JP3216064B2 - Surface coating agent for inkjet printing paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a surface coating agent for inkjet printing paper for improving the paper quality of the surface.
More specifically, by applying a water-soluble polymer having an amidine structural unit on the paper surface after papermaking, the color development of the ink is excellent, the resolution is high, the water resistance is high, and the light resistance is improved, and set of ink, to the surface coating agent of the ink jet printing paper to the surface strength and the internal strength improvement.

[0002]

2. Description of the Related Art In an ink jet recording system, recording is performed by generating and flying minute droplets of ink on a recording material such as paper according to various operating principles. This method has been rapidly spread as a recording method that generates little noise and can perform high-speed printing and multicolor printing. Conventionally, general paper has been used as a recording material used in the ink jet recording method. However, with the improvement of the performance of the device, such as high-speed recording or multi-color, and the expansion of applications,
Higher properties have also been required for ink jet recording materials.

That is, as a recording material for obtaining a high-resolution and high-quality recorded image comparable to a color photograph, (1) the ink should be rapidly absorbed. (2) When ink dots overlap, the ink that has adhered later does not flow out to the previous dot. (3) The shape of the ink dot is close to a perfect circle, and the periphery thereof is smooth. (4) The diameter of the ink dots does not become larger than necessary. (5) The density of the ink dots is high and the periphery of the dots is not blurred. (6) The color development of the ink is excellent. It is necessary to satisfy various requirements such as. Also water resistant,
Lightfastness is also required. However, a recording material satisfying all of these requirements has not yet been found.

For example, a urea-formaldehyde resin is contained in a coating layer in order to enhance ink absorption (Japanese Patent Application Laid-Open No. 53-49113), and non-colloidal silica powder is used as a pigment in the coating layer. (Japanese Patent Application Laid-Open No. 55-51583)
Publication) and the like. Although the ink absorbency is improved by these methods, there is a major problem that the recorded images lack water resistance. In order to improve the water resistance of a recorded image, a method of incorporating a cationic polymer into a coating layer has been adopted. For example, polyethyleneimine (Japanese Unexamined Patent Publication No.
No. 84992), organic acid salts of polyethyleneimine (JP-A-59-186186), dimethyldiallylammonium chloride (JP-A-59-20696), polyallylamine hydrochloride (JP-A-62-174).
184) and polyvinylamine homopolymers (JP-A-64-8085). However, although these polymer compounds improve the water resistance to some extent, the improvement of the light resistance is still insufficient, and in some cases, the light resistance is reduced.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to develop a recording material for ink jet printing which has excellent color development of ink, high resolution, high water resistance and improved light resistance.

[0006]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors to achieve the above-mentioned object, it has been found that a specific water-soluble polymer having an amidine structure is provided in or on a substrate. The present invention has been found to provide a recording material for ink-jet printing that forms a recorded image having water resistance and light resistance by being contained in the engineered layer, and has accomplished the present invention.

According to the first aspect of the present invention, a repeating unit represented by the following (1) and / or (2):
0 mol%, and a repeating unit represented by the following (3) is 1 to 4
0 mol%, and a repeating unit represented by the following (4) is 1 to 7
0 mol%, and 5 to 4 repeating units represented by the following (5):
0 mol%, and a repeating unit represented by the following (6) is 0 to 2
0 mol%, and a reduced viscosity value of 0.1 to 10 measured at 25 ° C. as a 0.1 g / dl solution in 1 N saline.
dl / g of water-soluble polymer
A surface coating agent for inkjet printing paper.

[0008]

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[0009]

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[0010]

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[0011]

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[0012]

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[0013]

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(Wherein R ¹ and R ² are a hydrogen atom or a methyl group, R ³ is an alkyl group having 1 to 4 carbon atoms, R ⁴ is a hydrogen atom, a methyl group or a carboxymethyl group, X ⁻ is an anion, and Y is an anion. Are COOM, C ₆ H ₄ SO ₃ M, CH ₂ SO ₃
M and CONHC (CH ₃ ) ₂ CH ₂ SO ₃ M and M each represent a cation. )

According to a second aspect of the present invention, the paper for ink-jet printing according to the first aspect, wherein the repeating unit (1) and / or (2) is 40 to 80 mol%. Surface coating agent.

[0016] The invention according to claim 3 of the present invention, the ink jet printing paper according to claim 1 or claim 2, wherein the consisting of acid hydrolysis product of a copolymer of N- vinylformamide and acrylonitrile It is a surface coating agent.

