JPH0197295A - Lightweight coating paper - Google Patents

Abstract

PURPOSE: To obtain lightweight coated paper not highlighting irregular coatings, giving good appearance and useful as raw paper for coated paper by adding a coloring agent to coating raw paper and a coating layer and adjusting a difference between the whiteness of the coating raw paper and the whiteness of the coated paper to a specific value or less. CONSTITUTION: This single- or double-sided coated paper having a coating amount of 3-15 g/m<2> for each single side is obtained by adding a coloring agent to coating raw paper and a coating layer and then adjusting the difference between the whiteness of the coating raw paper and the whiteness of the coated paper to <=6%. The coloring agent comprises a black or other color dye or pigment or their combination. The surface reflection characteristics of the colored coating raw paper comprise the equations: a*=-5.0 to 0.5 and b*=-1.0 to 8.0. The coating paper preferably comprises neutral paper containing at least 3-25 wt.% of calcium carbonate as a filler and made from a pulp slurry having paper pH 6.5-9.5.

Description

Detailed Description of the Invention (A) Industrial Field of Application The present invention relates to light-weight coated paper for printing, and particularly to light-weight coated paper with a coating weight on one side of 15 g/m" or less. The present invention relates to lightweight coated paper that improves the quality of printed matter by improving the poor visibility caused by uneven formation and uneven coating of the coating layer.

(B) Prior Art Coated paper for printing is usually manufactured by applying a coating liquid containing a white pigment and an adhesive as main components to a base paper using a coating device. In such cases, one way to improve the quality of the coated paper, especially its visual appearance, is to improve the coating liquid properties and coating equipment to reduce unevenness in the coating layer, or to reduce the unevenness in the formation of the base paper. There are ways to directly reduce the causes of poor visibility, such as by adopting improved papermaking methods. In addition, increasing the hiding power of the coating layer by increasing the thickness of the coating layer, using pigments with a high degree of opacity as coating pigments, and devising coating layer formation methods that improve opacity. There is a method to make uneven formation of the base paper and coating unevenness of the coated layer less noticeable. Alternatively, fillers that improve opacity may be added to the base paper for coating, or mechanical pulp or black dye may be added to improve the opacity and hiding power of the base paper layer. Measures have been used to improve visibility by making coating unevenness and formation unevenness of the paper more visible.

(C) Problems to be Solved by the Invention In order to improve the quality of coated paper for printing on the base paper side, especially the poor visibility caused by uneven formation, the degree of aggregation of slurry during paper making must be weakened. It is necessary to improve dispersion and prepare paper with good texture, but the degree of aggregation also affects the yield of the filler, and improving the texture may be accompanied by a deterioration in the yield. many.

For this reason, it is not easy to obtain base paper that has good fiber dispersion, that is, good formation, and improves the yield of filler, etc., and retains sufficient filler, especially when it is a lightweight coated base paper with a low basis weight. This is even more true in the case of In addition, in order to improve the hiding properties of base paper, it is necessary to internally add a filler with high opacification ability, but titanium oxide, which is highly effective in mold receiving, is expensive, followed by calcined kaolin, which has high ability, and organic synthetic pigment. and light calcium carbonate, etc. - each requires a larger amount to be added than titanium oxide depending on its capacity.

Also fillers with lower capacity, such as ground calcium carbonate,
Filler clay, talc, etc. require even more addition.
Even then, sufficient opacity may not be obtained. Furthermore, internally adding multiple fillers is accompanied by a decrease in paper strength, and it is quite difficult to obtain a strong, lightweight base paper for coating with internally adding enough filler to obtain sufficient hiding power. Furthermore, there is a method of using a black thread colorant to reduce the amount of internal fillers and maintain opacity, but this increases the difference in whiteness between the base paper for coating and the coating liquid, and in fact increases unevenness. It was found that this caused poor visibility.

