JP2780765B2 - Manufacturing method of 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 a color ink jet recording sheet which has the same feeling as high-quality paper, is inexpensive, and can provide excellent quality image recording. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Ink-jet recording papers using water-based inks are required to have a rapid absorption of ink and a high color density, and are basically bonded to a highly absorbent pigment such as synthetic silica having a large specific surface area. Generally, a coating layer (ink receiving layer) mainly composed of an agent is provided on the surface of a base paper mainly composed of cellulose pulp at a rate of 20 g / m ² or more per one side.

That is, various methods have been tried since the early development of ink jet recording paper. For example, a method using a silica pigment as a pigment (Japanese Patent Laid-Open No. 52-907).
4, JP-A-55-51583, JP-A-56-148
No. 583, JP-A-58-72495), a water-soluble polymer coating layer is provided on the ink-receiving layer (JP-A-55-72495).
No. 144172, JP-A-55-146786), or a method of using a porous pigment as a pigment to improve ink receptivity (JP-A-58-110287).

However, since pigments such as synthetic silica used in these methods are generally expensive, ink-jet paper provided with a receiving layer of 20 g / m ² or more per side is very expensive, and its appearance is high. Is the coated paper itself. Therefore, a method using a relatively inexpensive pigment such as silica or calcium carbonate having a small specific surface area has been considered, and various attempts have been made. However, the coating layer, due to the formation and irregularities of the base paper, the film thickness is likely to be non-uniform, because the ink absorption of the cheap pigment is low,
Since uneven absorption of ink occurs and the ability to retain a coloring component is low, problems such as low color density of an image occur.

[0005] Further, from the viewpoint that the absorption capacity must be ensured in order to improve the ink absorbency,
Usually, measures are taken to increase the amount of coating, but in this case, the cost is high and the problem of so-called coated paper far from the texture of plain paper cannot be solved. In addition, since these methods are based on a design concept of absorbing all the ink only by the ink receiving layer, as a base paper used in these methods, a base paper having a somewhat reduced ink absorbency is usually used. I have.

On the other hand, demand for paper that is inexpensive and has the feel of high-quality paper but has the suitability for ink-jet recording has rapidly increased in recent years. Even if non-size paper or low-size paper with no effective size is used, recording of relatively good image quality and print density has come to be obtained. However, particularly with the spread of color recording, demands for high image quality are increasing, and accordingly, there is a need for prints with further improved saturation and resolution. And
To meet such demands, the print quality using non-size paper is not sufficient, and the print density is insufficient, particularly in that the print density is low.

Therefore, in order to ensure the ink absorption capacity while maintaining the appearance of so-called plain paper similar to high quality paper,
The idea that it is important to give the base paper some degree of absorbency instead of minimizing the amount of coating has become influential. Based on the above concept, the size of the base paper is specified, and a receiving layer containing a pigment having good absorbability as a main component is provided so as to be 10 g / m ² or less per side (Japanese Patent Laid-Open Publication No. No. 219267) has been proposed, but this method prevents ink absorption unevenness in a low coating amount region where the texture of plain paper can be maintained.
The print density cannot be made sufficiently high.

In other words, it is difficult to produce paper having the ink jet recording suitability for color while maintaining the feeling of plain paper by the conventional methods. At present, only those having the appearance of coated paper have been obtained.

The inventors of the present invention have conducted intensive studies on paper having the appearance of plain paper and capable of obtaining high-quality recording when color ink jet recording is performed. As a result, the appearance of plain paper remains. Therefore, it is necessary that the coating amount is about 5 g / m ² or less on one side, and the ink absorption capacity of a color printer currently on the market is about 5 g / m ^{2 on} one side. The coating layer alone is not sufficient, and in the range of about 5 g / m ² or less on one side, the printing density depends on the coating amount, and the higher the coating amount, the higher the printing density. Is defined by the degree of size, and by providing an intermediate layer containing a water-soluble polymer as a main component, the coating amount of the ink receiving layer is reduced to 5 g / m ^2.
It has been found that, by providing the ink receiving layer using a curtain coater while the intermediate layer is not dried, the thickness of the receiving layer can be made sufficiently uniform. Reached.

