JPH0338376A - Ink jet recording sheet - Google Patents

Abstract

PURPOSE:To obtain an ink jet recording material printable at a high speed by providing an ink acceptive coating layer based on highly water-absorbing pigment and a water-soluble polymer adhesive on a paper sheet based on cellulose pulp and having the standard deviation of submerged elongation of a specific value or less in a specific ration. CONSTITUTION:An ink jet recording sheet is formed by providing an aqueous ink receptive coating layer based on highly water-absorbing pigment and a water-soluble polymer adhesive on a paper sheet, which is based on cellulose pulp and of which the standard deviation of submerged elongations in the CD directions of a 1cm-square in a unit sheet is 30% or less in a ration of 0.5 - 15g/m<2>. By providing the ink receptive coating layer to a sheet-like support, the excellent ink jet recording sheet generating no unevenness is obtained. When the aqueous ink receptive coating layer is too thick, the coating layer becomes insufficient in its strength and, when said layer is too thin, the initial absorption and initial transmission of ink become insufficient and it is difficult to obtain a uniform coating layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a water-based ink recording material, and more particularly to a recording sheet for an inkjet printer that has excellent dimensional stability and improved appearance after printing. It is something.

[Prior art and problems to be solved by the invention] Improvements in inkjet image recording devices and inks that use water-based inks have made it possible to obtain clear images and prints using plain paper as inkjet paper. It has become. However, on the other hand, there is a growing demand for recording materials with more advanced characteristics in order to make the quality, saturation, appearance, and images of prints more attractive.

Conventionally, paper with excellent absorbency such as sizeless paper has been used for absorbency, or an absorbent coating layer such as silica has been provided on substantially sizeless paper (Japanese Patent Publication No. 60-27588).
, a non-absorbent base material such as high-size paper or plastic film has been provided with an absorbent coating layer mainly composed of silica (Japanese Patent Publication No. 63-65037), which improves absorbency and color development. Improvements have been seen in concentration, etc.

In particular, slightly coated base paper absorption type inkjet paper is
It has a good balance of cost, texture, and performance, and is expected to be used as a future inkjet paper.

Base paper absorption type inkjet paper has good ink absorption properties, and the ink is absorbed inside the paper layer, leaving it in an apparently dry state, and curling and blurring caused by water-based ink absorbed by the paper. Two things are required: mastering one's skills. These two conditions are generally contradictory and cause problems, since paper with high ink absorption tends to be deformed by the water-based ink as a result. For example, if you use a small size paper and increase the absorption speed, the ink will penetrate faster, and the ink will penetrate deeper, causing curls and bumps.

On the other hand, if an absorbent coating layer is provided on a high-sized base paper, the absorption speed of only the absorbent layer can be increased, and ink absorption into the base paper can be suppressed. However, if the ink absorption limit of the absorbent coating layer is exceeded, bleeding may occur, and the risk of curling may increase, and the unevenness may not be completely eliminated.

In Japanese Patent Publication No. 6:3-52588, a proposal was made to weaken the bonds between pulp fibers by incorporating glass fibers and a large amount of water-absorbing pigment, thereby reducing curling and unevenness. .

In this case, the addition of glass fibers not only causes various problems in use, but also causes the paper to lose its strength, and its practical use as a base paper for printers is questionable.

Conventionally, papers with good dimensional stability are known and are used for OCR paper, NIP paper, and the like.

However, there are still no known technologies or properties that can reduce or improve the smudges and curls caused by water-based ink on paper.

The base paper of the inkjet recording sheet of the present invention is mainly composed of cellulose pulp made mainly of wood,6 usually bleached kraft pulp, but if necessary, it can be made of cellulose pulp made of wood as the main raw material. Any fibrous and water-dispersible material can be used as a component.

[Purpose of the invention]

The present invention is a recording material used in a multi-color or single-color inkjet printer using water-based ink, which has a fast ink absorption speed, a large absorption capacity, reduces bumps and curls, and prints at high speed. It is an object of the present invention to provide an inkjet recording material that can solve the drawbacks of the prior art.

