JP6985841B2 - Medium-quality uncoated paper - Google Patents

Description

The present invention relates to a neutral non-coated paper. More specifically, the present invention provides a medium-quality uncoated paper which is bulky, has excellent surface strength and stiffness, and has excellent offset and inkjet printing suitability. In particular, it is a book paper that has excellent hand-feeling when used as book paper and has excellent flanking during offset printing, and does not tire the eyes even when reading for a long time.

In recent years, publications have been required to reduce the cost of printed matter and the weight of paper, and books have also been made to reduce the density of paper.
Among publications, books such as paperback books, comic books, and literary books are often carried around, and especially lightweight paper is required. As a technology for reducing the weight of ^{paper, in bulky book paper mainly composed of chemical pulp with a density of 0.60 g / m 2} or less, specific hydrated distillic acid is added, and starch and styrene-butadiene latex are surfaced in a specific ratio. There is a technique for achieving opacity by applying to (Patent Document 1) and a technique for bulky medium-quality printing paper containing broad-leaved mechanical pulp of a specific tree species and a bulking agent (Patent Document 2). In addition, simple electronic books that do not require a storage space compared to paper are becoming widespread.

Generally, books are distributed from publishers under the consignment system of lining up at bookstores through agents, and some books that could not be sold at bookstores are returned. Since the fore edge of the returned book will fade, the fore edge is polished using a polishing machine, which is called "remodeling", so there is less sticking between the paper on the fore edge during the polishing process. , Paper with excellent remodelability is required. As a technique for book paper having excellent remodelability, there is a technique for pulp containing styrene-butadiene latex and starch and having a specific fiber length (Patent Document 3).

By the way, unlike newspapers and magazines, which look at the paper in a short time, books often keep looking at the paper for a long time, which causes eye fatigue. In addition to desks with lighting suitable for reading, there are many cases where reading is done in places with different lighting conditions, such as inside a train or outdoors on the move, in a hospital waiting room, or in a bedroom, so it takes a long time. There is a demand for paper and printing that will not tire your eyes even when reading. Regarding the relationship between color and eye strain, there was a technique related to the hue of notebook paper and eye strain (Patent Document 4). In addition, comparative studies on the reading of electronic books and paper books, which have become widespread in recent years, have also been conducted (Non-Patent Document 1).

Japanese Unexamined Patent Publication No. 2008-196083 Japanese Unexamined Patent Publication No. 2009-102977 Japanese Unexamined Patent Publication No. 2016-094678 Japanese Unexamined Patent Publication No. 2001-295200

Information Processing Society of Japan Research Report, Vol. 2011-HCI-141 No. 4

However, in the generally known conventional technology, the following problems occur.
Since the technique described in Patent Document 1 is a technique relating to low-density book paper mainly composed of chemical pulp, and the technique of Patent Document 3 is a technique relating to paper containing used paper pulp without containing mechanical pulp. In each case, the rigidity of the paper was low, and the feeling of hand flesh when used as book paper was inferior. Further, Patent Document 2 is a technique for reducing the rigidity, and further, since it is a medium-quality printing paper using only starch as a surface treatment agent, it is inferior in remodelability when used for books. rice field. The technique described in Patent Document 4 is a technique in which the manufacturing method is not clear and may be inferior in remodelability and hand flesh when used as a book. In addition, as described in Non-Patent Document 1, e-books have a higher degree of eye fatigue than paper books, and many people feel stress when turning pages, so they are not suitable for long-term reading. there were.

In view of such a situation, an object of the present invention is to provide a medium-quality uncoated paper which is bulky, has excellent surface strength and stiffness, and has excellent offset and inkjet printability. In particular, it is an object of the present invention to provide a book paper that has excellent hand-feeling, remodelability when used as a book paper, and has excellent flanking during offset printing, and does not tire the eyes even when reading for a long time.

As a result of diligent research on the above-mentioned problems, the present inventors have found that mechanical pulp is 5% by weight or more out of 100% by weight of starch, and a medium-based non-coated paper having a clear coated layer on a base paper. The present invention has been completed by finding that the above problems can be solved by setting the clear coating layer to contain latex and starch and the ratio of the latex to starch to be latex: starch = 10: 90 to 99: 1. ..

