JPH04298379A - Ink jet recording sheet - Google Patents

Abstract

PURPOSE:To provide an ink jet recording sheet which facilitates discrimination of the surface and the back of a sheet, in an ink jet recording sheet formed such that the surface of a base sheet is coated with an ink acceptable covering layer. CONSTITUTION:A layer having brightness higher by five points or more than that of a base sheet and opacity of 50% or more is formed on the surface side of the base sheet consisting mainly of cellulose pulp having sizing of 1-15 seconds, brightness of 70-85%, and opacity of 70% or more. An ink acceptable covering layer having brightness of 85% or more and opacity of 50% or less is further formed in thickness of 1-20g/m<2> thereon. This constitution enables execution of easy and reliable discrimination of the surface and the back of a sheet.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to inkjet recording paper, and more specifically, the present invention relates to an inkjet recording paper, and more specifically, it is provided with an ink-receptive coating layer on the surface that has excellent color image characteristics, and also makes it easy to distinguish between the front and back sides of the paper. The present invention relates to water-based inkjet recording paper.

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 a base paper mainly composed of cellulose pulp. has been done.

0004

[Problems to be Solved by the Invention] Among the coated papers mentioned above, so-called single-sided coated papers, in which an ink-receptive coating layer is provided only on the surface of the base paper, are generally used due to cost and usability requirements. It is. Since there is a large difference in image suitability between the front and back sides of such single-sided coated paper, it is necessary to reliably distinguish between the front and back sides to avoid using the front and back sides by mistake. However, the suitability of the ink-receptive coating layer requires that it has high liquid absorption, low opacity, and high whiteness, and as a result, the whiteness and color tone of the paper remain unchanged on both the front and back sides. Therefore, conventional single-sided coated paper had the disadvantage that the difference in appearance was small and it was difficult to distinguish between the front and back sides.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an inkjet recording paper that can print high-quality images at high speed using an inkjet printer using water-based ink, and also allows easy discrimination between the front and back sides of the paper.

[0006]

[Means for Solving the Problems] In view of the current situation, the present inventors have conducted intensive research on the whiteness and opacity of paper, and have found that the paper has a whiteness greater than the whiteness of the surface of the base paper and is 50% or more. It was discovered that by providing an intermediate layer having an opacity of , we have completed the present invention.

That is, the present invention provides a base paper having a size of 1 to 15 seconds, a whiteness of 70 to 85%, and an opacity of 70% or more, which is mainly composed of cellulose pulp, and on the surface side of the base paper, the whiteness is higher than that of the base paper. 5 points or more larger and 50% opacity
The above layer is provided, and on top of that, 1 to 20 ink receptive coating layers with a whiteness of 85% or more and an opacity of 50% or less are provided.
This inkjet recording paper is characterized in that it is provided with a thickness of g/m2.

The intermediate layer used in the present invention may be made of any material as long as it satisfies the required properties. For example, an intermediate layer consisting of a pigment with a high whiteness of 85% or more, such as titanium dioxide, aluminum hydroxide, or calcium carbonate, and a known adhesive can be preferably used. Further, it is desirable that this intermediate layer be permeable to aqueous ink, but this is not an essential requirement.

[0009] When an intermediate layer is composed of a pigment and an adhesive, in order to make the intermediate layer have a whiteness 5 points higher than that of paper and an opacity of 50% or more, it is necessary to The ratio of adhesive used and the amount of coating of the intermediate layer may be appropriately combined. Generally, the usage ratio of pigment is in the range of 30 to 90% by weight of the solid content of the intermediate layer, the usage ratio of adhesive is in the range of 10 to 70% by weight of the solid content of the intermediate layer, and the coating amount of the intermediate layer is 1 to 90% by weight. It can be appropriately selected from the range of 20 g/m2. The ratio of pigment and adhesive to be used is determined mainly by the difference in whiteness and hiding power of the pigment, and the amount of coating of the intermediate layer is also restricted by the feel of the recording paper when it is used. The intermediate layer can be applied using a blade coater, a roll coater, or the like.