In order to improve the quality of coated paper for printing on the coating side, it is possible to change the coating method, improve the properties of the coating liquid, select the coating pigment, adjust the amount of coating, etc. Of these, changes in coating methods are subject to constraints from existing equipment, while improvements in coating liquid properties and changes in coating pigments are subject to cost and other quality constraints. Increasing the amount of coating is the simplest method, but it is not preferable from the viewpoint of cost and above all because it goes against the objective of lightweighting.

The target coated paper of the present invention is 3 g/d or more on one side.
It is one-sided or double-sided coated paper with a coating weight of 5g/nf or less, and with such a light coating weight, unevenness in the coating layer due to unevenness on the surface of the base paper is extremely noticeable, and conventional Even with improved coating technology, it has been difficult to achieve complete improvement. In this way, we have solved the various problems required for coated paper for printing, and while keeping the opacity as high as possible on the base paper side, we have reduced the internal addition rate of filler to minimize the decline in paper strength, and are lightweight. As a result of repeated research into methods for improving the quality of coated paper for printing smear amount, particularly opacity and poor visibility, the present invention was completed.

(D) Means for solving the problem, that is, the present invention provides that the base paper for coating and the coating layer are colored in single-sided or double-sided coated paper with a coating weight of 3 g/d or more and 15 g/d or less. Contains a coating agent and adjusts the difference between the whiteness of the base paper for coating and the whiteness of the coated paper to within 6% to prevent unevenness in transmitted light due to uneven formation of the base paper and unevenness in thickness and thinness of the coating layer due to unevenness on the surface of the base paper. This is a transposition coated paper that offsets this and improves the quality of the coated paper, especially the visual appearance.

In the present invention, the difference in whiteness between the base paper for coating and the coated paper is 6
In order to adjust within %, use black or colored dyes or pigments as the colorant, and adjust the amount of the colorant according to the whiteness and color tone of the other materials, such as pulp, filler, or coating pigment. adjust.

Colored dyes and pigments are generally used alone or in combination to adjust the hue of base paper and coated paper, but this is because the pulp and white pigments used usually have a slightly yellowish tinge. In order to hide this yellow tinge and make it feel as white as possible, a very small amount of blue or blue-purple coloring agent (blueing agent) is used.The coloring agent used in the present invention does not change the hue too much. It is used to actively adjust the whiteness without changing it, especially to lower the whiteness and improve the apparent opacity.

Therefore, the hue is preferably black, and a black dye, a black pigment, or a combination of colored dyes and pigments that become black when mixed, such as yellow, magenta (reddish-purple), and cyan (blue), is used.

Examples of dyes include acid dyes, direct dyes, basic dyes,
Examples include various dyes that are soluble in water, such as water-soluble sulfur dyes.

Typical examples used alone include C, 1, Direct Black 154, 159° 19.170. Or C,1, Acid Black 2, C,1, Solbilized Sulfur Black 1°5, C,1, Food Black 2
etc. Examples of dyes that can be used in combination include C, 1, Dyref 1 to Yellow 157, 153.
133,142.50,86,12. C, 1, Direct Red 253.23.225. C, 1, Direct Blue 86° 200, C, 1, Paysic Yellow 9
4. C, 1, Paysic Red 111. C,1,
Examples include Paysic Blue 140. Examples of pigments include carbon black (C, 1, Pigment Black 7) dispersed with an activator and a protective polymer. Methods for retaining these dyes and pigments in base paper for coating include the so-called internal addition method, in which they are dissolved or dispersed in water and added to the paper stock for papermaking, and the so-called external addition method, in which they are applied using a size press, coater, etc. after paper manufacturing. There is an addition method. Among these, the internal addition method is preferable from the viewpoint of achieving the effect of the present invention and also from the viewpoint of uniformity of dyeing. In this case, a cationic or amphoteric water-soluble polymer substance is added to help fix the dye. It is desirable to add a water-soluble aluminum salt to the scraping pan. Examples of cationic or amphoteric polymeric substances that can be used in the present invention include cationic or amphoteric starch, polyacrylamide, etc. having secondary amines, tertiary amines, or quaternary ammonium groups. In particular, cationic starch or amphoteric starch having a cationic substituent with a Ta ratio of 0.01 to O-1 is preferred. In this case, the amount of the cationic or amphoteric polymer added is 0.1% by weight based on the weight of the bulb. ~
It is preferably 3.0% by weight, particularly preferably 0.3% to 1.5% by weight based on the weight of the pulp.

