JP2019026986A - High grade non-coated paper - Google Patents

Abstract

To provide a high grade non-coated paper excellent in surface strength and rigidity as well as excellent in off-set and inkjet printability, especially excellent in modification property, thick feeling when used as a book paper during off-set printing, and paper peeling and having eye friendly native feeling.SOLUTION: There is provided a high grade non-coated paper containing chemical pulp of 100 wt.% in 100 wt.% of pulp, and having a clear coating layer on a base paper and density of less than 0.75 g/cm, in which the clear coating layer contains latex and starch, and a ratio of the latex and the starch is latex:starch=10:90 to 99:1.SELECTED DRAWING: None

Description

  The present invention relates to a high-quality non-coated paper. More specifically, the present invention provides a high-quality non-coated paper that is bulky and excellent in surface strength and stiffness, and excellent in offset and ink jet printing suitability. In particular, it is a book paper that is excellent in refurbishment when used as a book paper, hand-feeling, and blanc separation during offset printing, and does not get tired even when reading for a long time.

  In recent years, publications have been required to reduce the cost of printed matter and reduce the weight of paper, and in books, the density of paper has been reduced. In addition, printing of publications by on-demand printing is also increasing, and the printability required for paper is not only offset such as blanc separation and surface strength, gravure printability, but also inkjet printability, wet electrophotographic method, etc. There is an increasing number of cases in which printing suitability is also required (Patent Document 1). Blan separation is one of the offset printing aptitudes, but blank separation is an important item when printing printed materials with many non-image areas such as paperbacks and books. This is a phenomenon where paper and bran sucked with dampening water stick together.

By the way, among publications, books such as paperback books, comics, and literary books are often carried around, and particularly lightweight paper is required. As a technique for reducing the weight of paper, it is common to use a bulking agent or mechanical pulp that tends to be bulky, and there is a technique (Patent Document 2) relating to a bulky medium-sized printing paper of a specific tree species.

In general, books are distributed based on a consignment system in which publishers line up with bookstores through distributors, and some books that could not be sold at bookstores are returned. The returned books often have fading on the small face, and the small face called “renovation” using a polishing machine is polished, so the paper on the small face sticks together during the polishing process. There are few papers that are excellent in renovation. As a technique related to book paper excellent in refurbishability, there has been a technique related to pulp having a specific fiber length (Patent Document 3) containing styrene-butadiene latex and starch.

Further, unlike newspapers and magazines that look at the paper in a short time, books often continue to look at the paper for a long time, and there is a problem that eyes are tired. In addition to desks equipped with lighting suitable for reading, there are many cases where reading is done in places where lighting conditions are different, such as in trains on the move, outdoors, hospital waiting rooms, bedrooms, etc. There is a need for paper and printed matter that will not get tired. Regarding the relationship between color and eye fatigue, there has been a technique related to the hue and eye fatigue of notebook paper (Patent Document 4).

Japanese Patent Laying-Open No. 2015-190087 JP 2009-102797 A Japanese Patent Application Laid-Open No. 2006-094678 JP 2001-295200 A

However, the following problems occur in the conventional techniques that are generally known.
Patent Document 1 was an invention related to a technique using mechanical pulp that tends to be bulky. Further, Patent Document 2 is a technique that assumes medium-sized book paper containing waste paper pulp, and there is a concern that the whiteness may be reduced due to the use of waste paper, and that it is less likely to cause eye fatigue during reading. The issue was not recognized.
Patent Document 3 is a technology that assumes medium-size book paper containing used paper, although it focuses on refurbishment properties, and does not have problems such as suitability for inkjet printing and resistance to eye fatigue.
Patent Document 4 is a technique relating to paper containing a used paper, whose manufacturing method is not clear.

In view of such a situation, an object of the present invention is to provide a high-quality non-coated paper that is bulky and excellent in surface strength and stiffness, and excellent in offset and ink jet printing suitability. It is to be. In particular, an object of the present invention is to provide a book paper that is excellent in refurbishment when used as a book paper, a hand feeling, and a blanc separation at the time of offset printing, and is less tiring even when reading for a long time.