[0010] The ink-receptive coating layer used in the present invention preferably comprises, for example, an ink-absorbing pigment that has high whiteness and has good water-based ink absorption and color development properties, and a hydrophilic adhesive. Can be used. Various types of ink-absorbing pigments can be used, such as particulate silica, precipitated calcium carbonate, and aluminum hydroxide. The hydrophilic adhesive is preferably one that has good adhesion to liquid-absorbing pigments and has affinity, permeability, or swellability for water-based ink, such as natural or synthetic water-soluble adhesives such as polyvinyl alcohol, starch, and various starch derivatives. An example is a polymer. These hydrophilic adhesives can also be used as adhesives in intermediate layers.

When the ink-receptive coating layer is composed of an ink-absorbing pigment and a hydrophilic adhesive, the ratio of the adhesive used is 8 to 50% by weight, preferably 10 to 3% by weight of the solid content of the coating layer.
It is 5% by weight. If the amount of adhesive used is small, the pigment will fall off from the surface, and if the usage ratio is 50% or more, the ink receptivity will decrease, which is not preferable. On the other hand, the usage ratio of the pigment is in the range of 50 to 90% of the solid content of the coating layer. If it is less than 50%, the ink absorption is not sufficient, and if it is less than 90%
Exceeding this is not preferable because the surface strength will be insufficient. A dispersant, a waterproofing agent, a humidity control agent, etc. may be added to the coating layer as necessary. Such a coating layer is formed by applying a paint having a predetermined composition. Paint is 1-20g/
m2, preferably in the range of 2 to 10 g/m2, using a known blade coater, roll coater, or the like. The ink receptive coating layer thus obtained has a whiteness of 8.
The opacity is 5% or more and the opacity is 50% or less. If the opacity is 50% or more, it is unsuitable because it blocks the color development of the ink and causes color fading.

The base paper used in the present invention is mainly made of ordinary wood pulp, and it is particularly preferable to use bleached hardwood kraft pulp together with other pulps if necessary. In order to improve the whiteness and opacity of the base paper, talc, clay, calcium carbonate, etc. may be added as fillers during paper making. The base paper used in the present invention has a whiteness of 7
The opacity should be 70% or more in the range of 0 to 85%. If the whiteness is less than 70%, the appearance after printing will be poor, and if the whiteness exceeds 85%, it will be impossible to make the difference in whiteness from the ink-receptive coating layer 5 points or more, which is not suitable. The opacity of the base paper is determined by the type and amount of filler added, and higher opacity is preferable because the ink develops better color. Addition rate of filler is 1 to 30 per absolute dry total solid content.
It is used by appropriately selecting from the range of weight %. The thickness of the base paper is determined by the final use of the print, but is between 10 and 20 mm.
A range of 0 μm and a basis weight of the base paper of 20 to 200 g/m 2 are preferably used in the present invention.

The sizing degree of the base paper is in the range of 1 to 15 seconds in terms of Steckigt sizing degree based on a basis weight of 64 g/m 2 . Within this size range, the base paper has excellent absorbency, and the liquid absorption effect of the ink-receptive coating layer is improved. If the sizing degree is less than 1 second, there are concerns about print image bleed through, irregular spreading of ink, and decreased water resistance of dyes, etc. If the sizing degree is more than 15 seconds, ink absorption will be insufficient and absorption This is unsuitable because it requires the ink-receptive coating layer to be significantly thickened in order to maintain its properties.

[0014] Such a range of sizing degrees can be obtained for both acidic, neutral and alkaline papers. In addition, the sizing degree can be adjusted by using known sizing agents and fixing agents for acidic paper, such as rosin size and band, or known sizing agents and fixing agents for acidic paper, such as alkyl ketene dimer, alkenyl succinic anhydride, and cationic starch. The amount of sizing agent and fixing agent added can be increased or decreased.

[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 Light calcium carbonate (Albafil: Pfizer MS
(manufactured by Company P) and 10 parts of ground calcium carbonate were added to an aqueous suspension of 100 parts of hardwood bleached kraft pulp with a Hunter whiteness of 84%, and 1 part of cationic starch (Cato-F: manufactured by Oji National Company), Neutral sizing agent (Fiberan 81
0.05 part (manufactured by Oji National Co., Ltd.) was added to produce high-quality paper with a basis weight of 64 g/m2 using a known paper machine. This high-quality paper had a whiteness of 82%, an opacity of 80%, an ash content (calcium carbonate equivalent) of 12.0%, and a Steckigt size degree of 8 seconds.