Examples of water-soluble aluminum salts used in combination include aluminum sulfate (band), aluminum chloride, potassium chloride, polyaluminum chloride, and polyaluminum hydroxide. Usually sulfate band is used,
It is used to increase the efficiency of cationic paper strength agents by blocking excess anionic substances coming in from coatbrokes, etc., and to improve the fixing properties of necessary anionic additives such as dyes. In this case, the amount of water-soluble aluminum salt added is 0.1% to 1.2% by weight based on the weight of the bulb, but it is not preferable to add such an amount that the pH of the stock becomes 6.5 or less. The amount of dye/pigment added is 5 ppm-700 pp@, preferably 10 pp per weight of fiber.
1 to 500 ppm, more preferably 20 ppm to 30
0 ppm, but it is closely related to the whiteness of other materials used to form the base paper, such as pulp and filler, and the amount used, so it is desirable to determine the whiteness to achieve the desired whiteness. The target whiteness of industrial base paper is preferably 60 to 80%, especially the whiteness of the coated paper after coating -6% to +3%.
In this case, J I 5Z-8722 and J I 5Z are recommended for measuring and displaying the color tone of paper, etc.
There is a method specified in -8730. This method changes the color tone to L* (elster) and a* (aceter).

b*C Beaster), where L* represents lightness, and the larger the value, the higher the lightness.

a* indicates reddishness, and the larger the value, the stronger the reddishness, -
゛ indicates that the green color becomes stronger.

b* represents a yellowish tinge; the larger the value, the stronger the yellowish tinge; and the negative value, the more bluish the color. In general, the position of a graph with a* on the horizontal axis and b* on the vertical axis. represents the color tone.

If all of the 8 lines and b* are 0, the color is expressed as colorless, and in this case, the L* value indicates the degree of whiteness (W). Generally, the color tone of paper with added filler is -2 to +1. It has a slight yellowish tinge with a bne of about +5 to +8.

In the present invention, we have found a method for making the unevenness less noticeable and improving the visual appearance of coated paper by reducing the difference between the whiteness of the base paper and the whiteness of the coated paper to within 6%, but in this case, the color tone is a * is -5, 0~+0.5° b* is -1, O~+ 8.
O, preferably 8 of them are -4.0 to 0.0. b* is 0.
0~+7.5. Particularly preferably, a* is -ao to 0.0.
b* is in the range of 0.5 to +7.5. When it is within this range, it is possible to adjust the whiteness of the base paper without significantly changing the color tone, that is, while making it feel white.

If a* is greater than +0.5, the paper will have a reddish tinge, and if it is less than -5, the paper will have an excessively strong greenish tinge. If b* is 8 or more, the yellowish tinge will be too strong, and if it is less than -1, the bluish tinge will be too strong, and in either case, the paper will not have the feel of white paper. Sho L
For books, the range of a*, b books mentioned above corresponds to the whiteness level, and the whiteness level of 60% to 80% is approximately 83.5 in the L value.
~93.5. Note that L* entered in this specification,
The values of a* and b* were measured using a color difference meter CR-Zoo model manufactured by Minolta Camera Co., Ltd.

