JPH04298378A - Ink jet recording sheet - Google Patents

Abstract

PURPOSE:To provide an ink jet recording device which uniformly applies coating liquid, forming a covering layer on a sheet, uniformly absorbs ink by means of the covering layer and as a result, prevents the occurrence of unevenness in absorption of water-color ink to provide a print picture of uniform quality, in an ink jet recording sheet formed by coating the surface of the sheet with ink acceptable covering layer. CONSTITUTION:An ink acceptable covering layer consisting mainly of 50-90wt.% pigment having oil absorption (according to JIS K 5101) of 50-300ml/100g and 10-50wt.% a soluble adhesive containing 3-30wt.% denatured starch per the solid content of a total water soluble adhesive is applied in a ratio of 1-10g/m<2> on the surface of a sheet consisting mainly of cellulose pulp. By using the denatured starch, uniformity of coating with coating liquid and uniform absorbency of ink of the covering layer can be improved.

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 paper, and more particularly to an aqueous ink jet recording paper having an ink receptive coating layer on its surface having excellent color image characteristics.

0002

[Prior Art] Improvements in the performance of inkjet printers that use water-based inks, especially in printing speed, resolution, and color saturation, have enabled them to absorb faster and faster on recording paper.
As more sophisticated properties such as high absorption capacity and regular ink bleeding are required, so-called coated papers having an ink-receptive coating layer on the surface have been developed.

For example, Japanese Patent Application Laid-Open No. 158084/1984 discloses a method for producing an inkjet recording medium using synthetic fine-grained 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 common practice to provide a coating layer mainly composed of a pigment with excellent liquid absorption properties, such as synthetic fine-grained silica, on the surface of paper whose main component is cellulose pulp. ing.

0004

[Problems to be Solved by the Invention] On the other hand, due to cost considerations, so-called micro-coating, in which an ink-receptive coating layer is provided thinly at a rate of 1 to 10 g/m2 on the surface and has sufficient performance, has been developed. paper has been developed. However, in such slightly coated paper, since the coating layer is thin, a portion of the pulp fibers are exposed on the surface, and uneven ink absorption remains a problem.

Therefore, the present invention is capable of printing high-quality images at high speed using an inkjet printer using water-based ink, and has uniform ink absorption even when a thin ink-receptive coating layer is applied. The purpose of the present invention is to provide an inkjet recording paper that has the following properties.

[0006]

[Means for Solving the Problems] In view of the current situation, the present inventors have conducted intensive research on uniform absorption of ink, and as a result, have developed an ink-receptive coating whose main components are a highly absorbent pigment and a water-soluble adhesive. By incorporating a specific amount of low-viscosity modified starch into the ink-receptive coating layer when forming the layer on the paper surface, the uniformity of coating of the coating layer as well as the uniformity of ink absorption can be significantly improved; The inventors have discovered that high-quality, homogeneous images can be obtained by printing on recording paper using an inkjet method, leading to the completion of the present invention.

[0007] That is, the present invention provides oil absorption (JIS K
5101) containing 50-90% by weight of pigment and 3-30% by weight of modified starch, based on the solids content of the total water-soluble adhesive.
An ink-jet recording paper characterized in that an ink-receptive coating layer mainly composed of is provided on the surface of paper mainly composed of cellulose pulp at a rate of 1 to 10 g/m2.

[0008] The pigment used in the coating layer of the present invention must be a pigment that has excellent liquid absorption properties such as ink, and examples of such pigments include fine particle silica, precipitated calcium carbonate, and calcium silicate. , aluminum hydroxide, plastic pigments, etc. The liquid absorption properties of these pigments can be expressed by the oil absorption amount measured according to JIS K 5101, and this oil absorption amount is 50~
A pigment within the range of 300 ml/100 g is appropriately selected and used. If a pigment with an oil absorption amount of less than 50ml/100g is used, the water absorption is insufficient and
If a pigment exceeding l/100g is used, relatively good homogeneity of the printed image can be obtained even without the addition of modified starch, and therefore it is outside the scope of the present invention.

The proportion of such pigments used is 50 to 90% by weight of the total coating layer solid content. If it is less than 50%, the uniformity of ink absorption will be insufficient, and if it exceeds 90%, there is a fear that the pigment may fall off from the coating layer, which is unsuitable.

As the adhesive used in the coating layer of the present invention, water-soluble polymers such as oxidized starch, starch derivatives, polyvinyl alcohol, and casein can be used. Such a water-soluble adhesive has good adhesion with pigments and good affinity with water-based ink, so it improves short-term liquid absorption by the coating layer. On the other hand, modified starch used for the purpose of improving the uniformity of coating of the coating liquid for forming the coating layer and the uniform absorption of the ink of the coating layer has a low viscosity (for example, one with a concentration of 10%). 10 cp or less at 40° C.), and those obtained by graft polymerization and cationization of vinyl acetate can be preferably used.

The proportion of the water-soluble adhesive used in the ink-receptive coating layer is 10 to 50% by weight, preferably 10 to 30% by weight of 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%, although the adhesiveness will be increased, the usage ratio of the pigment will decrease and problems will arise in the uniformity of ink absorption as described above, which is unsuitable. The proportion of modified starch used in the water-soluble adhesive is 3 to 30% by weight of the total solid content of the water-soluble adhesive. If it is less than 3%, the uniformity of coating of the coating liquid and the uniform absorption of ink due to the synergistic effect with the pigment will be insufficient, and if it exceeds 30%, the adhesive strength with the pigment will be insufficient, so it is unsuitable. .

