JPS62288076A - Sheet for ink jet recording - Google Patents

Abstract

PURPOSE:To obtain the title sheet excellent in ink absorbability, imparting excellent hue, reducing the spreading of ink on the surface thereof and enhanced in the bonding strength of pigment, by using a binder containing a polymer which is obtained by reacting polyvinyl alcohol, methyl methacrylate and acrylic acid and present in water as polymer particles and contains acrylic acid in specific percentage by wt. of the polymer particles. CONSTITUTION:A binder contains a polymer obtained by reacting polyvinyl alcohol, methyl methacrylate and acrylic acid and said polymer is present in water as polymer particles and contains 3-20% by wt. of polymer particles of acrylic acid. When acrylic acid is less than 3% by wt. of the total wt. of polymer particles, water resistance imparting effect is lost and, when more than 20 wt.%, the reaction of the dye in ink with chemicals causing the crosslinking reaction with a cation being a water resistance imparting agent or acrylic acid becomes fast and pot life lowers and the flowability of paint lowers.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an inkjet recording sheet, and in particular,
The present invention relates to an inkjet recording sheet that has excellent ink absorption and color properties, small spread of ink on the sheet surface, and excellent pigment binding strength.

[Conventional technology]

The inkjet recording method has low noise, high speed, multiple colors, and allows for compact equipment.
It is widely applied to facsimiles, printers, computer terminals, etc. In general, the characteristics required for inkjet recording sheets are: (1) Fast absorption of ink, (2) Small spread of ink on the sheet surface, (3) High recording density, (4) Sheet It is important that the ink spreads on the surface in a nearly perfect circle, and it is also required to have water resistance so that the image will not run off even if the recorded matter gets wet with water. In addition, as basic characteristics of recording sheets, if the sheet is paper, it is desired that there is little paper dust, especially that there is little paper dust that can clog inkjet nozzles, and that the sheet has high surface strength. .

In such an inkjet a self-recording apparatus, a coating layer consisting of an ink-absorbing pigment and a binder for holding it is formed on a water-insoluble support such as paper or polyester.

In general, pigments for high-resolution color inkjet sheets are used in Japanese Patent Application Laid-open No. 59-185690 or No. 59-2307 so that they can absorb and retain a large amount of ink.
Silica having a large specific surface area and high oil absorption, as shown in Japanese Patent No. 87, is used as the pigment. Such pigments are generally porous, and the primary particles usually aggregate with each other to form secondary particles.

[Problem that the invention seeks to solve]

However, in conventional inkjet recording sheets, the binder is a water-soluble polymer such as polyvinyl alcohol, starch, or sodium polyacrylate. This results in a significant decrease in the proportion of the pores that absorb ink or adsorb dyes. As a result, the ink absorbency of the resulting inkjet recording sheet deteriorates, the spread and circularity of the ink on the sheet surface deteriorates, and furthermore, the dye adsorption power of the pigment decreases, resulting in a decrease in dye density. There was a problem. In addition, as much as the binder is absorbed into the pores of the pigment,
Since the ability to bind pigments to each other decreases, problems such as pigment coating layers peeling off as powder during cutting and fanfold processing, and this powder clogging ink nozzles occur. Ta. On the other hand, it has been considered to increase the amount of binder in order to increase the binding force, but this would result in the binder further covering the active sites of pigments such as silica, reducing color development, and further pores in the particles. This caused problems such as the ink absorption capacity being significantly reduced.

In addition, commonly used polyvinyl alcohol (PVA)
Binders such as starch also have the disadvantage that it is difficult to make the pigment coating layer waterproof.

[Failure to solve the problem]

In order to solve the above-mentioned problems, the present invention provides an inkjet recording sheet in which a coating layer containing a binder and a pigment is provided on both sides of the support, the binder being polyvinyl alcohol and methacrylic acid. Contains a polymer obtained by reacting methyl and acrylic acid, the polymer exists as particles of the polymer in water, and the acrylic acid is contained in an amount of 3 to 20% by weight of the polymer particles. It is composed of

〔Effect of the invention〕

By configuring the present invention as described above, the binder is suspended in the paint for forming the pigment layer as polymer particles having a diameter larger than the diameter of the pores of the pigment. Since it does not penetrate into the sheet and can reliably bind pigment particles with a small amount, it has excellent ink absorption and coloring properties, the spread of ink spots on the sheet surface is small, and the roundness is excellent, and there is no peeling of pigment. Since the ink does not substantially stop, excellent effects such as no clogging of ink nozzles can be obtained.

