JP3295494B2 - Inkjet recording paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus, and more particularly to a coated paper type ink jet recording sheet which can be used in an image forming apparatus using a recording head having a plurality of nozzles.

[0002]

2. Description of the Related Art An ink jet recording apparatus, which directly ejects ink (recording liquid) onto recording paper, has attracted attention as a quiet recording method with a lower running cost than conventional recording apparatuses. In recent years, in the inkjet recording method, a multi-nozzle type recording apparatus has been used for the purpose of forming a full-color image using two or more colors of ink at a higher speed.

[0003] Ink used in such a recording system is water-based ink in terms of safety and printing characteristics, and the recording paper is such that the recording liquid absorbs the recording liquid quickly and overlapping of different color inks occurs. Even if there is no overflow, the ink dots applied to the recording surface must be properly spread, the dot shape should be close to a perfect circle, the dot edges should be clear, and As a matter of fact, it is required that the whiteness of the recording surface be sufficiently high in order to increase the dot density and enhance the contrast of the dots.

Conventionally, use of coated paper has been proposed to meet such a demand. However, in order to further increase the saturation of printed ink and to enhance the quality of an image, the coated paper is required to be smooth. When the super calender is applied to the ink, the ink absorbability is impaired, and the ink overflows. On the other hand, as described in JP-A-62-95285, improvement of cast-coated paper has been proposed in order to meet the demand for the above-mentioned inkjet image.

However, when the above-described recording paper is applied to an on-demand type ink-jet recording system having a plurality of nozzles and a multi-nozzle for locally applying a large amount of ink in a short time, the ink is required to be printed. Is absorbed from the surface of the recording paper to reduce the ink absorbency on the recording surface in an attempt to achieve a higher density, causing bleeding or selective absorption of the dye in the ink, causing yellow, cyan, Despite black printing with four color inks of magenta and black, a brown mottle pattern may occur on a black background (bronze phenomenon).

When the ink is absorbed by the surface layer of the recording layer, the ink swells near the surface of the recording layer, so that the surface of the cast coat is slightly roughened and the gross of the printed portion is increased. May be further reduced. If the prescription of the coating liquid for forming the recording layer is changed to increase the ink absorbency in order to cope with this roughness, these difficulties can be solved, but the print density decreases as described above. A new problem arises. Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to form a full-color image using a plurality of ink jet heads having a plurality of nozzles. An object of the present invention is to provide an ink jet recording paper capable of forming a density image.

[0007]

The above objects are achieved by the present invention described below. That is, the present invention relates to an ink jet recording sheet used in an ink jet recording method using an on-demand type head having a plurality of nozzles, wherein the ink jet recording sheet has a BET specific surface area of 300 m ² / g to 500 m ² / g of synthetic silica
A recording layer is formed from a coating liquid comprising a pigment containing 0% by weight or more and a binder containing casein and styrene-butadiene rubber, and the weight ratio of the pigment to the binder is the value of pigment / binder. And the solid content of the coating solution is 15 to 25 g / m ² , and the ten-point average roughness of the recording layer surface is 0.5 to 5 μm. An ink jet recording sheet characterized by the following.

[0008]

According to the present invention, there is provided a cast-coated paper type ink jet recording paper which can form a high-density and high-quality image which has good ink absorption during printing and does not cause ink overflow or bleeding. Further, the above-described inkjet recording paper can form a high-density and high-quality image in the same manner as described above even when a full-color image is formed in an on-demand type inkjet recording apparatus having multiple nozzles.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to preferred embodiments. The ink jet recording paper according to the present invention is obtained by forming a coating layer (recording layer) containing at least synthetic silica on casein and styrene butadiene rubber which are aqueous binders. as long as the use of styrene and butadiene et emissions as a main component, it can include a third component, also particularly synthetic silica used as a pigment, generally amorphous silica, amorphous silica, silicic anhydride, Silicates called hydrous silicic acid, finely divided silica or white carbon. Further, as a condition of the synthetic silica, a silica having a BET specific surface area of 250 to 500 m ² / g may be selected and used.

Other pigments that can be used in combination with the synthetic silica include, for example, kaolin, talc, calcium carbonate, barium sulfate, aluminum hydroxide, titanium dioxide, zinc oxide, satin white, diatomaceous earth, and acid clay. , Zeolite, colloidal silica, organic pigments and the like. At this time, the content of the synthetic silica in the pigment in the coating layer is preferably 80% by weight or more, and if it is less than 80% by weight, the absorption of the ink becomes local absorption on the surface of the coating layer, and Not only does the shape remarkably deviate from a perfect circle, but also the size of the dots becomes extremely small. Further, an extreme bronze phenomenon is caused due to poor ink absorption. In addition, when the weight ratio of the pigment and the binder exceeds 2.4 as the ratio of the pigment to the binder, the image density after printing is remarkably reduced. Causes a noticeable loss of gloss in subsequent images.