That is, the present invention includes, but is not limited to, the following contents.
(1) In a medium-sized non-coated paper having a clear coated layer on a base paper containing 5% by weight or more of mechanical pulp with respect to 100% by weight of pulp, the clear coated layer contains latex and starch, and the above-mentioned Medium-quality non-coated paper in which the ratio of latex to starch is latex: starch = 10: 90 to 99: 1.
(2) The neutral non-coated paper according to (1), which contains 0.1% by weight or more of a bulking agent.
(3) The neutral non-coated paper according to (1) or (2), which contains 30% by weight or more of mechanical pulp or deinked pulp with respect to 100% by weight of pulp.
(4) The neutral non-coated paper according to any one of (1) to (3), which contains 0.01% by weight or more and 5% by weight or less of an internal sizing agent with respect to 100% by weight of pulp.
(5) The neutral non-coated paper according to any one of (1) to (4), wherein the rigidity (Clark type) in the vertical (MD) direction measured according to JIS P8143 is 20 or more.
(6) The neutral non-coated paper according to any one of (1) to (5), wherein the rigidity (Clark type) in the lateral (CD) direction measured according to JIS P8143 is 10 or more.
(7) The neutral non-coated paper according to any one of (1) to (6), which has a whiteness of 85% or less.
(8) ^L by the light source including the ultraviolet by JIS P8150 ^{* a} * ^b * values respectively, ^{L *} values 80 or 98 or less, ^{a *} value is -5 to 3., ^{b *} value is -3 to 12 A medium-quality non-coated paper according to any one of (1) to (7).
(9) The medium-quality non-coated paper according to any one of (1) to (8), which is an inkjet and / or offset printing paper.
(10) The medium-quality non-coated paper according to any one of (1) to (9), which is a book paper.
(11) The steps (1) to (10) include 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.} The method for manufacturing medium-quality uncoated paper described in any of the above.

According to the present invention, it is possible to provide a medium-quality uncoated paper which is bulky, has excellent surface strength and stiffness, and has excellent offset and inkjet printability. In particular, it has excellent hand-feeling when used as book paper, remodelability, and flanking during offset printing. Further, since the whiteness is relatively low, the contrast between the paper and the printed matter is suppressed, and it is possible to provide a book paper that does not tire the eyes even when reading for a long time.

Neutral non-coated paper The neutral non-coated paper of the present invention contains 5% by weight or more of mechanical pulp with respect to 100% by weight of pulp. It is preferably 10% by weight or more, more preferably 15% by weight. Since mechanical pulp tends to be bulky, it is possible to obtain medium-quality uncoated paper that is excellent in stiffness by containing mechanical pulp and has an excellent hand-flesh feeling when made into a book. The surface texture tends to be rough and the whiteness tends to be low. Since books differ in the size and shape when bound, the required stiffness, surface properties, and whiteness depending on the application, the content of mechanical pulp is appropriately adjusted according to the application. Although not limited to these, the upper limit of the content of mechanical pulp is 90% by weight or less for comic paper, 80% by weight or less for literary paper and the like, and 60% by weight or less for paperback paper and the like.

