JP2002161495A - Sizing agent and chart paper using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a chart paper with the spreading of ink dots formed by ink droplets prevented, thus affording blur-free high-quality images despite being inexpensive. SOLUTION: This chart paper is obtained by subjecting the original paper to surface sizing with a sizing agent comprising a compound made by neutralizing with basic inorganic salt fine powder an ink fixing polymer having anionic group and cationic group with the affinity for ink-jet printer ink. The chart paper thus obtained is prevented from ink blurring since the ink fixing polymer stays in the vicinity of the surface of the paper without penetrating into the paper layer as a result of binding to the basic inorganic salt fine powder via the anionic group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sizing agent for providing plain paper, which is inexpensive and can obtain high-quality images without bleeding, and a recording paper using the same.

[0002]

2. Description of the Related Art Ink jet printers are widely used not only as output devices such as personal computers but also as means for printing on media of various materials. Currently widely used as inks for inkjet printers are those obtained by dissolving an organic dye in water or another solvent.
Azo dyes, anthraquinone dyes, indigo dyes, phthalocyanine dyes, carbonium ion dyes, nitro dyes,
And quinoline dyes and naphthoquinone dyes.

[0003] The above-mentioned ink is developed vividly,
In order to prevent ink bleeding, the inkjet printer is provided with an ink receiving layer made of a highly water-absorbent resin on the surface as disclosed in, for example, JP-A-59-35977 and JP-A-1-135682. So-called dedicated coated papers have been used. However, the coated paper has a problem in that the production cost is higher than that of plain paper due to the special coating, and the texture of plain paper is lacking. Also,
It is not preferable from the viewpoint of waste disposal, for example, a large amount of ash is generated during incineration. Therefore, there is a need for low-cost, versatile plain paper suitable for inkjet printers.

[0004] However, plain paper, when ink is absorbed into the paper layer, bleeds along the fibers of the paper, so that the dots bleed excessively, and the periphery of the dots becomes jagged or blurred. There is a problem that so-called feathering occurs and it is difficult to obtain clear characters and images.

To cope with such a problem, Japanese Patent Application Laid-Open No. Hei 10-119425 discloses a coating composition comprising a cationic polymer containing a polymer having a skeleton of a (meth) acrylamidoalkyl quaternary ammonium salt having a benzyl group as an active ingredient and a water-soluble resin. An ink jet recording plain paper coated with a working liquid is disclosed. However, since the ink fixing polymer easily penetrates into the inside of the paper layer, only a part of the ink fixing polymer stays on the surface, and the image clarity and ink bleeding property are not sufficient. Therefore, further improvement in quality is desired.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a recording paper which is inexpensive, has excellent color developability, suppresses the spread of ink dots formed by ink droplets, and provides a high quality image without bleeding. That is.

[0007]

Means for Solving the Problems As a result of intensive studies in view of the above-mentioned objects, the present inventors have found that an ink fixing polymer having an anionic group and a cationic group having an affinity for an ink for an ink jet printer is converted into a basic inorganic salt. The present inventors have found that by performing surface sizing using a sizing agent containing a compound obtained by neutralizing with a fine powder, the color developing property and the ink bleeding property are improved, and arrived at the present invention.

That is, the sizing agent of the present invention is characterized in that the ink fixing polymer is bonded to the basic inorganic salt fine powder. Since the anionic group of the ink fixing polymer becomes a bonding group and bonds to the basic inorganic salt fine powder, the ink fixing polymer does not penetrate into the paper layer but stays near the surface, so that the color developing property and the ink bleeding property are improved. .

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the sizing agent and recording paper of the present invention will be described in detail.

[A] Sizing Agent The sizing agent of the present invention is obtained by neutralizing an ink fixing polymer having an anionic group and a cationic group having affinity for an ink for an ink jet printer with a basic inorganic salt fine powder. Contains compounds. Hereinafter, the ink fixing polymer and the basic inorganic salt fine powder will be described in detail.

