JP2016075000A - Printing paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printing paper that has easiness in page turning, writability and cockling resistance.SOLUTION: The printing paper has a base paper, a first coating layer containing at least kaolin having an average particle size of not less than 0.5 μm to not more than 2.0 μm and a water-dispersible binder on at least one surface of the base paper and a second coating layer containing at least calcium carbonate and a water-soluble binder and/or a water-dispersible binder on a surface side opposite to a side in contact with the base paper in the first coating layer. The amount of calcium carbonate is 60 pts.mass or more based on 100 pts. mass of a pigment in the second coating layer. The total coating weight per single side calculated by summing up the coating weight of the first coating layer and the coating weight of the second coating layer is 15 g/mor less.SELECTED DRAWING: None

Description

  The present invention relates to printing paper. In particular, the present invention relates to a printing paper suitable for learning materials such as textbooks, reference books, and problem collections.

  In recent learning materials, in order to make it easy for users to understand, charts, photos, illustrations, etc. are posted in color, and important items are indicated in different colors.

  In recent years, digital printing machines that do not use printing plates have appeared. Industrial ink jet printers that use an ink jet recording system as the main system of digital printers are known (see, for example, Patent Documents 1 and 2 and Non-Patent Documents 1 and 2). Industrial inkjet printers are sold under the names such as Truepress Jet from Dainippon Screen Manufacturing, MJP series from Miyakoshi, Prosper and VERSAMAR from Kodak, and JetPress from FUJIFILM.

  Such an industrial inkjet printing machine, although depending on printing conditions, has a color printing speed of 10 to several tens of times faster than that of general-use and SOHO inkjet printers and large-format inkjet printers, and a printing speed of 15 m. / Min., More than 60 m / min at higher speeds. For this reason, industrial inkjet printers are distinguished from general household and SOHO inkjet printers and large format inkjet printers.

  Digital printers such as industrial inkjet printers can handle variable information and can be adapted for on-demand printing. Due to on-demand printing, learning materials for each individual that are tailored to the degree of learning progress and proficiency are gaining popularity. A system for producing a book by on-demand printing is known (for example, see Patent Document 3).

JP 2011-251231 A JP 2005-088525 A JP 2012-000773 A

Tokasu Michiko, “B2 size printing ink jet printer” (“Printing magazine”, published by the Japan Society of Printing Press, August 2010 (Vol.93), pp. 21-24) Yasutoshi Miyagi “Inkjet Printing Machine with Offset Quality” (“Printing Magazine”, published by the Printing Society Press, August 2010 (Vol.93), pp. 25-29)

  Since learning materials have an act of reading and writing when used, quality as book paper and quality as writing paper are required. Specifically, the quality as a book paper is the ease of turning pages, and the quality as a writing paper is a writing property such as a pencil.

  Furthermore, it is required that cockling can be suppressed to the extent that it does not become a defective product as a learning material when printing with a digital printing machine. In particular, ink used in industrial inkjet printers tends to cause cockling because it contains a larger amount of ink solvent than other printing systems.

An object of the present invention is to provide a printing paper suitable for a printing paper used as a learning material and having the following quality.
(1) Page turning ability (2) Writability (3) Cockling resistance

An object of the present invention is a printing paper used as a learning material, comprising at least a base paper and kaolin having an average particle diameter of 0.5 μm or more and 2.0 μm or less and a water-dispersible binder on at least one surface of the base paper. 1 coating layer, and having a second coating layer containing at least calcium carbonate and a water-soluble binder and / or a water-dispersible binder on the side opposite to the side in contact with the base paper in the first coating layer, Calcium carbonate is 60 parts by mass or more with respect to 100 parts by mass of the pigment in the second coating layer, and the total per one side of the total coating amount of the first coating layer and the coating amount of the second coating layer This is achieved by a printing paper characterized in that the coating amount is 15 g / m ² or less.

  According to the present invention, the quality of a book paper and the quality of a writing paper can be suppressed, and cockling can be suppressed to the extent that it does not become a defective product when printed by a digital printing machine such as an industrial inkjet printing machine. Printing paper on which educational materials can be printed can be provided.

  Hereinafter, the present invention will be described in detail.

