JPH11170688A - Ink jet recording sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording sheet having excellent external appearance of a printed matter and an easy to handle in the case of a preservation by effectively preventing a curl after printing. SOLUTION: In the ink jet recording sheet comprising at least one ink receptive layer provided on a surface of a base sheet, a thickness coating amount of the overall layer is 3 to 30 g/m<2> , and a moisture of the overall sheet is a range of 1 to 12%. In this case, a curvature of a curl 1/4 (m<-1> ) is represented by 20<1/r<0.3M+0.28C-2<20, wherein M is a moisture content (%)-C is a coating amount (g/m<2> ) of the layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording paper for ink jet recording using an aqueous ink, and in particular, effectively prevents curl after printing and has excellent appearance of printed matter.
The present invention relates to a recording paper for ink jet recording that is easy to handle when stored.

[0002]

2. Description of the Related Art In an ink jet recording system, minute ink droplets are made to fly by various operation principles and adhere to a recording sheet such as paper, thereby recording an image or a character. For this reason, high-speed, multi-color, and high-definition printing is easy. Particularly, in recent high-resolution full-color printers, it has become possible to print images that are almost inferior to color printing and color photographs. As described above, as a result of the high-resolution printer improving the image quality at the same level as a photograph, the appearance characteristics of the paper have become an important requirement item, and the neglected curl after printing in full-color printing and the like has also become important. Was.

[0003] The curl causes not only the handling of displaying and storing printed matter, but also the lack of a sense of quality, and also has become a major problem in running the printer when reprinting. This post-printing curl has surfaced as a phenomenon that cannot be ignored as a result of the recent increase in the amount of ink applied per unit area by high-resolution printers.

The curl after printing is presumed to be due to the fact that after printing, the paper (base paper) on the printing surface swells with ink and the paper expands, and then contracts in reverse as the ink dries. This is generated with the printing surface side inside, and in a remarkable case, it becomes cylindrical. Therefore, this phenomenon becomes remarkable especially when the printed matter is left on a desk with the printed surface facing upward.

[0005] This is because, when the ink after printing is left on a desk or the like in an undried state, "-" curl with the inside of the base paper being inside, which is caused by swelling due to ink absorption, is suppressed by the desk. On the other hand, since the “+” curl with the print surface side inside is free, it is considered that the curl with the print surface side inside is generated by the contraction force in the drying process.

In general, high quality paper or coated paper used for printing or writing may be used as the recording paper used in these ink jet recording methods, but in particular, full-color photographic images are printed. However, when it is desired to reproduce the color tone as much as possible, a special paper provided with an ink receiving layer having good coloring properties is usually used. For the ink receiving layer of this special paper, pigments having a large oil absorption or specific surface area, such as synthetic silica and alumina, which are excellent in ink absorption and coloring properties, are used. Unless it is particularly necessary for the application, most of the products are coated on one side only on the side to be printed and commercialized. However, in this case, it is necessary to correct the "+" curl with the ink receiving layer inside, which is caused by coating and drying the ink receiving layer, by some method.

As a method of correcting the curl, see Japanese Patent Application Laid-Open No.
No. 71207, a method of applying a synthetic polymer latex having a specific Tg, or a method of backing a pigment having an equilibrium water content in a specific range as described in JP-A-6-171206. Although there is a special treatment method like the method used for the coat layer, the simplest method is generally a treatment of applying water or steam to the back surface.

However, these methods are methods for suppressing the curl before printing, and do not suppress the left curl after the printing as in the present invention. As a method of suppressing the curl after printing, a method of providing a back coat layer made of a copolymer of styrene, maleic acid, acrylic acid, or a salt thereof (Japanese Patent Laid-Open No. 8-3101)
No. 11), but it was not always satisfactory.

That is, even if the curl before printing is adjusted to the same curl state using the back coating liquid having the same composition, a large variation occurs in the behavior of the curl after printing when actually printing. In particular, when the finish moisture was low, a phenomenon was observed in which the curl after printing was extremely deteriorated to form a tube. These phenomena also vary greatly depending on the coating amount of the ink receiving layer. As described above, a method for sufficiently suppressing the curl after printing has not yet been found.