(1) Ink fixing polymer The ink fixing polymer used in the present invention comprises a cationic group for fixing an ink for an ink jet printer,
Having an anionic group for binding to the basic inorganic salt fine powder. While the colorant contained in the ink penetrates into the inside of the paper layer in the recording paper, it associates with the cationic group of the ink fixing polymer existing near the surface by ionic interaction and instantaneously separates from the solution phase. Therefore, the fixing property and the coloring property of the ink can be further improved.

The ink fixing polymer used in the present invention has an anionic group. The anionic group binds the ink-fixing polymer to the basic inorganic salt fine powder, making it difficult for the ink-fixing polymer to penetrate into the paper layer, resulting in a high-quality image without bleeding compared to conventional cationic polymers. Can be

The ink fixing polymer used in the present invention is:
(i) a monomer containing a cationic group having an affinity for an ink for an ink jet printer, (ii) a monomer containing an anionic group, and (iii) polymerization of a hydrophilic acrylic monomer, vinyl monomer or allylic monomer. Things. Hereinafter, each monomer will be described in detail.

(I) Monomer containing cationic group having affinity with ink for ink jet printer Monomer (i) contributes to fixation of dye. The cationic group is not particularly limited as long as it is a cationic group having an affinity for the ink for an ink jet printer, but a quaternary amino group is preferable. Here, the “quaternary amino group” is represented by the following general formula

Embedded image (However, R _{1 to} R ₅ are groups composed of an alkyl group having 1 to 7 carbon atoms, an aryl group, a benzyl group, or a combination thereof, and these groups may be the same or different; X ^- is a counter ion such as a halogen group.).

A quaternary amino group can be obtained by adding an alkyl halide or the like to an alkylamino group. Examples of specific monomers for deriving the structural unit (i) include N, N
-Dimethylaminoethyl (meth) acrylate / methyl chloride quaternary, N, N-dimethylaminopropyl (meth) acrylamide / methyl chloride quaternary, N, N-
Diallylmethylamine / methyl chloride quaternary compound;

(Ii) Monomer Containing Anion Group The monomer (ii) contributes to binding to the basic inorganic salt fine powder. Examples of the anionic group include a sulfonic acid group, an acidic phosphoric acid ester group, and an acidic sulfuric acid ester group. Of these, a sulfonic acid group and an acidic phosphoric acid ester group are particularly preferable.

Preferred examples of the monomer from which the structural unit (ii) is derived include acrylamide 2-methylpropanesulfonic acid, 2-acryloyloxyethyl acid phosphate, and mono (2-methacryloyloxyethyl) acid phosphate.

(Iii) Structural unit derived from a hydrophilic acrylic monomer, vinyl monomer or allylic monomer Monomer (iii) has an action of rapidly absorbing water and a dye dissolved or suspended therein. . Among these,
In particular, a hydrophilic acrylic monomer is preferable. 1. aliphatic carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, maleic anhydride, fumaric anhydride, and itaconic anhydride, or anhydrides thereof; (Meth) acrylamide, dimethyl (meth) acrylamide, diethyl (meth) acrylamide, (meth)
2. acrylamides such as acryloylmorpholine, N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethylaminopropyl (meth) acrylamide; It is preferably composed of vinylpyrrolidones such as N-vinyl-2-pyrrolidone.

(Iv) Ratio of Each Monomer The weight ratio of the above monomers (i) to (iii) is such that (i) is 10 to 99% by weight, (ii) is 1 to 30% by weight, and (iii) ) Is 0 to 8
0% by weight, especially (i) is 50 to 99% by weight.
(Ii) is preferably 1 to 5% by weight, and (iii) is preferably 0 to 49% by weight. (Ii) / (i) = 1 / 99-3 / 1
Is preferred. The ink fixing polymer used in the present invention is obtained by dissolving the monomers (i) to (iii) and a polymerization initiator in an appropriate solvent and polymerizing the same. The weight average molecular weight of the ink fixing polymer used in the present invention is Mw = 2,000 to 200,000.
Is preferable, and Mw = 4,000 to 40,000 is particularly preferable. Mw
If it is less than 2,000, the dots are excessively blurred, which is not preferable.
On the other hand, if Mw exceeds 200,000, the viscosity is too high, and coating suitability is undesirably reduced.