The filler used in the present invention is heavy calcium carbonate or light calcium carbonate. Heavy calcium carbonate is dry-milled or wet-milled to reduce the average particle size to 4 μm.
Below, it is preferably 0.5 μm to 3 μm, and since these are usually used as coating pigments, waste paper generated from processes such as coating machines, cutters, super calenders, etc. is collected and redisintegrated. If used in the papermaking process, coating pigments can be effectively used as papermaking fillers together with virgin fillers. Light calcium carbonate can be produced using the carbonation method, which involves refining quicklime and carbon dioxide obtained by burning limestone, dissolving the quicklime in water to make lime milk, or by blowing carbon dioxide into it, or by mixing it with milk of lime or a calcium chloride solution. Calcium carbonate is synthesized by a carbonate solution synthesis method that involves reacting with carbonate. Calcium carbonate is preferably contained in paper in an amount of 3% to 25%, preferably 5% to 18%. In addition, in the present invention, calcium carbonate is not only used alone as a filler, but also generally used. Other fillers include kaolin, clay, talc,
There is no problem in using titanium oxide etc.
In that case, in order to obtain the desired effects of the present invention, the calcium carbonate content should be within the above range. Light calcium carbonate is particularly preferred because it has a high degree of whiteness and a large opacity effect.

The pulp used in the production of base paper for coating in the present invention includes:
Pulp obtained by chemically and/or mechanically treating plant materials such as needle II trees and broad-leaved trees can be used alone or in combination, and is not particularly limited.
In addition to these fillers, pulp, and colorants, there are also additives commonly used in paper making, such as sizing agents, antifoaming agents, fluorescent agents,
A dry paper strength improver, a wet paper strength improver, a slime control agent, a P aqueous strength improver, a retention improver, etc. can be included as necessary. Typical examples of the sizing agent include alkyl ketene dimer-based sizing agents and alkenylsuccinic anhydride-based sizing agents, but are not limited to these.

As described above, white inorganic pigments, organic synthetic pigments, and coatbroke (waste paper or recovered waste paper), which are usually used in papermaking systems, can be used as fillers.

In addition, starch, polyvinyl alcohol,
There is no problem with processing using a size press, a gate roll, etc. using water-soluble polymer substances such as various surface sizing agents, white pigments, etc.

In this case, the whiteness and color tone after surface treatment should be within the above range. Of course, it is possible to add the above-mentioned coloring agent to these surface treatment liquids for adjustment.

In the present invention, coated Kawahara paper thus prepared is coated with a coating liquid containing a white pigment, an adhesive, and a coloring agent to obtain a coated paper. As the colorant to be contained in the coating liquid, those mentioned in the section of the base paper can be used as they are. The content of the colorant is adjusted according to the whiteness of the white pigment, the whiteness of the base paper, and the target whiteness of the coated paper, and is determined so that the difference between the whiteness of the base paper and the whiteness of the coated paper is within 6%. Although it cannot be determined unconditionally, it should be 10p per white pigment.
It is thought that the above whiteness range can be obtained by adding about pm to 500 ppm.

The white pigments used in the coating layer of the present invention include heavy calcium carbonate, light calcium carbonate, kaolin, clay, satin white, titanium oxide, aluminum hydroxide,
Examples include zinc oxide, barium sulfate, calcium sulfate, silica, activated clay, diatomaceous earth, lake, and plastic pigments.

Adhesives include various copolymer adhesives such as styrene-butadiene, styrene-acrylic, acetic acid-vinyl acrylic, ethylene-vinyl acetate, butadiene-methyl methacrylic, and acetic acid-butyl acrylate-1, and polyvinyl. Alcohol, maleic anhydride-styrene copolymer, acrylic acid-
Synthetic adhesives such as methyl methacrylate copolymers, isobutyne-maleic anhydride copolymers, oxidized starches, etherified starches, esterified starches, enzyme-modified starches, cold water-soluble starches obtained by flash drying them, and casein. Generally known adhesives such as natural adhesives such as , soybean protein and the like can be mentioned. In addition, various auxiliary agents that are usually added to coating liquids, such as dispersants, thickeners, water retention agents, antifoaming agents, waterproofing agents, colorants, and fluorescent agents, can be used as necessary. The method of applying the coating liquid according to the present invention to the base paper for coating is not particularly limited, and various coating devices such as an air knife coater, a gate roll coater, various blade coaters, and a jaw-dwell coater can be used. It will be done.

