JP6833744B2 - How to make high-quality watercolor paper - Google Patents

Description

The present invention relates to a method for manufacturing a watercolor paper, and more particularly to a method for manufacturing a high-grade watercolor paper as a watercolor paper for advanced users, which has a high paint density and less color unevenness when an image is drawn with a watercolor paint. Is.

Watercolor paper is classified into three types, high-grade watercolor paper, high-grade watercolor paper, and watercolor paper, depending on the type of raw material pulp and its blending ratio. Generally, the finest watercolor paper is only cotton pulp or a mixture of cotton pulp in a high proportion, the high-grade watercolor paper is a combination of cotton pulp and wood pulp, and the watercolor paper does not contain cotton pulp. Among these, the finest watercolor paper and the high-grade watercolor paper are intended for advanced users because the water is quickly absorbed into the paper and the image lines are less likely to bleed.

Conventionally, various proposals have been made to impart the necessary characteristics to such a watercolor paper for advanced users. For example, Patent Document 1 has an object that water of a watercolor paint is quickly absorbed inside the paper, the image lines do not bleed, the paper has a uniform color development property, and the paper is less likely to be discolored or deteriorate in strength with time. , 30 to 550 ml of papermaking fibers made of cotton pulp in an amount of 30% by weight or more. S. F. A watercolor paper having a cold water extraction pH of 6.0 to 9.5 has been proposed, which is made by beating and containing 0.1 to 1.5% by weight of an epoxidized higher fatty acid amide.

Further, Patent Document 2 states that when drawn with a paintbrush or the like, the watercolor paint has remarkably excellent water absorption, has uniform color development, is less likely to cause fluffing, and has the same performance as inexpensive high-grade watercolor paper. The subject is 450 to 650 ml of C.I. S. F. A watercolor paper is proposed in which water-soluble molecules are contained in an amount of 1 to 20% by weight based on papermaking fibers by a wet impregnation method.

As described above, the watercolor paper for advanced users is considered to exhibit uniform color development in the image when the watercolor paint is diluted with water and drawn with a brush. Further, in recent years, in order to reproduce a visually recognized image on a watercolor paper with good reproducibility, it has been desired to provide a watercolor paper having a higher paint density and uniform color development.

Japanese Unexamined Patent Publication No. 10-018195 Japanese Unexamined Patent Publication No. 10-280293

However, the techniques described in Patent Documents 1 and 2 are not sufficient in terms of paint density and color unevenness.

The present invention has been made by paying attention to the above-mentioned problems, and an object of the present invention is that when an image is drawn with a watercolor paint, the paint density is high, the occurrence of color unevenness is small, and the present invention is intended for advanced users. The purpose is to provide a suitable watercolor paper.

Other objects of the invention and effects will be readily understood by those skilled in the art by reference to the following description.

As a result of repeated studies on the formulation of the paint receiving layer that can solve the above problems, it was found that the desired watercolor paper can be obtained by containing a specific amount of the alkyl ketene dimer and the water-based polyethylene resin.

That is, in the method for producing a watercolor paper according to the present invention, gelatin is 3 to 10% by mass, alkyl ketene dimer is 0.1 to 0.3% by mass, and water-based polyester resin is 0 on at least one surface of a base paper mainly composed of pulp. It is characterized in that a paint receiving layer is provided by applying a paint for a paint receiving layer contained in a concentration of 1 to 2.0% by mass and drying the paint.

According to such a configuration, when an image is drawn with a watercolor paint, the paint density is high, the occurrence of color unevenness is small, and a watercolor paper suitable for advanced users can be obtained.

In a preferred embodiment of the present invention, 50% by mass or more of the pulp is cotton pulp having a Canadian standard drainage (CSF) of 500 to 650 ml (CSF) according to JIS P 8121 and / or mercerized cotton. Let it be pulp.