(2) Basic Inorganic Salt Fine Powder The basic inorganic salt fine powder is not particularly limited as long as it is a basic inorganic salt fine powder capable of essentially neutralizing acidic substances. Specific examples of preferable basic inorganic salt fine powder include carbonate, phosphate, sulfate, and aluminate of Mg, Ca, or Ba.

The particle size of the basic inorganic salt fine powder is generally from nm to μ.
Although it is on the order of m, the average particle diameter of the primary particles obtained from the diameter when the projected area is converted into a circle is preferably from 10 to 100 nm, more preferably from 10 to 50 nm. The average particle size of the semiconductor fine particles (secondary particles) in the dispersion is 0.1 to 100 μm.
Is preferably, and more preferably 0.1 to 10 μm. If the average particle size of the secondary particles is 0.1 μm or less, the ink fixing polymer, which is an effective component of the sizing agent, permeates the paper layer, which is not preferable. On the other hand, if the average particle size is 100 μm or more, unevenness on the surface of the recording paper becomes remarkable, and the printing characteristics are rather deteriorated.

(3) Other Components In the sizing agent of the present invention, components other than the ink fixing polymer and the fine powder of the basic inorganic salt can be added as long as the effects of the present invention are not significantly impaired. Other components include binder resin (water-soluble resin, resin emulsion, etc.), fine powder other than basic inorganic salt fine powder (alumina powder, silica powder, natural inorganic powder, etc.), surfactant, pH adjuster, preservative And additives such as antioxidants.

Examples of the water-soluble resin include starch, polyacrylamide, polyvinylpyrrolidone, water-soluble cellulose (carboxymethylcellulose, hydroxymethylcellulose, hydroxypropylcellulose, etc.), polyvinyl methyl ether, polyethylene oxide, polyvinyl alcohol and the like.

Examples of the surfactant include higher alcohol ethylene oxide adduct, alkylphenol ethylene oxide adduct, fatty acid ethylene oxide adduct, polyhydric alcohol fatty acid ester ethylene oxide adduct, higher alkylamine ethylene oxide adduct, fatty acid amide ethylene oxide adduct. Additives, ethylene oxide adducts of fats and oils, polypropylene glycol ethylene oxide adducts, fatty acid esters of glycerol, fatty acid esters of pentaerythritol, fatty acid esters of sorbitol and sorbitan, fatty acid esters of sucrose, alkyl ethers of polyhydric alcohols, alkanolamines Fatty acid amides, sodium alkylbenzene sulfonates, sodium alkyl sulfates, trimethylalkylamines Chloride, and the like, but is not necessarily limited thereto. The addition of a surfactant increases image density and improves bleeding for some inks.

(4) Method for Preparing a Sizing Agent The sizing agent of the present invention can be obtained by neutralizing the ink fixing polymer with fine powder of a basic inorganic salt.

First, the ink fixing polymer is diluted with a solvent such as water to obtain a concentration suitable for sizing. Preferred concentrations are from 5 to 30% by weight (dry weight), particularly preferred from 10 to 20% by weight. The ink fixing polymer is bonded to the basic inorganic salt fine powder by adding and neutralizing the basic inorganic salt fine powder thereto. The pH of the aqueous solution of the ink fixing polymer is preferably adjusted to 5 to 9 by the neutralization and the addition of other components, and particularly preferably 6 to 8.

[B] Recording Paper The recording paper of the present invention is obtained by applying or impregnating the sizing agent of the present invention in a base paper or a paper machine.
By sizing, the ink fixing polymer bonded to the basic inorganic salt fine powder is fixed on the surface of the stock, so that the occurrence of feathering can be suppressed. The ink of the ink jet printer associates with the ink fixing polymer near the surface of the recording paper by ionic interaction and instantaneously separates from the solution phase, so that the fixing property and the color developing property of the ink are improved.

