JP2000159927A - Filler for ink-jet recording paper and recording paper using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a filler having excellent coating workability as an ink-jet recording paper, capable of forming an image having high printing concentration and clarity. SOLUTION: This filler comprises amorphous silica and has >=15 μm and <30 μm average particle diameter, <=400 μS/cm electrical conductivity, >=260 m2/g and <700 m2/g BET specific surface area and >=100 ml/100 g and <100 ml/100 g oil absorption. This ink-jet recording paper has the filler and a coated layer obtained by mixing water with a binder to give a coating solution, coating an ink-jet recording surface with the coating solution and drying.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel filler used for a recording layer of an ink jet recording paper and a recording paper using the same.

[0002]

2. Description of the Related Art Printing by an ink-jet recording system has advantages such as low noise, high-speed recording, and easy multi-color printing, and has been applied to various printers and facsimile machines. As recording paper used for this purpose, it is difficult to use ordinary high-quality paper or coated paper in terms of performance, and the absorption speed of ink attached to the paper is fast, and the spread of ink attached to the paper Characteristics such as low bleeding are required.

That is, recording paper having such characteristics is
: The roundness of the ink dots is maintained;: The spread of the ink dots is prevented;: The print density is increased;
Various characteristics are required, and by satisfying these characteristics, a clear printed image with high print density can be obtained.

Conventionally, as a method for imparting these characteristics to the surface of a paper substrate, a coating liquid obtained by mixing a liquid absorbing inorganic solid substance, a binder and water is coated on a base paper, dried and coated. Methods for forming layers are known.
As the above-mentioned inorganic solid substance having a liquid absorbing property, silica is known as the most typical one, and amorphous silica having various physical properties is frequently used.

[0005] This amorphous silica is generally classified into dry silica (silicic anhydride) obtained by a dry production method and wet silica (hydrous silicate) obtained by a wet production method. Is classified into a precipitated silica and a gel silica according to the production method.

[0006] By adjusting the manufacturing conditions, the physical properties of silica, such as specific surface area, porous structure, and surface condition, are variously controlled, and these are used in accordance with the intended use. For example, in Japanese Patent Publication No. 5-71394,
Amorphous silica having an average particle size of 2.5 to 3.5 μm, pores within a range of 60 to 130 ° measured by a nitrogen method in a range of 60 to 130 ° or more of all pores, and an oil absorption of 250 ml / 100 g or more. It has been proposed to use as a filler for ink jet recording paper.

[0007]

However, a filler having a relatively small particle size, a large oil absorption and a good liquid absorbing property is required to have the ink rapidly deposited in the coat layer when the ink is dropped on the coated surface. Although it is effective in that it can be absorbed to prevent bleeding or blurring of the ink dots, it has a drawback that it is difficult to obtain a sufficient print density.

[0008] In the production of ink jet recording paper, the viscosity of a coating liquid obtained by mixing the above-mentioned filler, binder and water is an important factor. That is, not only is the coating work difficult when the viscosity of the coating liquid is high, but also causes coating unevenness and cracks.To avoid this situation, for example, if the concentration of the filler in the coating liquid is reduced, In addition, since the ratio of binder and water is increased, problems such as an increase in the cost of drying the coating liquid and a decrease in productivity are caused. Furthermore, a coat layer applied under the condition that the filler concentration is low has a drawback of causing a problem that sufficient performance as an inkjet recording paper cannot be exhibited.

The inventors of the present invention have conducted intensive studies to solve the above problems, and have accomplished the present invention. The purpose of the present invention is to provide a novel ink jet recording paper having a recording layer (coat layer). And a recording paper coated with the recording layer.

[0010]

SUMMARY OF THE INVENTION The present inventor has made it possible to obtain good coating workability by using amorphous silica having a specific average particle size, electric conductivity, specific surface area, and oil absorption as a filler. The present invention has been found to be capable of forming a clear image having a high print density and high printing density.