Coating amount is 15 g/m' or less on one side, preferably 3 g/m' on one side.
g/rrIt to 13 g/r11t, particularly preferably 5 g/rn" to lOg/rrII' on one side. If the coating amount on one side is 15 g/nf or more, it is not suitable for the purpose of light tray coated paper, and the coating layer Since unevenness is not noticeable due to its own hiding power, there is no need to use a colorant to reduce the difference in whiteness with the base paper layer, and in fact, reducing the whiteness has a negative effect on printing paper.

The coated paper coated with the coating liquid and dried can be finished by passing through a finishing device such as a super calender or a gloss calender.

(E) When the effective coating amount is less than 15 g/rcF on one side, the ratio of the thickness of the thick part to the thin part of the coating layer becomes large due to the unevenness of the surface of the base paper, and the thin part is Sometimes it becomes visible. in this case.

If the difference in whiteness between the base paper layer and the coating layer is large, coating unevenness will be extremely noticeable, but if the whiteness of the coating layer is close to that of the base paper layer, the unevenness due to the thickness of the coating layer will be exactly the same as the color of the base paper. It is thought that they cancel each other out and become less noticeable. In particular, the whiteness is adjusted using a black colorant, and the color tone is adjusted so that a* is -
When 5.0 to Q, 5°b is kept in the range of -1.0 to +8.0 (in this case, L* is approximately 83.5 to 93.5), the wavelength range of visible light is It is thought that absorption occurs during the exposure process, making it less noticeable.

Furthermore, the opacity increases and the strength decreases in proportion to the filler content I in the base paper. The improvement in opacity is due to the scattering of light by the filler itself and the inhibition of interfiber bonding by the filler. This is explained by an increase in the degree of light scattering due to an increase in the non-coupling area between the fibers.

The decrease in strength is due to the decrease in the content of iai in the paper and uIII
This is explained by the decrease in the t-t coupling area. Here, opacity is mainly obtained by the scattering of light, but if we think of opacity as the degree to which the percentage of incident light does not pass through, in addition to the scattering of a single light, it also absorbs light. Affect.
Therefore, in order to maintain strength, it is necessary to reduce the filler content, but at the same time, it is thought that opacity can be maintained by compensating for the decreased light scattering ability with light absorption by dyes and the like. The increase in whiteness of paper due to high whiteness calcium carbonate filler is
Since the addition of a black colorant that exactly offsets this condition satisfies this condition, paper strength is improved by reducing the amount of filler, and the black colorant has a synergistic effect of reducing whiteness and improving opacity. ing.

Therefore, the whiteness is lower than usual, but by adding a coloring agent to the coating liquid, the whiteness is lowered and the difference with the whiteness of the base paper is reduced, making the unevenness more noticeable. It's probably gone.

(F) Examples The present invention will be explained in detail with reference to Examples below.
In the Examples, all parts, percentages, and ppm are by weight.

Incidentally, one measurement value in the examples was obtained by the following method.

1) The whiteness was measured in accordance with JISP-8123 and expressed as reflectance % measured with a blue filter (457 nm) using a Hunter reflectance meter.

2) Measurement of opacity follows J I 5P-8138,
Hunter reflectometer with green filter (557nm)
Measure with a standard plate with a whiteness of 89% on the back side. Rw and Ro with a black standard plate. Ratio of reflected light: Ro / Rw
is expressed as a percentage.

3) Surface reflection characteristics (L*a*b*) The method described in the text was used.

4) Visibility unevenness The visibility of unevenness is determined by visual perception.
Divided into 5 stages.