[0010]

Accordingly, a first object of the present invention is to provide a color ink jet recording using an aqueous ink, which is excellent in ink absorbency and image density, has a feel of plain paper, and has the same effect as ink. An object of the present invention is to provide an ink jet recording sheet which is free from uneven absorption and has good dot reproducibility. A second object of the present invention is to provide an inexpensive method for producing ink-jet recording paper that has the feel of plain paper and can achieve high-quality recording.

[0011]

SUMMARY OF THE INVENTION The above objects of the present invention are as follows.
Basis weight 50 to 100 g / m ² base paper, and at least the base paper provided on one surface, the intermediate layer 1 to 5 g / m ² and the intermediate layer containing a water-soluble polymer 50 to 100 wt% 20 to 300 ml / 100 g of pigment having an average oil absorption of 20 to
This was achieved by a method for producing an ink jet recording paper provided with 1 to 5 g / m ² of an ink receiving layer mainly containing 80% by weight and 20 to 80% by weight of a water-soluble polymer adhesive.

The base paper used in the present invention may be at least one selected from softwood bleached kraft pulp, hardwood bleached kraft pulp and the like, and may include a filler such as clay and talc, a sizing agent, a retention improver, and a paper strength. It is manufactured by appropriately adding various papermaking chemicals such as a strengthening agent, making paper, and then drying with a Yankee dryer or a multi-cylinder dryer. In the present invention,
Since the ink absorbency of the base paper is important, it is necessary to appropriately adjust the amount of the sizing agent added to improve the absorbability.

It is considered that the best method for measuring the ink absorption is to measure the ink absorption rate using a printer actually used. It is also possible to make it. In other words, when the Stighit sizing degree is 20 seconds or longer, problems such as the ink flowing without drying during printing and the contamination of the roll often occur. Therefore, when the base paper is used as it is as printer paper. Is preferably 10 seconds or less.

The basis weight of the base paper is appropriately determined according to the use within a range of 50 to 100 g / m ² . By the way, since the Stekigt sizing degree measures the permeation speed in the thickness direction of the paper, the value increases as the basis weight increases, even if the absorption rate is the same. Therefore, in the present invention, 70 g / m
^{On the} basis of ² , the Stekigt sizing degree must be 5 seconds or less. This is when the base layer is coated with an intermediate layer provided to efficiently keep the ink receiving layer on the surface layer,
This is because the binder or the like used for the intermediate layer penetrates into the base paper, and the absorbency of the base paper is slightly reduced.

When a coating layer containing a water-soluble polymer as a main component in an amount of 50 to 100% by weight in terms of solid content is provided as an intermediate layer on both sides or one side of the base paper in a range of 1 to 5 g / m ^2. Is not particularly limited, and may be a known coating method. For example, an on-machine or off-machine coater such as a size press, a gate roll, a blade coater, an air knife coater, a bar coater, a rod blade coater, a gravure coater, and a curtain coater can be appropriately used.

The water-soluble polymer used for the intermediate layer can be appropriately selected from known ones. In particular, starch and its derivatives are preferably used. These water-soluble polymers may be used alone or in combination of two or more. In the present invention, it is preferable to provide the ink receiving layer while the intermediate layer is not dried in order to further improve the yield of the ink receiving layer and make the thickness of the receiving layer uniform. As a coating device for providing an intermediate layer,
It is preferable that the apparatus be capable of performing so-called wet-on-wet coating, which can be applied online with a coating apparatus provided with an ink receiving layer.

In the present invention, the first reason for using a binder such as a water-soluble polymer for the intermediate layer is that an intermediate layer having high ink receptivity is formed after drying, and the second reason is that these are used. This is because the water retention of the solution is high, and the undried state, which can be expected to be a high barrier when the ink receiving layer is provided, can be maintained for a long time.

