to the invention described in claim 4, by using aragonite type light calcium carbonate having a major axis of 3.0 to 5.0 μm and a minor axis of 0.1 to 0.6 μm as light calcium carbonate, glossiness of the coating layer is exhibited. And surface coverage are further improved.

  According to the invention described in claim 5, as the adhesive contained in the coating layer, a polymer latex having a Tg of 0 ° C. or more is blended in an amount of 5 to 20 parts by weight with respect to 100 parts by weight of the pigment. Smoothing can be performed with a thermal calendar that provides high gloss.

  The raw material pulp of the base material of the single-sided printing coated paper for labels of the present invention is chemical pulp such as hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), bleached chemical thermomechanical pulp (BCTMP), thermomechanical pulp (TMP), pressured ground wood pulp (PGW), chemical ground pulp (CGP), ground pulp (GP), refiner ground pulp (RGP) and other mechanical pulp, waste paper pulp, or kenaf, bamboo, straw, etc. Non-wood pulp can be used alone or in admixture of two or more.

The basis weight of the base paper is not particularly limited, but the single-sided printing coated paper for labels is generally used in the form of tack paper bonded with release paper with an adhesive. Considering the bonding suitability with the labeler and the adhesion to the adherend, the range of 70 to 100 g / m ² is preferable.

  Further, the paper making method of the base paper is not particularly limited, and any of acid paper making, neutral paper making, and alkaline paper making may be used. Further, neither the dewatering method nor the drying method of the paper machine is particularly limited.

  The component of the coating agent is mainly composed of a pigment and an adhesive.

  Examples of the pigment include kaolin, organic pigment, and light calcium carbonate. The content in terms of solid content is 5 to 40 parts by weight of light calcium carbonate and 3 to 30 of organic pigment with respect to 100 parts by weight of the total pigment. The total of light parts calcium carbonate, organic pigment and kaolin is 80 parts by weight or more.

  Examples of the organic facial include styrene-acrylic copolymer particles, styrene-butadiene copolymer particles, polystyrene particles, and polyethylene particles, and two or more of these organic pigments may be mixed. Among these, in consideration of gloss development and coverage on the paper substrate surface, hollow styrene-acrylic copolymer particles having an average particle diameter of 0.5 to 3.0 μm and a porosity of 40% or more are more preferable. Preferably used.

  On the other hand, the light calcium carbonate can be used in both calcite type and aragonite type, but in the form of needle shape, columnar shape or spindle shape, etc. The use of light calcium carbonate in the range of 3.0 to 5.0 μm and the minor axis of 0.1 to 0.6 μm is preferred, and acicular aragonite type light calcium carbonate is particularly preferred. This is because the coating agent is subjected to a shearing action during coating with a blade coater, and the needle-like particles are oriented in the longitudinal direction (flow direction) of the paper substrate. A mixed system of the organic pigment and light calcium carbonate. In the case of the above-mentioned blending amount, glossiness is particularly enhanced.

  As the kaolin, known kaolins such as calcined kaolin and delaminated kaolin can be used, and kaolin having a particle size ratio of 2 μm or less of 80% by weight or more is particularly preferably used in terms of glossiness.

  When the total content of the light calcium carbonate, the organic pigment, and kaolin is less than 80 parts by weight, it is difficult to obtain higher gloss. In addition, when the light calcium carbonate is less than 5 parts by weight and the organic pigment is less than 3 parts by weight, the gloss development effect is small. When light calcium carbonate exceeds 40 weight part, the fluidity | liquidity of a coating liquid will deteriorate and it will become easy to generate | occur | produce a coating defect. Also, if the organic pigment exceeds 30 parts by weight, the solid content concentration of the coating liquid will not increase, resulting in problems such as increased drying load after coating and difficulty in controlling the coating amount profile. There is.

  Examples of the pigment other than kaolin, organic pigment and light calcium carbonate include, for example, heavy calcium carbonate, calcium sulfate, calcium hydroxide, aluminum hydroxide, magnesium hydroxide, magnesium carbonate, titanium dioxide, talc, zinc oxide, and satin white. Etc. can be used in combination.

  As the adhesive, a polymer latex having a glass transition temperature (Tg) of 0 ° C. or higher is used.

  When the Tg is less than 0 ° C., the film-forming property of the polymer latex is enhanced, the orientation of the pigment is suppressed, and when performing a smoothing treatment with a thermal calendar as described later, In particular, a part of the coating layer peels off and adheres to the surface of the metal roll, causing a problem that continuous operation cannot be performed. On the other hand, the upper limit of Tg is not particularly limited, but Tg is 90 ° C. or less, and more desirably 80 ° C. or less when a gloss improvement effect is intended by thermal deformation (plasticization) of the coating layer by a thermal calendar.