The neutral non-coated paper of the present invention preferably contains 30% by weight or more of the total content of deinked pulp (DIP, also called used paper pulp) and mechanical pulp with respect to 100% by weight of pulp. It is preferably 40% by weight or more. Examples of the mechanical pulp include crushed wood pulp (GP), refiner crushed wood pulp (RGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), chemigrand pulp (CGP), semi-chemical pulp (SCP) and the like. .. Deinked pulp includes selected recycled paper such as high-quality paper, medium-quality paper, low-grade paper, newspaper, leaflets, and magazines, unsorted recycled paper mixed with these, copy paper, heat-sensitive paper, no-carbon paper, and confidential waste paper. It is not particularly limited as long as it is a deinked pulp made from used office paper containing. In addition, by containing deinked pulp and mechanical pulp, which have a lower whiteness than chemical pulp, in the above range, the whiteness can be reduced to 85% or less without using a large amount of coloring agents such as black dyes and pigments. Since it can be made low, it is possible to obtain a medium-sized non-coated paper having a calm hue. For the above reason, the medium-quality non-coated paper of the present invention does not make the contrast between the characters and the paper too strong when it is made into a book, so that the eyes do not get tired even after reading for a long time.
The medium-based uncoated paper of the present invention may contain other pulp. There are no particular restrictions on the pulp raw materials used, and in addition to wood pulp such as coniferous pulp (NP) and broadleaf pulp (LP), non-wood pulp such as linter pulp, hemp, bagasse, kenaf, esparto grass, and straw, rayon, etc. Semi-synthetic fibers such as acetate, synthetic fibers such as polyolefin, polyamide and polyester can be used. Specifically, kraft pulp (KP) and other materials generally used as a papermaking raw material for printing paper can be preferably used, and one or more of these can be appropriately used in combination. Will be done.

Various internal chemicals may be added to the paper material of the present invention as long as the effects of the present invention are not impaired. The internal chemicals are not limited to this, but are limited to polyacrylamide-based polymers, polyvinyl alcohol-based polymers, oxidized starch, esterified starch, cationized starch, various other modified starches, and styrene-butadiene copolymers. Adhesives such as latex and vinyl acetate; Cellulosic derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose; Internal paper strength enhancers such as urea / formarin resin and melamine / formalin resin; rosin-based sizing agents, AKD-based sizing agents, ASA-based Internal sizing agents such as sizing agents, petroleum-based sizing agents, and neutral rosin sizing agents; Agents, colorants (dye, pigment), fluorescent dyes and the like may be added. The medium-sized non-coated paper of the present invention has effects such as prevention of roll stains on the machine during papermaking, separation of blanks during offset printing, and liquid absorption during inkjet printing, and thus is a chemical that controls liquid absorption. Is preferable, and a sizing agent is preferable as the agent for controlling the liquid absorbency. More preferably, it is an AKD sizing agent that has self-fixing property and exhibits an effect with a low addition amount. The content of the sizing agent is preferably 0.01% by weight or more and 5.0% by weight or less, more preferably 0.05% by weight or more and 1.0% by weight or less, still more preferably 0.1% by weight, based on 100% by weight of the pulp. It is 50% by weight or more and 0.5% by weight or less. By containing the sizing agent in the above range, stains on the machine during manufacturing are reduced, and brand separation during printing is improved.

The neutral non-coated paper of the present invention may contain a bulking agent. Since the medium-based non-coated paper of the present invention contains mechanical pulp, it tends to be bulky at a low density, but when it is to be further bulky, it is preferable to contain a bulking agent. The content of the bulking agent is 0.1% by weight or more and 1.0% by weight or less, preferably 0.9% by weight or less, and more preferably 0.8% by weight or less with respect to 100% by weight of the pulp. , More preferably less than 0.7% by weight. When the content of the bulking agent is within the above range, the bonding between the fibers is not excessively hindered while imparting an appropriate bulking effect, and the delamination strength, surface strength, and stiffness are unlikely to decrease. Further, for the above reason, the stiffness is unlikely to decrease, so that the feeling of hand flesh when used as a book is excellent. As described above, when the content of the bulking agent is more than 1.0% by weight, the hydrophobicity of the polyfibers progresses and the interfiber bonds do not proceed, so that the wet paper strength at the time of manufacture and the delamination strength of the product decrease. The smaller the amount added, the more the decrease in strength can be suppressed. On the other hand, if the amount of the bulking agent added is too small, the bulking effect will be low, so the lower limit is preferably 0.1% by weight or more.