In the present invention, when providing the ink receiving layer on the intermediate layer, it is particularly preferable to use a curtain coater. When the ink receiving layer is applied after the drying of the intermediate layer, not only auxiliary agents such as a binder and a waterproofing agent in the ink receiving layer, but also fine pigments penetrate into the base paper without remaining in the intermediate layer. Therefore, if the amount of coating is such that the texture of plain paper can be maintained, the ink holding capacity will not be sufficient,
Inkjet suitability such as print density and water resistance is reduced.

On the other hand, when the intermediate layer is in an undried state, the barrier properties of the intermediate layer are high as described above, and it is necessary to minimize the penetration of each component constituting the ink receiving layer into the base paper. Can be. This is the reason why in the present invention, it is particularly preferable to use a curtain coater as a coating device for the ink receiving layer. That is, when a base paper having good absorbency is used as a base paper and the base paper is coated at a coating amount of 5 g / m ² or less, the curtain coater may have a uniform coating thickness. The most suitable coater, and if it is a curtain coater, the condition of the base paper (that is, surface properties) is poor, and even if the unevenness is large or wet, the ink receiving layer is hardly affected by these. Can be applied.

On the other hand, when a blade or air knife coating, which is a general coating device, is used, there are the following problems. That is, the blade coating is easily affected by the surface properties (irregularities) of the base paper, so that when the base paper has large irregularities, the thickness of the coating layer becomes uneven.
Further, in the case of a smooth base paper with a small amount of irregularities, a relatively good coating layer can be obtained, but there is a problem that streak frequently occurs in operation.

In the case of air knife coating, a coating liquid is scraped off by air, so that it can be used only for a coating liquid having a low viscosity. There are many penetration rates. In particular, when a base paper having good absorbency is used as in the case of the present invention, since the coating liquid penetrates significantly into the base paper, the coating layer is required to satisfy the final quality. Need to be increased.

In blade coating or air knife coating, excess coating liquid is supplied, and then excess coating liquid is scraped off with blades or air. Will be weighed after penetrating into the base paper,
The coating liquid is required more than the coating layer necessary for the printing density. Also, weighing while filling the irregularities of the base paper,
The thickness of the coating layer becomes uneven.

Therefore, in the present invention, an intermediate layer is provided between the ink receiving layer and the base paper to suppress the penetration of the ink receiving layer into the base paper. This makes it possible to improve the printing suitability when compared with the same coating amount, and also to reduce the coating amount for obtaining the same printing suitability.
However, if blade coating or air knife coating is used, the ink receiving layer can only be coated after the intermediate layer has been dried, which complicates the process and increases the manufacturing cost, but before coating on the base paper. By using a curtain coater, which is a method of weighing, the coating can be performed even when the intermediate layer is in a wet state.

As the pigment used in the ink receiving layer, synthetic silica, calcium carbonate, barium sulfate, titanium oxide,
Inorganic pigments such as zinc oxide, zinc carbonate, satin white, aluminum silicate, magnesium silicate, and alumina; organic pigments such as plastic pigments, urea resin pigments, and melamine resin pigments; and general organic / inorganic composite pigments Oils having an oil absorption of 20 to 300
ml / 100 g, preferably 100-300 ml
/ 100 g can be appropriately selected and used. These pigments can be used alone or in combination of two or more.

Further, even if the pigment having an oil absorption of 20 ml / 100 g or less is combined with, for example, a pigment having an oil absorption of 400 ml / 100 g or more, the oil absorption (average oil absorption) of the mixed system is reduced to 2%.
It is also possible to use by setting it in the range of 0 to 300 ml / 100 g. The average oil absorption of the pigment used is 2
Since in the case of less than 0 ml / 100 g is small absorption oil amount of the ink, the ink absorbency is insufficient in coating amount of 5 g / ^{m 2} or less, in the case of more pigments 300 ml / 100 g is reversed, with a binder If the amount of a certain water-soluble polymer is not increased, the strength of the ink receiving layer becomes insufficient, and if the binder is increased until the strength can be ensured, the absorptivity deteriorates.