According to such a configuration, since the blending ratio of the cotton pulp and / or the mercerized cotton pulp in the base paper is high and the degree of drainage is also in an appropriate range, it has an appropriate absorbency and color unevenness occurs. A difficult watercolor paper can be obtained.

In a preferred embodiment of the present invention, the paint for the paint receiving layer further contains potassium aluminum sulfate hydrate.

According to such a configuration, by blending potassium aluminum sulfate hydrate in the paint receiving layer, it can be crosslinked with gelatin to further improve water resistance.

In a preferred embodiment of the present invention, the cold water extraction pH value according to JIS P-8133 is 7 to 9.

According to such a configuration, since the watercolor paper is a neutral paper, it is preferable that the color change with time is small even when the picture is stored for a long period of time after it is completed.

The present invention can also be regarded as an invention relating to a paint for a paint receiving layer of watercolor paper.

The paint for the paint receiving layer of the watercolor paper according to the present invention contains 3 to 10% by mass of gelatin, 0.1 to 0.3% by mass of alkyl ketene dimer, and 0.1 to 2.0% by mass of water-based polyester resin. It is characterized by being contained in a concentration.

According to such a configuration, by applying the paint for the paint receiving layer of the above configuration to the base paper, the paint density is high when the image is drawn with the watercolor paint, the occurrence of color unevenness is small, and it is for advanced users. It is possible to produce a watercolor paper suitable for this.

By containing a specific amount of alkyl ketene dimer and water-based polyester resin, the watercolor paper produced according to the present invention can have a higher color density after application and drying of the watercolor paint and have uniform color development.

It is a figure which shows the composition and the physical property of the paint for a paint receiving layer in an Example and a comparative example.

Next, the present invention will be described in detail, but the present invention is not construed as being limited to these descriptions.

In the method for producing a watercolor paper according to the present invention, 3 to 10% by mass of gelatin, 0.1 to 0.3% by mass of alkyl ketene dimer, and 0. A paint for a paint receiving layer contained in a concentration of 1 to 2.0% by mass is applied and dried to provide a paint receiving layer.

(Base paper)
As the raw material pulp of the base paper used in the present invention, chemical pulps such as LBKP (broadwood bleached kraft pulp), NBKP (coniferous bleached kraft pulp), NBSP (coniferous bleached sulfite pulp), TMP (thermomechanical pulp), CTMP Mechanical pulp such as (chemythermomechanical pulp), wood pulp such as DIP (deinked pulp), non-wood pulp such as Kenaf, Bagas, bamboo, cotton, and marcelized cotton are used alone or optionally. It is possible to mix and use at the ratio of. Among these, in the present invention, cotton pulp and / or mercerized cotton pulp are used because they have an appropriate absorbency of watercolor paint and can reduce color unevenness when the watercolor paint is spread with water. It is preferable to use them alone or in combination with chemical pulp. When the cotton pulp and / or the mercerized cotton pulp and the chemical pulp are used in combination, the proportion of the cotton pulp and / or the mercerized cotton pulp is preferably 50% by mass or more of the total amount of the pulp. From the viewpoint of absorbability, 60% by mass or more is more preferable, and 70% by mass or more is further preferable.

When cotton pulp and / or mercerized cotton pulp is used as the raw material pulp, the Canadian standard drainage degree (CSF) specified in JIS P 8121 "Pulp Curability Test Method" of pulp in pulp slurry. Is preferably in the range of 500 to 650 ml. If the drainage degree of the cotton pulp is less than 500 ml, the base paper after papermaking does not have sufficient water absorption, so that the absorbability of the paint for the paint receiving layer is impaired, and there is a risk that a sufficient coating amount cannot be secured. is there. On the other hand, if the degree of drainage of the cotton pulp exceeds 650 ml, it is difficult to adjust the texture of the base paper, and the surface strength may be further weakened. The Canadian standard drainage level (CSF) of chemical pulps such as LBKP and sulfide pulp is preferably 400 to 600 ml for mixing.