A filler can be internally filled in the medium-quality non-coated paper of the present invention, but the filler to be internally filled is not particularly limited and can be appropriately selected from known fillers and used. .. Examples of such fillers include calcium carbonates such as talc, kaolin, clay, light calcium carbonate, and heavy calcium carbonate, titanium dioxide, silica, and organic fillers such as plastic pigments, which are preferable. It is calcium carbonate. It is preferable to use calcium carbonate as an internal filler in the neutral non-coated paper of the present invention because it has the effect of improving print quality such as opacity and printability. Among calcium carbonates, light calcium carbonate is more preferable because it has a high specific scattering coefficient and imparts high opacity. When printing on medium-quality uncoated paper, especially when using it as book paper, double-sided printing is often performed, and opacity is an important quality item to prevent strike-through after printing. It becomes.

In the neutral non-coated 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, and more preferably 13% by weight or more and 40% by weight. %. If the ash content in the paper is less than 5% by weight, the opacity and smoothness of the obtained clear coating value may be insufficient. On the other hand, if the ash content in the paper is higher than 45% by weight, the filler in the paper may hinder the bonding between the fibers, resulting in a shortage of the paper. Insufficient paper waist causes problems such as deterioration of processing suitability, deterioration of turning suitability when processed as a book, and deterioration of hand flesh.

Papermaking process In the present invention, the paper material prepared as described above is appropriately diluted, and if necessary, foreign matter is removed from the paper material with a screen or cleaner, and then the paper is sprayed onto the papermaking wire from the head box of the paper machine. Will be 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 the twin wire paper machine include a gap former and an on-top former. The press line pressure after papermaking is appropriately used within the range of the density of the present invention, but it is preferable that the press line pressure is low in order to obtain the bulky effect of the present invention.
The papermaking method may be neutral papermaking or acidic papermaking, but neutral papermaking is preferable. Specifically, in the present invention, the pH of the paper material at the time of papermaking 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, impart printability, etc., a surface treatment liquid is applied to the base paper obtained above, and a clear coating layer is provided. You may. The type of adhesive used for the surface treatment liquid is not particularly limited, but it is produced by thermochemical modification or enzyme modification in a papermaking factory using raw starch, oxidized starch, esterified starch, cationized starch, and acetylated tapioca starch as raw materials. It is preferable to contain starch such as self-modified starch, aldehyded starch, and modified starch such as hydroxyethylated starch. Cellulous derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, cellulose nanofibers, modified alcohols such as polyacrylamide, polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, and acetoacetylated polyvinyl alcohol, latex, styrene-butadiene copolymer, polyvinyl acetate. , Vinyl chloride-vinyl acetate-based copolymer, polyvinyl chloride, polyvinylidene chloride, polyvinylic acid ester and the like can also be used in combination. The surface treatment liquid preferably contains at least latex, and more preferably styrene-butadiene-based latex (SBR), from the viewpoint of surface strength and prevention of sticking during edge polishing. The average particle size measured by the photon correlation method of the latex is preferably 70 nm or more and 200 nm or less, and more preferably 75 nm or more and 150 nm or less. If 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 on a heating roll. The average particle size and Tg of the latex of the present invention can be measured by a dynamic light scattering method, a differential scanning calorimeter, or the like, respectively.

Further, it is preferable to use latex and starch in combination in the surface treatment liquid, and the mixing ratio when latex and starch are mixed is preferably latex: starch = 10: 90 to 99: 1. When the latex is used alone, the cost is high, so it is preferable to use it in combination with starch. However, by increasing the mixing ratio of the latex, the effect of preventing the small surface from sticking during polishing of the present invention becomes higher. .. On the other hand, if the mixing ratio of the latex is too high, stains on the afterdryer during manufacturing and deterioration of water absorption during inkjet printing occur, so that the ratio is more preferably 15:85 to 50:50, more preferably. , 20: 50-40: 60. Styrene-butadiene latex can obtain the effect of improving surface strength and remodelability even in a small amount.
The mechanism for the effect of preventing small-sized sticking is not clear, but the following hypotheses are conceivable. It is considered that the effect of preventing the small surface from sticking 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 a property of easily gelling when the solid content concentration is high, and it is considered that gelation occurs in the coating layer during the drying process. When a highly water-retaining surface treatment liquid containing a large amount of starch is used, the surface treatment liquid does not penetrate into the base paper between the steps from coating to drying, and the surface treatment liquid exists only on the very surface of the paper. It will be in a state where it does not. Therefore, since the fibers inside 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 fore-edge surface have been displayed for a long time at bookstores, and it is assumed that moisture absorption occurs during that time. Therefore, when a large amount of starch having higher hygroscopicity is used, it is assumed that the clear coating layer containing water is softened and the starch is likely to be stretched during polishing.