The synthetic silica has a BET specific surface area of 250.
When the ratio is less than m ² / g, even if synthetic silica having the above-mentioned ratio of pigment / binder is present in the coating layer, the ink absorbency becomes extremely poor, and the ink overflows. Will happen. Further, when the BET specific surface area exceeds 500 m ² / g,
Conversely, the ink absorption in the entire coating layer is too good, causing a disadvantage that the ink is diffused in the entire coating layer and the image density is reduced.

As the coating machine used in the present invention, any coating machine having a coating part such as a blade coater, an air knife coater, a roll coater, a curtain coater, a bar coater, a gravure coater, a comma coater, etc. is applicable. You can do it. In the present invention, nitric acid, sulfuric acid, formic acid, acetic acid such as zinc, calcium, barium, magnesium, and aluminum is used to solidify casein in the coating layer while the coating layer is in a wet state immediately after the coating. It is possible to use a coating machine having equipment capable of performing a cast coating method by a so-called coagulation method after the coating section, in which the coating layer is treated with an aqueous solution containing a salt such as described above. Furthermore,
When drying the coating layer after solidification, a method of applying the coating layer to the heated finished surface by pressing is used.

The ink jet recording paper dried by the above means has a ten-point average roughness of 0.5 to 5.0 μm on the surface, and high gloss can be obtained. If the ten-point average roughness exceeds 5.0 μm, the gloss of the ink jet recording paper decreases, while if it is less than 0.5 μm, the ratio of the pigment / binder in the outermost layer relatively decreases, and the ink absorbency decreases. descend. A more preferred range is 0.5 to 3.0 μm. May be coated in the range of 15-25 g / m ² as solid content of the coating amount is less than 15 g / m ^2, tend to cause overflow of the ink, a decrease in image density exceeds 25 g / m ² Occurs. In the present invention, a pigment dispersant, a water retaining agent, a thickener, a defoaming agent, a release agent, a coloring agent, a water-proofing agent, a wetting agent, a fluorescent dye, an ultraviolet absorber, etc. It can be appropriately blended.

[0014]

Next, the present invention will be described more specifically with reference to examples and comparative examples. Example 1 (Inkjet recording paper 1) Synthetic silica having a BET specific surface area of 300 m ² / g (Mizukasil P-707, manufactured by Mizusawa Chemical Industry Co., Ltd.) 8 as a pigment
5 parts by weight, 15 parts by weight of light calcium carbonate (trade name: Tamapearl 121, manufactured by Okutama Kogyo Co., Ltd.), and casein (Lactic casein, manufactured by New Zealand) 25 as a binder
Parts by weight and 25 parts by weight of styrene butadiene rubber (manufactured by Sumitomo Nogatack Co., Ltd., trade name SN307) (pigment / binder = 2.0), and 2 parts by weight of calcium stearate (manufactured by Sannobuco, trade name: Knobcoat C104) as a release agent Were uniformly mixed to prepare an aqueous coating solution having a solid content of 30% by weight.

The obtained coating solution is applied to a base paper having a basis weight of 191 g / m ^{2 by} a roll coater, and then the coating film is coagulated with a 2% by weight aqueous solution of zinc formate to make the coating film wet. Meanwhile, the ink-jet recording paper of the present invention having a coating amount of 23 g / m ² was obtained by drying by pressing against a mirror-surface drum heated to 100 ° C. The 10-point average roughness of the recording layer surface of this ink jet recording paper was 1.48 μm, and the white paper gloss was 72% by the 60 ° method.

Example 2 (Inkjet recording paper 2) Synthetic silica (Mizukasil P-78F, manufactured by Mizusawa Chemical Industry Co., Ltd.) having a BET specific surface area of 390 m ² / g as a pigment 1
00 parts by weight, 30 parts by weight of casein (Lactic casein, New Zealand) and styrene butadiene rubber (Nippon Synthetic Rubber Co., Ltd., trade name JSR-08) as a binder
01) 25 parts by weight, (pigment / binder = 1.82) and 2 parts by weight of calcium stearate (manufactured by Sannobuco Co., Ltd., Nobcoat C104) as a release agent were uniformly mixed to obtain a solid content of 30% by weight. An aqueous coating solution was prepared.

The obtained coating solution is coated on a base paper having a basis weight of 191 g / m ^{2 by} a roll coater, and then the coating film is coagulated with a 5% by weight aqueous solution of zinc formate to make the coating film wet. Meanwhile, the ink-jet recording paper of the present invention having a coating amount of 18 g / m ² was obtained by being pressed against a mirror-surface drum heated to 100 ° C. and dried. The 10-point average roughness of the recording layer surface of this ink jet recording paper was 1.37 μm, and the white paper gloss was 69% by the 60-degree method.

[0018]

[0019]

Comparative Example 1 (Coated Paper A) 100 parts by weight of Mizical P-707 as a pigment, 30 parts by weight of lactic casein as a binder and SN307
Except for using 30 parts by weight (pigment / binder = 1.67), a coated paper of Comparative Example was obtained in exactly the same manner as in Example 1. The 10-point average roughness of the recording layer surface of this coated paper was 1.2.
The white paper gloss was 78% by the 60-degree method.

