Note paper

Abstract

This paper offers excellent writing comfort when writing with a pencil, and is also easy to erase when erasing pencil marks with an eraser, while minimizing eraser residue. [Solution] The erasing rate measured in accordance with JIS S 6050 is 92% or higher, and the ash content in the paper is 5% by mass or higher.

Description

[Technical Field]

[0001] This invention relates to writing paper. [Background technology]

[0002] Regarding technologies related to paper intended for writing with pencils, such as notebooks and writing paper, technologies relating to writing paper with excellent writing feel (Patent Document 1) are known. Furthermore, regarding technologies relating to the erasing performance of pencil-written lines, technologies relating to erasers and their composition (Patent Document 2) are known.

[0003] Regarding the writing suitability of paper, various studies have been conducted considering a wide range of writing instruments, including fountain pens, ballpoint pens, pencils, permanent markers, and highlighters. For example, as a paper that takes into account the writing suitability of pencils, fountain pens, ballpoint pens, and highlighters, there are low-basis-weight, low-density high-quality papers, and in particular, there are technologies related to notebook paper (Patent Document 3) and technologies that focus on bleed-through when marking with highlighters (Patent Document 4). As a paper that has excellent writing suitability when writing with high pressure using writing instruments such as pencils and ballpoint pens, there is a known technology related to double-sided writing paper (Patent Document 5). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2015-145543 [Patent Document 2] Japanese Patent Publication No. 2011-235608 [Patent Document 3] Japanese Patent Publication No. 2016-17239 [Patent Document 4] Japanese Patent Publication No. 2016-199818 [Patent Document 5] Japanese Patent Publication No. 2015-4138 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] By the way, writing papers such as drills and notebooks used in learning are repeatedly written with pencils or erased with erasers for repeated practice and correction of writing mistakes. However, infants and children have weak grip strength, and depending on the paper used, erasure marks may remain. Therefore, in addition to excellent writing comfort, it is required that characters written in pencil are easy to erase, and furthermore, the paper should have few remaining erasure marks.

[0006] However, there has been no examination of papers regarding the ease of erasing characters written in pencil and the remaining erasure marks until now.

[0007] Therefore, an object of the present invention is to provide a writing paper that is excellent in writing comfort when writing with a pencil and ease of erasing characters written in pencil using an eraser, and furthermore has few remaining erasure marks. In particular, it is an object of the present invention to provide a writing paper used for learning purposes such as notebooks, drills, books, textbooks, reference books, etc., which is excellent in writing suitability when writing with a pencil and erasability when erasing with an eraser.

Means for Solving the Problem

[0008] As a result of intensive studies to achieve such an object, the present inventors completed the present invention by including a predetermined ratio or more of ash content in the paper.

[0009] The present invention provides the following. (1) A writing paper having an erasure rate measured according to JIS S 6050 of 92% or more and an ash content in the paper of 5% by mass or more. (2) The writing paper according to (1), having a König smoothness measured according to JIS P 8155 of 300 seconds or less. (3) A clear coating layer containing starch is provided on the base paper, and the coating amount of the clear coating layer is 10 g / m per side in terms of solid content 2 The writing paper according to (1) or (2) below.

[0010] According to the present invention, it is possible to provide writing paper that offers excellent writing comfort when writing with a pencil, and ease of erasing when erasing pencil marks using an eraser, and furthermore, leaves minimal residue. [Modes for carrying out the invention]

[0011] The present invention will now be described in detail. In this invention, "~" includes the endpoints. That is, "X~Y" includes the values ​​X and Y at both ends.

[0012] The writing paper of the present invention has an erasability of 92% or more and an ash content of 5% or more, as measured in accordance with JIS S 6050.

[0013] (writing paper) The writing paper of the present invention can be manufactured by forming a pulp stock, which is made by blending various fillers and various papermaking chemicals as needed, using a conventionally known papermaking machine. The writing paper includes paper that has been calendered after papermaking, and paper that has been coated with a surface treatment solution containing starches, surface sizing agents, pigments, etc. Furthermore, it also includes paper that has been calendered after being coated with a surface treatment solution.