The binder used in the present invention has good adhesion to the pigment and has an affinity for aqueous inks.
Those having permeability or swelling are preferred. Specific examples of such binders include, for example, water-soluble polymers such as polyvinyl alcohol, starch, and various derivatives thereof, and natural or synthetic polymers such as polyvinyl acetate, and polymer latex such as styrene / butadiene. Aqueous polymers can be mentioned. The compounding amount of the binder is appropriately selected depending on the kind of the pigment or the binder to be used within a range of 20 to 80% by weight of the whole coating layer. In the present invention, if necessary, various auxiliaries such as a dispersant, a thickener, an antifoaming agent, an antioxidant, a wetting agent, and a waterproofing agent can be further added.

[0027]

The recording paper of the present invention has a large ink receiving capacity because the ink receiving layer does not penetrate into the base paper, although the ink receiving layer does not penetrate into the base paper even though it has the feel of plain paper because the ink receiving layer is thin. It is suitable for obtaining high quality ink jet recording.

[0028]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. In Examples and Comparative Examples,% and parts mean weight% and parts by weight, respectively, and the amount of each addition is a solid content. Further, those having a coating amount of more than 5 g / m ² are clearly judged to be coated paper and are not included in the present invention.

Embodiment 1 Pulp consisting of 80 parts of hardwood bleached kraft pulp and 20 parts of softwood kraft pulp was mixed with 10 parts of heavy calcium carbonate and a paper strength agent (Polymalon 61).
9, Arakawa Chemical Industry Co., Ltd.) Paper is made using a fourdrinier paper machine from a slurry to which 0.1 part is added, and dried with a multi-cylinder dryer, and the basis weight is 70 g / m ² , 0
A second base paper was obtained.

Starch (Oji Ace A: manufactured by Oji Cornstarch Co., Ltd.) was applied to the base paper at 2 g / m ^{2 using} a rod blade to form an intermediate layer. While the intermediate layer is in a wet state, 60 parts of fine particle silica (Fine Seal X-37: manufactured by Tokuyama Soda Co., Ltd.) and polyvinyl alcohol (Kuraray 1)
17: Kuraray Co., Ltd.) 40 parts of a coating liquid for an ink receiving layer to which a water-proofing agent, an antifoaming agent, an ink fixing agent and the like are appropriately added using a curtain coater so as to be 4 g / m ^2. Then, the ink was dried until the water content became 6% to obtain an ink jet recording paper.

Embodiment 2 FIG. The pulp slurry used in Example 1 was further mixed with 1 part of a carotin starch (Cato-F: manufactured by Oji National Co., Ltd.) and a neutral sizing agent (Fibran 81,
Paper made from a slurry to which 0.03 part of the slurry was added using a Fourdrinier paper machine, dried with a multi-cylinder dryer, and a base paper having a basis weight of 70 g / m ² and a Stekigt sizing degree of 5 seconds. I got An ink jet recording paper having a water content of 6% was obtained in the same manner as in Example 1 except that the base paper thus obtained was used and the coating amount of the ink receiving layer was 5 g / m ² . .

Comparative Example 1 4 g / m ^{2 of} starch (Oji Ace A: manufactured by Oji Cornstarch Co., Ltd.) is applied on both sides of the base paper obtained in Example 2 and having a Stekihito sizing degree of 5 seconds by a size press, and dried with a cylinder dryer. After that, an ink jet recording sheet having a water content of 6% was obtained in exactly the same manner as in Example 2 except that the ink receiving layer was applied.

Comparative Example 2 An ink jet recording paper was obtained in the same manner as in Example 1 except that the coating liquid for the ink receiving layer was applied using a blade coater.

Comparative Example 3 An ink jet recording paper was obtained in exactly the same manner as in Example 1, except that an air knife coater was used as a coating device for the ink receiving layer.

Comparative Example 4 Neutral sizing agent (Fibran 8
1, except for changing 0.06 parts usage Oji National Co., Ltd.) was paper under the same conditions as in Example 2, and dried in a multi-cylinder dryer, Stockigt sizing degree of basis weight 70 g / m ² Obtained a base paper of 10 seconds. An intermediate layer and an ink receiving layer were provided on the base paper in exactly the same manner as in Example 2 to obtain an ink jet recording paper having a water content of 6%.