As a result of intensive studies on the above problems, the present inventors have found that chemical pulp is 100% by weight out of 100% by weight of pulp and has a clear coating layer on the base paper, and the density is less than 0.75 g / cm ^3. In the high-quality non-coated paper, the clear coating layer contains latex and starch, and the ratio of the latex and starch is latex: starch = 10: 90 to 99: 1, so that the above problem is solved. As a result, the present invention has been completed.

That is, although not limited thereto, the present invention includes the following contents.
(1) A clear coating layer in a high-quality non-coated paper having a density of less than 0.75 g / cm ³ , wherein the chemical pulp is 100% by weight out of 100% by weight of the pulp and has a clear coating layer on the base paper. Contains latex and starch, and the ratio of the latex to starch is latex: starch = 10: 90 to 99: 1.
(2) The high-quality non-coated paper according to (1), which contains 1.0% by weight or less of a bulking agent with respect to 100% by weight of pulp.
(3) The high-quality non-coated paper according to any one of (1) and (2), which contains 0.01% by weight to 3.0% by weight of an internal sizing agent with respect to 100% by weight of the pulp.
(4) The high-quality non-coated paper according to any one of (1) to (3), which has a Steecht sizing degree of 1 second to 100 seconds.
(5) The high-quality non-coated paper according to any one of (1) to (4), wherein the stiffness in the transverse (CD) direction (Clark formula) measured according to JIS P8143 is 10 or more.
(6) The high-quality non-coated paper according to any one of (1) to (5), wherein the rigidity (Clark type) in the machine direction (MD) direction measured according to JIS P8143 is 40 or more.
(7) L ^* a ^* b ^* values by light sources including ultraviolet rays according to JIS P8150 are L ^* values of 90 to 98, a ^* values of -5 to 0, and b ^* values of 10 to 15, respectively (1 ) To (6).
(8) The high-quality non-coated paper according to any one of (1) to (7), which is an inkjet and / or offset printing paper.
(9) High-quality non-coated paper according to any one of (1) to (8), which is book paper (10) A step of mixing starch and latex, and a single side of 0.1 g / m ² or more by a gate roll coater The manufacturing method of the quality uncoated paper in any one of (1)-(9) which has the process of providing a 3.0 g / m < ² > or less clear coating layer, and the process of giving a calendar process.

  ADVANTAGE OF THE INVENTION According to this invention, although it is bulky, it can provide the high quality non-coating paper which was excellent in surface strength and stiffness, and excellent in offset and inkjet printing suitability. In particular, it is possible to provide a book paper that is excellent in refurbishment when used as a book paper, a feeling of hand feeling, and a blank separation at the time of offset printing.

High-quality uncoated paper The paper stock used in the present invention is 100% by weight of chemical pulp with respect to 100% by weight of pulp. As the pulp material to be used, chemical pulp generally used as a papermaking material for printing paper, such as hardwood kraft pulp (LKP) and softwood kraft pulp (NKP), can be suitably used. Pulp can be used, and one or two or more of these are appropriately blended. From the viewpoint of whiteness, it is preferable to use bleached chemical pulp that has undergone a bleaching step. Since the high-quality non-coated paper of the present invention comprises 100% by weight of chemical pulp, it is excellent in whiteness and color resistance. In addition, since chemical pulp has a higher whiteness than used paper pulp and mechanical pulp, color is good when a colorant for adjusting hue is added.