[0014] (pulp) Examples of pulp include chemical pulps such as LBKP (Leaf Bleached Kraft Pulp) and NBKP (Needle Bleached Kraft Pulp), mechanical pulps such as GP (Groundwood Pulp), PGW (Pressure Groundwood Pulp), RMP (Refiner Mechanical Pulp), TMP (ThermoMechanical Pulp), CTMP (ChemiThermoMechanical Pulp), CMP (ChemiMechanical Pulp), and CGP (ChemiGroundwood Pulp), and recycled paper pulp such as DIP (DeInked Pulp). At least one of these pulps can be used.

[0015] The writing paper of the present invention preferably contains LBKP as at least one type of pulp, and more preferably contains 20% by mass or more of LBKP when the total pulp is considered as 100% by mass.

[0016] (filler) Examples of fillers include calcium carbonate such as light calcium carbonate and heavy calcium carbonate, inorganic fillers such as talc, clay, kaolin, calcined kaolin, magnesium carbonate, barium carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, delaminated kaolin, titanium dioxide, zinc oxide, silicon dioxide, amorphous silica, urea-polymarin resin, polystyrene resin, phenolic resin, and fine hollow particles. One or more of these can be used in combination. Using calcium carbonate as an internal filler in the writing paper of the present invention is preferable because it has the effect of improving opacity. Among calcium carbonates, light calcium carbonate is particularly preferable because it has a high specific scattering coefficient and imparts high opacity. When printing on the writing paper of the present invention, especially when used as book paper, double-sided printing is often performed, and opacity is an important indicator in order to prevent bleed-through after printing. The blending ratio of fillers in the writing paper is such that the ash content is within the range of the present invention, preferably 5 to 30% by mass, and more preferably 10 to 25% by mass.

[0017] (Papermaking chemicals) As papermaking chemicals used as necessary when manufacturing the writing paper of the present invention, known chemicals used in acidic or neutral papermaking can be used. For example, one or more selected from oxidized starch, esterified starch, cationized starch, various other modified starches, paper strength enhancers or fixatives such as polyacrylamide and polyamine polyamide epichlorohydrin, rosin sizing agents, emulsion sizing agents, reinforcing rosin sizing agents, internal sizing agents such as alkyl ketene dimer (AKD) and alkenyl succinic anhydride (ASA), dyes, water drainage improvers, water resistance agents, defoaming agents, slime control agents, pitch control agents, aluminum sulfate, anion trash chelating agents, bulking agents, yielding agents, and opacifying agents can be appropriately blended within a range that does not impair the desired effects of the present invention.

[0018] (Internal sizing agent) Internal sizing agents are sizing agents that are blended into the pulp to be incorporated into the paper. Examples of internal sizing agents that can be used in the present invention include those conventionally known in the papermaking field, such as rosin-based sizing agents for acidic paper, and alkenyl succinic anhydride (ASA)-based sizing agents, alkyl ketene dimer (AKD)-based sizing agents, neutral rosin-based sizing agents, fatty acid-based sizing agents, or cationic styrene-acrylic sizing agents for neutral paper. Alkyl ketene dimer-based sizing agents are preferred because they provide a sizing effect even in relatively small amounts. When internal sizing agents are included in writing paper, the content of the internal sizing agent is preferably 0.08 parts by mass or more and 8 parts by mass or less per 100 parts by mass of pulp, from the viewpoint of preventing ink bleeding with writing instruments.

[0019] Papermaking is carried out by adjusting the pulp to be acidic, neutral, or alkaline. Examples of conventionally known papermaking machines include screenwound papermaking machines, cylinder screen papermaking machines, twin-wire papermaking machines, on-top twin-wire papermaking machines, papermaking machines using a combination of screenwound and cylinder screens, various formers, and other known papermaking machines.

[0020] (Surface treatment liquid) The writing paper of the present invention may have a coating layer provided by applying a surface treatment liquid to a base paper obtained by papermaking using a paper machine. Components that can be included in the surface treatment liquid include starches such as raw starch, oxidized starch, esterified starch, cationized starch, and auto-modified starch produced in a paper mill by thermochemical or enzymatic modification using acetylated tapioca starch as raw materials, as well as modified starches such as aldehyde starch and hydroxyethylated starch, which can be used as adhesive components.

