JP3074743B2 - 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 sheet, and more particularly, to an aqueous ink jet recording sheet provided with an ink receptive coating layer having excellent color image characteristics on its surface.

[0002]

2. Description of the Related Art The performance of ink-jet printers using water-based inks, especially the improvement of printing speed, resolution, saturation, etc., allows high-speed absorption of recording paper.
Higher absorption capacity and more advanced properties such as regular ink bleeding have been required, and so-called coated papers provided with an ink-receiving coating layer on the surface have been developed.

For example, Japanese Patent Application Laid-Open No. Sho 62-158084 discloses a method for producing an ink jet recording medium using synthetic finely divided silica and having high aqueous ink absorption, color reproducibility and color density. That is, in order to meet the above-mentioned required characteristics, it is usually practiced to provide a coating layer mainly composed of a pigment excellent in liquid absorbing property such as synthetic fine silica on the surface of paper mainly composed of cellulose pulp. ing.

[0004]

On the other hand, due to cost requirements, a so-called fine coating having an ink receptive coating layer provided on the surface as thin as 1 to 10 g / m ² and having sufficient performance has been provided. Papermaking is being developed. However, such a finely coated paper has a problem in that the coating layer is thin, so that a part of the pulp fiber is exposed on the surface, and uneven ink absorption such as uneven ink absorption.

Accordingly, the present invention is capable of printing a high-quality image at high speed using an ink jet printer using an aqueous ink, and has a uniform ink absorbability even when a thin ink-receiving coating layer is applied. It is an object of the present invention to provide an ink jet recording sheet which becomes as follows.

[0006]

In view of the above situation, the present inventors have made intensive studies on the uniform absorption of ink. As a result, the present inventors have found that an ink receptive coating containing a highly absorbent pigment and a water-soluble adhesive as main components. When a layer is provided on the surface of the paper, a specific amount of a modified starch having a low viscosity is contained in the ink-receiving coating layer, whereby the coating uniformity of the coating layer and the uniformity of ink absorption can be remarkably improved. It has been found that high quality and uniform images can be obtained when the recording paper thus printed is printed by the ink jet method, and the present invention has been completed.

That is, the present invention relates to a water-soluble adhesive containing 50 to 90% by weight of a pigment having an oil absorption (according to JIS K 5101) of 50 ml / 100 g or more and modified starch in an amount of 3 to 30% by weight based on the solid content of the total water-soluble adhesive. An ink receptive coating layer containing 10-50% by weight of an agent as a main component is provided on the surface of a paper containing cellulose pulp as a main component .
Polyvinyl alcohol, modified polyvinyl alcohol and
At least one water-soluble polymer selected from casein;
An ink jet recording paper comprising a modified starch . The ink receptive coating layer is 1 to 10 g / m ²
It is preferable to provide in the ratio of.

[0008] The pigment used in the coating layer of the present invention must be a pigment having excellent liquid absorbability such as ink, and examples of such a pigment include fine particle silica, precipitated calcium carbonate and calcium silicate. , Aluminum hydroxide,
Plastic pigments and the like can be mentioned. The liquid absorption of these pigments can be represented by the oil absorption measured by JIS K 5101, and the oil absorption is 50 ml /
A pigment of 100 g or more is appropriately selected and used. It is is inadequate water absorption when the oil absorption pigments are used in less than 50 ml / 100 g. Oil absorption is 300ml / 100g
When a pigment exceeding 50% is used, relatively good uniformity of a printed image can be obtained without adding a modified starch, so that a pigment having an oil absorption of 50 to 300 ml / 100 g is used.
Preferably .

The proportion of the pigment used is 50 to 90% by weight of the total solid content of the coating layer. If it is less than 50%, the uniformity of ink absorption is insufficient, and if it is more than 90%, there is a concern that the pigment may fall off from the coating layer, which is referred to as powder dropping.

The water-soluble adhesive used in the coating layer of the present invention includes modified starch, polyvinyl alcohol, and silanol.
Modified polyvinyl such as polyvinyl alcohol containing
Water-soluble polymers such as alcohol and casein can be used.
Such a water-soluble adhesive has good adhesiveness with a pigment and good affinity with a water-based ink, and thus improves the short-time liquid absorption by the coating layer . Modified starch used for the purpose of improving the uniform ink absorption of the uniformity and the coating layer of the coating of the coating liquid for forming the under clad layer, a low viscosity (for example, 10
% That of concentration was 10cp or less) at 40 ° C., oxidation lees
Powder, starch derivative, starch obtained by graft polymerization of vinyl acetate ,
Examples include cationized starch .