Further, for the purpose of enhancing the sizing property, it is also possible to use a surface sizing agent such as a styrene-based sizing agent, an olefin-based sizing agent, an acrylate-based sizing agent, a styrene-acrylic sizing agent, and 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 or more and 1% by weight or less, more preferably 0.01 or more and 0.5% by weight or less, and more preferably 0.015 or more and 0. .1 or less. When the amount of the surface sizing agent added is within the above range, it is possible to prevent stains on the machine during manufacturing, and it is possible to control ink penetration when printing by an inkjet method, and it is possible to print a fine image. It is preferable because it can be done.

Further, when the surface treatment is performed in the present invention, various kinds of agents to be blended with ordinary surface treatment agents such as dispersants, thickeners, water retention materials, defoamers, water resistant agents, colorants, conductive agents, etc., if necessary. Auxiliary agents are used as appropriate.

The amount of the surface treatment agent applied 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.} It is preferably 0.1 g / m ² or more and 2.0 g / m ² or less, and more preferably 0.15 g / m ² or more and 1.5 g / m ² or less. As the coating amount increases, the absolute amount of water in the coating layer increases, so that the drying load increases and drying defects are likely to occur. Therefore, the stickiness of the coating layer is increased, and sticking is likely to occur at the time of cutting the edge surface.

The device for applying the surface treatment agent is not particularly limited, and a known coating machine such as a 2-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 can be used. Although it can be applied, the neutral non-coated paper of the present invention can obtain the effect of the present invention even with a low coating amount, and the gate roll coater is a coating method suitable for coating with a low coating amount. Because it is. A gate roll coater is preferred. When the medium-sized coated paper of this first smile is used for book paper, the weight and thickness of the coated layer on the entire paper increase as the amount of coating increases. In addition, an increase in the weight of paper leads to hand fatigue during reading, and an increase in paper thickness leads to a decrease in the number of books that can be loaded when loading on a truck or the like.

The obtained medium-quality uncoated paper may be passed through a publicly known and public finishing device such as a super calendar, a gloss calendar, a soft calendar, a high-temperature soft nip calendar, etc. to finish the product, or the product of the present invention may be finished. The medium-based uncoated paper of the present invention may be untreated or bypassed for a density range, but the medium-based uncoated paper of the present invention is a soft-nip calendar or a high-temperature soft-nip calendar in order to impart smoothness while maintaining bulkiness. It is preferable to treat with.

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

Basis weight The medium-weight uncoated paper of the present invention preferably has a basis weight of 40 g / m ² or more and 150 g / m ² or less, more preferably 45 g / m ² or more and 120 g, as measured according to JIS P8124. It is / m ² or less, more preferably 100 g / m ² or less. The medium-weight uncoated paper of the present invention is particularly suitable for paper having a low basis weight because it can obtain appropriate rigidity even if the basis weight is low, and has high opacity and few strike-throughs.

Paper thickness The medium-weight uncoated paper of the present invention has a paper thickness of 60 μm or more, preferably 65 μm or more, measured according to JIS P8118.

Density The medium-based uncoated paper of the present invention preferably has a paper density measured according to JIS P8118 of 0.40 g / m ³ or more and 0.90 g / cm ³ or less. It is preferably 0.43 ^{g / cm 3} or more and 0.85 g / m ³ or less. Generally, when the content of the bulking agent is high, the interfiber bond of the paper may be weakened, and the strength and stiffness may be lowered. Since it contains 5% by weight or more of%, the decrease in strength is suppressed, and even if the density is ^{relatively bulky at 0.90 g / cm 3} or less, there is little decrease in stiffness and surface strength, and offset printing suitability and Excellent hand-feeling when made into a book.