[0021] To enhance sizing properties, surface sizing agents such as AKD-based sizing agents, rosin-based sizing agents, styrene-maleic acid-based sizing agents, olefin-based sizing agents, acrylate-based sizing agents, styrene-acrylic-based sizing agents, and cationic sizing agents can be included in the surface treatment solution. When surface sizing agents are used in combination, the solid content concentration in the surface treatment solution is preferably 0.005% by mass or more and 1% by mass or less, more preferably 0.01% by mass or more and 0.015% by mass or more and 0.1% by mass or less. Since surface sizing agents are effective in reducing friction and exhibiting sizing properties even in small amounts compared to internally added sizing agents, sufficient effects can be obtained with the above-mentioned addition amounts. From the viewpoint of processing during cutting and printing, it is preferable to use a styrene-acrylic-based surface sizing agent.

[0022] Furthermore, the surface treatment solution can also contain various types of polyvinyl alcohol and various types of modified polyvinyl alcohol.

[0023] The surface treatment solution may also contain a white pigment. Suitable white pigments include inorganic pigments such as calcium carbonate, kaolin, clay, engineered kaolin, delaminated clay, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicates, colloidal silica, and satin white, as well as organic pigments such as solid, hollow, or core-shell types. When the surface treatment solution contains a white pigment, the coating amount is 0.5 g / m² of solid content per side. 2 More than 7g / m 2 The following is preferred, and more preferably, 0.5 g / m2 6 g / m or less. 2 When the coating amount is large, the fibers on the paper surface may be completely covered by the pigment, which may deteriorate the writing suitability and erasability of the pencil. Therefore, it is preferable that the coating amount is such that the fibers of the base paper are exposed.

[0024] When the surface treatment liquid is a clear coating liquid that does not contain a white pigment, the coating amount of the clear coating layer obtained by applying the clear coating liquid is preferably 10 g / m or less in terms of solid content on both sides, more preferably 8 g / m or less, even more preferably 6 g / m or less, and most preferably 4 g / m or less. Also, as the lower limit, 0.5 g / m or more is preferable, and 1 g / m or more is more preferable. By setting the range as described above, writing paper excellent in erasure rate can be obtained. If the coating amount is too large, the pencil may slide easily on the paper, making it difficult to write. In this specification, the clear coating liquid means a coating liquid that does not contain pigments such as white pigments, and the clear coating layer means a coating layer obtained by applying the clear coating liquid. 2 or less, 2 more preferably 8 g / m 2 or less, even more preferably 6 g / m 2 or less, and most preferably 4 g / m 2 or more. 2 In the present invention, it is also possible to use a surface treatment liquid containing a white pigment to obtain writing paper provided with a coating layer containing a pigment on the base paper. However, since it is difficult for the lead powder of the pencil to adhere to an excessive pigment coating layer, it is preferable to use writing paper provided with a clear coating layer on the base paper.

[0025]

[0026] ​Apparatus for applying (coating) surface treatment liquids includes, for example, a film transfer type rod metering size press, a roll metering size press, and a blade metering size press. Examples of rod metering size presses include shim sizers, opti sizers, speed sizers, and film presses, while examples of roll metering size presses include gate roll coaters. Other examples include pound size presses, bill blade coaters, twin blade coaters, velvapa coaters, tab size presses, calender size presses, roll coaters, air knife coaters, bar coaters, rod blade coaters, and various other blade coaters, as well as short dwell coaters and curtain coaters. Preferably, a roll metering size press or a pound size press is used.

[0027] The base paper or surface-treated paper may be fed through known finishing equipment, such as a supercalender, gloss calender, soft calender, or high-temperature soft nip calender (also called a "hot soft nip calender"), for product finishing, or it may be left untreated or bypassed. However, from the viewpoint of writing suitability, calendering is preferable. When calendering is performed, the processing line pressure is appropriately adjusted within a range in which the paper's Ouken-type smoothness is preferably 300 seconds or less.

[0028] (ash) The ash content of writing paper, as measured in accordance with JIS P-8251, is preferably 5% by mass or more, and more preferably 10% by mass or more, when the total mass of the writing paper is considered to be 100% by mass. From the viewpoint of the amount of paper cut during printing and contamination of the blanket, the upper limit is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less. The ash content can be adjusted by the amount added, the dewatering conditions during papermaking, and whether or not a yield agent is added.