The base paper used in the present invention is mainly made of a chemical pulp represented by LBKP, NBKP and the like and a filler, and is further made by an ordinary method using an inner surface sizing agent and a papermaking aid as required. As the pulp material to be used, mechanical pulp or waste paper recycled pulp may be used in combination, or may be mainly composed of these. Examples of the filler include calcium carbonate, kaolin, talc, titanium dioxide and the like.

After the above base paper is made or in a paper machine,
The sizing agent of the present invention is applied or impregnated so as to have a solid content of 1 to 20 g / m ² , preferably 3 to 10 g / m ² .

The recording paper sized using the sizing agent of the present invention has a water extraction pH of 5 to 9, more preferably 6 or less.
~ 8. Water extraction pH is JIS-P-81
The pH of the extract was measured in accordance with JIS-Z-8802 when about 1.0 g of the test piece specified in 33 was immersed in 70 ml of distilled water.

The recording paper of the present invention does not involve a significant change in the surface shape and physical characteristics other than the recording characteristics even when compared with the conventional neutral PPC paper. Applicable to both types of paper.

[0032]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Examples 1 to 5 The monomers shown in Table 1 were polymerized to synthesize ink fixing polymers. To a 6 wt% aqueous solution (solid basis) of this ink fixing polymer, 20 g / L of synthetic magnesium silicate fine powder (manufactured by Kyowa Chemical Industry Co., Ltd.) with an average particle size of 6.2 μm and 60 g / L of oxidized starch are added. Then, a sizing agent having a pH of 5.7 was prepared.

Table 1 Monomer weight ratio of ink fixing polymer (numerical values in parentheses are parts by weight) Cationic monomer anionic monomer and other monomer viscosities (30% mPa · S, 20 ° C.) Example 1 DAC (95) AMPS (5 -4000 Example 2 DAC (90) AMPS (10)-6000 Example 3 DAC (57) AMPS (3) AAM (40) 5000 Example 4 DAC (57) AMPS (3) VPN (40) 2000 Example 5 DAC (57) AMPS (3) DMAA (40) 1000 (Note) DAC: N, N-dimethylaminoethyl acrylate / methyl chloride quaternary compound AMPS: acrylamide 2-methylpropanesulfonic acid AAM: acrylamide VPN: N- Vinylpyrrolidone DMAA: dimethylacrylamide

This sizing agent is applied to base paper having a basis weight of 70 g / m ² ,
The composition was applied with a squeeze roll to about 5 g / m ² (weight of solid content), and dried in an oven at 120 ° C. for 5 minutes to prepare recording papers of Examples 1 to 5.

Examples 6 to 10 A 5 wt% aqueous solution (based on solid content) of an ink fixing polymer having the composition shown in Table 2 was mixed with synthetic magnesium silicate fine powder having an average particle size of 52 μm (“Kyoward 600”, Kyowa Chemical Industry Co., Ltd.).
25 g / L and oxidized starch 50 g / L, pH 6.2
Was prepared.

Table 2 Weight ratio of monomers of ink fixing polymer (numerical values in parentheses are parts by weight) Cationic monomer anionic monomer and other monomer viscosities (15% mPa · S, 20 ° C.) Example 6 DMC (95) PM (5 -3000 Example 7 DMC (90) PM (10)-5000 Example 8 DMC (77) PM (3) HPMA (20) 2000 Example 9 DMC (77) PM (3) DMAA (20) 4000 Example 10 DMC (77) PM (3) M90G (20) 6000 (Note) DMC: N, N-dimethylaminoethyl acrylate / methyl chloride quaternary compound PM: Mono (2-methacryloyloxyethyl) acid phosphate “Light ester PM "Kyoeisha Oil & Fat Co., Ltd. HPMA: hydroxypropyl methacrylate, Osaka Organic Chemical Industry Co., Ltd. DMAA: dimethylacrylamide, Kojin Co., Ltd. M90G: methoxypolyethylene glycol monomethacrylate" NK Ester M90G "Shin-Nakamura Chemical Co., Ltd. ) Made

This sizing agent is applied to base paper having a basis weight of 70 g / m ² ,
Coating was performed with a squeeze roll to a weight of about 5 g / m ² (weight of solid content), and dried in an oven at 120 ° C. for 5 minutes to prepare recording papers of Examples 6 to 10.