The quality-based non-coated paper in the stiffness <br/> present invention, stiffness measured according to JIS P8143 (Clark type) is, longitudinal (MD: Machine flow) direction of the stiffness is preferably 20 or more 270 or less, further It is preferably 30 or more and 260 or less. The rigidity in the lateral (CD: machine width) direction is preferably 10 or more and 100 or less, and more preferably 15 or more and 90 or less. If the rigidity is lower than the above range, the paper will be too soft when used as a paperback book, or the pages will stick to each other due to static electricity, making it difficult to turn. Double feeding may occur when printing in lithographic printing or electrophotographic printing. On the other hand, when the rigidity is higher than the above range, it is difficult to align the papers at both ends of the page when the book is spread, and it is difficult to read because the papers stand up. Also, if the rigidity in the CD direction is lower than 10, there is no feeling of flesh when the book is opened and the pages are flattened, so it is difficult to hold the book in the open state, and if the rigidity in the MD direction is lower than 20, when printing. There is a risk that the running performance will deteriorate.

Opacity The neutral non-coated paper of the present invention preferably has an ISO opacity of 80 or more, more preferably 85 or more, more preferably 87 or more, as measured according to ISO2471. Is. If the ISO opacity is less than 80, strike-through will occur during printing, making the book difficult to read when binding.

Hue The neutral non-coated paper of the present invention has L ^* a ^* b ^* values of L ^* 80 or more and 98 or less, a ^* -5 or more and 3 or less, respectively, by a light source containing ultraviolet rays according to JIS P8150. b ^* -3 or more and 12 or less, more preferably L ^* 82 or more and 96 or less, a ^* -4.5 or more and 2 or less, b ^* -2.5 or more and 11 or less, still more preferably L. ^* 83 or more and 95 or less, a ^* -4 or more and 1.5 or less, b ^* -2.5 or more and 10.5 or less. Within the above range, it is possible to obtain a medium-quality uncoated paper having a natural texture that is easy on the eyes. In addition, when used as book paper, it is possible to obtain book paper that does not tire the eyes even after reading for a long time.

Drip water absorption The medium-sized non-coated paper of the present invention is produced by J. Pulp Technology Association, except that the amount of drip water is 1 μl (0.001 ml). TAPPI No. It was measured according to the drip water absorption degree specified in 32-2: 2000. The drip water absorption is preferably 1 second or more and 100 seconds or less, and more preferably 80 seconds or less. Since offset printing is printed at high speed, the time that the paper and the dampening water come into contact is momentary, but if the drip water absorption is less than 1 second, the paper will stick to the bran due to the dampening water. The separation gets worse. On the other hand, the higher the drip water absorption degree, the better the blank separation, but if it is higher than 100 seconds, the liquid absorption property of the ink at the time of inkjet printing may be inferior. Therefore, by setting the drip water absorption to the above range, it is possible to obtain a medium-quality uncoated paper having both offset printing suitability and inkjet printing suitability.

The degree of stekihito size The neutral non-coated paper of the present invention preferably has a degree of stekihito size measured according to JIS P 8155 for 80 seconds or less, more preferably 70 or less. If the degree of nice human size exceeds 80 seconds, the absorption of ink during inkjet printing is slow, and it becomes difficult to increase the printing speed.

The present invention will be described below with reference to examples, but the present 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)% by weight, and the numerical range is described as including the end points thereof.

<Evaluation method>
Paper quality measurement method ・ Basis weight: Measured according to JIS P8124.
-Paper thickness and density: Measured according to JIS P8118.
-Ash content: Measured according to ISO1762-1974.
-ISO opacity: Measured according to ISO2471.
-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.

-Drip water absorption: J.I., except that the amount of drip water was 1 μl (0.001 ml). TAPPI No. It was measured according to 32-2: 2000.
-Sutekihito size: Measured according to JIS P8155.
-Stiffness (Clark type): The rigidity in the vertical direction was measured according to JIS P8143.