  Moreover, the compounding quantity of the said polymer latex is 5-20 weight part with respect to 100 weight part of pigments. When the amount is less than 5 parts by weight, the adhesive strength of the coating layer is weak, and paper peeling occurs during printing. When the amount exceeds 20 parts by weight, the porosity of the coating layer decreases and the ink acceptability decreases during printing. There is a fear.

  Examples of the polymer latex include a conjugated diene copolymer latex such as a styrene / butadiene copolymer latex, a styrene / methyl methacrylate / butadiene copolymer latex, a polymer of an acrylate ester and / or a methacrylate ester, An acrylic latex such as a copolymer latex, a vinyl polymer latex such as an ethylene / vinyl acetate polymer latex, and an alkali partial solubility or non-modified in which these various polymer latexes are modified with a functional group-containing monomer such as a carboxyl group. For example, soluble latex.

  Examples of adhesives other than polymer latex include, for example, oxidized starch, phosphated starch, positive starch, urethane esterified starch, starches such as dextrin, polyvinyl alcohol, polyvinylpyrrolidone, carboxymethylcellulose, and hydroxymethylcellulose. Various known adhesives such as can be used in combination.

  Moreover, the coating agent used for the single-sided printed coated paper for labels of the present invention includes pigments, adhesives, dispersants, lubricants, thickeners, antifoaming agents, water resistance agents, colorants, and the like. Various auxiliaries can be appropriately blended according to the purpose of use and needs.

  The solid content concentration of the coating agent at that time is suitably about 55 to 65% by weight.

The coating amount of the coating agent of the single-sided printing coated paper for labels of the present invention is provided in the range of 5 to 30 g / m ^{2 in} terms of solid content, and more preferably 8 to 20 g / m ² .

  The coating agent mainly composed of the pigment and the adhesive as described above is applied by a blade coater. In order to improve the orientation of the pigment particles and the smoothness of the coating layer surface, a blade coater is preferably used. As long as the coating amount is measured and the coating layer is smoothed with a blade, the applicator for the coating agent on the paper substrate may be of any method such as a roll method or a jet method. In addition, before applying the coating agent of the present invention, one or more layers of a coating agent mainly composed of a pigment and an adhesive may be undercoated on the paper substrate.

  After coating the coating agent as described above, the wet state is applied by various known heating methods such as hot air heating, steam heating, gas heater heating, infrared heater heating, high frequency heating, electric heater heating, laser heating and the like. The construction layer can be dried. In addition, about drying conditions, it is necessary to adjust suitably according to the chemical | medical agent etc. to be used.

  In the single-sided printed coated paper for labels of the present invention, the white paper glossiness is adjusted to be 85% or more in terms of 75 ° specular glossiness based on JIS P8142. When the glossiness of the blank paper is less than 85%, the impact property as a label that attracts people's eyes with glossiness is insufficient. The glossiness of blank paper is preferably 88% or more, particularly preferably 90% or more.

  In order to obtain the above glossiness, a known smoothing processing device such as a super calender, gloss calender, soft calender or the like can be used, but it is preferable to use a soft calender that can obtain high gloss under a lower linear pressure. A soft calender composed of a metal roll having a surface temperature of at least ° C. and an elastic roll is preferably used. More preferably, it is 130 ° C. or higher.

  Furthermore, in order to obtain a uniform coated surface without uneven gloss over the width direction of the single-sided printed coated paper for labels of the present invention, the metal roll is equipped with an internal heating device by electromagnetic induction that can be divided and controlled in the width direction. In particular, a soft calender configured with an external heating device by an external electromagnetic induction action that can be divided and controlled in the roll width direction in the vicinity of the metal roll is particularly preferably used.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The part and% in the examples are based on weight.

(Example 1)
A pulp slurry made of 80% LBKP, 20% NBKP, 0.3% neutral sizing agent (alkyl ketene dimer), and calcium carbonate added as a filler so that the ash content is 10% is made with a paper machine. In the size press step, the oxidized starch was applied so that the solid content was 2 g / m ^{2 on} both sides to produce a base paper for coating having a basis weight of 50 g / m ² .

  As a pigment, 15 parts of hollow styrene-acrylic copolymer particles (trade name: HP-1055, manufactured by Nippon Zeon Co., Ltd.) having an average particle size of 1.0 μm and a porosity of 55%, light calcium carbonate 20 having an average particle size of 0.94 μm And 65 parts of kaolin, 10 parts of a styrene-butadiene copolymer latex having a Tg of 5 ° C. and 5 parts of oxidized starch were added as an adhesive, and water was further added to prepare a coating agent having a solid concentration of 61%.

This coating agent is applied at a coating speed of 500 m / min with a blade coater so that the solid content is 20 g / m ² on one side of the base paper, and after drying, a super calender treatment (metal roll temperature 120 C., linear pressure 200 N / mm, and nip number 11) to obtain a single-sided coated paper for labeling. Table 1 shows the quality evaluation results.