In the present invention, the base paper may contain a filler. The filler used here is not particularly limited, and is appropriately selected from general fillers such as light calcium carbonate, heavy calcium carbonate, talc, clay, kaolin, calcined clay, titanium dioxide, barium sulfate, and calcium silicate. Although it can be selected and used, it is preferable to use titanium dioxide and / or barium sulfate when whiteness is required for the watercolor paper. Further, as the average particle size of the filler to be used, it is preferable to select one having a volume average particle size of 5 μm or less measured by a laser method using Microtrac HRA (manufactured by Honeywell Co., Ltd.) in consideration of yield and the like.

The watercolor paper according to the present invention is preferably acid-free paper having a cold water extraction pH value of 7 to 9 according to JIS P-8133. This is because watercolor paper is often stored for a long period of time after the picture is completed, and therefore acid-free paper is preferable because the color of the paper surface does not change over time. In order for the cold water extraction pH value according to JIS P-8133 to be in the range of 7 to 9, it is preferable that the pH of the raw material slurry at the time of papermaking is 7 to 9.

Since the watercolor paper according to the present invention is written with a brush containing a large amount of water, it imparts water resistance to the paper to prevent rough skin such as fluffing on the surface, and waves of the watercolor paper after the watercolor paint has dried. It is necessary to prevent the inside and deformation. Therefore, it is preferable that the base paper contains a paper strength enhancer. Examples of the paper strength enhancer that can be used here include polyamide epichlorohydrin-based paper strength enhancers, starch-based paper strength enhancers, polyacrylamide-based paper strength enhancers, and polyvinyl alcohol-based paper strength enhancers. However, a polyamide epichlorohydrin-based paper strength enhancer is particularly preferable because it is easy to improve the wet paper strength.

In the present invention, the base paper includes a cationic starch, an internal neutral sizing agent, a sulfuric acid band, a bulking agent, a yield improver, a drainage improver, a coloring dye, and a coloring pigment, as long as the object of the present invention is not impaired. Various auxiliary agents such as fluorescent whitening agents, fluorescent decoloring agents, and pitch control agents can be appropriately used.

In the present invention, the method for making the base paper is not particularly limited, and a conventionally well-known paper machine such as a circular net paper machine, a short net paper machine, a long net paper machine, and a combination paper machine of these paper machines is used. Can be made in a single layer or as a paper machine. In the case of abstracting, a paper strength agent such as starch for interlayer coating may be spray-coated to prevent delamination of each layer of abstracting.

(Paint receiving layer)
The watercolor paper according to the present invention is provided with a paint receiving layer on at least one surface of the base paper so that the color density after the watercolor paint is applied and dried is higher and color unevenness does not occur. In the present invention, the paint receiving layer contains at least gelatin, an alkyl ketene dimer, and an aqueous polyester resin.

Here, gelatin is blended as a binder, and it is preferable that the binder is mainly gelatin and contains 3 to 10% by mass of gelatin per one side of the base paper with respect to the entire paint receiving layer. If the content of gelatin in the paint receiving layer is less than 3% by mass, a sufficient gelatin film may not be formed on the surface of the paint receiving layer and the wet surface strength may be insufficient. In addition, the retention of the watercolor paint is inferior, and there is a possibility that the previously applied watercolor paint may easily come off when recoating with the watercolor paint. On the other hand, if the content of gelatin in the paint receiving layer exceeds 10% by mass, the viscosity of the paint for the paint receiving layer becomes high, resulting in poor pump-up, liquid splashing with a size press, and the knife not being cut by the air knife method. Problems may occur, making it difficult to stably apply the paint to the surface of the base paper. In addition, the coating process, the drying process after application, and the piping are likely to be soiled, which is economically disadvantageous.