The amidine unit represented by the above (1) and (2) has an amidine structure composed of a five-membered ring, such as nuclear magnetic resonance spectroscopy (NMR) and infrared spectroscopy (IR). Is usually observed equivalently in the analysis of (1)
And (2). However, as shown in the following conceptual diagram, when considering a repeating unit of a produced polymer in an amidation reaction of a polymer described below,
Two types of repeating units represented by (1) and (2) must be considered. In the following conceptual diagram, the CN group and the NH ₂ group indicate a cyano group unit and an amino group unit which did not participate in the amidination reaction.

[0018]

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The method for producing the above-mentioned water-soluble polymer having an amidine structure is not particularly limited. In general, a primary amino group or a substituted amino group capable of forming a primary amino group by a conversion reaction is used. It can be obtained by producing a copolymer of an ethylenically unsaturated monomer having the same and an acrylonitrile or methacrylonitrile nitrile, and further reacting a cyano group and a primary amino group in the copolymer to form an amidine. .

The above-mentioned ethylenically unsaturated monomer has a general formula

[0021]

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(Wherein R ² represents a hydrogen atom or a methyl group, and R ³ represents an alkyl group having 1 to 4 carbon atoms or a hydrogen atom).

In the copolymer, a substituted amino group derived from such a compound is easily converted to a primary amino group by hydrolysis or alcoholysis. This one
A secondary amino group reacts with an adjacent cyano group to form an amidine. The compound includes N-vinylformamide (R
² = H, R ³ = H), N-vinylacetamide (R ² =
H, R ³ = CH ₃ ).

The copolymerization molar ratio of these ethylenically unsaturated monomers to nitriles is usually from 20:80 to 80: 2.
0, but if desired, a polymerization molar ratio outside this range,
For example, a polymerization mole having a larger proportion of the ethylenically unsaturated monomer can be employed. In consideration of application as a surface coating agent, the higher the ratio of amidine units in the cationic polymer, the higher the performance. It is considered that the amine unit also contributes to the performance as a surface coating agent. Accordingly, the copolymerization molar ratio of the ethylenically unsaturated monomer to the nitrile which gives a copolymer suitable as a coating agent is generally from 20:80 to 80:20, particularly preferably 40:80.
60 to 60:40.

As a method of copolymerizing the ethylenically unsaturated monomer with the nitrile, a usual radical polymerization method is used, and any of bulk polymerization, aqueous solution precipitation polymerization, suspension polymerization, emulsion polymerization and the like can be used. . When the polymerization is carried out in a solvent, the reaction is usually carried out at a raw material monomer concentration of 5 to 80% by weight, preferably 20 to 60% by weight. Although a general radical polymerization initiator can be used as the polymerization initiator, an azo compound is preferable, and 2,2'-azobis-2-
Amidinopropane hydrochloride and the like are exemplified. The polymerization reaction is generally carried out at a temperature of 30 to 100 ° C. under a stream of inert gas. The obtained copolymer can be subjected to an amidination reaction as it is or diluted, that is, in the form of a solution or a suspension. After the solvent is removed and dried by a known method to separate the copolymer as a solid, the copolymer can be subjected to an amidination reaction in a solid state.

In the amidination reaction, when an N-vinylamide compound represented by the above general formula is used as the ethylenically unsaturated monomer, the substituted amino group of the copolymer is converted into a primary amino group, and then the formed primary The water-soluble polymer according to the present invention can be produced by a two-step reaction of reacting an amino group with an adjacent cyano group to generate an amidine structure. Then, preferably, the copolymer is heated in a water or alcohol solution in the presence of a strong acid or a strong base to generate an amidine structure in one step. Also in this case, it is considered that a primary amino group is firstly generated as an intermediate structure.

The specific conditions of the reaction are, for example, generally 0.9 to 0.9 for the substituted amino group of the copolymer.
Add 5.0 times, preferably 1.0 to 3.0 times equivalent of a strong acid, preferably hydrochloric acid, and heat at a temperature of usually 80 to 150 ° C, preferably 90 to 120 ° C, usually for 0.5 to 50 hours. Thereby, a cationic polymer having an amidine unit can be obtained. In general, as the equivalent ratio of the strong acid to the substituted amino group is larger and the reaction temperature is higher, the amidination proceeds. In addition, upon amidine formation, water is usually present in the reaction system in an amount of 10% by weight or more, preferably 20% by weight, based on the copolymer to be subjected to the reaction.