1. The unevenness is extremely noticeable.

2. Unevenness is noticeable.

3. Some unevenness is noticeable.

4. The unevenness is hardly noticeable.

5. No unevenness is noticeable at all.

5) Internal bond strength is measured using an internal bond tester (fl
The value obtained by converting the value determined for a 1-inch square piece of paper using a 1-inch paper (manufactured by Tani Riki Co., Ltd.) to 10rr12 square was used.

6) Calcium carbonate content is expressed as % calcium carbonate content based on the difference between a piece of paper whose bone dry weight was measured and which was soaked in a 1% HCI solution for about 5 minutes to dissolve the calcium carbonate and then washed. Ta.

Examples 1 to 6 and Comparative Examples 1 to 8 Canadian Standard P water level of 370 using a disc refiner
80 parts of hardwood craft valves beaten to 11+1, 4
A valve slurry was prepared consisting of 20 parts of softwood kraft valves beaten to 70 ml. This valve solid content is 10
0 parts, 15 parts of heavy calcium carbonate was added, and a black water-soluble sulfur dye (C, 1, manufactured by Nippon Kayaku Co., Ltd.) was added as a coloring agent.
Oppm each of Solbilized Sulfur Black 1)
, 20ppm.

80ppm, 150ppm, 220ppm,
290ppm.

0.5 part of 0 and then sulfuric acid added at 360 ppm,
Tertiary cationic starch (Cato2M manufactured by Tamago National Co., Ltd.)
) 0.4 parts, alkyl ketene dimer sizing agent 0.06
A paper stock slurry was prepared by adding 0.02 parts of cationic polyacrylamide with a high molecular weight as a retention aid. The pH of this slurry was 7.8-7.9. From this slurry it is 40g/nf
, and dry it for 3 minutes in a cylindrical dryer at 90°C to obtain base papers 1~7 with different degrees of whiteness.Then, these base papers were coated with the following two types of coating liquids 1~2 using a blade coater. Both sides were coated at 12 g/d on one side and supercalendered to obtain coated papers of Examples 1 to 6 and Comparative Examples 1 to 8, respectively. Table 1 shows the results of measuring the physical properties of base paper and coated paper.

<Coating liquid 1> Kaolin (Jossia Kaolin) 70 parts Wet deuterium salt (Carbital 90) 308BR8 Oxidized starch 5 Dispersant
C1,1p) (C1,5 Conc, 63% <Coating liquid 2> Kaolin (Jossia kaolin) 70 parts wet deuterium (Carbital 90) 30SBR8 Oxidized starch 5 Dispersant
0.1 Colorant (C, 1, Direct Black 159) 0.02 pH 9.5 Conc, 63% (blank below) Examples 7 to 10 and Comparative Examples 9 to 13 37 at Canadian WWIF water level by disc refiner
50 parts of hardwood kraft pulp beaten to 0ml, 470
20 parts softwood kraft pulp beaten to m1, 330m
Semi-chemical pulp beaten to 1 (whiteness 62%) 20
Prepare a pulp slurry consisting of 10 parts of coated broque containing 0 parts and 3 parts of light calcium carbonate, respectively, for 100 parts of pulp solids.
．． 5 parts, 10 parts, 16 parts, and 23 parts were added, and 40 ppm + each of Sandai DP Black P Paste 2904 (anionic surfactant-dispersed carbon black manufactured by Sanyo Shiki Co., Ltd.) was added as a coloring agent, followed by polyaluminum chloride 0.
．． 3 parts, amphoteric starch (Cato32 manufactured by Tamago National Co., Ltd.)
10) 1.2 parts, alkyl ketene dimer sizing agent 0.
A paper stock slurry was prepared by adding 0.01 part of high molecular weight anionic polyacrylamide and 0.5 part of bentonite as retention improvers. The pH of these slurries is 6.2.6.8.7.7.8 respectively.
．． It was 2.8.8.

From this slurry, paper with a tsubo ML of 40 g/m'' was made and dried in a cylindrical dryer at 90° C. for 3 minutes to obtain six types of base papers 8 to 12 having different filler content and whiteness.