  Various internal additives may be added to the stock of the present invention as long as the effects of the present invention are not impaired. The internal additive is not limited to this, but polyacrylamide polymer, polyvinyl alcohol polymer, oxidized starch, esterified starch, cationized starch, other various modified starches, styrene-butadiene copolymer. Adhesives such as latex and vinyl acetate; Cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose; Internal paper strength enhancers such as urea / formalin resin and melamine / formalin resin; Rosin-based sizing agent, AKD-based sizing agent, ASA-based Internally added sizing agents such as sizing agents, petroleum-based sizing agents, and neutral rosin sizing agents; sulfate bands, yield improvers, UV inhibitors, fading inhibitors, drainage improvers, coagulants, pH adjusters, slime control Agents, colorants (dyes, pigments) and fluorescent dyes may be added. The high-quality non-coated paper of the present invention has a liquid absorption control agent in order to achieve both the prevention of roll contamination of the machine during papermaking and the separation of the blank during offset printing and the liquid absorption during inkjet printing. A sizing agent is preferable as the drug for controlling the liquid absorption. More preferably, it is an AKD sizing agent that has self-fixing properties and exhibits an effect with a low addition amount. The content of the sizing agent is preferably 0.01% by weight or more and 3.0% by weight or less, more preferably 0.05% by weight or more and 1.5% by weight or less, and still more preferably 0.1% by weight or less with respect to 100% by weight of the pulp. % By weight or more and 0.5% by weight or less. By containing the sizing agent in the above range, the stain on the machine at the time of manufacture is reduced, and the separation of the blank at the time of printing becomes good.

The high-quality non-coated paper of the present invention contains a bulking agent. The content of the bulking agent is 1.0% by weight or less, preferably 0.9% by weight or less, more preferably 0.8% by weight or less, more preferably 0.8% by weight or less with respect to 100% by weight of the pulp. It is less than 7% by weight. If the content of the bulking agent is 1.0% by weight or less, it is possible to obtain a high-quality uncoated paper having a relatively high bulk without using a bulky pulp such as mechanical pulp, Excellent hand feeling and stiffness when used as a book. If the content of the bulking agent is more than 1.0% by weight, the hydrophobization of the multi-fibers progresses and the inter-fiber bonding does not proceed, so there is a risk that the wet paper strength at the time of manufacture and the delamination strength of the product may decrease. As the added amount decreases, the strength reduction can be suppressed. On the other hand, if the addition amount of the bulking agent is too small, the bulking effect is lowered, so the lower limit is preferably 0.1% by weight or more.

The high-quality non-coated paper of the present invention can be filled with a filler, but the filler to be filled is not particularly limited, and can be appropriately selected from known fillers. Examples of such a filler include organic carbonates such as calcium carbonate such as talc, kaolin, clay, light calcium carbonate, and heavy calcium carbonate, titanium dioxide, silica, and plastic pigment. It is calcium carbonate. When calcium carbonate is used as an internal filler in the high-quality non-coated paper of the present invention, it is preferable because it has an effect of improving printing quality such as opacity and printability. Among calcium carbonates, light calcium carbonate is particularly preferable because of its high specific scattering coefficient and high opacity. When printing on high-quality uncoated paper, especially when used as book paper, duplex printing is often performed, and opacity is an important quality item to prevent back-through after printing. Become.

In the high-quality uncoated paper of the present invention, the lower limit of the ash content in the paper is preferably 5% by weight or more and 45% by weight or less, more preferably 10% by weight or more and 43% by weight or less, more preferably, based on the absolute dry weight of the paper. Is 13 wt% or more and 40 wt%. Further, from the viewpoint of opacity, it is more preferable that the ash content in the paper is 20% by weight or more because opacity comparable to that of pigment-coated paper can be obtained. If the ash content in the paper is less than 5% by weight, the opacity and smoothness of the resulting clear coating value may be insufficient. On the other hand, if the ash content in the paper is higher than 45% by weight, the bond between the fibers is hindered by the filler in the paper, and the paper may be insufficient. The shortage of paper causes problems such as poor processability, poor turning ability when processed as a book, and poor hand feeling.

Papermaking process In the present invention, the stock prepared as described above is appropriately diluted, and if necessary, removes foreign matter from the stock with a screen or a cleaner, and then sprays onto the papermaking wire from the headbox of the paper machine. Is done. The present invention is manufactured by various paper machines such as a long net type, a circular net type, a short net type, and a twin wire type paper machine. Examples of twin wire paper machines include gap formers and on-top formers. The press linear pressure after papermaking is appropriately used within the range of the density of the present invention, but the press linear pressure is preferably low or low in order to obtain the bulky effect of the present invention.
The papermaking method may be neutral papermaking or acidic papermaking, but is preferably neutral papermaking. Specifically, in the present invention, the paper pH at the time of paper making is preferably 5.0 to 9.0, and more preferably 6.0 to 8.0.