  Base paper consists of chemical pulp such as LBKP and NBKP, mechanical pulp such as GP, PGW, RMP, TMP, CTMP, CMP, and CGP, and waste paper pulp such as DIP, plus filler such as calcium carbonate, sizing agent, retention agent , Cationic compounds, pigment dispersants, thickeners, fluidity improvers, antifoaming agents, antifoaming agents, mold release agents, foaming agents, penetrating agents, colored dyes, colored pigments, fluorescent whitening agents, UV absorbers Acid, neutral and alkaline conditions from paper stocks containing various additives as required, such as antioxidants, antiseptics, antibacterial agents, water resistance agents, wet paper strength enhancers, and dry paper strength enhancers Paper made with

  The base paper can be subjected to size press treatment using a size press liquid. The surface sizing agent used in the size press liquid is conventionally known in the papermaking field, and examples thereof include styrene-acrylic sizing agents, olefinic sizing agents, and styrene-maleic sizing agents. The size press liquid may contain various additives in addition to the surface sizing agent. In addition, the layer formed by size press processing shall not be included in the 1st coating layer of this invention, or a 2nd coating layer.

  The printing paper of the present invention has a base paper and a first coating layer on at least one side of the base paper, and a second coating layer on the side opposite to the side in contact with the base paper in the first coating layer. That is, the printing paper has a first coating layer and a second coating layer laminated in this order with reference to the base paper. Moreover, the printing paper can have a 1st coating layer and a 2nd coating layer on both surfaces of a base paper.

  The first coating layer contains kaolin having an average particle diameter of 0.5 μm or more and 2.0 μm or less as a pigment. The second coating layer contains calcium carbonate as a pigment. The calcium carbonate may be either light calcium carbonate or heavy calcium carbonate. Moreover, you may use together.

  The content of kaolin having the average particle diameter in the first coating layer is preferably 60 parts by mass or more with respect to 100 parts by mass of the total pigment in the first coating layer. This is because the cockling resistance is good.

  Moreover, content in the 2nd coating layer of a calcium carbonate is 60 mass parts or more with respect to 100 mass parts of all the pigments in a 2nd coating layer.

  In the present invention, the average particle size is the average particle size of single particles in the case of single particles, and the average particle size of aggregated particles when forming aggregated particles such as secondary particles. The average particle diameter can be determined from the state of the printing paper. As the method, for example, a scanning electron microscope with an element analysis function such as an energy dispersive X-ray spectrometer is used to take an electron micrograph of the coating layer surface of the printing paper, and the area of the photographed particles is approximated. This is a method of calculating the average particle size by calculating the particle size assuming that it is a spherical shape and measuring the particles from 100 particles present in the photographed image. The surface of the first coating layer can be measured by removing the second coating layer.

  The first coating layer or the second coating layer may contain a conventionally known pigment in the papermaking field in addition to kaolin or calcium carbonate. Examples of such pigments include clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, and synthetic amorphous. Silica, colloidal silica, aluminum hydroxide, alumina, lithopone, zeolite, magnesium carbonate, magnesium hydroxide and other inorganic pigments, styrene plastic pigments, acrylic plastic pigments, styrene-acrylic plastic pigments, polyethylene, microcapsules, urea resin And organic pigments such as melamine resin.

  The first coating layer contains a water dispersible binder as a binder. A water-dispersible binder is a substantially water-insoluble resin compound, and is distinguished from a water-soluble binder in that it does not substantially dissolve in hot water once dried from the water-dispersed state. Examples of the water dispersible binder include conjugated diene copolymer latex such as styrene-butadiene copolymer or acrylonitrile-butadiene copolymer, acrylate ester or methacrylate ester polymer, or methyl methacrylate-butadiene copolymer. Acrylic copolymer latex such as ethylene-vinyl acetate copolymer, vinyl copolymer latex such as vinyl chloride-vinyl acetate copolymer, polyurethane resin latex, alkyd resin latex, unsaturated polyester resin latex, or these Examples include functional group-modified copolymer latex with functional group-containing monomers such as carboxyl groups of various copolymers, thermosetting synthetic resins such as melamine resin and urea resin, and natural rubber latex. Completion Is preferably at least one selected from the group. Of these, styrene-butadiene copolymers are more preferred. The first coating layer can contain a water-soluble binder in addition to the water-dispersible binder. However, the amount of the water-dispersible binder in the binder of the first coating layer is preferably 60% by mass or more. This is because the cockling resistance is good.

  The second coating layer contains a water-soluble binder and / or a water-dispersible binder as a binder. The water-soluble binder is a binder that can be dissolved in water at 20 ° C. in an amount of 1% by mass or more after being dissolved with hot water or the like. Examples of the water-soluble binder include starch derivatives such as oxidized starch, etherified starch and phosphate esterified starch, cellulose derivatives such as methylcellulose, carboxymethylcellulose, and hydroxyethylcellulose, polyvinyl alcohol derivatives such as polyvinyl alcohol and silanol-modified polyvinyl alcohol, Casein, gelatin or modified products thereof, soy protein, pullulan, gum arabic, karaya gum, albumin and other natural polymer resins or their derivatives, polyacrylic acid soda, polyacrylamide, polyvinylpyrrolidone and other vinyl polymers, sodium alginate, polypropylene Glycol, polyethylene glycol, maleic anhydride or a copolymer thereof, and the like, and at least selected from the group consisting of these And it is preferable that one. The water dispersible binder is a binder similar to the water dispersible binder used for the first coating layer. Moreover, a water-soluble binder and a water-dispersible binder can be used together.