In addition, since acrylic acid is inserted into the binder polymer, the water resistance of the binder is improved and
It causes soft aggregation with polyamide polyamine epichlorohydrin resin, which is a water resistance agent, and other cationic substances added to improve the water resistance of dyes, making the pigment layer more porous, resulting in improved ink absorption and coloring properties. is further improved.

The present invention will be explained in more detail below.

The support used in the present invention is usually made of paper, for example, non-sized, weak-sized, strong-sized paper such as high-quality paper, etc., but it can also be made of cloth, nonwoven fabric, synthetic paper, plastic film, etc. It's okay.

Pigments used in the present invention include known pigments, such as synthetic silica, synthetic calcium silicate, synthetic aluminum silicate, synthetic magnesium silicate, and other synthetic silicates, zeolite, magnesium hydroxide, potassium aluminate, Sodium aluminate, synthetic hydrotalcite, magnesium hydroxide, magnesium oxide, alumina, satin white, zinc oxide, diatomaceous earth, magnesium sulfate, clay, titanium oxide, barium sulfate, calcium sulfate, magnesium carbonate, heavy calcium carbonate, light Examples include white inorganic pigments such as calcium carbonate, talc, and aluminum hydroxide, and white organic pigments such as ion exchange resin powder, urea resin powder, and polystyrene resin powder. Pigments that exist in the form of secondary particles are preferred because they tend to exhibit the excellent properties of the binder described in detail below, but it is possible to use them satisfactorily even in the form of secondary particles. .

In the present invention, the luhainter used in combination with the pigment is produced from polyvinyl alcohol (PVA), acrylic acid, and methyl methacrylate. This PV
The molecular weight of A is generally 200 to 2000, and the degree of saponification is 40 to 90%, preferably 80 to 90%. The ratio of this PVA and methyl methacrylate is 95:5 to 10:
90, preferably 90:10-20:go, particularly preferably 70:30-30:go. If the amount of methyl methacrylate is less than the above lower limit, the coloring effect will be reduced, while if it is more than the upper limit, the binding force will be reduced. Further, acrylic acid is used in an amount of 3 to 20% by weight based on the total weight of the binder polymer particles. If it is less than 3% by weight, the effect of imparting water resistance disappears;
If it exceeds 0% by weight, the reaction between cations, which are waterproofing agents for the dye in the ink, and chemicals that cause crosslinking reactions with acrylic acid will be rapid, resulting in a decrease in pot life and a decrease in the fluidity of the paint. There are things.

When the polymer used as the binder is suspended in water, it is suspended in the water as particles having a diameter larger than the pore size of the pigment. Usually the diameter is 0.1 to 1 μm
That's about it. The polymerization method for obtaining such particles is as follows:
For example, predetermined amounts of PVA, metinope methacrylate, and acrylic acid are mixed and stirred, preferably maintained at 70 to 90°C, and a polymerization initiator such as ammonium persulfate or potassium persulfate is generally added at a rate of 0.05% based on the weight of the monomer.
Added at ~5%, preferably 0.2%, e.g. about 2-10
There is a method of obtaining a polymer by stirring for a period of time and then polymerizing, and then adjusting the pH to 3 to 9.

If there is a lot of heat generated during polymerization, monomers may be added dropwise one after another.The pH may be adjusted in advance before polymerization. The binder polymer produced in this way generally exists in water as particles consisting of a core part mainly composed of a copolymerized part of acrylic acid and methyl methacrylate, and a shell part mainly composed of a PVA part surrounding the core part. ,PVA
It is thought that the shell part acts as a protective colloid for the core part.

A paint for forming a pigment layer on a support is generally a mixture of water and a pigment such as silica. It is prepared by dispersing 8 turbidly and mixing with a polymer as a binder.

In this case, the binder may be used alone or in combination with other binders. Such other binders include known binders such as polyvinyl alcohol, polyvinyl alcohol derivatives such as acetoacetylated polyvinyl alcohol, starch, oxidized starch,
Starch derivatives such as cationic starch, cellulose derivatives such as methylcellulose, carboxymethylcellulose, and hydroxyethylcellulose, proteins such as casein, gelatin, and soybean protein, maleic anhydride resin, styrene-butadiene copolymer, melamine resin, urea resin, vinyl acetate resin , acrylic resin, and other synthetic resin adhesives are used.

Among them, it is possible to control the dot diameter to the desired size by mixing it with a binder that works to increase the dot diameter, such as acetoacetylated polyvinyl alcohol or polyvinylalconopevinyl alcohol-acrylamide-acrylic acid copolymer. Become.