The surface coating composition comprising the water-soluble polymer according to the present invention most typically follows the description given above.
By copolymerizing N- vinylformamide and acrylonitrile, the resulting copolymer generally prepared by the aqueous suspension is heated in the presence of hydrochloric acid from the cyano group and the adjacent substituted amino group to form an amidine unit Is done. By selecting the molar ratio of N-vinylformamide and acrylonitrile to be used for copolymerization and the conditions for amidification of the copolymer, surface coating agents composed of water-soluble polymers of various compositions can be produced.

One of the representative surface coating agents comprising a water-soluble polymer according to the present invention comprises 20 to 90 mol% of the repeating unit represented by the above (1) and / or (2).
1 to 40 mol% of the repeating unit represented by the above (3),
1 to 70 mol% of the repeating unit represented by the above (4) and 5 to 40 mol% of the repeating unit represented by the above (5)
It has a reduced viscosity of 0.1 to 10 dl / g. In the present invention, the reduced viscosity is measured at 25 ° C. as a 0.1 dl / g solution in 1 N saline. In the above-mentioned surface coating agent, it is considered that the amidine unit largely contributes to the performance of the fixing agent.

As the ratio of amidine units increases, the performance as a surface coating agent generally tends to improve. However, it is difficult to produce an amidine unit having a ratio of more than 90 mol% by heating the copolymer in an aqueous hydrochloric acid solution. Therefore, the ratio of amidine units in the surface coating agent is usually preferably from 20 to 85 mol%.

The repeating unit (3) is derived from an N-vinyl compound which is more expensive than acrylonitrile, but its presence does not seem to advantageously contribute to the performance as a coating agent. When the number of repeating units (3) increases, the water resistance of the surface coating agent may decrease. However, when the amidine unit ratio is 50 mol% or more, even if the repeating unit (3) is present in a large amount, the surface coating agent will have excellent performance. Since the resulting water-soluble polymer generally has poor stability as it is, it is necessary to add a strong acid to completely neutralize the cationic units of the repeating units (1), (2) and (5). preferable.

Although the effect of the repeating unit (4) on the performance as a surface coating agent is not clear, it is presumed that the repeating unit (4) has a somewhat good effect on the water resistance and light resistance of the recorded image, and there is at least no adverse effect. it is conceivable that. Although the repeating unit (4) is present in the polymer in an amount of 0 to 70 mol%,
Since nitrile is an inexpensive monomer, the presence of the repeating unit (4) is effective in lowering the production cost of the surface coating agent and improving the superiority of the performance with respect to the cost. The preferred abundance of the repeating unit (4) is 5 to 60 mol%, particularly 5 to 50 mol%.

In the surface coating composition according to the present invention, the molar ratio of the repeating unit (4) to the amidine unit [(1) +
(2)] / (4) should generally be in the range of 0.5 to 10.0. This is because it is generally considered that the larger the number of amidine units, the better the surface paper quality improving function.

The repeating unit (5) is cationic,
Like the amidine unit, it is considered to be effectively acting to improve surface paper quality. The repeating unit (5) is present in the coating composition in an amount of 5 to 40 mol%, preferably 5 to 40 mol%. The repeating units (1), (2) and (5) are all derived from the repeating unit (3). Therefore, generally speaking, it is preferred that as many repeating units (3) as possible have been converted into repeating units (1), (2) or (5). The total of the repeating units (1), (2) and (5) in the surface coating agent is generally 30 mol%.
As described above, the content is preferably 40 to 95 mol%.

This means that among the repeating units constituting the polymer, most of the repeating units are considered to contribute to the function of the surface coating agent. In addition,
In the surface coating agent according to the present invention, the molar ratio of the repeating unit (5) to the amidine unit [(1) + (2)] / (5)
Is generally in the range 0.5-18. Since it is considered that the amidine unit acts more effectively on the performance of the coating agent than the repeating unit (5), [(1) + (2)] /
(5) is more preferably in the range of 1.0 to 10.0.