Evaluation method of hand flesh 200 sheets of medium-quality uncoated paper sample in A6 size (paperback book size), soft cover, and bookbinding sample were prepared by wireless binding. Regarding the paper tension (feeling of hand flesh) when holding the closed part with the left hand and handling the paper 20 times with the right hand, the one that is not taut and the paper is worn out and cannot be handled well is "x", but the tension is not a problem. The feeling of flesh was evaluated as "△" for those that can handle the pages without any problems, and "○" for those that do not lose their pages while they are being processed.

Evaluation method of remodelability 200 sheets of medium-quality uncoated paper sample were prepared in A6 size (paperback book size), and a binding sample was created by soft cover and wireless binding. Four bookbinding samples were set in a belt grinding machine (manufactured by NIPPO), and the edge surface was polished twice in a round trip according to the standard usage. For bookbinding samples with a polished edge surface, when the book is opened, multiple pages are strongly attached at the polished part and are difficult to unravel, "x", and when the book is opened, multiple pages are attached at the polished part but are easy to unravel. When the book was opened, the sticking of the polishing part was loosened, or the sticking to the polishing part was not marked as "○", and the small surface sticking was evaluated.

Evaluation method of eye strain A laser printer was used to print a 4000-character sentence in 10pt Mincho black on a piece of paper cut into A4, and the degree of eye strain after reading it three times was evaluated. The ones that have a strong contrast with the paper and are easy to get tired of the eyes are marked with "x", and the ones that are hard to get tired of the eyes are marked with "○".

Printability, blank separation (offset)
Single-color solid printing was performed on an A3 size sample with indigo ink using an offset sheet-fed printing press R202 manufactured by Roland Corporation.
(Inkjet)
Black solid printing (size: length 2 cm x width 3 cm) was performed using a commercially available pigment inkjet printer (product name: CM8060 Color MFP, manufactured by Hewlett-Packard Co., Ltd., printing conditions: matte / broker mode).
(Evaluation of printability)
○: Offset and inkjet printing could be performed without problems △: Offset printing suitability or inkjet printing suitability was slightly inferior, but could be used without problems ×: There was a problem with offset printing, inkjet printing, or both printing methods. (Evaluation away from Blanc)
○: There was no problem with the blank separation △: Although it was slightly inferior to the blank separation, it could be used without problems ×: It was inferior to the blank separation and could not be printed.

Experiment 1 (Example)
In a pulp slurry obtained by mixing 8% by weight of NBKP, 40% by weight of bleached GP, and 52% by weight of bleached TMP with respect to 100% by weight of pulp, calcium carbonate, bulking agent, and sizing agent were added to 100% by weight of pulp at 3% by weight and 0. Addition was made so as to be 6% by weight and 0.03% by weight, and the paper material was adjusted.

Then, the above-mentioned paper material was ejected from the head box onto a twin-wire type papermaking wire to make paper, water was squeezed by a press part, dried by a pre-dryer, and a base paper was made at a papermaking speed of 700 m / min. Oxidized starch, styrene-butadiene latex and water were added to the obtained base paper as binders, and oxidized starch: styrene-butadiene latex (manufactured by A & L, PB9501, average particle size 83 nm, Tg-15 ° C.) = 2: 1. Using a gate roll coater, an aqueous solution (clear coating liquid) containing 300 g / t (paper) of yellow dye was mixed so that the coating amount on both sides was 2.4 g / m ^2. It was evenly coated and dried so as to have (solid content), and a medium-quality uncoated paper was obtained. Table 1 shows the measured values and evaluation results of the paper quality.

Experiment 2 (Example)
The pulp composition was 14% by weight of NBKP, 37% by weight of bleached GP, 46% by weight of bleached TMP, and 3% by weight of DIP with respect to 100% by weight of pulp, and the bulking agent and sizing agent were 0.5% by weight and 0% by weight of 100% by weight of pulp, respectively. A neutral uncoated paper was obtained in the same manner as in Experiment 1 except that the weight was set to 0.02% by weight.

Experiment 3 (Example)
A medium-sized uncoated paper was obtained in the same manner as in Experiment 1 except that a sizing agent was added to the clear coating liquid so as to be 0.8% by weight with respect to 100% by weight of the binder.