[0029] (erasure rate) The writing paper of the present invention has an erasability of 92% or higher, as measured in accordance with JIS S 6050. More preferably, the erasability is 93% or higher, and even more preferably 94% or higher. In the present invention, the erasability is measured using a plastic eraser made of polyvinyl chloride resin. As the plastic eraser made of polyvinyl chloride resin, a MONO eraser manufactured by Tombow Pencil Co., Ltd. (product number: PE-XXA, where XX is one of 01, 03, 04, 07, or 09) or an eraser having equivalent erasability is used.

[0030] (Basic weight) The basis weight of the writing paper is 40 g / m², chosen based on factors such as ease of turning pages and portability. 2 More than 300g / m 2 The following is preferable, and more preferably, 50 g / m² 2 More than 200g / m 2 The following applies: The basis weight is determined according to JIS P8124:2011 "Paper and cardboard - Method for measuring basis weight".

[0031] (paper thickness) The thickness of the writing paper is preferably 60 μm to 110 μm, and more preferably 75 μm to 95 μm, from the viewpoint of ease of turning pages and ease of carrying. The paper thickness is determined in accordance with JIS P8118:1998 "Paper and cardboard - Test methods for thickness and density".

[0032] (density) The density of the writing paper is 1.0 g / cm³. 3 Preferably, it is 0.9 g / cm³. 3 The following is preferable. If the density is higher than the aforementioned range, the fibers on the paper surface become too dense, causing the pencil to slip when writing, resulting in poor writing suitability. Furthermore, writing on such paper requires higher pressure, resulting in poor erasability. The lower limit is 0.4 g / cm³. 3 Preferably, it is 0.5 g / cm³ or more. 3It is more preferable that the density is within the specified range. If the density is lower than the aforementioned range, the tip of the pencil will catch on the paper when writing with it, resulting in poor writing suitability. The density is a value determined in accordance with JIS P8118:1998 "Paper and cardboard - Test methods for thickness and density".

[0033] (whiteness) The ISO whiteness of writing paper, measured in accordance with JIS P8148, is preferably 70% to 90%, and more preferably 75% to 85%, from the viewpoint of the legibility of characters and drawings written with a pencil.

[0034] (hue) From the viewpoint of the legibility of characters and drawings written with a pencil, the hue of the writing paper is preferably such that the L*a*b* values, measured with a light source including ultraviolet light in accordance with JIS P8150, are L*90 to 98, a*-6 to 1, and b*0 to 20, respectively, and more preferably L*92 to 96, a*-4 to -1, and b*5 to 15.

[0035] (Opacity) The ISO opacity of writing paper, as measured according to ISO 2471, is preferably 80% or higher, and more preferably 85% or higher. If it is lower than the above range, problems may occur such as written characters showing through from the back, or characters on the paper underneath showing through.

[0036] (Oken type smoothness) The smoothness of the writing paper, measured according to JIS P8155, is preferably 300 seconds or less, more preferably 250 seconds or less, and even more preferably 200 seconds or less. If the smoothness is higher than the above range, the tip of the pencil may slip when writing with a pencil, resulting in insufficient writing performance. Furthermore, when erasing with an eraser, traces are more likely to remain, resulting in poor erasability. From the viewpoint of preventing the pencil from catching when writing, the lower limit is preferably 10 seconds or more, and more preferably 30 seconds or more.

[0037] (PPS smoothness) In accordance with ISO 8791-4:1992 for writing paper, the ParkerPrintSurf smoothness (hereinafter also referred to as "PPS smoothness") measured under soft packing and a clamping pressure of 1 MPa is preferably 1 μm to 4 μm, and more preferably 1.5 μm to 3.5 μm, from the viewpoint of writing comfort when writing with a pencil and the clarity of the written characters. Note that a smaller PPS smoothness value indicates less unevenness in the paper. [Examples]

[0038] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to these examples.