The surface coating composition according to the present invention contains an anionic repeating unit such as the repeating unit (6). For example, a carboxyl group represented by the following repeating unit (7) is generally produced by hydrolysis of the repeating unit (4) in an amount of 0 to 5 mol%. However, when an amphoteric polymer is produced, acrylic acid or methacrylic acid is used. It is more convenient to copolymerize anionic monomers such as acids, allylsulfonic acid, styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and itaconic acid. Generally, 0 to 20 mol% is preferable, but 0 to 10 mol% is more preferable.
If it is 20 mol% or more, the anionicity becomes too strong, and the characteristics of the amidine structure are not expressed, which is not practical. The surface coating agent according to the present invention may contain other repeating units in addition to the above-mentioned repeating units. However, the total of the above-mentioned repeating units (1) to (6) should account for 90 mol% or more. Other repeating units that can be included in the surface cloth adhering agent according to the present invention include the following (8) to (10). The repeating unit (8) is formed by hydrolysis of the repeating unit (4), and is usually in the range of 0 to 5 mol%. The repeating units (9) and (10) are formed by the repeating unit (5) and the repeating unit (8), and usually form 0 to 5 mol%.

[0037]

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[0038]

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[0039]

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[0040]

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As described above, the reduced viscosity of the surface coating agent comprising a water-soluble polymer according to the present invention is usually 0.1 to 10 dl /.
g, preferably in the range of 0.5 to 7.0 dl / g. The reason for this is that if the viscosity is too high, it will hinder the process of surface coating on the paper and the handling will be poor. On the other hand, if the viscosity is too low, the effect of improving the surface strength, the water resistance, and the like deteriorate, which is not practical.

The method for using the water-soluble polymer according to the present invention is surface coating. After performing papermaking drying, a size press of a coating solution mixed with a single solution of the water-soluble polymer according to the present invention or another coating agent, a gate roll coater,
It is common to use a blade coater or a calender.

The water-soluble polymer according to the present invention can be used in combination with other coating agents. For example, the coating can be carried out in the form of a mixture with a cation-modified starch, oxidized starch, polyvinyl alcohol, polyacrylamide for surface coating, or a surface sizing agent. Examples of the coating pigment include finely divided silica, clay, talc, diatomaceous earth, calcium carbonate, barium sulfate, titanium oxide, zinc oxide, satin white, and aluminum silicate. In addition, additives such as a surface sizing agent, an anti-slip agent, a preservative, an antifoaming agent, a viscosity modifier, and a dye may be used in combination.

The amount of the water-soluble polymer according to the present invention to be added to these coating layers is usually 0.05 g / m ² to 1 g.
0 g / m ^2, and preferably from ^{0.2g / m 2 ~5g / m 2} . The coating base paper when the water-soluble polymer according to the present invention is used as a surface coating agent is not particularly limited, and may be an acidic paper, a neutral paper-coated base paper, a newsprint, a printing writing paper, a foam paper, a PPC paper, or the like. Each base paper can be coated.

[0045]

EXAMPLES In order to further clarify the present invention, a production example of a water-soluble polymer which is a surface coating agent of the present invention is shown as a reference example, and then the treatment of paper with the coating agent of the present invention and the results are described. The following shows an example. The embodiments are representative examples, and the present invention is not limited to the embodiments. In addition,
In Examples, "%" means "% by weight" unless otherwise specified.

(Production Example of Water-Soluble Polymer) 20 g of a monomer having the composition shown in Table 1 and 133.1 g of deionized water were charged into a reactor equipped with a stirrer, a nitrogen inlet tube, and a condenser. After raising the temperature to 60 ° C. for 30 minutes in a nitrogen gas stream, 0.19 g of a 10% aqueous solution of 2,2′-azobisamidinopropane dihydrochloride was added, and the mixture was maintained at 60 ° C. for 4 hours with stirring. Thus, a suspension in which the polymer was precipitated in water was obtained. In order to control the degree of polymerization, NO. 1 and NO. 2 is 0.8% relative to monomer, N
O. 3 and NO. 4 and NO. 7 to NO. 10 is 0.
2%, NO. 5 and NO. 6 was added at the time of polymerization in 0.05%. NO. 7 and NO. No. 8 copolymerized acrylic acid, and NO. 9 and NO. Numeral 10 is an N-vinylformamide homopolymer. After polymerization, an equivalent amount of hydrochloric acid as shown in Table 1 was added to the suspension to formyl groups in the polymer, and the mixture was stirred and maintained at 90 ° C. for 4 hours to amidine the polymer. The obtained polymer solution was added to acetone to cause precipitation, and this was dried to obtain a solid polymer NO. 1
From NO. 10 was obtained. The polymer NO. 1 to NO. 1
The composition and the reduced viscosity were measured by the following methods for 0. Table 1 shows the results.