  In each of the first coating layer and the second coating layer, the binder content is preferably 5 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the total pigment contained in each coating layer. . This is because the cockling resistance or the writing property is improved.

  Each coating layer includes a dye fixing agent, a pigment dispersant, a thickener, a fluidity improver, a viscosity stabilizer, a pH adjuster, a surfactant, an antifoaming agent, a foam suppressor, a release agent, a foaming agent, Conventional penetrants, coloring dyes, colored pigments, fluorescent brighteners, UV absorbers, antioxidants, leveling agents, preservatives, antibacterial agents, water resistance agents, wet paper strength enhancers, dry paper strength enhancers, etc. A well-known additive can be contained suitably.

  In this invention, the coating method which provides each coating layer is a method of coating a coating layer coating liquid using a conventionally well-known coating apparatus, and is not specifically limited. Examples of coating apparatuses include air knife coaters, curtain coaters, slide lip coaters, die coaters, blade coaters, bill blade coaters, short dwell blade coaters, gate roll coaters, film transfer coaters, bar coaters, rod coaters, roll coaters, A size press etc. can be mentioned.

  In the present invention, the method of drying the coating layer coating liquid after coating is a method of drying using a conventionally known drying apparatus and is not particularly limited. Examples of the drying device include a straight tunnel dryer, an arch dryer, an air loop dryer, a hot air dryer such as a sine curve air float dryer, an infrared heating dryer, a dryer using a microwave, and the like.

In the printing paper of the present invention, the total coating amount of the coating amount of the first coating layer and the coating amount of the second coating layer is 15 g / m ² or less per side in terms of dry solid content. Furthermore, the coating amount of the first coating layer is preferably 1 g / m ² or more and 9 g / m ² or less per side in terms of dry solids, and the coating amount of the second coating layer is 3 g per side in terms of dry solids. / M ² or more and 9 g / m ² or less is preferable. This is because the page turning property and cockling resistance are improved. In addition, the coating amount of the layer formed by size press processing shall not be included in the said total coating amount of this invention.

  After coating / drying the base paper or each coating layer, the surface can be smoothed by calendering using a machine calendar, soft nip calendar, super calendar, multi-stage calendar, multi-nip calendar, etc. as necessary. it can.

The second coating layer contains calcium carbonate, the first coating layer contains kaolin having a specific average particle size and a water-dispersible binder, and the total coating amount per side is 15 g / m ² or less. Accordingly, the printing paper can have page turning and writing properties, and cockling resistance to the extent that it does not become a defective learning material when printed by a digital printer, particularly an industrial inkjet printer. The reason for this is not clear, but the first coating layer is specified for page turning and writing properties when the coating amount is 15 g / m ² or less, and for page turning and writing properties by the calcium carbonate of the second coating layer. It is considered that the kaolin and the water-dispersible binder having an average particle diameter of the above effectively act on the cockling resistance.

Printing paper of the present invention, in consideration of the portability of the learning material, basis weight 50 g / ^{m 2} or more 90 g / ^{m 2} or less, preferably a density 0.95 g / cm ³ or more 1.15 g / cm ³ or less. Basis weight and density are known physical properties in the papermaking field, and can be adjusted by a conventionally known method. The basis weight is a value determined in accordance with the paper and paperboard-basis weight measuring method specified in JIS P 8124. The density is a value determined based on the paper and paperboard-thickness and density measuring method specified in JIS P 8118.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Moreover, the mass part shown in an Example shows the value of dry solid content or a substantial component.

<Measurement of average particle diameter>
In the printing paper obtained as follows, the surface from which the second coating layer was removed was photographed with a scanning electron microscope (JSM-6490LA, manufactured by JEOL Ltd.). From the photographed image, the particle diameter of particles photographed as a sphere having a diameter with an approximate area was calculated, and the average particle diameter was determined by measuring 100 particles present in the photographed image.

<Preparation of pigment>
A commercially available pigment having a relatively large average particle size was used, and water and a commercially available polyacrylate-based dispersant were added and stirred to obtain a pre-dispersed slurry having a solid content of about 75% by mass. This pre-dispersed slurry was processed using a wet pulverizer manufactured by Ashizawa Finetech Co., Ltd. (horizontal and cylindrical pulverization chamber dimensions: diameter of about 0.5 m, length of about 1.3 m). The beads are made of zirconia having a diameter of about 0.2 mm, and the filling rate is changed in the range of 80% to 85% by volume. The flow rate is about 15 liters / minute, and the number of passes is changed to obtain various average particle sizes. A pigment was prepared.