Surface treatment step In the present invention, in order to improve surface strength, impart water resistance, printability, etc., a surface treatment solution is applied to the base paper obtained above, and a clear coating layer is provided. May be. The type of adhesive used in the surface treatment liquid is not particularly limited, but is produced by thermochemical or enzymatic modification in a paper mill using raw starch, oxidized starch, esterified starch, cationized starch, and acetylated tapioca starch as raw materials. It is preferable to include starch such as self-modified starch, modified starch such as aldehyde-modified starch and hydroxyethylated starch. Cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, and cellulose nanofiber, polyacrylamide, polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, modified alcohols such as acetoacetylated polyvinyl alcohol, latex, styrene-butadiene copolymer, polyvinyl acetate , Vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, polyacrylic acid ester, and the like can be used in combination. The surface treatment liquid preferably contains at least latex, and more preferably styrene-butadiene latex (SBR), from the viewpoint of preventing surface strength and sticking during small edge polishing. The average particle size of the latex measured by the optical correlation method is preferably 70 nm or more and 200 nm or less, more preferably 75 nm or more and 150 nm or less. When latex having an average particle size larger than 200 nm is used, the surface strength of the obtained paper may be lowered. The glass transition temperature (Tg) of the latex used is preferably −50 to 10 ° C., more preferably −30 to 5 ° C., from the viewpoint of achieving both surface strength and stickiness with a heating roll. The average particle diameter and Tg of the latex of the present invention can be measured by an optical correlation method, a dynamic light scattering method, or the like, respectively.

Furthermore, it is preferable to use latex and starch together in the surface treatment liquid, and the mixing ratio when mixing latex and starch is preferably latex: starch = 10: 90 to 99: 1. When latex is used alone, the cost becomes high, so it is preferable to use it together with starch. . On the other hand, if the mixing ratio of the latex is too high, afterdrying stains at the time of production and a decrease in water absorption at the time of inkjet printing occur, and more preferably 15:85 to 50:50, more preferably 20: 50-40: 60. Even if the styrene-butadiene latex is a small amount, the effect of improving the surface strength and the refurbishability can be obtained.
Although the mechanism regarding the effect of preventing sticking to the facet is not clear, the following hypothesis can be considered. There is a possibility that the effect of preventing the sticking to the facet during polishing when starch and latex are mixed depends on the water retention of starch and the difference in hygroscopicity between latex and starch. Starch has the property of easily causing gelation when the solid content concentration is high, and it is considered that gelation occurs in the coating layer during the drying process. When a surface treatment solution with high water retention that contains a large amount of starch is used, the surface treatment solution permeates into the base paper between processes from coating to drying, and the surface treatment solution exists only on the very surface of the paper. It will be in a state that does not. For this reason, since the fibers in the paper layer are not coated with the surface treatment agent, fluffing is likely to occur, and the fibers are more likely to be entangled.
In addition, all the books used for polishing the small face are long displayed at the bookstore, and it is assumed that moisture absorption occurs during that time. For this reason, when more highly hygroscopic starch is used, it is assumed that the clear coating layer containing moisture is softened, and is likely to be sticky during polishing.

Further, for the purpose of increasing the size property, it is possible to use a surface sizing agent such as a styrene sizing agent, an olefin sizing agent, an acrylate sizing agent, a styrene-acrylic sizing agent, or a cationic sizing agent in combination. When a surface sizing agent is used in combination, the solid content concentration in the surface treatment agent is preferably 0.005 to 1% by weight, more preferably 0.01 to 0.5% by weight, and more preferably 0.015 to 0. .1 or less. Since the surface sizing agent is effective for reducing friction and exhibiting size properties in a small amount as compared with the internally added sizing agent, a sufficient effect can be obtained with the addition amount described above.

Furthermore, when performing the surface treatment in the present invention, various kinds of additives, such as a dispersant, a thickening agent, a water retention material, an antifoaming agent, a water resistant agent, a colorant, and a conductive agent, which are blended in a normal surface treatment agent as necessary. Auxiliaries are used as appropriate. Since the high-quality non-coated paper of the present invention contains a yellow colorant, a long-time reading is performed.