(Method of Analyzing Composition) The compositions of the various combinations before the amidination were calculated from the integrated values of the absorption spectra corresponding to each monomer unit in the ¹³ C-NMR spectrum ( ¹³ C-nuclear magnetic resonance spectrum).
The polymer NO. 1 to NO. The composition of 10
^It was calculated from the integrated value of the absorption peak corresponding to each repeating unit in the ¹³ C-NMR spectrum. The repeating units (1) and (2) were determined as the total amount thereof without distinction. The repeating units (9) and (10) were also determined as the total amount thereof without distinction. Also, repeat unit (1)
The absorption peaks of (2), (8) and (9) and (10) were observed at positions near 170 to 185 ppm, and the structures corresponding to the respective absorption peaks were assigned by the following method. That elemental analysis of the polymer confirms the weight balance by measuring the water content, still ¹³ C of the polymer
The method employs a method in which an IR spectrum is measured in addition to the NMR spectrum, and the polymer spectrum is compared with the spectrum of a known compound in detail for the amidine group, amide group, lactam group and the like.

(Measurement of Reduced Viscosity) 1 to NO. The measurement was performed using an Ostwald viscometer at 25 ° C. as a 0.1 g / dl solution in 1N saline solution.

[0049]

[Table 1]

(Examples 1 to 8) (1) Coating of Water-Soluble Polymer A high-quality paper having a basis weight of 70 g / m ² and a Steckigt size of 25 seconds was used as a support. 3 g of water-soluble polymer of the invention, 500 g of water
The coating solution was prepared by mixing at a ratio of 18.8 g / m ^2, and was applied on one surface at 18.8 g / m ^{2 as a} solid content by a test size press (manufactured by Kumagaya Riki Co., Ltd.) After printing as described below, an ink fixing test was performed. (2) Ink fixability test a. Printing: inkjet printer [BJC-600
J (manufactured by Canon Inc.)], magenta (M), cyan (C), yellow (Y), and black (B). b. Water resistance: The printed image was allowed to stand in running water of 3 liter / min for 5 minutes, the image density before and after the test was measured with a Macbeth densidometer RD918, and the degree of residual color was displayed as a percentage. c. Light fastness: The printed image was put into a fade meter, irradiated at 60 ° C. for 24 hours, the image density before and after the irradiation was measured with a Macbeth densidometer, and the degree of residual color was displayed as a percentage. Table 2 summarizes the above results.

Comparative Examples 1 to 5 For comparison, N-vinylformamide homopolymer hydrochloride hydrolyzate (Polymer No. 9, Polymer No. 10) (Comparative Examples 1 and 2), polyethyleneimine (Polymer) Polymer No. 1
1) (Comparative Example 3) and each polymer of dicyandiamide-formalin resin (polymer No. 12) (Comparative Example 4) were prepared by applying a dispersion in the same ratio, and then tested. The same test was conducted without using the polymer (Comparative Example 5). Table 2 summarizes the above results.

[0052]

[Table 2]

(Examples 9 to 16) In the same manner as in Example 1, application of the water-soluble polymer, printing of the test piece after application, and water resistance and light resistance tests were performed.
The same base paper as in Example 1 was used as a support, and 100 g of white carbon for papermaking, 50 g of polyvinyl alcohol, 4.5 g of a water-soluble polymer, and 500 g of water were mixed at a ratio of 14.0 g / m ² on a solid side. did. Table 3 shows the results.

Comparative Examples 6 to 10 For comparison, polymer NO. 9 (Comparative Example 6), polymer NO.
10 (Comparative Example 7), polymer NO. 11 (Comparative Example 8), polymer NO. A test was conducted in the same manner as in Example 9 using each polymer of Comparative Example 9 (Comparative Example 9). The same test was conducted without using the polymer (Comparative Example 10). Table 3 summarizes the above results.

[0055]

[Table 3]

(Examples 17 to 24) In the same manner as in Example 1, application of a water-soluble polymer and printing of a test piece after application, and water resistance and light resistance tests were performed. As the base paper, the same product as in Example 1 was used as a support, and fine silica 100
g, polyvinyl alcohol 45 g, water-soluble polymer 6.0
g, water at a ratio of 500 g, and a solid content of 10.0 g /
m ² was one-sided application. Table 4 shows the results.