[0010]

SUMMARY OF THE INVENTION Accordingly, it is a first object of the present invention to provide a recording paper for ink-jet recording which has a small curl toward the printing surface after printing and is suitable for full-color printing. A second object of the present invention is to provide a recording paper for ink jet recording which has a high-grade appearance, has less curl after printing, and is excellent in handling for storage and posting. Further, a third object of the present invention is to provide a recording paper for ink jet recording, which has less head rubbing when reprinting after printing, and has excellent transportability and handling properties.

[0011]

SUMMARY OF THE INVENTION The above objects of the present invention are attained in an ink jet recording sheet having at least one ink receiving layer provided on the surface of a base paper, wherein the coating amount of the entire ink receiving layer is 3 to 30 g / m ^2. The water content of the recording paper is 2 to 1
This is achieved by an ink-jet recording sheet characterized by being in the range of 2% and having a curl curvature 1 / r (m ^-1 ) of -20 <1 / r <0.3M + 0.28C-2 <20. Was.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The base paper used in the present invention is not particularly limited, and it includes chemical pulp such as LBKP and NBKP, pulp such as mechanical pulp such as GP and TMP, and pulp such as waste paper pulp, filler and size. And various internal additives such as a paper-strengthening agent and a paper-strengthening agent, and the mixture may be used. In addition, starch or surface size may be pressed or coated. In this case, the sizing degree of the base paper is preferably 2 to 60 seconds.

The ink receiving layer provided on these base papers preferably contains a white pigment, a water-soluble binder and a cationic dye fixing agent as main components. In this case, as the white pigment, light calcium carbonate or heavy calcium carbonate, kaolin, clay, talc, titanium dioxide, zinc oxide, zinc carbonate, satin white, magnesium silicate, calcium silicate, aluminum silicate, aluminum hydroxide, alumina, Pseudo-boehmite alumina, synthetic amorphous silica, magnesium carbonate, zeolite and the like can be mentioned. In the present invention, it is particularly preferable to use a pigment having a large specific surface area.

Examples of the aqueous binder include polyvinyl alcohol derivatives such as polyvinyl alcohol and silyl-modified polyvinyl alcohol, casein, gelatin, soy protein,
Oxidized starch, phosphated starch, starch derivatives such as etherified starch, carboxymethylcellulose, cellulose derivatives such as hydroxyethylcellulose, styrene-butadiene copolymer, acrylate and methacrylate polymers or copolymers, ethylene Various latexes such as a vinyl acetate copolymer and a polyurethane resin are exemplified.

As the cationic dye fixing agent, various cationic resins such as cationic polyacrylamide, polyethyleneimine and polyamide polyamine epichlorohydrin can be used. In addition, a pigment dispersant, a thickener, a dye, an antifoaming agent, and the like can be appropriately added to the ink receiving layer according to the invention, if necessary.

Various means such as a roll coater, a blade coater, a curtain coater, an air knife coater, a gravure coater, a bar coater, a rod blade coater, and a gate roll coater are used as means for providing the ink receiving layer on the base paper surface. It can be used in machine or off-machine form. Further, as the surface finish, various calendar devices such as a machine calendar, a TG calendar, and a soft calendar can be used.

The curl can be controlled by supplying moisture to the back side of the base paper, or by using a copolymer of styrene and acrylic acid or a salt thereof, and a back coat layer of a water-soluble polymer such as SBR or polyvinyl alcohol. Or a process such as simple humidification with steam can be performed online or offline. In this case, it is necessary to control the curl curvature according to the finish moisture and the coating amount of the ink receiving layer.

It is not preferable that the water content is too high or too low, and it is usually adjusted to 2 to 12%, preferably 3 to 10%. If the water content is less than 2%, it is difficult to maintain the water content in the atmosphere because the water content in the atmosphere is absorbed instantaneously. In addition, the smoothing by the calendar is also insufficient, and most of the moisture absorption occurs on the base paper side. Therefore, even if the surface is flattened with this moisture, the "+" curl becomes undesirably large. Conversely, if the water content exceeds 12%, the so-called burning phenomenon, in which the calendar effect becomes too strong and the surface becomes dark,
It is not preferable because it also causes a blocking phenomenon in which the front and back surfaces are bonded after being wound on a reel.