[0039] <Pharmaceuticals> The chemicals used in the examples and comparative examples are as follows: Filler: Light calcium carbonate 1: Manufactured by Nippon Paper Industries Co., Ltd. (Average particle size: 3.9 μm, specific surface area: 10 m²) 2 / g) Light calcium carbonate 2: Manufactured by Nippon Paper Industries Co., Ltd. (Average particle size: 4.5 μm, specific surface area: 5 m²) 2 / g) Talc: Manufactured by Fukuoka Talc Industry Co., Ltd., E-Talc (average particle size: 5.0 μm, specific surface area: 10 m²) 2 / g) Aluminum sulfate: Manufactured by J.O. Chemical Co., Ltd., liquid band Sizing agent (AKD): Manufactured by Seikou PMC, AD-1614 Sizing agent (neutral rosin type): Seikoh PMC Co., Ltd., CC1401 Cationized starch: Manufactured by NSC Japan, Cato304 Internal paper strength enhancer: Harima Chemicals Co., Ltd., Hermid EX-283 (main component: amphoteric polyacrylamide) Yield enhancer: ND-300, manufactured by Hymo Co., Ltd. Bulking agent: Kao Corporation, KB-130 Oxidized starch: Manufactured by Nippon Corn Starch Co., Ltd., SK-20 Self-modified starch: Manufactured by Nippon Paper Industries, ammonium persulfate modified low-concentrate Styrene-acrylic surface sizing agent: Harima Chemicals Co., Ltd., Harsize KN630

[0040] <Evaluation Method> <Paper quality measurement method> • Basis weight: Measured in accordance with JIS P 8124. • Paper thickness and density: Measured in accordance with JIS P 8118. • ISO whiteness: Measured using a color difference meter CMS-35 SPX manufactured by Murakami Color Co., Ltd., under a light source including ultraviolet light, in accordance with JIS P 8148. • Hue: Measured using a light source including ultraviolet light in accordance with JIS P 8150. • ISO Opacity: Measured in accordance with ISO 2471. • Ash content: Measured in accordance with ISO 1762-1974. • Wangyan-style smoothness: Measured according to JIS P 8155. • PPS smoothness: Measured according to ISO 8791-4:1992, under conditions of soft backing and clamp pressure of 1 MPa.

[0041] <Erasing rate> • Measurements were taken in accordance with JIS S 6050. Specifically, a Mono eraser (product number: PE-03A, made of polyvinyl chloride resin) manufactured by Tombow Pencil Co., Ltd. was used as the plastic eraser, and the paper samples obtained in the examples and comparative examples were used as the paper for creating the colored paper.

[0042] <Writing aptitude (pencil)> The ease of writing on the obtained paper samples with a 2B pencil, including how well the pencil gripped the paper and how smoothly it glided, was scored on a scale of 1 to 5 and evaluated as follows. ○: The pencil has just the right amount of grip and glide on the paper, making it very easy to write with (5 points) △: The pencil has just the right amount of grip and glide on the paper, making it easy to write with (3 or 4 points) ×: The pencil catches on the paper too much, or slides too much, making it difficult to write (1 or 2 points)

[0043] (Comparative Example 1-1) (Paper manufacturing) A pulp stock was prepared by adding 0.1% of the internal paper strength enhancer PAM and 100 ppm of the yield enhancer to a solids mass of bleached hardwood kraft pulp (LBKP) slurry (CSF: 340 mL). Hand-made paper was then produced using a circular hand-made paper machine in accordance with JIS P8222:2015. However, after the second press, drying was not performed using an air circulation device such as a blower; instead, the hand-made paper was peeled from the drying plate and passed through a lab cylinder dryer with the test surface in contact with the heat roll. The paper was then passed through a lab gloss calender with the test surface in contact with the heat roll to obtain a paper sample with a Wang Ken smoothness score of 62 seconds. The ash content of the obtained paper sample was 0.5%.

[0044] (Example 1-1) Hand-made paper was prepared in the same manner as in Comparative Example 1-1, except that light calcium carbonate 1 was added to the pulp so that the ash content in the paper was 11.1% by mass, and a yield agent was added at a rate of 100 ppm relative to the total solid content of the pulp and light calcium carbonate 1 as filler. A paper sample with a Wang Ken smoothness test surface of 99 seconds was obtained.

[0045] (Examples 1-2) Hand-made paper was prepared in the same manner as in Example 1-1, except that light calcium carbonate 1 was added to the paper pulp so that the ash content in the paper was 16.4% by mass, and a paper sample with a Wang Ken smoothness test of 95 seconds on the test surface was obtained.