Comparative Example 5 Except that the pigment used for the ink receiving layer in Example 1 was replaced with sedimentable calcium carbonate (Univar 70: manufactured by Shiraishi Industry Co., Ltd.), and that the coating amount of the ink receiving layer was 5 g / m ² , the same as in Example 1 Similarly, an ink jet recording paper having a water content of 6% was obtained.

Comparative Example 6 0.8 coating amount of ink receiving layer
g / m ² , except that the water content was 6
% Ink-jet recording paper was obtained.

Comparative Example 7 15 parts of fine particle silica (Fine Seal X-37: manufactured by Tokuyama Soda Co., Ltd.) and polyvinyl alcohol (Kuraray 117:
An ink jet recording sheet having a water content of 6% was obtained in exactly the same manner as in Example 2 except that 85 parts were used (manufactured by Kuraray Co., Ltd.).

Comparative Example 8 85 parts of fine particle silica (Fine Seal X-37: manufactured by Tokuyama Soda Co., Ltd.) and polyvinyl alcohol (Kuraray 117:
An ink jet recording sheet having a water content of 6% was obtained in exactly the same manner as in Example 2 except that 15 parts were used (manufactured by Kuraray Co., Ltd.).

Table 1 shows the recording suitability results of the ink jet recording papers obtained in Examples and Comparative Examples.

[Table 1] Here, the evaluation of the recording was performed by using an inkjet printer (trade name: Color Image Jet IO-735X, manufactured by Sharp Corporation) to perform color printing of a single color and a mixed color, and to examine the ink absorbency (drying speed), absorption unevenness, and the like. The printing density and the coating layer strength were measured according to the following criteria.

(4) Ink Absorbency The ink absorbency (drying speed) of the printing portion was visually evaluated in four steps. ◎ : Absorbed completely as a whole. ：: The ink is slightly overflowing in a large amount of ink. Δ: Partial overflow. D: Almost all of the ink overflowed, and ink flow was also observed.

(4) Absorption unevenness The absorption unevenness of the print was visually evaluated in four steps. A: No unevenness is observed at all. ：: Some unevenness is observed in a portion where the amount of ink is large. Δ: Partial unevenness is observed. X: Unevenness is observed on almost the entire surface.

(4) Print density The mixed color portion after printing was measured with a Macbeth densitometer.

(4) Coating Layer Strength A pencil having different hardness was used on the surface of the coating layer, and a determination was made in a state where a line was drawn at a constant writing pressure. A: Lines can be drawn with a hardness of 6H or more. ：: Lines can be drawn up to a hardness of 4H. Δ: Lines can be drawn up to a hardness of 2H. ×: No line could be drawn even with HB hardness. As is clear from the results in Table 1, the ink jet recording paper of the present invention can be used for a water-based ink jet recording type color printer, has excellent ink absorbency and image density, and has the feel of plain paper. It was proved that the ink jet recording paper had no uneven absorption and had a good dot diameter.

Continuation of the front page (56) References JP 5-124329 (JP, A) JP 1-295878 (JP, A) JP 62-134285 (JP, A) JP 6-48017 (JP) JP-A-7-119083 (JP, A) JP-A-4-22676 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41M 5/00

Claims (1)

(57) [Claims] 1. An intermediate layer having a water-soluble polymer as a main component in an amount of 50 to 100% by weight in terms of solid content is provided on at least one side of a base paper having a basis weight of 50 to 100 g / m ^{2 in} an amount of 1 to 5 g per side. / M ²
20 to 80% by weight of a pigment having an average oil absorption of 20 to 300 ml / 100 g on the intermediate layer.
And an ink-receiving layer containing 20 to 80% by weight of a water-soluble polymer adhesive as a main component while the intermediate layer is not dried, so that the ink receiving layer has a weight of 1 to 5 g / m ² per one side. The production method, wherein the base paper has a basis weight of 70 g.
/ M ² , wherein the degree of stiffness is 5 seconds or less and the ink receiving layer is applied by a curtain coater.