Comparative Examples 11 to 15 For comparison, polymer NO. 9 (Comparative Example 11), polymer N
O. 10 (Comparative Example 12), polymer NO. 11 (Comparative Example 1
3), polymer NO. A test was conducted in the same manner as in Example 17 using each polymer of Comparative Example 12 (Comparative Example 14). The same test was carried out when no polymer was used (Comparative Example 1).
5). Table 4 summarizes the above results.

[0058]

[Table 4]

(Examples 25 to 32 ) In the same manner as in Example 1, the water-soluble polymer was applied alone, and the test pieces after application, and the water resistance and light resistance tests were performed. The same base paper as in Example 1 was used as a support, and 0.4 g of a solid content was coated on one side with a solution prepared by dissolving 2.5 g of a water-soluble polymer in 97.5 g of water. Table 5 shows the results.

(Comparative Examples 16 to 20 ) For comparison, polymer Nos. 9, polymer no. 10, polymer No. 11, polymer No. A test was conducted in the same manner as in Example 25 using each of the 12 polymers (Comparative Examples 16 to 19) . In addition, a paper coated with no polymer was also tested (Comparative Example 2).
0 ). Table 5 summarizes the above.

[0061]

[Table 5]

(Examples 33 to 41 ) In the same manner as in Example 25 , a water-soluble polymer and a commercially available surface strength agent A (polyacrylamide type), a commercially available surface strength agent B (polyvinyl alcohol type), and a commercially available surface strength agent C ( (Oxidized starch). Base paper is Example 1
Using the same paper as the support, 2.0 g of a water-soluble polymer and 4.0 g of a commercially available surface strength agent were dissolved in 94.0 g of water, and 0.4 g of a solution was applied on one side. Table 6 shows the results.

(Comparative Examples 21 to 29 ) For comparison, polymer Nos. 10 and polymer no. A test was conducted in the same manner as in Example 25 using each of the 12 polymers (Comparative Examples 21 to 26 ). In addition, papers coated with only a commercially available surface strength agent were also tested (Comparative Examples 27 to 29 ). Table 6 summarizes the above.

[0064]

[Table 6]

[0065]

[Effect of the Invention The present invention relates to a surface coating agent for inkjet printing paper, by applying a specific water-soluble polymer having an amidine structural unit on the paper surface after the paper, the surface strength of paper, It can improve the internal strength, water resistance, light resistance, fixability of an anionic aqueous ink, and the like. Paper with improved surface quality of paper with a surface coating agent of the present invention is a high-resolution degree comparable to a color photograph, a high-quality recorded images obtained Lee
It is also preferably used as a recording material for ink jet printing .

Continuation of the front page (56) References JP-A-6-123096 (JP, A) JP-A-4-11094 (JP, A) JP-A 64-8085 (JP, A) JP-A-7-290817 (JP) , A) JP-A-8-27693 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/00 B41J 2/01 D21H 19/10

Claims (3)

(57) [Claims] 1. A repeating unit represented by the following (1) and / or (2): 20 to 90 mol%; a repeating unit represented by the following (3): 1 to 40 mol%; 1 to 70 mol% of a repeating unit represented by the following formula (5), 5 to 40 mol% of a repeating unit represented by the following formula (5), and 0 to 20 mol% of a repeating unit represented by the following formula (6). surface coating agent for ink jet printing paper comprising a water-soluble polymer, wherein the value of the reduced viscosity measured at 25 ° C. as a solution of saline 0.1 g / dl is 0.1~10dl / g of. Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image (Wherein R ¹ and R ² are a hydrogen atom or a methyl group, R ³ is an alkyl group having 1 to 4 carbon atoms, R ⁴ is a hydrogen atom, a methyl group or a carboxymethyl group, X ⁻ is an anion, and Y is CO
OM, C ₆ H ₄ SO ₃ M, CH ₂ SO ₃ M, CONHC
(CH ₃ ) ₂ CH ₂ SO ₃ M, M represents a cation. ) Wherein the repeating units (1) and / or (2) a surface coating material of the ink jet printing paper according to claim 1, characterized in that 40 to 80 mol%. 3. The ink-jet ink according to claim 1, wherein the ink-jet ink is made of an acid hydrolyzate of a copolymer of N-vinylformamide and acrylonitrile.
Surface coating agent of paper for printing.