The coating amount of the surface treatment agent is appropriately determined depending on the required surface strength and the like, and is not particularly limited, but is usually in the range of 0.1 g / m ² or more and 3.0 g / m ² or less on both sides. 0.1 g / m ² or more and 2.0 g / m ² or less is preferable, and 0.15 g / m ² or more and 1.5 g / m ² or less is more preferable. When the coating amount increases, the absolute amount of moisture in the coating layer increases, resulting in an increase in the drying load and the occurrence of poor drying. For this reason, the coating layer is increased in stickiness, and sticking is likely to occur when cutting a small face.

The apparatus for applying the surface treatment agent is not particularly limited, and can be applied by a known coating machine such as a two roll size press, a pound type size press, a gate roll coater, a lot metering size press, a blade coater, a spray coater, or a curtain coater. The high-quality non-coated paper of the present invention can obtain the effects of the present invention at a low coating amount, and the gate roll coater is a coating method suitable for coating at a low coating amount. Therefore, a gate roll coater is preferable. When the high-quality non-coated paper of the present invention is used for book paper, if the amount of coating increases, the weight and paper thickness derived from the coating layer may increase. Also, if the weight increases, the paperback books themselves become heavier, making it easier to get tired of the hands you hold during reading, and if the paper thickness increases, the number of books that can be loaded when loading trucks etc. May decrease.

The obtained high-quality non-coated paper may be passed through a known public finishing device such as a super calender, gloss calender, soft calender, high temperature soft nip calender, etc. to finish the product, or the density of the present invention However, the high-quality uncoated paper of the present invention can impart surface smoothness with little reduction in paper thickness. Processing with a calendar or soft calendar is preferred.

The high-quality non-coated paper obtained in the present invention may be used as a base paper for pigment coating.

Basis weight The high-quality uncoated paper of the present invention preferably has a basis weight measured according to JIS P 8124 of 40 g / m ² or more and 150 g / m ² or less, more preferably 45 g / m ² or more and 140 g. / M ² or less. The technique of the present invention is particularly suitable for paper having a low basis weight because high rigidity can be obtained even when the basis weight is low.

Paper thickness The high-quality uncoated paper of the present invention has a paper thickness (50 kPa) measured according to JIS P 8118 of 90 µm or more.

Density The high-quality non-coated paper of the present invention preferably has a paper density measured in accordance with JIS P 8118 of less than 0.75 g / cm ³ , more preferably 0.70 g / m. ³ or less. The lower the density of the paper, the smaller the sticking of the facet at the time of cutting according to the present invention, so there is no particular lower limit. However, in order to maintain the smoothness required for book paper, 0.50 g / cm ³ Higher is preferred.

Quality-based non-coated paper stiffness <br/> present invention, stiffness measured according to JIS-P8143 (Clark type) is, longitudinal (MD: Machine flow) direction of the stiffness is preferably 40 or more 210 or less, further Preferably they are 50 or more and 200 or less. Further, the stiffness in the transverse (CD: machine width) direction is preferably 10 or more and 100 or less, more preferably 15 or more and 90 or less. If the stiffness is lower than the above range, paper will be too soft when used as a paperback book, and pages will stick together due to static electricity, making it difficult to turn over, and double feeding will occur when printing in lithographic printing or electrophotography There is a thing to do. On the other hand, when the stiffness is higher than the above range, it is difficult to align the paper at both ends of the page when the book is spread, and furthermore, the paper rises and is difficult to read. Also, if the stiffness in the CD direction is lower than 10, the book will not be felt when the book is opened, and the page will be bent. Therefore, it is difficult to hold the book in the opened state, and if the stiffness in the MD direction is lower than 40, There is a risk that the running performance will deteriorate.

Opacity The high- quality non-coated paper of the present invention preferably has an ISO opacity measured according to ISO 2471 of 80 or more, more preferably 85 or more. If the ISO opacity is less than 80, a show-through occurs during printing, and the book becomes difficult to read when bound.