4 g/m2 of the following intermediate layer paint-1 was applied to the surface of this base paper using a blade coater in the laboratory.
After coating and drying at a rate of 8g/m2 to form an intermediate layer, on the surface of this intermediate layer, the following ink-receptive coating layer coating material-1 was further coated at a rate of 8g/m2 and dried to form a coating layer. An inkjet recording paper was prepared, and the whiteness and opacity of this coated paper were measured.

[0018] Intermediate layer paint-1 Rutile type titanium dioxide

100 copies SBR latex (S265
, manufactured by Japan Synthetic Rubber Co., Ltd.) 100 copies 5
Titanium dioxide and 810 parts of water were added to the latex having a solid content of 0% and thoroughly mixed to obtain a coating liquid having a concentration of 18%.

Coating layer paint-1 Silica (Fine Seal: manufactured by Tokuyama Soda Co., Ltd.)
100 copies
Polyvinyl alcohol (PVA117: manufactured by Kuraray Co., Ltd.) 20 parts 10 dissolved at 90°C
Silica and water in polyvinyl alcohol aqueous solution containing 3% solids
70 parts were added and thoroughly mixed to obtain a coating liquid with a concentration of 18%.

[0020]Furthermore, the above-mentioned intermediate layer paint-1 and coating layer paint-1 coating liquids were respectively applied onto a glass plate in the same amount as applied to the base paper, and After drying, it was peeled off from the glass plate to prepare single layers of the intermediate layer and the coating layer, and the whiteness and opacity of each of these single layers were measured.

Comparative Example 1 On the surface of the base paper produced in Example 1, coating layer coating material 1 was applied at a rate of 5 g/m2 in the same manner as in Example 1, and then dried and the ink was applied to the surface. An inkjet recording paper provided with only a receptive coating layer was prepared, and the whiteness and opacity of this coated paper were measured.

[0022] Also, the coating solution for coating layer 1 was applied on a glass plate in the same amount as that applied to the base paper, and after drying, it was peeled off from the glass plate and the coating layer was removed. A single layer was prepared, and the whiteness and opacity of this single layer were measured.

Comparative Example 2 5 g/m2 of the following ink-receptive coating layer paint-2 was applied to the surface of the base paper produced in Example 1 in the same manner as in Example 1.
An ink jet recording paper having only an ink-receptive coating layer on the surface was prepared by coating the coated paper at a ratio of 100 to 100 mL, drying it, and measuring the whiteness and opacity of this coated paper.

[0024] Also, the coating liquid for coating layer 2 was applied on a glass plate in the same amount as that applied to the base paper, and after drying, it was peeled off from the glass plate and the coating layer was removed. A single layer was prepared, and the whiteness and opacity of this single layer were measured.

Coating layer paint-2 Calcium carbonate (Fine Seal: manufactured by Tokuyama Soda Co., Ltd.) 80 parts Rutile type titanium dioxide
20
Part Polyvinyl alcohol (PVA117: manufactured by Kuraray) 30 parts Calcium carbonate, titanium dioxide and 320 parts of water were added to a polyvinyl alcohol aqueous solution with a solid content of 10% dissolved at 90°C, and mixed thoroughly to form a coating liquid with a concentration of 18%. did.

Table 1 shows the measurement results of the whiteness and opacity of the base paper before coating, the intermediate layer, and the coating layer obtained in Example 1, Comparative Example 1, and Comparative Example 2. paper whiteness,
Table 2 shows the measurement and evaluation results of the discriminability and color development of the front and back sides of the coated paper. The ability to distinguish between the front and back sides of the paper was determined by visually checking the front and back sides of the inkjet recording paper, and the color development of the ink was determined by visually checking the image after inkjet recording.

[0027]

[0028]

As is clear from Table 2, the inkjet recording paper according to the present invention is suitable for multicolor printing because it is extremely easy to distinguish between the front and the back, and it also has excellent color development.

[0030]

The inkjet recording paper of the present invention has the advantage that ink images can be printed clearly and that the front and back sides of the paper can be easily and reliably distinguished by visual inspection.

Claims (1)

[Claims] [Claim 1] On the surface side of a base paper that is mainly composed of cellulose pulp and has a size of 1 to 15 seconds, a whiteness of 70 to 85%, and an opacity of 70% or more, the whiteness is 5 points or more than the base paper. A large layer with an opacity of 50% or more is provided, and an ink-receptive coating layer with a whiteness of 85% or more and an opacity of 50% or less is provided on top of the layer with a thickness of 1 to 20 g/m2. Inkjet recording paper.