That is, the invention of the filler for ink jet recording paper according to claim 1 of the present invention has an average particle diameter of 15 to 30 μm.
Less than 400 μS / cm, a BET specific surface area of 260 m ² / g or more and less than 700 m ² / g, and an oil absorption of 100 ml / 100 g or more of 400 ml / 10
It is characterized by being composed of less than 0 g of amorphous silica. Further, the invention of the ink jet recording paper according to claim 2 of the present application is characterized in that it has a coat layer formed by applying a coating liquid obtained by mixing the above-mentioned filler, water and a binder onto the ink jet recording surface and drying it. And

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

In the present invention, the amorphous silica needs to have an average particle size of 15 μm or more and less than 30 μm, and preferably 16 μm or more and less than 28 μm. When the average particle size is smaller than the above range, when adjusting the coating liquid, the viscosity of the coating liquid increases when the filler is dispersed in water or an aqueous binder solution, and the filler concentration of the coating liquid is sufficiently increased. It is difficult to increase the print density, and a better print density cannot be obtained. Conversely, when the average particle size is larger than the above range, the surface smoothness of the obtained coat layer is undesirably reduced.

The electric conductivity needs to be 400 μS / cm or less, and preferably 200 μS / cm or less. As described above, the viscosity of the coating liquid largely depends on the average particle diameter of the amorphous silica. In the case of the same particle diameter, the effect of the coating liquid viscosity is affected by the electric conductivity, although the reason is not clear. It becomes important. This electric conductivity represents the total amount of water-soluble impurities contained in the silica, and it is presumed that the interaction between the silica particles changes depending on the amount of the water-soluble impurities, thereby affecting the viscosity of the coating solution. .

The BET specific surface area needs to be 260 m ² / g or more and less than 700 m ² / g, and preferably 400 m ² / g or more and less than 600 m ² / g. When silica having a BET specific surface area outside the above range is used, although the reason is not clear, a sharp decrease in print density is observed and a clear printed image cannot be provided.

The amount of oil absorption is 4 at 100 ml / 100 g or more.
It is necessary to be less than 00 ml / 100 g, preferably 130 ml / 100 g or more and 300 ml / 100 g
g. If the oil absorption is smaller than the above range,
Ink absorption is inferior, causing bleeding. Conversely, if the oil absorption is larger than the above range, the viscosity when applying the coating liquid becomes too high, and good coating workability cannot be obtained.

The amorphous silica of the present invention as described above is not particularly limited, but can be typically produced by the following method. For example, JP-A-7-1876
No. 45, SiO ₂ 10-2
9 wt%, sodium silicate having a molar ratio of 2.95 to 3.4, and sulfuric acid 35 to 45 wt% were mixed with a mixing nozzle to adjust the pH.
A method in which a silica hydrosol is obtained by mixing at a temperature of 0.5 to 2.0 and a temperature of 50 ° C. or lower, and the silica hydrogel is adjusted by gelling the silica hydrosol. Alternatively, the amorphous silica can be prepared by a simultaneous dropping method. The silica hydrogel obtained as described above is crushed to a size of 1 to 30 mm, and washed with water to remove by-product salts and control the electrical conductivity of the product. If necessary, an aqueous solution of sodium hydroxide or ammonia may be added to the washing liquid to perform a hydrothermal treatment for controlling the specific surface area. When performing the hydrothermal treatment, the treatment temperature is 30 to 95 ° C. and the pH is 7.0 depending on the target specific surface area.
It can be selected as appropriate within the range of ~ 11.0.

The silica hydrogel prepared by the above-mentioned crushing, washing and, if necessary, hydrothermal treatment, is dried to control the pore distribution, and crushed to control the average particle size. Classification according to the, it is possible to finally produce the target amorphous silica,
By coating a coating liquid prepared using this amorphous silica on a base paper by a known method, an ink jet recording paper having a coat layer having required characteristics can be obtained.

As the binder used in preparing the coating liquid, water-soluble binders such as polyvinyl alcohol, starches, water-soluble cellulose derivatives, and water-soluble proteins are used in the same manner as in general. Although the concentration of the filler in the coating liquid is not limited, it is often appropriate to set the concentration to, for example, 5 to 30%. In the case of using the amorphous silica of the present invention, It can be preferably carried out at a high concentration.

The above coating liquid is generally coated on a base paper at a solid content of 5 to 20 g / m ² , dried and calendered to obtain an ink jet recording paper.

[0021]

EXAMPLES Hereinafter, the present invention will be further described with reference to specific examples, but it goes without saying that the present invention is not limited to these examples. The contents of the performance tests performed in the examples are described below.

(1) Measurement of Electric Conductivity A 4 g sample was suspended in 50 ml of distilled water, boiled for 2 to 3 minutes, filtered, allowed to cool, adjusted to 100 ml, and a commercially available electric conductivity meter (model: DS- 15 (manufactured by Horiba, Ltd.).