Gelatin has higher paint retention than other binders such as starch and polyvinyl alcohol, and can impart even higher water resistance, so that the surface of the paper becomes rough when overcoating with watercolor paint with a brush. Can be prevented. In addition, by using gelatin and potassium alum hydrate in combination, gelatin can be crosslinked to enhance the water resistance effect. When potassium aluminum sulphate hydrate is used in combination, the blending ratio is preferably in the range of 0.5 to 5.0% by mass with respect to gelatin.

In the present invention, the paint receiving layer contains an alkyl ketene dimer. By including the alkyl ketene dimer in the paint receiving layer, it is possible to adjust the bleeding of the watercolor paint and prevent the watercolor paint from sinking too much into the paper. Alkyl ketene dimers are effective under neutral conditions and enable long-term storage of images. Neutral sizing agents other than alkyl ketene dimers have too good wettability and cause color unevenness.

Here, the alkyl ketene dimer is contained in the paint receiving layer on at least one side of the base paper in a solid content per side in the range of 0.1 to 0.3% by mass with respect to the entire paint receiving layer. If the content of the alkyl ketene dimer in the paint receiving layer is less than 0.1% by mass, the content of the alkyl ketene dimer is not sufficient, so that the water absorbency of the watercolor paint into the paper becomes high and the watercolor paint is applied. When this is done, brush strokes and color unevenness are likely to occur. On the other hand, if the content of the alkyl ketene dimer exceeds 0.3% by mass, the absorbability of the watercolor paint into the paper becomes too low, the drying is slow, and the retention of the watercolor paint is impaired.

Further, the paint receiving layer contains an aqueous polyester resin as a penetrant. The water-based polyester resin is polymerized so as to contain a sulfonic acid base or a carboxylic acid base as a hydrophilic group in the molecule in order to impart water solubility or water dispersibility, and is generally used as an SR agent (Soil Release agent). It's being used. The inventors of the present application have found that by incorporating a water-based polyester resin in the paint receiving layer, the wettability of the paper surface can be improved and the color density after application and drying of the watercolor paint can be increased.

Here, the water-based polyester resin is contained in the paint receiving layer on at least one side of the base paper in the range of 0.1 to 2.0% by mass with respect to the entire paint receiving layer in terms of solid content per side. If the content of the water-based polyester resin in the paint receiving layer is less than 0.1% by mass, the content of the water-based polyester resin is insufficient and it becomes difficult to obtain a sufficient color density of the watercolor paint. On the other hand, if the content of the water-based polyester resin exceeds 2.0% by mass, the water absorption of the watercolor paint becomes too large, causing color unevenness when the watercolor paint is applied, or impairing the suitability of the paint such as gradation. To do.

The inventors of the present application have studied aqueous polyester resin, sodium linear alkylbenzene sulfonate, polyoxyethylene fatty acid ester, and polyoxyethylene styrenated phenyl ether as penetrants for improving the color density after coating and drying of watercolor paint. However, the water-based polyester resin had the best effect.

Further, in the present invention, the composition of the paint receiving layer is adjusted so that the contact angle 60 seconds after dropping 4 μl of distilled water on the surface of the paint receiving layer provided on the base paper is 100 degrees or more and less than 116 degrees. did. Originally, alkyl ketene dimer imparts the effect of preventing bleeding of watercolor paint, while water-based polyester resin imparts the effect of improving the permeability of watercolor paint into paper, and both are additives that have opposite effects. is there. In the present invention, the contact angle of the paper surface is adjusted to 100 degrees or more and less than 116 degrees by applying the alkyl ketene dimer and the water-based polyester resin on the base paper at the above-mentioned contents, whereby the image is printed on the watercolor paper with the watercolor paint. After drawing and drying, the paint density is high and the occurrence of color unevenness is reduced.