<Preparation of base paper>
In a pulp slurry consisting of 100 parts by mass of LBKP having a freeness of 400 mlcsf, 15 parts by mass of light calcium carbonate as a filler, 0.8 parts by mass of amphoteric starch, 0.8 parts by mass of sulfate band, 0.05 parts by mass of alkyl ketene dimer type sizing agent Was added, and the paper was made with a long paper machine. Oxidized starch was attached at 2.5 g / m ² on both sides with a size press machine, and machine calendering was performed to prepare a base paper. The papermaking conditions and the like were adjusted so that the basis weight of the printing paper was finally 62 g / m ² and the density was 1.01 g / cm ³ .

<Preparation of first coating layer coating solution>
The first coating layer coating solution was prepared according to the following contents.
Pigment type, average particle size, and number of blended parts are listed in Table 1. Styrene-butadiene copolymer latex Number of blended parts is listed in Table 1. Phosphate esterified starch (MS # 4600, manufactured by Nippon Shokuhin Kako Co., Ltd.)
The number of parts is listed in Table 1.

<Preparation of second coating layer coating solution>
The 2nd coating layer coating liquid was prepared by the following content.
Pigment types and number of parts are listed in Table 1. Styrene-butadiene copolymer latex 6 parts by mass Phosphate esterified starch (MS # 4600, manufactured by Nippon Shokuhin Kako Co., Ltd.) 6 parts by mass

  The printing paper of each Example and each comparative example was produced in the following procedures.

<Preparation of printing paper>
On the base paper, the 1st coating layer coating liquid was apply | coated and dried to both surfaces so that it might become 7 g / m < ² > per single surface using a blade coater. Next, the 2nd coating layer coating liquid was applied and dried on both surfaces so that it might become 7 g / m < ² > per single surface using a blade coater. After drying, a calendar process was applied to produce a printing paper.

However, in Comparative Example 8, the first coating layer coating solution was applied and dried on both sides so that the first coating layer coating solution was 10 g / m ² per side and the second coating layer coating solution was 10 g / m ² per side.

<Page turning ability>
Sensory evaluation was performed by each subject in the following five stages on the ease of turning the pages of the sample that was collated so that the book vertical direction and the paper making direction (longitudinal direction) were aligned. The number of subjects was 20, and the average value of 20 subjects (rounded to the nearest decimal place) was used. If the average value of evaluation is 3-5, it shall have page turning ability.
5: Very easy to turn.
4: Easy to turn.
3: Neither.
2: It is hard to turn.
1: Very difficult to turn.

<Writing>
As a writing instrument, a recycled pencil tree story (registered trademark) HB made by Dragonfly Pencil Co., Ltd. was used. One piece of printing paper was placed on a steel office desk, and the writing comfort of each subject was sensorially evaluated in the following five stages. The number of subjects was 20, and the average value of 20 subjects (rounded to the nearest decimal place) was used. In this invention, if the average value of evaluation is 3-5, it shall have writing property.
5: Extremely good 4: Good 3: Slightly good 2: Normal 1: Inferior

<Cockling resistance>
An evaluation image was printed at 6000 m at 75 m / min using an industrial inkjet printing machine Prosper 5000XL Press manufactured by Kodak equipped with water-based pigment ink. Printing was performed by a method of recording a black solid print pattern with a mixed color of cyan, magenta, and yellow in 17.5 cm × 17.5 cm square. The state of wrinkles recognized in the printed portion was visually determined, and sensory evaluation was performed in the following three stages. In this invention, if it is evaluation 2 or 3, it shall have cockling resistance.
3: Very little wrinkle on the printed part and very good.
2: Good with little generation of wrinkles in the printed portion.
1: There are many wrinkles in the printed part.

  The results are listed in Table 2.

  From Table 2, it can be seen that Examples 1 to 7 corresponding to the present invention have page turning, writing, and cockling resistance. On the other hand, it turns out that Comparative Examples 1-8 which do not satisfy the structure of this invention cannot have about all of these effects.

Claims (1)

A base paper, a first coating layer containing at least one of kaolin and a water-dispersible binder having an average particle size of 0.5 μm or more and 2.0 μm or less on at least one surface of the base paper, and a side of the first coating layer in contact with the base paper And a second coating layer containing at least a water-soluble binder and / or a water-dispersible binder on the opposite surface side, and calcium carbonate with respect to 100 parts by mass of the pigment in the second coating layer Is 60 parts by mass or more, and the total coating amount per side of the total coating amount of the first coating layer and the coating amount of the second coating layer is 15 g / m ² or less. Printing paper.