Experiment 4
A medium-sized uncoated paper was obtained in the same manner as in Experiment 1 except that a sizing agent was not added to the pulp slurry.

Experiment 5 (Example)
A medium-sized uncoated paper was obtained in the same manner as in Experiment 1 except that the yellow dye was added to the pulp slurry at 50 g / t.

Experiment 6
Calcium carbonate is 21% by weight based on 100 parts by weight of pulp in a pulp slurry obtained by mixing 10% by weight of LBKP, 15% by weight of NBKP, 15% by weight of bleached GP, 25% by weight of bleached TMP, and 35% by weight of DIP with respect to 100% by weight of pulp. A medium-quality uncoated paper was obtained in the same manner as in Experiment 1 except that the paper material was adjusted.

Experiment 7
The pulp, with respect to 100 wt% pulp, LBKP60 wt%, NBKP10 wt%, and DIP30 wt%, except that calcium carbonate added to the pulp slurry was 24 wt%, the non-coated medium quality system in the same manner as Experiment 1 I got the paper.

Experiment 8
A neutral non-coated paper was obtained in the same manner as in Experiment 1 except that the binder of the clear coated layer was only oxidized starch.

Experiment 9
A neutral uncoated paper was obtained in the same manner as in Experiment 1 except that the binder of the clear coated layer was only styrene-butadiene latex.

Experiment 10
Calcium carbonate is added to the pulp slurry so as to be 8% by weight, and 100 parts by weight of heavy calcium carbonate (Carbital 90), 14 parts by weight of styrene-butadiene latex, and 17 parts by weight of oxidized starch are added without providing a clear coating layer. A medium-quality finely coated paper was obtained in the same manner as in Experiment 6, except that the pigment coating liquid in which the mixture was mixed ^{was evenly applied to 5 g / m 2 on both sides.}

Claims (11)

A medium-sized non-coated paper having a clear coated layer on ^{a base paper, having an L *} value of 80 to 98 measured by a light source containing ultraviolet rays based on JIS P8150 and an ISO opacity of 85 or more.
Of the 100% by weight of the pulp constituting the base paper, the mechanical pulp is 5% by weight or more, and the base paper contains 0.01 to 5% by weight of the internal sizing agent with respect to 100% by weight of the pulp.
Clear coating layer contains latex and starch, latex weight ratio of starch 10: wood containing based non-coated paper is 90 50:50. The neutral non-coated paper according to claim 1, wherein the base paper contains at least one kind of mechanical pulp selected from the group consisting of crushed wood pulp and thermomechanical pulp and deinked pulp. The neutral non-coated paper according to claim 1 or 2 , which contains 0.1% by weight or more of a bulking agent. The neutral non-coated paper according to any one of claims 1 to 3, which contains 30% by weight or more of mechanical pulp or deinked pulp with respect to 100% by weight of pulp. The neutral non-coated product according to any one of claims 1 to 4 , wherein the clerk rigidity in the horizontal (CD) direction is 10 or more and the clerk rigidity in the vertical (MD) direction is 20 or more as measured according to JIS P8143. Coated paper. The neutral non-coated paper according to any one of claims 1 to 5 , wherein the whiteness is 85% or less. A ^* value measured I by the light source including ultraviolet light based on JISP8150 -5 to 3, ^{b *} value is -3 to 12, the quality system in according to any one of claims 1 to 6 Uncoated paper. The medium-quality non-coated paper according to any one of claims 1 to 7 , which is a printing paper for inkjet printing and has a nice human size degree of 70 seconds or less. The medium-quality non-coated paper according to any one of claims 1 to 8 , which is a printing paper for offset printing and has a drip water absorption degree of 1 to 80 seconds. The medium-quality non-coated paper according to any one of claims 1 to 9 , which is a book paper. A method for producing a medium-quality uncoated paper according to any one of claims 1 to 10.
Preparing a clear coating solution by mixing the starch and latex, and a step provided on the base paper on one side 0.1 g / m ² or more 3.0 g / m ² or less clear coating layer by a gate roll coater, a Have the above method.