[0012] The paper used in the present invention is acidic paper, neutral paper, or alkaline paper whose main raw material is ordinary wood pulp. In particular, paper containing talc, clay, light calcium carbonate, etc. at a ratio of 30% by weight or less, and paper with a basis weight of 64g/
Paper having a Steckigt size degree in the range of 1 to 15 seconds based on m2 can be preferably used.

The sizing of the paper used is adjusted by increasing or decreasing the amount of sulfuric acid band, rosin size, fixing agent such as cationic starch, and neutral sizing agent such as alkyl ketene dimer or alkenyl succinic anhydride. It will be done. If the sizing degree is less than 1 second, there are concerns about print image bleed through, irregular spread of ink, and decreased water resistance of the dye. If the sizing degree exceeds 15 seconds, ink absorption may be insufficient and this In order to compensate for this, it is necessary to make the ink-receptive coating layer much thicker than 10 g/m2, which is not preferable.

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

[0015]

[Examples] The present invention will be explained in more detail with reference to Examples below, but the present invention is of course not limited to these. In Examples and Comparative Examples, % and parts indicate weight % and parts by weight, respectively.

Example 1 20 parts of light calcium carbonate (PC: manufactured by Shiraishi Kogyo Co., Ltd.) was added to an aqueous suspension of 100 parts of bleached hardwood kraft pulp with a Hunter whiteness of 91%, and 1 part of cationic starch and 1 part of neutral starch were added. Sizing agent (Fiberan 81: manufactured by Oji National Co., Ltd.)
0.05 part was added to prepare a papermaking raw material. Using this papermaking raw material, a known Fourdrinier multi-tube paper machine was used to produce paper with a basis weight of 64g/
m2 of high quality paper was produced. This paper had a Hunter whiteness of 92%, an ash content of 15.0% (calcium carbonate equivalent), a Steckigt sizing degree of 5 seconds, and a pH of 6.5.

The following paint 1 was applied to the surface of this paper using a blade coater in a laboratory at a rate of 5 g/m 2 and dried to prepare an inkjet recording paper.

Paint-1 Silica

100 parts (Fine Seal (oil absorption 200ml/100g): manufactured by Tokuyama Soda Co., Ltd.)
30 parts of polyvinyl alcohol copolymer containing silanol groups (R-11
30: Manufactured by Kuraray Co., Ltd.)

Modified starch (Petrocoat C-104: manufactured by Nippon Star Chemical Co., Ltd.) Add silica to 3 parts of a copolymer with a 10% solid content concentration, a modified starch aqueous solution with a 10% solid content concentration, and 310 parts of water, and mix thoroughly. The coating liquid had a concentration of 18%.

Example 2 The following paint 2 was applied to the surface of the paper obtained in Example 1 at a rate of 5 g/m 2 using a blade coater in a laboratory and dried to prepare inkjet recording paper.

Paint-2 Precipitated calcium carbonate

100 parts (Univer 70 (oil absorption 70ml)
/100g): Manufactured by Shiraishi Kogyo Co., Ltd.) (Primary particles are needle-shaped and secondary particles are bur-shaped.)
Polyvinyl alcohol (PVA117: manufactured by Kuraray Co., Ltd.) 20 parts Modified starch (Cato Kote 485CS: manufactured by Oji National Co., Ltd.) 5 parts Add 345 parts of water to an aqueous solution of dissolved polyvinyl alcohol and modified starch at a solid content of 10%. Precipitated calcium carbonate was added and thoroughly mixed to give a coating solution with an 18% concentration.

Comparative Example 1 The following paint 3 was coated on the surface of the paper obtained in Example 1 at a rate of 5 g/m 2 using a blade coater in a laboratory and dried to prepare inkjet recording paper.

Paint-3 Silica

100 parts (Fine Seal (oil absorption 200ml/100g): manufactured by Tokuyama Soda Co., Ltd.)
30 parts of polyvinyl alcohol copolymer containing silanol groups (R-113
0: manufactured by Kuraray Co., Ltd.) copolymer with a solid content concentration of 10% and water 32
Silica was added to 0 parts and thoroughly mixed to obtain a coating liquid with a concentration of 18%.

Comparative Example 2 The following paint 4 was coated on the surface of the paper obtained in Example 1 at a rate of 5 g/m 2 using a blade coater in a laboratory and dried to prepare inkjet recording paper.

Paint-4 Precipitated calcium carbonate

100 parts (Univer 70 (oil absorption 70ml)
/100g): Manufactured by Shiraishi Kogyo Co., Ltd.) (Primary particles are needle-shaped and secondary particles are bur-shaped.)
Precipitated calcium carbonate was added to 20 parts of 10% polyvinyl alcohol and 365 parts of water, and thoroughly mixed to obtain a coating liquid with a concentration of 18%.

The inkjet recording papers obtained in Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were used in an inkjet printer (Paint Jet: Hewlett
(manufactured by Packard, Inc.) and visually evaluated the uniformity of the color density of the ink, the vividness of the color, and the absorbency of the ink. The results are shown in Table 1.

[0026]

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

[0028]

Effects of the Invention The inkjet recording paper of the present invention not only has good ink absorption properties, but also absorbs ink uniformly, so that homogeneous and clear images can be obtained. As a result, high-quality images can be produced using inkjet printing at high speed.
Enables full-color printing.

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

Claims (1)

[Claims] Claim 1: 50-90% by weight of a pigment with an oil absorption (according to JIS K 5101) of 50-300ml/100g and 3-30% by weight of modified starch based on the solid content of the total water-soluble adhesive.
An inkjet, characterized in that an ink-receptive coating layer containing 10 to 50% by weight of a water-soluble adhesive as a main component is provided on the surface of paper whose main component is cellulose pulp at a rate of 1 to 10 g/m2. Recording sheet.