The coating amount of the whole ink receiving layer is usually 3 to 30.
g / m ^2, preferably a 5 to 25 g / m ^2, the coating layer may have a multilayer structure even more. If the coating amount is less than 3 g / m ^2, it is insufficient for full-color applications in terms of color development, absorptivity, or strike-through during printing, and if it exceeds 30 g / m ² , Since the ink absorption is too good and the penetration of the ink in the vertical direction is large, the print density is low, and the print density is remarkably reduced particularly in the portion where the amount of ink ejection is small, and it is disadvantageous in terms of manufacturing cost, Further, there is a problem in handling such that the ink receiving layer easily falls off.

The curl before printing may be adjusted to a curl curvature (1 / r) within a range satisfying the following conditional expression. -20 <1 / r <0.3M + 0.28C-2 <20 When the curl curvature is -20 or less and +20 or more, it is difficult to handle both when the product is cut into sheets (lithographic) with a guillotine or the like. And cannot be adjusted to the specified size. In particular, when the curvature of the curl is +20 or more, the amount of coating is too large, so that the curl after printing is very large even when the amount of ink penetrating into the base paper is small, and in an extreme case, the shape becomes cylindrical.

Since the left curl after printing is a curl with the printing surface side inside, it is more advantageous to curl the sheet to the side opposite to the printing surface (base paper) in advance before printing, as long as there is no problem in handling. However, when the coating amount is large, the amount of ink on the base paper on the printing surface side when printing under the same conditions is small, so that the swelling and shrinkage are reduced, the permissible range is increased, and the curl curvature is somewhat positive. It does not matter if you shift to.

[0022]

The recording paper for ink jet recording of the present invention not only has the advantage of being inexpensive but capable of reproducing an image similar to a photograph, and has good handleability since the curl after printing is small. In addition, since the variation between products is small, it is particularly suitable for full-color inkjet recording.

[0023]

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited thereto. However, all amounts are by weight unless otherwise specified. The evaluation method is as follows.

1) Curl curvature a) Curl curvature of blank paper A A. After adjusting the humidity in an environment of 20 ° C. and 65% for 4 hours or more in a state where five sheets of the _4th plate are stacked vertically, the center of the long side and the short side is obtained. The neighborhood is lifted together by five sheets, and the curl state is copied on paper. Next, the curl radius of the drawn curl line is measured by a digitizer, and the reciprocal thereof is defined as the curl curvature. Therefore, the larger the value of the curl curvature, the larger (stronger) the curl.

(B) Leaving curl curvature of the printed matter The five samples for which the blank curl was measured were each measured under the same environment using a full-color ink jet printer MJ-700V2C manufactured by EPSON and having a width of 1 cm.
After printing a green solid image of 8cm x 25cm in length,
The sheets are allowed to stand on a flat laboratory table one by one so as not to overlap each other, and after 48 hours or more, the curl curvature of each sheet is measured for all five sheets and averaged. "Evaluation criteria" ：: The average of the curl curvature is 20 or less. Δ: The average of the curl curvature is in the range of 20 to 30. X: The average of the curl curvature is 30 or more.

Embodiment 1 FIG. As base paper, 95 parts of LBKP and 5 parts of NBKP are mixed and beaten, and 0.5 part of a rosin sizing agent, 1 part of aluminum sulfate and 12 parts of talc are added to a pulp slurry having a Canadian standard freeness of 380 ml. The paper was made using a Fourdrinier paper machine and pre-dried with a cylinder dryer. Then, 1.8 g / m ^{2 of} oxidized starch was applied on both sides by a size press device, and dried with an after-dryer.
This was adjusted to 0 seconds, and finally a base paper having a basis weight of 85 g / m ² was obtained.

Next, a BET specific surface area of 380 is used as a pigment.
m ² / g synthetic amorphous silica (Mizukasil P-78C:
Using 100 parts of Mizusawa Chemical Co., Ltd., 20 parts of polyvinyl alcohol (PVA117: manufactured by Kuraray Co., Ltd.) and 5 parts of acrylic emulsion as a binder, and 10 parts of a commercially available polyvinylamine polymer as a dye fixing agent were mixed and stirred by a laboratory mixer. The coating solution adjusted to a solid content concentration of 20% was applied to an absolute dry weight of 15 using an air knife coater.
g / m ² was applied to the base paper surface to provide a coating layer.