Further, in order to improve water resistance, a water resistant agent such as polyamide polyamine epichlorohydrin resin may be added to the paint. The ratio is 1:10 or more, preferably 3:10 or more to the binder.

Furthermore, the coating material can contain a dye fixing agent, a disinfectant, a fluidity improver, a water retention agent, a fluorescent dye, a preservative, a surfactant, and the like. Further, the above-mentioned coating material can be applied to the support by various commonly used coating methods, such as bar, rod, air knife, blade, roll, curtain, gravure, spray, and other coaters. The coating amount of the paint is 2 to 30 g/m' in terms of solid content, preferably 4 to 30 g/m.
15 g/m'.

The coating layer thus obtained is dried and, if necessary, subjected to a calender treatment or the like.

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to these examples. Note that parts and percentages shown in Examples are based on weight.

〔Example〕

Production Examples 1 to 10 A lipolymer (PVA/MM/Δa polymer) consisting of PVA, methyl meccrylate (MM), and acrylic acid (Δa) used as a binder is mixed in the ratio shown in Table 1 below. The mixture was maintained at 80° C. with stirring, 0.2% ammonium persulfate was added as a polymerization initiator, and stirring was continued for about 4 hours to polymerize, and the pH was adjusted to 7 to complete the synthesis.

The molecular weight of the PVA used here was 600, the degree of saponification was 88%, and the PVA was used in a 20% solution. The PVA/MM/Aa polymer thus obtained was used as a binder with polymer numbers 1 to 10.

In addition, Table 1 also shows the size of the diameter of suspended particles of PVA/MM/Aa polymer in water.

Table-1 18010100,6 26030100,6 3673030,6 43565100,6 5356050,7 62070100,6 7207730,5 g 30 67 3 0.
79 35 45 20 0.
610 35 40 25 0
．． 6 Examples 1 to 9 Fine powder silica (manufactured by Tokuyama Soda Co., Ltd.) Pore diameter 0. OO5～0
．． 04μ, average particle size 4.5μ) was dispersed in 400 parts of water, 257 parts of a 15% solution of acetoacetylated PVA (manufactured by Nippon Gosei Co., Ltd.), and each binder of polymer numbers 1 to 9 in Table 1 were added. After adding 193 parts and 77 parts of 30% polyamide polyamine epichlorohydrin resin (manufactured by Showa Denko Co., Ltd.) and stirring, 8 parts of a cationic dye fixing agent (manufactured by Nippon Shokubai Kagaku Co., Ltd.) was added to the pigment, and the pigment/binder (P /B) A paint with a ratio of 50150 and a solid content of 19.5% was prepared, applied to sizeless paper using a Mayer bar to a solid content of 5 g/m2, dried, and then lightly passed through a super calender to form an inkjet recording sheet. Formed and used PVΔ
Examples 1 to 9 correspond to the polymer number of the /MM/Aa polymer.

In addition, as a method for measuring the pore size of pigments, C
The measurement was carried out using Arlo Erba model 220, and the average particle size was measured using Coulter Counter Model TΔIJ ((:allo Elect
(manufactured by ronics).

Example 10 An inkjet recording sheet was prepared in the same manner as in Example 4, except that acetoacetylated PVA was not used.

, PVA (Example 11), cationized starch (Example 1)
2) or oxidized starch (Example 13).
Example 1 was repeated to prepare an inkjet recording sheet.

Comparative Example 1 Without using the PVA/MM/Aa polymer of the present invention, 15
An inkjet recording sheet was prepared according to Example 1, except that only % acetoacetylated PVA was used (pigment/binder (P/B) ratio = 50150).

Comparative Example 2 Without using the PVA/MM/Aa polymer of the present invention,
PVA117 (manufactured by Kuraray Corporation) (degree of polymerization 1700, degree of saponification 99%, aqueous solution), PVA1'05 (manufactured by Kuraray Corporation) (degree of polymerization 500, degree of saponification 99%) in a ratio of 1:3. Example 1 was repeated except that:

Comparative Example 3 Without using the PVA/MM/Δa polymer of the present invention,
Example 1 was repeated with the exception of 1 using cationized starch (in aqueous solution) (P/B=50150).

Comparative Example 4 Without using the PVA/MM/Aa polymer of the present invention,
Using oxidized starch (in aqueous solution) (P/B=501
Example 1 was repeated with the exception of 50).

Comparative Example 5 Using a vinyl acetate emulsion without using the PVA/MM/Aa polymer of the present invention (P/B=501
Example 1 was repeated except for 50).