Hue The high-quality uncoated paper of the present invention has L ^* a ^* b ^* values of L ^* 90 to 98 and a ^* −5 to 0 and b, respectively, according to JIS P8150. ^* It is preferably 10 or more and 15 or less, more preferably L ^* 92 or more and 97 or less, a ^* −3 or more and −1 or less, and b ^* 11 or more and 14 or less. If it is in the above range, it is possible to obtain a natural texture-quality coated paper that is creamy and gentle to the eyes. Further, when used as a book paper, it is possible to obtain a book paper that is less tiring even when reading for a long time.

Sticky sizing degree The high-quality non-coated paper of the present invention preferably has a sticky sizing degree measured according to JIS P8155 of 100 seconds or less, more preferably 5 seconds or more and 80 or less. It is preferable that the Steecht sizing degree is in the above-mentioned range because it is possible to achieve both a blank separation at the time of offset printing and a liquid absorption at the time of ink jet printing.

The present invention will be described below with reference to examples, but these examples are not intended to limit the scope of the present invention. In the description of the present specification, the concentration and% are (solid content) wt%, and the numerical range is described as including the end points.

<Evaluation method>
Paper quality measuring method / basis weight: Measured according to JIS P 8124.
-Paper thickness and density: Measured according to JIS P 8118.
Ash content: Measured according to ISO 1762-1974.
ISO opacity: Measured according to ISO 2471.
ISO whiteness: Measured with a color difference meter CMS-35SPX manufactured by Murakami Color Co., Ltd. according to JIS P8148.
-Hue: Measured with a light source containing ultraviolet rays according to JIS P8150.
Oken type smoothness: measured according to JIS P 8155.
・ Stick human sizing degree: Measured according to JIS P 8155.
-Stiffness (Clark type): Stiffness in the longitudinal direction was measured according to JIS-P8143.
Evaluation method of hand feeling A high-quality uncoated paper sample of 200 sheets in A6 size (paperback book size), a soft cover, and a bookbinding sample by wireless binding were prepared. Holding the closed part with the left hand and handling the paper 20 times with the right hand, the paper tension (hand feeling) is “x” if the paper does not stretch well and the paper does not stick well, but the tension is slightly less The hand feeling was evaluated with “△” indicating that the page could be judged without exception, and “◯” indicating that each page did not become loose while the tension was being measured.
Evaluation method of refurbishment quality 200 non-coated paper samples of A6 size (paperback book size), soft cover, and bookbinding samples were created by wireless binding. Four bookbinding samples were set in a belt polisher (NIPPO), and the facet was polished twice back and forth according to standard usage. For bookbinding samples with a polished facet, “×” indicates that multiple pages are firmly attached to the polishing part when the book is opened, and “△” indicates that multiple pages are attached to the polishing part when the book is opened. “When the book was opened, the sticking of the polishing part was loosened, or the sticking of the polishing part was not sticking, and“ small circle ”was evaluated as“ ◯ ”.
Eye fatigue evaluation method On a paper sheet cut to A4, a 10 pt Mincho body black text was printed with a laser printer, and the degree of eye fatigue when reading three times was evaluated. “X” indicates that the paper and character contrast is strong and the eyes are easily tired, and “○” indicates that the eyes are not easily tired.
Evaluation Method of Machine Dirt The machine dirt condition at the time of manufacture was confirmed, and “X” indicates that the machine was dirty, and “◯” indicates that the machine was not dirty.

Example 1
To the pulp slurry in which 90 parts of LBKP and 10 parts of NBKP were mixed, calcium carbonate and sizing agent were added to 38% by weight, 0.5% by weight and 0.08% by weight, respectively, with respect to 100% by weight of the pulp. Was prepared. Thereafter, the stock was ejected from the head box onto a twin-wire type paper making wire, paper was made, squeezed with a press part and dried with a predryer, and a base paper was made at a paper making speed of 650 m / min. To the obtained base paper, oxidized starch, styrene-butadiene latex and water as binders, oxidized starch: styrene-butadiene latex (A & L, PB9501, average particle size 83 nm, Tg-15 ° C.) = 67:33 Then, an aqueous solution (clear coating solution) in which a yellow dye is further added to 300 g / t (paper) is further mixed using a gate roll coater so that the coating amount on both sides is 2.4 g / m ^2. A high-quality non-coated paper was obtained by coating and drying uniformly so as to be (solid content). The measured values and evaluation results of the paper quality are shown in Table 1.