[0046] (Examples 1-3) Hand-made paper was prepared in the same manner as in Example 1-1, except that light calcium carbonate 1 was added to the paper pulp so that the ash content in the paper was 18.3% by mass, and a paper sample with a Wang Ken smoothness test surface of 178 seconds was obtained.

[0047] (Examples 1-4) Hand-made paper was prepared in the same manner as in Example 1-1, except that light calcium carbonate 2 was added to the paper pulp so that the ash content in the paper was 11.1% by mass, and a paper sample with a Wang Ken smoothness test of 92 seconds on the test surface was obtained.

[0048] (Examples 1-5) Hand-made paper was prepared in the same manner as in Example 1-1, except that talc was added to the paper stock so that the ash content in the paper was 15.1% by mass, and a paper sample with a Wang-Gan smoothness test surface of 86 seconds was obtained.

[0049] (Examples 1-6) Hand-made paper was prepared in the same manner as in Example 1-1, except that a mixture of light calcium carbonate 1 and talc in a 1:1 ratio was added to the paper pulp so that the ash content in the paper was 15.1% by mass, and a paper sample with a Wang Ken smoothness test surface of 78 seconds was obtained.

[0050] Table 1 shows the evaluation results of the paper samples obtained in Comparative Example 1-1 and Examples 1-1 to 1-6. [Table 1]

[0051] Table 1 shows that a good erasing rate can be obtained by incorporating fillers. Furthermore, it can be seen that light calcium carbonate is preferable to talc, and light calcium carbonate 1 is even preferable to light calcium carbonate 2.

[0052] (Example 2-1) (Paper manufacturing) A pulp slurry (total water content CSF: 400 mL) was prepared by mixing 90 parts LBKP and 10 parts bleached softwood kraft pulp (NBKP). Light calcium carbonate 1 was added to the slurry so that the paper ash content was 17.5% by mass. Furthermore, 1.0% aluminum sulfate, 0.1% AKD sizing agent, 0.8% cationized starch, 0.4% internally added paper strength enhancer PAM, and 0.4% bulking agent (fatty acid ester / fatty acid salt) were added to the total mass (solids) of pulp and filler to prepare the paper stock. Subsequently, using a screen printing machine, paper with a basis weight of 59 g / m² was produced from this paper stock. 2 The base paper was manufactured. An aqueous solution (surface treatment solution) was prepared by mixing 13% oxidized starch and 1.2% styrene-acrylic surface sizing agent, and a coating amount of approximately 1.8 g / m² was applied to both sides using a gate roll coater. 2 (Approximately 0.9g / m² per side) 2The paper was coated in such a manner. After drying, no calendering treatment was performed, and a paper sample with a clear coating layer was obtained.

[0053] (Example 2-2) The paper sample obtained in Example 2-1 was subjected to hot soft nip calendering (300 m / min, 80°C, 15 kN / m, 2 nips) to obtain a paper sample having a clear coating layer with a Wang-Ran smoothness score of 105 seconds on the test surface.

[0054] (Examples 2-3) The paper sample obtained in Example 2-1 was subjected to hot soft nip calendering (300 m / min, 80°C, 15 kN / m, 4 nips) to obtain a paper sample having a clear coating layer with a Wang-Ran smoothness score of 185 seconds on the test surface.

[0055] (Examples 2-4) The paper sample obtained in Example 2-1 was subjected to hot soft nip calendering (300 m / min, 80°C, 60 kN / m, 4 nips) to obtain a paper sample having a clear coating layer with a Wang-Ran smoothness score of 295 seconds on the test surface.

[0056] (Examples 2-5) The paper sample obtained in Example 2-1 was subjected to hot soft nip calendering (300 m / min, 80°C, 120 kN / m, 4 nips) to obtain a paper sample having a clear coating layer with a Wang-Ran smoothness score of 469 seconds on the test surface.

[0057] (Example 3-1) (Paper manufacturing) A pulp slurry (total water content CSF: 400 mL) was prepared by mixing 90 parts LBKP and 10 parts NBKP. Light calcium carbonate 1 was added to achieve a paper ash content of 19.3% by mass. Furthermore, 1.0% aluminum sulfate, 0.1% neutral rosin-based sizing agent, and 0.8% cationized starch were added to the total mass (solids) of pulp and filler to prepare the paper stock. Subsequently, using a wire screen paper machine, a basis weight of 62 g / m² was produced from this paper stock. 2 Paper was produced from the base paper and paper samples were obtained.