Comparative Example 1 A sizing agent was prepared by dissolving poly (N, N-dimethylaminoethyl acrylate / methyl chloride quaternized product) in water so as to have a solid content of 10 wt%. This sizing agent is applied to a base paper having a basis weight of 70 g / m ² by using a squeeze roll to about 5 g / m ^2.
(Solid content weight), and dried in an oven at 120 ° C. for 5 minutes to prepare a recording sheet of Comparative Example 1.

The recording papers of Examples 1 to 10 and Comparative Example 1 thus obtained were subjected to full-color printing using an ink jet printer (“Color Bubble Jet Printer BJF-600”, manufactured by Canon Inc.). Did.
The printed image was evaluated for the recorded image.
Table 2 shows the results.

[0041] Table 3 evaluation results ink bleeding ^{(Note 1)} the color of the ink ^{(Note 2)} red yellow blue black Example 1 ○ ○ ○ ○ ○ Example 2 ○ ○ ○ ○ ○ Example 3 ○ ○ ○ ○ ○ implementation Example 4 ○ ○ ○ ○ ○ Example 5 ○ ○ ○ ○ ○ Example 6 ○ ○ ○ ○ ○ Example 7 ○ ○ ○ ○ ○ Example 8 ○ ○ ○ ○ ○ Example 9 ○ ○ ○ ○ ○ Example 10 ○ ○ ○ ○ ○ Comparative Example 1 △ × (thin) ○ ○ × (brown) (Note 1) Evaluation method of ink bleeding In addition to solid printing of recording paper in yellow, black stripes were further printed. A magnified copy of the border was taken (1.988x) and bleeding of the black ink into the yellow area was observed. Evaluation criteria: Bleed 0.3 mm or less Bleed 0.3 to 1.0 mm × Bleed 1.0 mm or more (Note 2) Color development was visually observed.

As is clear from Table 3, Examples 1 to 10 were clearly brighter in three primary colors and black and less bleeding than Comparative Example 1.

[0043]

As described in detail above, low-cost and high-performance plain paper can be obtained by using the sizing agent of the present invention. The recording paper of the present invention does not involve a significant change in the surface shape and physical characteristics unlike the special coated paper, and thus can be applied to both toner transfer paper for electrophotographic recording and ink jet recording paper.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H086 BA21 BA37 BA41 4L055 AG05 AG06 AG08 AG10 AG23 AG48 AG64 AG65 AG71 AG72 AG73 AG89 AG98 AH02 AH13 AH37 AH50 AJ04 BE08 EA16 EA31 FA11 GA09 GA11

Claims (8)

[Claims] 1. A sizing agent comprising a compound obtained by neutralizing an ink fixing polymer having an anionic group and a cationic group having an affinity for an ink for an ink jet printer with fine powder of a basic inorganic salt. . 2. The sizing agent according to claim 1, wherein the ink fixing polymer is an acrylic polymer, a vinyl polymer or an allylic polymer. 3. The sizing agent according to claim 1, wherein the cationic group is a quaternary amino group. 4. The sizing agent according to claim 1, wherein the anion group is a sulfonic acid group or an acidic phosphoric ester group. 5. The sizing agent according to claim 1, wherein the basic inorganic salt fine powder has an average particle size of 0.1.
A sizing agent, which is a secondary particle having a size of about 100 μm. 6. The sizing agent according to any one of claims 1 to 5, wherein the basic inorganic salt fine powder is Mg, Ca, or
A sizing agent characterized by being Ba carbonate, phosphate, sulfate or aluminate. 7. The sizing agent according to claim 1, wherein the sizing agent is adjusted to pH 5 to 9. 8. A recording paper mainly composed of fibrous pulp and filler, characterized in that the sizing agent according to claim 1 is subjected to surface sizing.