[Structure of the invention]

The present invention is based on a papermaking sheet containing cellulose pulp as a main component and having a standard deviation of elongation in water of 1 cm square in the CD direction within a unit sheet of 30% or less. This is an inkjet recording sheet characterized in that an ink receptive coating layer containing an agent as a main component is provided at a ratio of 0.5 to 15 g/m2.

Inkjet paper is usually used in the form of cut sheets such as A4 or fanfold, and we discovered that the smudges caused by water-based ink are caused by variations in elongation in water within these unit sheets. Ta. In particular, as a result of observing the bumping phenomenon caused by water-based ink on high-quality paper made using a regular Fourdrinier paper machine, we found that the bumpiness caused by water-based ink, which causes problems in appearance, has a period of several mm to several cm. Do you get it. As a solution to problems caused by variations in the physical behavior of paper, it is important to manage the standard deviation of physical properties and behavior. Even if the absolute value of the underwater elongation of paper made from cellulose pulp can be reduced to some extent, there is a limit.

Therefore, we cut the sample sheet into 1 cm square pieces that are close to the period of the bumps caused by the water-based ink, and
Underwater elongation was measured. As a result, the larger the standard deviation of the underwater elongation in the CD direction was than the absolute value of the underwater elongation, the more conspicuous the cot-cling phenomenon caused by the water-based ink was.

From the aesthetic evaluation, etc., the standard deviation of the underwater elongation in the CD direction is considered to be 30% of the absolute value of the underwater elongation.
% or less, and on such paper sheets, a water-based ink-receptive coating layer containing a super absorbent pigment and a water-soluble polymer adhesive as main components is applied at a rate of 0.5 to 15 g/m2. When a base paper absorption type inkjet paper was manufactured by providing a base paper, an optimal ink image receiving image was obtained with small unevenness of uneven distribution of unevenness and dimensional changes due to absorption of water-based ink, while the water absorption speed of the paper as the base material remained high. I found out that it is possible.

That is, in order to eliminate the drawbacks of the prior art described above, the present inventors have made various studies, and as a result, the present inventors have developed a sheet-like support that has been paper-formed or post-processed to reduce the deviation in underwater elongation of the paper described above.
An excellent inkjet recording sheet that does not cause dusting can be obtained by applying a coating liquid mainly composed of highly water-absorbing fine particles and a water-soluble polymer adhesive and drying it to form an ink-receptive coating layer. This is what we discovered.

A configuration in which the body is used as an absorbent body is conceivable, but other configurations are not excluded as long as the requirements of the present invention are met.

In the present invention, the ink-receptive coating layer, whose main components are highly water-absorbing fine particles such as synthetic silicic acid and a water-soluble polymer adhesive, is made permeable and the shape and spread of ink dots are controlled. By doing so, a clear image can be obtained. Incorporating a cationic vinyl acetate copolymer emulsion into the ink-receptive coating layer is one of the preferred means for achieving the object of the present invention, which further improves control of permeability and shape and spread of ink dots.

The materials used in the present invention will be explained.

- Paper sheet The paper sheet used in the present invention is produced by drying wet paper made using a Fourdrinier paper machine or the like using a dryer. As the dryer, a Yang dryer, a key dryer, a multi-barrel dryer, etc. can be used, but cellulose pulp made from ordinary wood is preferred.

The thickness of the sheet is determined by the final use of the print, but the grammage is 20 to 200 g/m2,
Those with good surface smoothness are usually used.

Since a paper sheet is used as an absorbent material, a Steckigt size of 1 to 20 seconds (for a basis weight of 64 g/m'),
Particularly preferred is a sheet with a water absorption rate of 5 to 15 seconds.

- Pigment The pigment used in the ink-receptive coating layer of the present invention is a highly liquid-absorbing and color-developing white pigment.

Preferably, the main component is fine particle synthetic silicic acid.