[0058] (Example 3-2) The paper sample obtained in Example 3-1 was coated on both sides with a surface treatment solution containing oxidized starch (concentration 1.2%) using a Lab 2-roll coater, with a coating weight of 2.4 g / m². 2 (Approximately 1.2g / m² per side) 2 The paper was coated in such a manner that a paper sample with a clear coating layer was obtained.

[0059] (Example 3-3) The paper sample obtained in Example 3-1 was coated on both sides with a surface treatment solution containing oxidized starch (concentration 2.5%) using a Lab 2-roll coater, with a coating weight of 5.1 g / m². 2 (Approximately 2.6g / m² per side) 2 The paper was coated in such a manner that a paper sample with a clear coating layer was obtained.

[0060] (Comparative Example 3-1) The paper sample obtained in Example 3-1 was coated on both sides with a surface treatment solution containing oxidized starch (3% concentration) using a Lab 2-roll coater, with a coating weight of 6.3 g / m². 2 (Approximately 3.2g / m² per side) 2 The paper was coated in such a manner that a paper sample with a clear coating layer was obtained.

[0061] (Comparative Example 3-2) The paper sample obtained in Example 3-1 was coated on both sides with a surface treatment solution containing oxidized starch (4% concentration) using a Lab 2-roll coater, with a coating weight of 8.4 g / m². 2 (Approximately 4.2g / m² per side) 2 The paper was coated in such a manner that a paper sample with a clear coating layer was obtained.

[0062] (Examples 3-4) The paper sample obtained in Example 3-1 was coated on both sides with a surface treatment solution (concentration 1.2%) containing ammonium persulfate (APS) automodified starch using a Lab 2-roll coater, with a coating weight of 2.6 g / m². 2 (Approximately 1.3g / m² per side) 2 The paper was coated in such a manner that a paper sample with a clear coating layer was obtained.

[0063] (Examples 3-5) The paper sample obtained in Example 3-1 was coated on both sides with a surface treatment solution (concentration 2.5%) containing ammonium persulfate (APS) automodified starch using a Lab 2-roll coater, with a coating weight of 5.3 g / m². 2 (Approximately 2.7g / m² per side) 2 The paper was coated in such a manner that a paper sample with a clear coating layer was obtained.

[0064] (Examples 3-6) The paper sample obtained in Example 3-1 was coated on both sides with a surface treatment solution (concentration 3.5%) containing ammonium persulfate (APS) automodified starch using a Lab 2-roll coater, with a coating weight of 7.5 g / m². 2 (Approximately 3.8g / m² per side) 2 The paper was coated in such a manner that a paper sample with a clear coating layer was obtained.

[0065] (Examples 3-7) The paper sample obtained in Example 3-1 was coated on both sides with a surface treatment solution (concentration 4.5%) containing ammonium persulfate (APS) automodified starch using a Lab 2-roll coater, with a coating weight of 9.3 g / m². 2 (Approximately 4.7g / m² per side) 2 The paper was coated in such a manner that a paper sample with a clear coating layer was obtained.

[0066] [Table 2]

[0067] Table 2 shows that when a clear coating layer is applied, self-modified starch is preferable to oxidized starch in terms of erasability, and when oxidized starch is used, the amount is 5.1 g / m² on both sides. 2 It is found that the following is preferable. It is also found that the erasing rate is better when a clear coating layer is provided than when no clear coating layer is provided. It is found that the paper smoothness is more preferable for erasing rate if it is less than 469 seconds on the Oken smoothness scale.

Claims

1. Writing paper having an erasability of 92% or higher, as measured in accordance with JIS S 6050, and a paper ash content of 5% by mass or higher.

2. The writing paper according to claim 1, wherein the Wangyan smoothness measured according to JIS P 8155 is 300 seconds or less.

3. A clear coating layer containing starch is provided on the base paper. The amount of the aforementioned clear coating layer applied is 10 g / m² in terms of solid content (both sides). ２ The writing paper according to claim 1 or 2, which is as follows:

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