The above-mentioned contact angle is a dynamic contact angle and is measured by the following procedure. Using a dynamic contact angle tester 1100 DAT (manufactured by Fibro System AB) on the surface of the paint receiving layer of the watercolor paper to be tested, the contact angle was measured for 60 seconds after dropping 1 drop of 4 μl of distilled water, and contact after 60 seconds. The wettability of the surface of the watercolor paper is judged from the numerical value of the corner. The contact angle indicates the angle at which the free surface of the liquid forms a flat surface of the solid when the liquid is in contact with the solid. The blunter the angle, the worse the wettability, and conversely, the sharper the angle, the wetter the liquid. The sex gets better. If the contact angle exceeds 116 degrees and the wettability becomes too poor, the retention and fixability of the watercolor paint on the surface of the watercolor paper deteriorates, which reduces the color density after application and drying of the watercolor paint, and also causes color unevenness. It is more likely to occur. On the other hand, if the contact angle is less than 100 degrees and the wettability is too good, the watercolor paint on the paper surface will settle quickly and the color density after application and drying of the watercolor paint will increase, but on the other hand, the watercolor paint will be brushed. Since the watercolor paint cannot be applied evenly because it is quickly separated from the paint, color unevenness of the watercolor paint tends to occur. For these reasons, it is preferable that the surface of the paper has an appropriate wettability.

In the present invention, the method for applying the paint for the paint receiving layer to the base paper is not particularly limited, and conventionally known coating methods such as a size press method, a depping method, a coater coating method, and a spray method are appropriately selected and used. can do.

Further, the paint for the paint receiving layer of the present invention may contain various known additives such as an antifoaming agent, a preservative, and a viscosity modifier as long as the effects of the present invention are not impaired.

The watercolor paper of the present invention can be embossed to give an uneven surface to give a texture. The basis weight of watercolor drawing paper is not particularly limited, but is 100 to 400 g / ^{m 2,} preferably 120~360g / ^{m 2.}

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" and "%" in Examples and Comparative Examples indicate parts by mass or% by mass in terms of solid content, respectively.

Using a pulp slurry containing 100 parts of cotton pulp (600 ml CSF) and 5.0 parts of heavy calcium carbonate (trade name: Softon 1500, manufactured by Shiraishi Calcium Co., Ltd.) as a filler, the paper density is 300 g / m ^2. As described above, papermaking was carried out at a papermaking pH of 7.5 to obtain a base paper. Next, 0.1% by mass of alkylketen dimer (trade name: SE2360, manufactured by Seikou PMC) as a neutral sizing agent in 100 parts of a watercolor aqueous solution having a concentration of 9% by mass (the number of parts as a gelatin aqueous solution instead of a gelatin solid content). , Aqueous polyester resin (trade name: SR-1800, manufactured by Takamatsu Oil & Fat Co., Ltd.) was mixed as a penetrant in an amount of 0.1% by mass to prepare a paint for the paint receiving layer, and this paint for the paint receiving layer was applied to both sides of the base paper. , The coating amount per one side was 7.2 g / m ² in terms of dry solid content to obtain a watercolor paper.

In Example 1, the blending amount of alkyl ketene dimer (trade name: SE2360, manufactured by Seiko PMC) was changed to 0.3% by mass, and the type of water-based polyester resin was changed (trade name: SR-1000, Takamatsu oil and fat). A watercolor paper was obtained in the same manner as in Example 1 except that the coating amount of the paint for the paint receiving layer ^{was changed to 5.8 g / m 2 per side of the base paper.}

In Example 2, the blending amount of the water-based polyester resin (trade name: SR-1000, manufactured by Takamatsu Oil & Fat Co., Ltd.) was changed to 2.0% by mass, and the coating amount of the paint for the paint receiving layer was changed to a dry solid per side of the base paper. A watercolor paper was obtained in the same manner as in Example 2 except that the amount was changed to 6.8 g / m ^2.

In Example 3, the blending amount of the alkyl ketene dimer (trade name: SE2360, manufactured by Seiko PMC) was changed to 0.1% by mass, and the coating amount of the paint for the paint receiving layer was changed to 6 dry solids per side of the base paper. A watercolor paper was obtained in the same manner as in Example 3 except that the content was changed to 1 g / m ^2.