Furthermore, a 10% concentration acrylic emulsion (Movinyl 8020: manufactured by Hoechst Gosei Co., Ltd.) was used to adjust the curl by using a roll coater at a dry weight of 2 g / b.
After coating on the back surface so as to obtain m ² , the drying temperature and the line speed were adjusted while performing a soft calendering process at a linear pressure of 100 kg / cm online to obtain a water content of 6% and a curl curvature of +1.6. Thus, an inkjet-coated paper of the present invention was obtained.

Embodiment 2 FIG. 10 g of ink receiving layer
/ M ² , finish moisture 5%, and curl curvature −
An ink jet-coated paper of the present invention was obtained in exactly the same manner as in Example 1, except that 2.3 was used. Embodiment 3 FIG. An ink jet coated paper of the present invention was obtained in exactly the same manner as in Example 1, except that the coating amount of the ink receiving layer was 5 g / m ² , the finish moisture was 5%, and the curl curvature was -3.5. Was.

Comparative Example 1 The concentration of the acrylic emulsion for curl adjustment was 2%, and the absolute dry coating amount was 0.5 g /
An inkjet-coated paper was obtained in exactly the same manner as in Example 1 except that m ² , the finish moisture was 6%, and the curl curvature was +6.5. Comparative Example 2. The concentration of the curl-adjusted acrylic emulsion was 2%, the absolute dry coating amount was 2 g / m ² , and the finished moisture was 14%.
%, And the curl curvature was set to +8.4.
In the same manner as above, an inkjet coated paper was obtained. Comparative Example 3 Except that the concentration of the acrylic emulsion for curl adjustment was 10%, the absolute dry coating amount was 0.5 g / m ² , the finish moisture was 1.5%, and the curl curvature was +4.6,
An inkjet coated paper was obtained in exactly the same manner as in Example 2. Comparative Example 4. Exactly the same as Example 2 except that the concentration of the acrylic emulsion for curl adjustment was 5%, the absolute dry coating amount was 0.5 g / m ² , the finish moisture was 5%, and the curl curvature was +3.8. An inkjet coated paper was obtained. Comparative Example 5 The coating amount of the ink receiving layer was 5 g / cm ² ,
Acrylic emulsion concentration for curl adjustment of 5
%, The absolute dry coating amount was 0.5 g / m ² , and an inkjet-coated paper having a finish moisture of 5% and a curl curvature of +3.8 was obtained.

The results of evaluation of the curl curvature after blocking, calender burn, and printing of the ink-jet coated papers obtained in Examples and Comparative Examples are shown in Table 1 together with the coating amount, moisture, and curl curvature of the ink receiving layer. Was. As is evident from the results in Table 1, the recording paper of the present invention has good ink jet suitability and can improve the curl after standing after printing, so that it has excellent appearance and handleability during storage, and also has a head for reprinting. It is an excellent one without rubbing.

[0032]

[Table 1]

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[Procedure amendment]

[Submission date] February 20, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

[Title of the Invention] Recording paper for inkjet recording

 ────────────────────────────────────────────────── ─── Continued from the front page (72) Inventor Yukio Kobayashi 1-30-6 Kamiochiai, Shinjuku-ku, Tokyo Japan Paper Manufacturing Co., Ltd.

Claims (4)

[Claims] 1. In an ink jet recording paper having at least one ink receiving layer provided on the surface of a base paper, the thickness of the entire ink receiving layer is 3 to 30 g / m ² , and the water content of the entire recording paper is 2 to 12%. Range and curl curvature 1
/ R (m ^-1 ) is -20 <1 / r <0.3M + 0.28C
-2 <20, an ink jet recording sheet. Here, in the above formula, M is the moisture percentage (%), and C is the coating amount (g / m ² ) of the ink receiving layer. 2. The recording paper for ink jet recording according to claim 1, wherein the ink receiving layer is a layer containing a white pigment, a water-soluble binder and a cationic dye fixing agent as main components. 3. The water content of the entire recording paper is 3 to 10%.
The recording paper for inkjet recording according to claim 1. 4. The coating amount of the whole ink receiving layer is 5 to 25 g.
/ M ² , the recording paper for inkjet recording according to claim 1.