Next, these two types of coating liquids 1 to 2 were coated on both sides using a blade coater at a rate of 10 g/# on one side, and super calendering was applied to coat these base papers in Examples 7 to 10 and Comparative Examples 9 to 13, respectively. It was made into paper.

Table 2 shows the results of measuring the physical properties of base paper and coated paper.

(Left below) Examples 11 to 16 and Comparative Examples 14 to 18 70 parts of hardwood kraft pulp refined to 370 ml at Canadian standard P water level using a disc refiner - Needle 1 refined to 470 ml [20 parts of kraft pulp and coated brocade] A pulp slurry consisting of 10 parts (consisting of 3 parts ground calcium carbonate, 3 parts kaolin and 10 parts pulp) was prepared.
To 100 parts of this pulp solid content, 13 parts of light calcium carbonate was added, and 200 ppm of C,1, Direct Black 159 was added as a coloring agent.

Next, 0.8 parts of sulfate, quaternary cationic starch (AVE
0.7 part of Perfect Amyl PW (manufactured by BE), 0.06 part of an alkyl ketene dimer sizing agent, and 0.02 part of high molecular weight cationic polyacrylamide as a retention improver were added to achieve a pulp concentration of 1%. A stock slurry was prepared. The pH of this slurry was 7.9.

Paper with a weight of 40 g/nr' was made from this slurry and dried for 3 minutes in a cylindrical dryer at 90°C.
A base paper 14 was obtained. The whiteness of this base paper 14 is 70.2
, opacity is 77.3.

L book 8B, 61, a* -2, 11, b* +0.
45 and calcium carbonate content was 10.4%.

Further, the following four types of coating liquids 3 to 6 were applied to both sides of these base papers in varying amounts using a blade coater to obtain coated papers of Examples 11 to 16 and Comparative Examples 14 to 18, respectively.

Table 3 shows the results of measuring the physical properties of base paper and coated paper.
Shown below.

<Coating liquid 3 to 6> Kaolin (Jossia kaolin) 70 parts wet deuterium salt (Carbital 90) 30SBR8 Oxidized starch 5 Dispersant
0.1 colorant
*pH9,5Conc, 63
%* <Coating liquid No.> Colorant added ppm Table 3 (G) Effect of the invention The content of calcium carbonate is 3 to 25% by weight, and the surface reflection characteristics are a*--5 when the colorant is contained. ,0 to 0
．． 5- Paper made so that b* = -1.0 to 8.0 has higher opacity than paper made with only calcium carbonate and no coloring agent if it contains the same calcium carbonate. With the same opacity, a paper with high strength and suitable for use as a base paper for printing paper, especially coated paper, can be obtained. Furthermore, if the coating liquid contains a coloring agent and is applied to the base paper described above to obtain a coated paper, and the difference between the whiteness of the base paper and the whiteness of the coated paper is within 6%, the coating unevenness becomes noticeable and the visual appearance is good. Light coated paper can be easily obtained.

Claims (3)

[Claims] (1) For single-sided or double-sided coated paper with a coating weight on one side of 3 g/m^2 or more and 15 g/m^2 or less, the base paper for coating and the coating layer contain a colorant, and A lightweight coated paper characterized in that the difference between the whiteness of the base paper and the whiteness of the coated paper is within 6%. (2) The coloring agent is black or colored dyes or pigments alone or in combination, and the surface reflection characteristics of the coating base paper colored with the coloring agent are determined by the measurement method and display specified in JISZ-8722 and JISZ-8730. a*=-5.0 to 0.5, b*=-1.0 to 8
．． 0. The lightweight coated paper according to claim 1, wherein the weight is 0. (3) The base paper for coating contains at least 3% to 25% by weight of calcium carbonate as a filler, and the papermaking pH is 6.5 to 25% by weight.
The lightweight coated paper according to any one of claims 1 to 2, which is an acid-free paper made from a pulp slurry of No. 9.5.