Comparative Example 2 (Coated paper B) 100 parts by weight of Mizical P-707 as a pigment, 20 parts by weight of lactic casein as a binder and SN307
Except for using 20 parts by weight (pigment / binder = 2.50), a coated paper of Comparative Example was obtained in exactly the same manner as in Example 1. The 10-point average roughness of the recording layer surface of this coated paper is 1.5
The white paper gloss was 65% by the 60-degree method.

Comparative Example 3 (Coated paper C) Except that synthetic silica having a BET specific surface area of 240 m ² / g (trade name: Fine Seal X70, manufactured by Tokuyama Soda Co., Ltd.) was used as a pigment, the procedure was the same as in Example 3. A coated paper of a comparative example was obtained. The 10-point average roughness of the recording layer surface of this coated paper was 1.45 μm, and the white paper gloss was 72% by the 60-degree method.

Comparative Example 4 (Coated Paper D) A coated paper of Comparative Example was obtained in exactly the same manner as in Example 2 except that the coating amount was 13 g / m ² . The 10-point average roughness of the recording layer surface of this coated paper was 1.39 μm, and the white paper gloss was 6
It was 63% by the 0 degree method. Comparative Example 5 (Coated Paper E) A coated paper of Comparative Example was obtained in exactly the same manner as in Example 2 except that the coating amount was 28 g / m ² . The 10-point average roughness of the recording layer surface of this coated paper was 1.32 μm, and the white paper gloss was 6
It was 75% by the 0 degree method.

Comparative Example 6 (Coated Paper F) A coated paper of Comparative Example was obtained in exactly the same manner as in Example 1, except that 70 parts by weight of synthetic silica and 30 parts by weight of light calcium carbonate were used as pigments. 10 of the surface of the recording layer of this coated paper
The point average roughness was 1.30 μm, and the glossiness of blank paper was 88% by the 60-degree method.

Comparative Example 7 (Coated Paper G) Commercial Cast Coated Paper (Nippon Paper Industries Co., Ltd., trade name: Esprit Coat FP 209.3 g / m ² ) Printing Test Ink jet recording paper of the above Examples and Comparative Examples (coated Paper), using an on-demand ink jet recording apparatus that uses yellow, magenta, cyan, and black inks, applies thermal energy to the ink in the recording head to generate droplets, and performs recording. Recording was performed on inkjet recording paper. The printing results are shown in Table 1 below.
Shown in The following measurements were performed as each evaluation method.

(1) Bleed / Overflow The four inks used in the above were printed in equal amounts, and when one color full record was converted to 100%, the print was performed to 250%, and the print level was evaluated. . The print was made as a solid rectangle, and the mark "O" was written if no ink protruded from the rectangle. (2) Density A solid image was formed for each color, and this density was measured with a Macbeth densitometer. The value of yellow is described as a representative value.

(3) Gloss after printing The four colors of ink used above are printed in equal amounts, and printing is performed so as to be 250% when one color full recording is converted to 100%, and then at 23 ° C. and 60% RH. After being left in the environment for 30 minutes, the gloss was measured by the 60 ° method. 4) Bronze Phenomenon The four colors of ink used in the above are printed in equal amounts, and printing is performed so that when one color full recording is converted to 100%, the printing becomes 250%. Then, the printing is performed at 23 ° C. and 60% RH for 30 minutes. After standing, 50% or more of the solid printed area was discolored brown, and x was 25% or less.

[0028]

[Table 1] * If the density is lower than 1.20, the dynamic range becomes too small and the image quality deteriorates. or,
If the gloss is less than 30% after printing, the glossiness increases sharply, and it cannot be used satisfactorily.

[0029]

As described above, according to the present invention, even when used as a recording paper of an on-demand type ink jet recording system having a plurality of nozzles, a cast-coated paper based on plain paper is used. To provide an ink jet recording paper which is capable of forming a high-density image without causing ink overflow and bleeding, suppressing a decrease in gloss after printing as much as possible, and further capable of forming a high-quality image without a bronzing phenomenon. Can be done.

Continued on the front page (72) Inventor Teruhisa Shimada 1-30-6 Kamiochiai, Shinjuku-ku, Tokyo Inside Nihon Paper Co., Ltd. (72) Yoshihiro Kuroyama 1-30-6 Kamiochiai, Shinjuku-ku, Tokyo Nihon Paper Stocks In-house (56) References JP-A-5-59694 (JP, A) JP-A-6-72017 (JP, A) JP-A 2-113986 (JP, A) (58) Fields investigated (Int. . ^7, DB name) B41M 5/00

Claims (1)

(57) [Claims] 1. An ink jet recording sheet for use in an ink jet recording method using an on-demand head having a plurality of nozzles, the ink jet recording sheet having a BET specific surface area of 300 m ² / g on one surface of a base paper.
A recording layer is formed from a coating solution comprising a pigment containing not less than 80% by weight of synthetic silica of about 500 m ² / g and a binder containing casein and styrene butadiene rubber, and the weight of the pigment and the binder The ratio is from 1.8 to the value of pigment / binder
2.4, and the solid coating amount of the coating liquid is 15 to 25.
g / m ² , and the ten-point average roughness of the recording layer surface is in the range of 0.5 to 5 μm.