(Example 2)
In Example 1, instead of 15 parts of hollow styrene-acrylic copolymer particles, a hollow styrene-butadiene copolymer having an average particle diameter of 1.0 μm and a porosity of 50% (trade name: HP-91, manufactured by Nippon Zeon Co., Ltd.) A single-sided coated paper for labeling was obtained in the same manner as in Example 1 except that 15 parts were used. The results of this quality evaluation are shown in Table 1.

(Example 3)
Example 1 was the same as Example 1 except that 15 parts of hollow styrene-acrylic copolymer particles were changed to 30 parts, light calcium carbonate 20 parts to 30 parts, and kaolin 65 parts to 40 parts. Thus, a single-sided coated coated paper for labeling was obtained. The results of this quality evaluation are shown in Table 1.

Example 4
Single-sided printing coated paper for label in the same manner as in Example 1, except that 20 parts of light calcium carbonate was replaced with 20 parts of argonite type light calcium carbonate having a major axis of 4.0 μm and a minor axis of 0.4 μm. Got. The results of this quality evaluation are shown in Table 1.

(Example 5)
In Example 1, except that the smoothing process was changed to a soft calender process (metal roll temperature 230 ° C., linear pressure 200 N / mm, nip number 2), the single-sided printed coated paper for labels was prepared in the same manner as in Example 1. Obtained. The results of this quality evaluation are shown in Table 1.

(Comparative Example 1)
A single-sided printed coated paper for label was obtained in the same manner as in Example 1 except that the light calcium carbonate was replaced with heavy calcium carbonate having an average particle size of 1.1 μm in Example 1. The results of this quality evaluation are shown in Table 1.

(Comparative Example 2)
In Example 1, a single-sided printed coated paper for labels was obtained in the same manner as in Example 1 except that the coating agent was applied at a coating speed of 90 m / min with a cast coater. The results of this quality evaluation are shown in Table 1.

[quality evaluation]
(Surface smoothness) Measured according to JIS P8119 and indicated as Beck smoothness.
(Blank Gloss) Measured at an angle of 75 degrees according to JIS P8142.
(Coating of base paper) The coating state of the coating layer of the product subjected to the calendar treatment after coating was visually observed.
(Double-circle): Pulp fiber does not protrude and pits are not generated.
○: Slightly raised pulp fibers but no pits.
Δ: Slightly raised pulp fibers and pits.
X: Both pulp fibers are raised and pits are frequently generated.
XX: Pulp fibers are raised and pits are very much generated.
(Gloss unevenness) The gloss unevenness of the coated surface was visually evaluated. ○ is good, Δ is slightly inferior, × is inferior.
(Printing smoothness) Printing was performed using an RI printing suitability tester (manufactured by Meisei Seisakusho). The ink is TRANS-G (indigo) manufactured by Dainippon Ink and the ink volume is 0.5 ml.
A: Unevenness in imprinting, poor ink transfer, etc. are not visible.
◯: There are slight unevenness of ink and poor ink transfer.
Δ: Ink unevenness, poor ink transfer, etc., but no problem in practical use.
X: There are many unevenness of ink, poor ink transfer, etc.

Claims (5)

In the single-sided printing coated paper in which a coating layer mainly composed of a pigment and an adhesive is provided on a paper substrate,
The pigment contains an organic pigment, light calcium carbonate, and kaolin, and the coating layer is coated at a speed of 200 m / min or more by a blade coater, and JIS P8142 (75 A single-sided printing coated paper for labels, characterized by a glossiness of 85% or more according to (° specular glossiness).   The pigment content in terms of solid content in the coating layer is 5 to 40 parts by weight of light calcium carbonate and 3 to 30 parts by weight of organic pigment with respect to 100 parts by weight of the total pigment, and further, light calcium carbonate, organic pigment and kaolin. The single-sided printing coated paper for labels according to claim 1, wherein the total is 80 parts by weight or more.   3. The single-sided label according to claim 1, wherein the organic pigment is a hollow styrene-acrylic copolymer particle having an average particle size of 0.5 to 3.0 [mu] m and a porosity of 40% or more. Print coated paper.   The said light calcium carbonate is an aragonite type light calcium carbonate in the range of a major axis of 3.0-5.0 μm and a minor axis of 0.1-0.6 μm. Single-sided coated paper for labels. As an adhesive for the coating layer, a polymer latex having a glass transition temperature of 0 ° C. or higher is contained in an amount of 5 to 20 parts by weight with respect to 100 parts by weight of the pigment, and is smoothed with a thermal calendar of 100 ° C. or higher after coating and drying. The single-sided printing coated paper for labels according to any one of claims 1 to 4.