(Example 2)
A high-quality uncoated paper was obtained in the same manner as in Example 1 except that the basis weight was 68 g / m ² and the paper thickness was 109 μm.

(Example 3)
Calcium carbonate is 16% by weight and bulking agent is 0.6% by weight with respect to 100% by weight of pulp. Oxidized starch of clear coating solution: styrene-butadiene latex = 84: 16, yellow dye is 80 g / t. Thus, a high-quality non-coated paper was obtained in the same manner as in Example 1 except that 2.4 g / m ² (solid content) was coated on both sides.

Example 4
A high-quality uncoated paper was obtained in the same manner as in Example 3 except that the basis weight was 80 g / m ² .

(Example 5)
Example except that the sizing agent was added to the clear coating solution so that the amount was 1.25% by weight with respect to 100% by weight of the binder, and the coating amount on both sides was 1.6 g / m ^2. As in Example 1, a high-quality uncoated paper was obtained.

(Comparative Example 1)
A high-quality non-coated paper was obtained in the same manner as in Example 1 except that only the oxidized starch was used as the binder of the clear coating layer.

(Comparative Example 2)
A high-quality non-coated paper was obtained in the same manner as in Example 1 except that only the styrene-butadiene latex was used as the binder of the clear coating layer.

(Comparative Example 3)
A high-quality uncoated paper was obtained in the same manner as in Example 4 except that the bulking agent was not added to the stock, the binder of the clear coating layer was only oxidized starch, and the basis weight was 87 g / m ² .

(Comparative Example 4)
A high-quality uncoated paper was obtained in the same manner as in Comparative Example 3, except that a bulking agent was added to the paper stock at 1.50% by weight with respect to 100% by weight of the pulp and the basis weight was changed to 80 g / m ² .

(Comparative Example 5)
A high quality uncoated paper is obtained in the same manner as in Comparative Example 1 except that the pulp slurry is NBKP 8% by weight, GP 40% by weight, and TMP 52% by weight with respect to 100% by weight of pulp, and does not contain an internal additive sizing agent or yellow dye It was.

Claims (10)

In a high-quality non-coated paper having a clear coating layer on a base paper whose chemical pulp is 100% by weight out of 100% by weight of pulp, a density of less than 0.75 g / cm ³ ,
The clear coating layer contains latex and starch,
High-quality non-coated paper in which the ratio of latex to starch is latex: starch = 10: 90 to 99: 1. The high-quality non-coated paper according to claim 1, comprising 1.0% by weight or less of a bulking agent with respect to 100% by weight of pulp. The high-quality non-coated paper according to any one of claims 1 and 2, wherein the internal sizing agent is contained in an amount of 0.01 wt% to 3.0 wt% with respect to 100 wt% of the pulp. The high-quality non-coated paper according to any one of claims 1 to 3, which has a Steecht sizing degree of 1 second to 100 seconds. The high-quality non-coated paper according to any one of claims 1 to 4, wherein the stiffness (Clark type) in the transverse (CD) direction measured according to JIS P8143 is 10 or more. The high-quality non-coated paper according to any one of claims 1 to 5, wherein the rigidity (Clark type) in the longitudinal (MD) direction measured according to JIS P8143 is 40 or more. The L ^* a ^* b ^* values by a light source including ultraviolet rays according to JIS P8150 are L ^* values of 90 to 98, a ^* values of -5 to 0, and b ^* values of 10 to 15, respectively. High-quality non-coated paper as described in any of the above. The high-quality non-coated paper according to any one of claims 1 to 7, which is an inkjet and / or offset printing paper. The high-quality non-coated paper according to any one of claims 1 to 8, which is a book paper. The method according to claim 1, comprising a step of mixing starch and latex, and a step of providing a clear coating layer of 0.1 g / m ² or more and 3.0 g / m ² or less on one side by a gate roll coater. A method for producing high-quality uncoated paper.