The proportion of the water-soluble adhesive used in the ink-receiving coating layer is 10 to 50% by weight, preferably 10 to 30% by weight, based on the total solid content of the coating layer. If it is less than 10%, the adhesive strength will be insufficient, and if it exceeds 50%, the adhesiveness will be large, but the use ratio of the pigment will be reduced, and as described above, it will be unsuitable because it will cause a problem in the uniformity of ink absorption. The usage ratio of the modified starch in the water-soluble adhesive is 3 to 30% by weight of the solid content of the whole water-soluble adhesive. If it is less than 3%, the uniformity of coating of the coating liquid and the uniform absorption of the ink due to the synergistic effect with the pigment become insufficient, and if it exceeds 30%, the adhesive strength with the pigment becomes insufficient, which is not suitable. .

The paper used in the present invention is an acidic paper, a neutral paper or an alkaline paper mainly made of ordinary wood pulp. Particularly, paper in which talc, clay, light calcium carbonate and the like are internally added at a ratio of 30% by weight or less, or a basis weight of 64 g /
Paper having a Steckigt sizing degree in the range of 1 to 15 seconds based on m ² can be preferably used.

[0013] The sizing degree of the paper used is adjusted by increasing or decreasing the addition amount of a sulfuric acid band and a rosin size, a fixing agent such as cationic starch, and a neutral sizing agent such as alkyl ketene dimer and alkenyl succinic anhydride. It is. If the sizing degree is less than 1 second, there is a concern that strike-through of the printed image, irregular spread of the ink, and a decrease in the water resistance of the dye, and if the sizing degree exceeds 15 seconds, the ink absorbency is insufficient. In order to compensate for this, it is necessary to make the ink receptive coating layer significantly thicker than 10 g / m ² , which is not preferable.

The thickness of the paper to be used is determined by the final use of printing, but is preferably in the range of 15 to 200 μm and the basis weight in the range of 20 to 200 g / m ² .

[0015]

EXAMPLES The present invention will be described more specifically with reference to examples below, but the present invention is of course not limited to these. In Examples and Comparative Examples,% and parts indicate% by weight and parts by weight, respectively.

Example 1 20 parts of light calcium carbonate (PC: manufactured by Shiraishi Industry Co., Ltd.) was added to a suspension of 100 parts of bleached hardwood kraft pulp having a hunter brightness of 91% in water, and further 1 part of cationic starch and neutral Sizing agent (Fibran 81: Oji National)
0.05 part was added to prepare a papermaking raw material. Using this papermaking raw material, a known fourdrinier multi-cylinder paper machine is used to obtain a basis weight of 64 g /
m2 ^high quality paper was produced. The hunter whiteness of this paper is 9
The ash content was 25.0%, the ash content was 15.0% (calculated as calcium carbonate), the Stöckigt sizing degree was 5 seconds, and the pH was 6.5.

On the surface of this paper, the following paint-1 was applied in a laboratory at a rate of 5 g / m ² by a blade coater and dried to prepare an ink jet recording paper.

Paint-1 Silica 100 parts (Fine Seal (oil absorption 200 ml / 100 g): manufactured by Tokuyama Soda Co.) Silanol group-containing polyvinyl alcohol-based copolymer 30 parts (R-1130: manufactured by Kuraray Co.) Modified starch (Petro) (Coat C-104: manufactured by Nisse Chemical Co., Ltd.) 3 parts 10% solid content copolymer, 10% solids modified starch aqueous solution, and 310 parts water were mixed with silica, mixed well, and mixed to 18% concentration. A coating liquid was used.

Example 2 The following paint-2 was applied to the surface of the paper obtained in Example 1 by a blade coater at a rate of 5 g / m ^{2 in} a laboratory and dried to prepare an ink jet recording paper.