(2) Average particle size measurement The average particle size was measured by a Coulter counter method common in the art.

The apparatus is a Coulter counter TA-II
(Coulter Electronics Ins.
The maximum diameter of the particles is less than 51 μm (average particle size of about 4 to 13 μm), and the maximum diameter of the particles is less than 64 μm (average diameter of about 13 to 13 μm). 18 μm) uses a 100 μm aperture tube, and the maximum particle size of the particles is 161 μm.
200 μm (within average particle size of about 18-50 μm)
An aperture tube of m was used (there is an optimum measurement range and a measurement limit depending on the size of the aperture tube).

The dispersion of the sample was performed by ultrasonic dispersion for 40 seconds, and the dispersion was added to the Isoton-II attached to the above apparatus.
The liquid was used.

(3) BET specific surface area measurement Cantersorb (manufactured by Quantachrome, USA)
Was measured by a one-point method.

(4) Measurement of Oil Absorption Measurement was carried out according to an oil absorption measurement method according to JIS K5101 (pigment test method).

(5) Coating method on paper polyvinyl alcohol (PVC11 manufactured by Kuraray Co., Ltd.)
15 parts of silica was added to 100 parts of the 5% aqueous solution of 7), and the mixture was sufficiently stirred with a disper to obtain a coating liquid. Apply this coating solution with a basis weight of 6
A 6 g / m ² PPC sheet was coated with a bar coater so that the coating amount was 10 g / m ^2, and air-dried. After air drying, calendering was performed at a linear pressure of 20 kg / cm to obtain a coated paper (inkjet recording paper).

(6) Viscosity of Coating Liquid The viscosity of the above coating liquid was measured using a B-type viscometer (model BL, manufactured by Tokyo Keiki Co., Ltd.).

(7) Inkjet recording method and evaluation of print density Solid colors (4 cm × 4 cm) of black, magenta, cyan, and yellow were applied using an MJ-800C printer manufactured by Epson Corporation. Was evaluated as follows.

The evaluation of the print density is performed by using a colorimeter (Suga Test Instruments Co., Ltd., color meter, model: MSC-CH), and the hue and lightness (print density) are one of the color display methods. It was represented by an L ^* a ^* b ^* diagram (CIE 1976 L ^* a ^* b ^* Diagram) which can be represented simultaneously. The evaluation of the print density of each single color is as follows.

(A) By L ^* of black, And

(B) According to L ^* of magenta, And

(C) According to L ^* of cyan, And

(D) By L ^* of yellow, And

(E) Comprehensive Evaluation of Print Density Among the print evaluations of (a) to (d), those that are fair with only ○ or more: ◎ Two of the print evaluations of (a) to (d) The above consists of only ○ and Δ ... ○ Among the print evaluations (a) to (d), those which consist of only ○, Δ, × or only one or less ○ and Δ ... △ Among the print evaluations of (a) to (d), those composed of only Δ and X: × The evaluation of ◎, ○, Δ, × of the print density of each single color is the same as that of commercially available PPC paper. L ^* printed on the reference
L ^* printed on commercially available paper dedicated to an ink jet printer was determined as a reference of Δ.

Example 1 An aqueous solution of sodium silicate having a SiO ₂ concentration of 25 wt% and a molar ratio of SiO ₂ / Na ₂ O of 3.3 was reacted with a 40 wt% aqueous solution of sulfuric acid using a mixing nozzle to obtain a silica hydrosol. .

After leaving the silica hydrosol to obtain a silica hydrogel, the silica hydrogel is reduced to about 10 mm.
After crushing the mixture, the mixture was subjected to hydrothermal treatment at 90 ° C. and pH 8.0 for 10 hours, and then washed. Next, the washed silica hydrogel was dried to obtain a silica xerogel.

This silica xerogel was pulverized by a jet mill using superheated steam so as to have an average particle diameter of 21 μm to obtain amorphous silica.

Table 1 below shows the physical properties of the amorphous silica and the image properties of the ink jet recording paper on which a coating layer was formed by applying a coating liquid prepared using the same as a filler. . FIG. 1 shows the results of measuring the pore distribution. The pore distribution was measured by ASAP-2400 (manufactured by Shimadzu Corporation).

Example 2 The silica xerogel obtained in Example 1 was treated with an average particle size of 17
Pulverization was performed so as to obtain an amorphous silica.