In order to ensure voids between particles for appropriate initial absorption, that is, short-term absorption, it is preferable that the main component be particles with a somewhat large secondary particle diameter of 1 to 5 μm. Examples of white pigments that can be used or used in combination with fine particle synthetic silicic acid include, for example, kaolin clay, talc, zeolite, precipitated calcium carbonate,
Examples include heavy calcium carbonate, aluminum hydroxide, white carbon, and organic pigments (plastic pigments).

・Water-soluble polymer adhesive The adhesive of the present invention is a natural water-soluble polymer such as polyvinyl alcohol, a protein such as casein, a starch derivative, or a base water-soluble polymer such as polyvinyl alcohol, which can be used to bond with a super absorbent pigment. It is preferable because it has good properties and good affinity with aqueous ink, which improves liquid absorption in a short time.

Polymer latex adhesives such as polyvinyl acetate and styrene butadiene can also be used.

The blending ratio of components such as pigments and adhesives is determined based on the absorption behavior and strength requirements of the aqueous ink-receptive coating layer, but it also depends on the operational characteristics of the coating solution (e.g. viscosity, fluidity, drying properties of the coating film). It is also limited by the request of The amount of water-soluble polymer adhesive is 10 to 50% by weight, especially 2% by weight of the solid content of the coating layer.
0 to 35% by weight is preferred. The cationic vinyl acetate copolymer (used in emulsion polymers) is
-25% by weight is preferred, particularly 5-15% by weight. Furthermore, by adding a cationic polymer emulsion, particularly vinyl acetate microspheres, to the coating layer, it is possible to impart permeability to the ink-receiving layer and improve ink absorption.

Cationic water-soluble polymers such as polyethyleneimine,
By adding 2 to 25% by weight of the solid content of the coating layer, the water-based ink image is made waterproof.

The thickness of the coating layer is determined by the required amount of water absorption by the coating layer, but if it is too thick, the coating layer will lack strength and cause various problems when used in printers, such as paper dust, so it should not exceed 15 g/m2. It is desirable that

If it is too thin, the initial absorption and initial permeation of the ink will be insufficient and it will be difficult to obtain a uniform coating layer, so 0.5
g/m2 or more, especially 2 to 10 g/m2 is preferred.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

In the examples, parts indicate parts by weight of solid content.

Example 1 100 kg of bleached kraft pulp, 25 kg of light calcium carbonate
kg, cationic starch 200 g, paper strength enhancer 100 g
, 100 g of alkyl ketendermer sizing agent and 50 g of water.
After mixing 00 kg and forming a wet paper using a Fourdrinier paper machine, one side was brought into close contact with the surface of a Yankee dryer to reduce the moisture content to 75%.
It was dried from 10% to 10% to obtain 58 g/m2 single gloss paper (Support Sheet-1). The resulting paper had a Beck smoothness of 135 seconds on one side and a smoothness of 18 seconds on the other side.

Water was added to 100 parts of fine-particle silicic acid (Fine Seal: Tokuyama Soda) having 70% or more of secondary particle diameters of 2 to 5 μm, and after stirring at high speed, silanated polyvinyl alcohol (R-1130= Kuraray), 101 parts of a cationic vinyl acetate copolymer (Yodozol IE503 -4: Kanebo N5C), and 10 parts of polyethyleneimine were added to produce paint-1 (concentration 15%).

Paint-1 is applied to one side of support sheet-1 at a solid content of 10 g/m
'A recording sheet was produced by coating and drying. The smoothness of the recording surface was 100 seconds, and the Stekicht size was 10 seconds.

The amount of water absorbed by the coating layer in 5 seconds was 7, measured by the brist method.
It was 5m1/m2.

The elongation of the base paper in ice in the CD direction is 1.8%, which is 1 c
The standard deviation of m-square was 15%.