In Example 1, the blending amount of alkyl ketene dimer (trade name: SE2360, manufactured by Seiko PMC) was changed to 0.2% by mass, and a water-based polyester resin (brand name: SR-1800, manufactured by Takamatsu Oil & Fat Co., Ltd.) was blended. A watercolor paper was obtained in the same manner as in Example 1 except that the amount was changed to 1.5% by mass and the amount of the paint for the paint receiving layer was changed to 6.5 g / m ^{2 of dry solid content per side of the base paper.} It was.

Comparative Example 1

A watercolor paper was obtained in the same manner as in Example 1 except that an aqueous polyester resin (trade name: SR-1800, manufactured by Takamatsu Oil & Fat Co., Ltd.) was not added as a penetrant in Example 1.

Comparative Example 2

In Example 1, the blending amount of the water-based polyester resin (trade name: SR-1800, manufactured by Takamatsu Oil & Fat Co., Ltd.) was changed to 5.0% by mass, and the coating amount of the paint for the paint receiving layer was changed to a dry solid per side of the base paper. A watercolor paper was obtained in the same manner as in Example 1 except that the content was changed to 5.9 g / m ^2.

Comparative Example 3

In Example 1, the blending amount of alkyl ketene dimer (trade name: SE2360, manufactured by Seiko PMC) was changed to 0.6% by mass, and the coating amount of the paint for the paint receiving layer was changed to 6 dry solids per side of the base paper. A watercolor paper was obtained in the same manner as in Example 1 except that it was changed to .7 g / m ^2.

Comparative Example 4

In Example 1, the blending amount of alkyl ketene dimer (trade name: SE2360, manufactured by Seiko PMC) was changed to 0.01% by mass, and the coating amount of the paint for the paint receiving layer was changed to 6 dry solids per side of the base paper. A watercolor paper was obtained in the same manner as in Example 1 except that the content was changed to 0.8 g / m ^2.

Comparative Example 5

In Example 1, the neutral sizing agent was changed from an alkyl ketene dimer to a neutral rosin-based sizing agent (trade name: Size Pine NT-78, manufactured by Arakawa Industrial Chemical Co., Ltd.) to 0.1% by mass, and the paint for the paint receiving layer was changed. A watercolor paper was obtained in the same manner as in Example 1 except ^{that the coating amount of the above was changed to 7.0 g / m 2} of dry solid content per side of the base paper.

The composition and evaluation result of the watercolor paper obtained in each Example and Comparative Example are shown in FIG. In the figure, the water-based polyester resin 1 is SR-1800 manufactured by Takamatsu Oil & Fat Co., Ltd., and the water-based polyester resin 2 is SR-1000 manufactured by Takamatsu Oil & Fat Co., Ltd. In addition, each evaluation in FIG. 1 was performed by the following method.

(Contact angle)
Using a dynamic contact angle tester 1100 DAT (manufactured by Fibro System AB) on the surface of the paint receiving layer of the watercolor paper obtained in Examples and Comparative Examples, the contact angle was measured for 60 seconds after dropping 1 drop of 4 μl of distilled water. The numerical value of the contact angle after 60 seconds was taken as the contact angle (degree). If the contact angle is in the range of 100 to 116 degrees, it is passed.

(Color density after application and drying of watercolor paint)
The watercolor papers obtained in Examples and Comparative Examples are cut into strips having a width of 1.5 cm and a length of 15 cm to prepare test papers. Make a solution of watercolor paint (trade name: Quinacridone Red, manufactured by Holbein Art Materials Co., Ltd.) diluted 1: 9 by weight with distilled water in a plastic cup, and immerse the entire brush in it. After that, rub the brush twice with the edge of a plastic cup to remove excess watercolor paint, and then apply the brush six times on the surface of the test paper. After the image dries, X-Rite eXact (Video Jet X-Rite) The concentration was measured at (manufactured by). The color density of the watercolor paint after application and drying was evaluated on a 4-point scale, and those with a circle or above were considered to have no practical problem.
⊚: The color density of the image after drying is 0.81 or more.
◯: The color density of the image after drying is 0.75 to 0.80.
Δ: The color density of the image after drying is 0.71 to 0.74 (there is a problem in practical use).
X: The color density of the image after drying is 0.70 or less (there is a problem in practical use).