Table 1 below shows the physical properties of the amorphous silica and the image properties of the ink jet recording paper on which a coating layer was formed by applying a coating liquid prepared using the same as a filler. .

Example 3 The silica xerogel obtained in Example 1 was pulverized by changing only the pulverization conditions so as to have an average particle size of 26 μm to obtain amorphous silica.

Table 1 below shows the physical properties of the amorphous silica and the results of measuring the image characteristics of the ink jet recording paper having a coating layer formed by applying a coating liquid prepared using the same as a filler. .

Example 4 A silica xerogel was prepared in the same manner as in Example 1 except that the product was washed with water so that the electric conductivity of the product was about 100 μS / cm. Obtained. The obtained silica xerogel was used in the same manner as in Example 1,
Pulverization was performed to obtain an average particle size of 21 μm, thereby obtaining amorphous silica.

Table 1 below shows the physical properties of the amorphous silica and the image properties of the ink jet recording paper on which a coating layer was formed by applying a coating liquid prepared using the same as a filler. .

Example 5 A silica xerogel was obtained in the same manner as in Example 1 except that the hydrothermal treatment was performed for 7 hours. The obtained silica xerogel was treated in the same manner as in Example 1 to obtain an average particle size of 21%.
Pulverization was performed so as to obtain an amorphous silica.

Table 1 below shows the physical properties of the amorphous silica and the image properties of the ink jet recording paper on which a coating layer was formed by applying a coating liquid prepared using the same as a filler. .

Comparative Example 1 The silica xerogel obtained in Example 1 was pulverized so as to have an average particle diameter of 10 μm by changing only the pulverization conditions to obtain amorphous silica.

Table 1 below shows the physical properties of the amorphous silica and the image properties of the ink jet recording paper on which a coating layer was formed by applying a coating liquid prepared using the same as a filler. .

Comparative Example 2 The silica xerogel obtained in Example 1 was pulverized so as to have an average particle size of 32 μm by changing only the pulverization conditions to obtain amorphous silica.

Table 1 below shows the physical properties of the amorphous silica and the image properties of the ink jet recording paper having a coating layer formed by applying a coating liquid prepared using the same as a filler. .

Comparative Example 3 The same procedure as in Example 1 was repeated except that the product was washed with water so that the electric conductivity of the product was about 400 μS / cm. Obtained. The obtained silica xerogel was used in the same manner as in Example 1,
Pulverization was performed to obtain an average particle size of 21 μm, thereby obtaining amorphous silica.

Table 1 below shows the physical properties of the amorphous silica and the image properties of the ink jet recording paper on which a coating layer was formed by applying a coating liquid prepared using the same as a filler. .

Comparative Example 4 In Example 1, except that the hydrothermal treatment was performed for 18 hours.
Silica xerogel was obtained in the same manner as in Example 1. The obtained silica xerogel was treated in the same manner as in Example 1 to obtain an average particle size of 2
Pulverization was performed to 1 μm to obtain amorphous silica.

Table 1 below shows the physical properties of the amorphous silica and the image properties of the ink jet recording paper on which a coating layer was formed by applying a coating liquid prepared using the same as a filler. .

Comparative Example 5 A silica xerogel was obtained in the same manner as in Example 1 except that the hydrothermal treatment was performed for 3 hours. The obtained silica xerogel was treated in the same manner as in Example 1 to obtain an average particle size of 21%.
Pulverization was performed so as to obtain an amorphous silica.

[0058]

[Table 1]

[0059]

As can be seen from the above description, according to the present invention, a coating liquid is prepared by mixing amorphous silica, which is a filler for forming a coat layer of an ink jet recording paper, with a binder. In this case, there is an effect that the rise in viscosity is small and the coating workability is excellent.

Further, there is an effect that a clear image can be formed with a high print density while being excellent in the above-mentioned coating workability.

[Brief description of the drawings]

FIG. 1 is a view showing the results of measuring the pore distribution of amorphous silica produced in Example 1.

Claims (2)

[Claims] An average particle size of 15 to less than 30 μm, an electric conductivity of 400 μS / cm or less, and a BET specific surface area of 26
0 m ² / g or more and less than 700 m ² / g, and an oil absorption of 1
A filler for ink-jet recording paper, comprising amorphous silica of at least 00 ml / 100 g and less than 400 ml / 100 g. 2. An ink jet recording paper having a coating layer formed by applying a coating liquid obtained by mixing the filler of claim 1, water and a binder onto an ink jet recording surface and drying the coating liquid.