Paint-2: 100 parts of sedimentable calcium carbonate (Univar 70 (oil absorption: 70 ml / 100 g): manufactured by Shiraishi Kogyo Co., Ltd.) (Primary particles are needle-like, secondary particles are burr-shaped calcite-like materials) Polyvinyl alcohol (PVA117: Kuraray Co., Ltd.) 20 parts Modified starch (cationized starch) 5 parts (Cato Kote 485CS: Oji National Co., Ltd.) And the precipitated calcium carbonate were added and mixed well to obtain a coating solution having a concentration of 18%.

Comparative Example 1 The following paint-3 was applied to the surface of the paper obtained in Example 1 at a rate of 5 g / m ² by a blade coater in a laboratory and dried to prepare an ink jet recording paper.

Paint-3 Silica 100 parts (fine seal (oil absorption 200 ml / 100 g): manufactured by Tokuyama Soda Co.) Silanol group-containing polyvinyl alcohol-based copolymer 30 parts (R-1130: manufactured by Kuraray Co., Ltd.) 10% solids Silica was added to the copolymer having a partial concentration and 320 parts of water, and sufficiently mixed to obtain a coating solution having a concentration of 18%.

Comparative Example 2 The following paint-4 was applied to the surface of the paper obtained in Example 1 at a rate of 5 g / m ² by a blade coater in a laboratory and dried to prepare an ink jet recording paper.

Paint-4: 100 parts of sedimentable calcium carbonate (Univar 70 (oil absorption: 70 ml / 100 g): manufactured by Shiraishi Kogyo Co., Ltd.) (Primary particles are needle-like, secondary particles are burr-like calcite materials. Precipitating calcium carbonate was added to 20 parts of polyvinyl alcohol (PVA117: manufactured by Kuraray Co., Ltd.), 10 parts of 10% polyvinyl alcohol and 365 parts of water, and mixed well to obtain a coating liquid of 18% concentration.

The ink jet recording papers obtained in Examples 1, 2 and Comparative Examples 1 and 2 were printed using an ink jet printer (Paint Jet: manufactured by Hewlett Packard), and the uniformity of the color density and color of the ink were printed. And the ink absorbency were visually evaluated. Table 1 shows the results.

[0026]

As can be seen from Table 1, the ink jet recording papers obtained in Examples and Comparative Examples had almost no difference in the vividness of color development and the ink absorbency, but the uniformity of the color density was the same in the Examples. The obtained ink jet recording paper is superior to that of the comparative example.

[0028]

The ink jet recording paper of the present invention not only has good ink absorbency, but also has a uniform ink absorption, so that a uniform and clear image can be obtained. As a result, high-quality images and high-speed inkjet
Make full color printing possible.

Further, when the ink receptive coating layer is provided on the surface of the paper, there is also an effect that the coating uniformity of the coating layer can be improved.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-1-24785 (JP, A) JP-A-61-66686 (JP, A) JP-A-1-30780 (JP, A) JP-A-1- 30781 (JP, A) JP-A-60-87089 (JP, A) JP-A-55-51583 (JP, A) JP-A-62-158084 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) B41M 5/00 D21H 17/00

Claims (5)

(57) [Claims] 1. Oil absorption (according to JIS K 5101) of 50
an ink-receiving layer comprising 50 to 90% by weight of a pigment of not less than 100 ml / 100 g and 10 to 50% by weight of a water-soluble adhesive containing 3 to 30% by weight of modified starch per solid content of the total water-soluble adhesive. Is provided on the surface of paper containing cellulose pulp as a main component , and the water-soluble adhesive is a polyvinyl alcohol.
From alcohol, modified polyvinyl alcohol and casein
At least one water-soluble polymer selected and modified starch
Ink-jet recording sheet, wherein the Ranaru. 2. The pigment has an oil absorption of 50 to 300 ml / 1.
The inkjet recording paper according to claim 1, which weighs 00 g. Wherein the water-soluble adhesive claim comprising at least one water-soluble polymer and modified starch selected Ri by polyvinyl alcohol and modified polyvinyl alcohol 1
Or the inkjet recording paper according to 2. 4. The method according to claim 1, wherein the ink-receiving coating layer is 1 to 10 g /
4. The ink jet recording paper according to claim 1, which is provided at a ratio of m ² . 5. The modified starch comprises oxidized starch and vinyl acetate.
Selected from graft-polymerized starch and cationized starch
The method according to claim 1, 2, 3, or 4, which comprises at least one kind.
Ink jet recording paper.