Comparative Example 6 Without using the PVΔ/MM/Aa polymer of the present invention,
Using polymer number 10 PVA/MM/Δa polymer (acrylic acid 25%) (acetoacetylated PV
Example 1 was repeated except for A/Polymer No. 1O-50150).

Test Method The inkjet recording sheets obtained in the above Examples or Comparative Examples were subjected to the following tests.

Test method 1, dot diameter: Canon inkjet printer A-
Printed with 1210 black ink and measured with 100x magnification.

2. Dot density: Canon inkjet printer-A
Regarding the dots printed with -1210 black ink, the density of each dot was measured using a Sakura Microdensitometer Model PDM-5.

3. Coating layer strength: Measured by J 15K-5400 (pencil scratch test described in 6, 14).

4. Color quality: Sanyo inkjet printer CJ-
Yellow (Y), magenta (M), cyan (C), and black (B) were printed at 5700 (12 dots/mm) and measured using a Macbeth densitometer RD-918 model.

5. Water resistance of coating layer: When soaked in water and rubbed with fingers, the coating layer was rated ○ if it did not peel off, △ if it peeled off slightly, and × if it peeled off.

6. Ink absorption: Sharp inkjet printer 1
0-700 yellow, mine ink, cyan, and black inks were simultaneously jetted onto the same spot, and after 1 second, the paper was rubbed with a paper press plate. Those with no stains on the white paper by ink were marked as ○, and those that were slightly smeared were marked as △. .

Results The results of the above tests performed on the inkjet recording sheets obtained in Examples 1 to 13 and Comparative Examples 1 to 6 are listed in Table 2 below.

From Table 2, in Examples 1 to 13, the dot diameter was 23
0 to 240μ, while in Comparative Examples 1 to 4 it was 250 to 240μ.
The dot diameter is 270μ, and in the case of the present invention, the dot diameter is small. In addition, the strength, color properties, ink absorption properties of the coating layer,
The dot density, water resistance, etc. were generally superior to Comparative Examples 1 to 4. In addition, although the water resistance was evaluated as Δ in Examples 3.7 and 8, there was no particular disadvantage in practical use. Furthermore, when vinyl acetate was used as a binder (Comparative Example 5) and when PVA/MM/Aa polymer containing 25% acrylic acid was used (Comparative Example 6),
), the paint agglomerated when the polyamide polyamine epichlorohydrin resin and cationic dye fixing agent were added, making it difficult to apply.

On the other hand, from Examples 1.2 and 4, the ratio of PVA:MM is preferably 80:1.0, more preferably 70:
It can be seen that when the number of MM is higher than that of 30, the color property and dot density are improved.

Example 14 Finely powdered silica with a smaller particle size than the pigment used in Example 4 (manufactured by Tokuyama Soda Co., Ltd., pore size 0.005-0.04μ)
Example 4 was repeated except that a particle size of 2.3 μm, average particle size 2.3 μm) was used. The inkjet recording sheet obtained in Example 14 was subjected to each of the above tests, and the results are shown in the table below.
Shown in 3.

Compared to Example 4, the dot diameter was even smaller at 220 μm, providing an inkjet recording paper with excellent coating layer water resistance, ink absorbency, and coating layer strength.

Example 15 An aqueous chiller with a solid content concentration of 40% was prepared using 100 parts of synthetic aluminum silicate (manufactured by Kyowa Chemical Industry Co., Ltd.) and 5 parts of polyvinyl alcohol (Gosenal T-350, manufactured by Nihon Gosei Kagaku Kogyo Co., Ltd.) as a dispersant. Two parts of heavy magnesium carbonate was used as a coagulation aid, and the average particle diameter was adjusted to 5 μm using a sand grinder. (Average pore size 0.01-0.3
μm). Polymer No. 4 was added as a binder to this slurry, and the above PVA/M
It was added in an amount of 30% of the weight of the M/Aa polymer to give a Pigment/Bingu (P/B) -8/2 and was applied to a fine paper with a sizing degree of 15 seconds at a solid content of 15 g/m'. The mixture was coated and dried, passed through a super calender, and an inkjet recording sheet was obtained, which was subjected to each of the above-mentioned tests. The results are shown in Table 4 below.