(Coloring uniformity: color unevenness)
Make a solution of watercolor paint (trade name: Quinacridone Red, manufactured by Holbein Art Materials Co., Ltd.) diluted 1: 9 by weight with distilled water in a plastic cup, and immerse the entire brush in it. After that, the brush was rubbed once with the edge of a plastic cup, a line of about 10 cm was drawn on the surface of the watercolor papers obtained in Examples and Comparative Examples, and after the image was dried, color unevenness was visually observed. The evaluation was carried out in four stages, and those with a circle or above were considered to have no practical problem.
⊚: There is no color unevenness in the image after drying.
◯: There is slight color unevenness in the image after drying.
Δ: There is some color unevenness in the image after drying (there is a problem in practical use).
X: The image after drying has partial color unevenness (there is a problem in practical use).

As is clear from the results of FIG. 1, the watercolor papers obtained in Examples 1 to 5 can be obtained as a watercolor paper having a higher color density and less color unevenness after application and drying of the watercolor paint.

On the other hand, the watercolor paper obtained in Comparative Example 1 did not contain the water-based polyester resin, so that the color density of the watercolor paint after application and drying was low.

Further, the watercolor paper obtained in Comparative Example 2 has a high color density after application and drying of the watercolor paint, and there is no problem in practical use. However, due to the excessive content of the water-based polyester resin, the method of permeating the watercolor paint onto the paper surface is improved. It became uneven, and some color unevenness occurred, resulting in a particularly dark part.

Further, in the watercolor paper obtained in Comparative Example 3, the fixability of the watercolor paint was deteriorated due to the excessive content of the alkyl ketene dimer, the color density after the application and drying of the watercolor paint was low, and some color unevenness occurred.

Further, the watercolor paper obtained in Comparative Example 4 is excellent in color density after application and drying of the watercolor paint, but the content of the alkylken dimer is extremely reduced so that the paper surface when the watercolor paint is applied. Was absorbed quickly and some color unevenness occurred.

Further, the watercolor paper obtained in Comparative Example 5 is excellent in color density after application and drying of the watercolor paint, but when the watercolor paint is applied by using a neutral rosin-based sizing agent instead of the alkyl keten dimer. It was quickly absorbed by the paper surface and partial color unevenness occurred.

As described above, the watercolor paper produced according to the present invention can have a higher color density and uniform color development after the application and drying of the watercolor paint.

Claims (5)

Containing 3 to 10% by mass of watercolor, 0.1 to 0.3% by mass of alkyl ketene dimer, and 0.1 to 2.0% by mass of aqueous polyester resin on at least one surface of a base paper mainly composed of pulp. A method for producing watercolor paper, which comprises applying a paint for a paint receiving layer and drying it to provide a paint receiving layer. Claim that 50% by mass or more of the pulp is cotton pulp having a Canadian standard drainage (CSF) of 500 to 650 ml (CSF) according to JIS P 8121 and / or mercerized cotton pulp. The method for manufacturing watercolor paper according to 1. The method for producing a watercolor paper according to claim 1 or 2, wherein the paint for the paint receiving layer further contains potassium aluminum sulfate hydrate. The method for producing watercolor paper according to any one of claims 1 to 3, wherein the cold water extraction pH value according to JIS P-8133 is 7 to 9. Paint acceptance of watercolor paper characterized by containing gelatin in a concentration of 3 to 10% by mass, alkyl ketene dimer in a concentration of 0.1 to 0.3% by mass, and an aqueous polyester resin in a concentration of 0.1 to 2.0% by mass. Layer paint.

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