Example 2 Bleached kraft pulp 100kg5I! quality calcium carbonate 2
5kg, cationic starch 200g, paper strength enhancer 100g,
After mixing 80 g of alkenylsuccinic anhydride with 5000 kg of water, a wet paper was formed using a Fourdrinier paper machine and dried from 75% to 5% using a multi-barrel dryer to produce 75 g/m2 of high-quality paper (support sheet -2) was obtained. The resulting paper had a Beck smoothness of 53 seconds on one side and a smoothness of 48 seconds on the other side.

Water was added to 100 parts of fine-particle silicic acid (Mizukashiru: Mizusawa Chemical Co., Ltd.) in which 70% or more of secondary particles have a diameter of 6 to 9 μm, and after high-speed stirring, polyvinyl alcohol (PVA1
07: Kuraray) 20 parts, water-soluble cationic polymer (PA
S-J81: Nittobo) 10 parts added to paint -2<8 degrees 1
5%) was produced.

Paint-2 was applied to one side of support sheet-2 at a solid content of 10 g/
m'' coating and drying to produce a recording sheet. The smoothness of the recording surface was 100 seconds, and the Steckigt size was 15 seconds.

The amount of water absorbed by the coating layer in 5 seconds was 9, measured by the brist method.
It was 0 mf/m'.

The underwater elongation of the base paper in the CD direction is 2.0%, which is 1 cm.
The standard deviation of the angle was 18%.

Comparative Example 1 Using substantially the same raw materials as in Example-1, wet paper was formed using a paper machine and dried from 75% to 8% moisture using a multi-barrel dryer to produce double-sided paper with a weight of 56 g/m2. (Support sheet-
3) Paper was obtained. The produced paper had a Bekk smoothness of 35 seconds on the felt surface, a smoothness of 28 seconds on the wire surface, and a Steckigt size degree of 9 seconds.

The amount of water absorbed by the coating layer in 5 seconds is 2, measured by the brist method.
It was 5mf/m'.

The underwater elongation of the base paper in the CD direction is 4.1%, which is 1 cm.
The standard deviation of the angle was 47%.

Comparative Example 2 Paint-1 was applied to the felt surface of the support sheet-4 of Comparative Example 1.
was coated with a solid content of 10 g/m''.The smoothness of the recording surface was 31.
The average size of cows and humans in seconds was 10 seconds.

The amount of water absorbed by the coating layer in 5 seconds was 4, measured by the brist method.
5m1! /m”.

The elongation of the base paper in water in the CD direction is 3.6%, which is 1 cm.
The standard deviation of the angle was 45%.

Table 1 shows the evaluation results for each of these recording sheets.

The amount of water absorbed per hour can be measured using a brist tester (J, TAP).
It was measured using PI test method No. 57).

Underwater elongation is determined by the underwater elongation test method for paper and paperboard (JTAPPI).
No. 27).

The inkjet recording properties were evaluated using an inkjet printer (HP Inc. Sinkjet) in terms of ink absorbency and unevenness after printing.

To evaluate paper dustiness, the printed portion of the printed portion was visually observed. Graded in order of least unevenness: excellent, good, fair, and slightly difficult.

Ink absorption was evaluated by measuring the number of seconds it took for the printed ink to dry. Ink absorption was ranked from good to good, fair, fair, and slightly difficult.

〔Effect of the invention〕

The inkjet recording sheet of the present invention has a high ink absorption speed and amount, and has an excellent dot shape that is close to a perfect circle, but it also eliminates the unevenness that is a drawback of conventional methods, and is an excellent high-speed inkjet full-color sheet.・It makes it possible to conduct business IJ and projects, and it will greatly contribute to the industrial world.

Claims (1)

[Claims] 1. The main component is cellulose pulp, and the standard deviation of elongation in water in the CD direction of a 1 cm square in a unit sheet is 30.
% or less, a water-based ink-receptive coating layer containing a highly water-absorbing pigment and a water-soluble polymer adhesive as the main components,
An inkjet recording sheet characterized by being provided at a ratio of 0.5 to 15 g/m^2.