Comparative Examples 7 to 10 In Example 15, P■Δ/M of polymer No. 4
In place of M/Aa polymer, oxidized starch (manufactured by Tamago National Co., Ltd., Tamago Ace Δ) was used (Comparative Example 7), cationic starch was used (Comparative Example 3), PVA117
Example 15 was repeated, except that a mixture containing PVA 105 and PVA 105 in a ratio of 1:3 was used (Comparative Example 9) and acetoacetylated PVA was used (Comparative Example 10). The inkjet recording sheet obtained here was subjected to each of the above tests. The results are also listed in Table 4 below.

All of the oxidized starches used here were used in the form of aqueous solutions.

Table-4 Dot diameter Dot Coating layer Coating layer (μ) Concentration Water resistance Strength example 15 250 0.
90 0 2H Comparative Example 7 300 0.78
×HB Comparative Example 8 300 0.8Q
x B Comparative Example 9 35(] Q, 6
8 X H Comparative Example 10 350 0
．． 8. In OΔH Example 15, the dot diameter of the inkjet recording sheet was small, and the dot density, water resistance of the coating layer, and surface strength were superior to those of the comparative example.

Example 16 Fine powder silica (manufactured by Mizusawa Chemical Co., Ltd., pore size 0.005-0.0
4μ, average particle size 3.8μ) was dispersed in 400 parts of water, 226 parts of 15% acetoacetylated PVA, Poly? -No, 4 P■Δ/MM/Δa Polymer 17
0 parts, 30% polyamide polyamine epichlorohydrin resin 40 parts were added, and after stirring, 8 parts of cationic dye fixing agent (manufactured by Nippon Shokubai Kagaku Co., Ltd.) and 80 parts of water were added to the pigment to give a solid content of 18%, A slurry with a P/B ratio of 55/45 was obtained. This slurry was coated on a high-quality paper with a sizing degree of 15 seconds at a solid content of 665 g/m', dried, and then lightly passed through a supercalender to obtain inkjet recording paper, which was used in each of the above tests. The results are shown in Table 5 below.

Examples 17-19 In Example 16, 15% acetoacetylated PVA and poly? - In place of the PVA/MM/Aa polymer in No. 4, only the PVΔ/MM/Δa polymer in Polymer No. 5 was used (Example 17); - No. 5 PVA/MM/Aa polymer was used (Example 18), and oxidized starch and polymer No. 5 P■Δ/MM/Aa polymer were used (Example 19). , Example 16 was repeated to obtain inkjet recording paper, which was subjected to the above test,
The results are shown in Table 5 below.

When only acetoacetylated PVA was used without using MM/Aa polymer (Comparative Example 11), MM/Δ to PV8 of acetoacetylated PVA and polymer No. 4
a When oxidized starch is used instead of polymer (Comparative Example 1
2) When using cationized starch (Comparative Example 13),
Example 16 except when a mixture containing PVA117 and PVA105 at a ratio of 1:3 was used (Comparative Example 14).
repeated. The inkjet recording papers obtained in these comparative examples were subjected to each of the above tests, and the results are shown in Table 5 below. Note that all other binders used here, such as acetoacetylated PVA, were used in the form of aqueous solutions.

Table-5 Dot diameter Dot Coating layer (μ) a
Degree Water resistance Strength example 16 2' 20
1.00 0 2H Example 17 220
0.97 0 2H Example 18 220 0
．． 97 0 2H Example 19 220 0
．． 97 0 2H Comparative Example 11 260 0
．． 99 △H Comparative Example 12 230 0
．． 9'3 X B Comparative Example 13 230
0.93 x 4B comparative example 14 25
0 0.93 X 3B Example 16~
It can be seen that No. 19 is a well-balanced inkjet recording paper with a small dot diameter and overall excellent dot density, coating layer water resistance, and coating layer strength.

〔Effect of the invention〕

According to the present invention having the above configuration, an inkjet recording sheet having excellent ink absorbency, color development, and water resistance, as well as excellent ink spotting properties and roundness on the recording sheet can be obtained.

Claims (3)

[Claims] (1) In an inkjet recording sheet in which a coating layer containing a binder and a pigment is provided on at least one surface of a support, the binder is a polymer obtained by reacting polyvinyl alcohol, methyl methacrylate, and acrylic acid. an inkjet recording sheet, characterized in that the polymer exists as particles of the polymer in water, and the acrylic acid is contained in an amount of 3 to 20% by weight of the polymer particles. (2) The inkjet recording sheet according to claim (1), wherein the ratio of the polyvinyl alcohol to the methyl methacrylate is 95:5 to 10:90. (3) The inkjet recording sheet according to claim (2), which contains a polyamide polyamine epichlorohydrin resin as a waterproofing agent for the acrylic acid.