JP2003291515A - Base paper for inkjet recording paper and inkjet recording paper using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet substrate which has high ink receptivity and high opacity, and in which offset printability is provided on a surface opposite to an ink receiving layer. <P>SOLUTION: A surface layer of the base paper serves as a filler highly- contained layer; a backside layer serves as the base paper which is composed of a plurality of layers serving as filler low-contained layers; and the ink receiving layer is provided on the filler highly-contained layer of the base paper. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet recording paper and its base paper, and more particularly to an inkjet recording paper which is excellent in printability and print density and is particularly suitable for use in postcards.

[0002]

2. Description of the Related Art Ink jet recording methods have become popular rapidly in recent years because they are easy to achieve full color printing and have little printing noise. In this method, minute droplets of ink are ejected from a nozzle toward a recording medium at high speed to adhere to the recording medium to record images or characters, and the ink contains a large amount of solvent. Therefore, it is necessary for the recording medium to quickly absorb the ink. Also, with the recent widespread use of computers and digital cameras, images close to those of silver halide photographs have been demanded. Therefore, the inkjet recording paper is required to have high color developability, resolution and color reproducibility, and so-called coated type inkjet recording paper provided with an ink receiving layer on the surface has been developed in order to meet these requirements.

In recent years, the number of postcards such as New Year's postcards, summer greeting cards, greeting cards, and the like has been increasing with an inkjet printer. Inkjet recording using these postcards requires recording a large amount of ink and high recording accuracy because it corresponds to recording an image or a pattern on the entire recording surface.
Therefore, usually, an ink receiving layer containing a pigment and an adhesive as a main component is provided on one side of a postcard base paper to form an entire inkjet recording surface. A part of the ink recorded on the ink receiving layer passes through the ink receiving layer and is absorbed by the underlying paper portion. Therefore, the base paper needs to have a certain ink receptivity. Further, since a postal code frame or the like is printed on the opposite surface of the ink receiving layer, suitability for offset printing, that is, high surface strength capable of withstanding offset printing is required.
In addition, the base paper must have high opacity so that the permeated ink cannot be seen from the back side. In the case of a postcard or a card, the paper is thick, so it does not matter so much.
For papers of g / m ² or less, the base paper needs to have high opacity so that the permeated ink cannot be seen from the back surface.

In general, a single-layer paper is used as the ink jet paper. As a method for imparting offset printing suitability to a so-called plain paper type inkjet recording paper in which a single-layer paper is used as an inkjet recording paper as it is, a method of performing size press treatment has been proposed.
For example, Japanese Patent Application Laid-Open No. 2000-71606 discloses means for size-pressing a cationic resin and a water-soluble polymer such as polyvinyl alcohol onto the surface of a base paper containing a filler and a rosin-based size emulsion. JP 200
Japanese Patent Laid-Open No. 1-64893 proposes that the surface of a base paper is surface-treated with a quaternary ammonium salt formed from ammonia, amine, and epichlorohydrin by a size press.

However, these are so-called high-quality inkjet papers or PPC / inkjet co-papers in which an ink receiving layer is not provided on the base paper, and an ink receiving layer containing a pigment as a main component is provided on the base paper. Inkjet suitability is inferior when compared with special paper. Further, as a method of forming an ink receiving layer suitable for offset printing on a base paper instead of a size press, for example, in JP-A-10-337980, synthetic silica, polyvinyl alcohol, ethylene. By applying a coating solution containing a vinyl acetate copolymer, an acrylic amide-based cationic polymer, a dimethyldiallylammonium chloride / sulfur dioxide copolymer, and a polyamide polyurea resin, an offset-printable inkjet receiving layer is formed. A method is disclosed. In all of these methods, the surface of the base paper is size-pressed or coated to improve the offset printability, and the offset printability is not improved depending on the structure or composition of the base paper.

On the other hand, as a method for providing ink jet aptitude by changing the structure and composition of the base paper, for example, in JP-A-62-162588, wood pulp is the main component and zeolite or silica is used as a filler together. Therefore, without using a coating layer or special pigment,
The color of the ink attached to the sheet structure is vivid,
The ink jet recording sheet is said to be capable of giving an image having a circular dot shape and a sharp edge, having a large surface strength of the sheet, and capable of recording a high resolution image at a high speed. Furthermore, JP-A-8-389
No. 2 discloses that by incorporating a filler and a cation-modified bacterial cellulose disaggregate having a degree of substitution within a specific range, a recording medium having excellent opacity and strength and excellent image density uniformity can be obtained. Disclosure.

[0007]

However, when the proportion of the filler in the base paper increases, the ink receptivity and opacity improve, but the surface strength decreases and the paper powder increases from the surface of the base paper, resulting in offset printing. This will cause the blanket used in the process to become dirty. Ink receptivity,
Since the opacity and the suitability for offset printing have contradictory characteristics, it is limited to provide a plurality of contradictory properties in a single-layer paper as a support for the ink receiving layer. In addition, even if the one-pass retention gives a difference between the front and the back, another problem such as deterioration of the formation occurs.

Therefore, an object of the present invention is to provide an ink jet recording paper which has high surface strength, excellent offset printing suitability, high ink receptivity and high opacity.

[0009]

As a result of intensive studies to solve the above problems, the present inventors have made the base paper a multi-layered structure, and greatly change the filler content on the front and back sides of the base paper to obtain a high filler content layer. The present invention has been completed by finding that the above problems can be solved by forming an ink receiving layer on the side. That is, the present invention is a base paper for ink jet recording paper, which is mainly composed of pulp and filler, and has a multilayer structure of at least two layers, the filler content of the surface layer is larger than the filler content of the back layer, and the surface layer is The high-filler layer is sufficient to satisfy the desired ink receptivity, the back layer is a low-filler layer sufficient to satisfy the desired surface strength, and the amount of the filler in the surface layer is preferably 5 to 40% by weight based on the pulp of the surface layer. %, And the amount of the filler in the back layer is preferably 0 to 10% by weight based on the pulp in the back layer, and the base paper having such a structure is preferably made at once by a multi-layer paper machine. An ink receiving layer containing a filler and an adhesive as main components is provided on the surface layer, which is a layer, to form an inkjet recording paper.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. <Base Paper> The base paper of the present invention is mainly composed of wood pulp and filler. LBKP, NBK as wood pulp
Chemical pulp such as P, GP, PGW, RMP, TMP, C
They are mechanical pulp such as TMP, CMP, CGP, etc., waste paper pulp such as DIP, etc., and these can be appropriately mixed and used. If necessary, other vegetable fibers, synthetic fibers,
Alternatively, inorganic fibers can be blended. Fillers include natural calcium silicate such as heavy calcium carbonate, light calcium carbonate, magnesium carbonate, calcium / magnesium carbonate, kaolin, calcined clay, bentonite, sericite, zeolite, talc, synthetic aluminum silicate, synthetic calcium silicate, etc. Silicates, silicic acids such as diatomaceous earth and synthetic silica, aluminum hydroxide, aluminum hydrates such as pseudo-boehmite, calcium sulfate, titanium dioxide, known fillers such as zinc oxide can be used, but among these, talc, Kaolin, calcium carbonate, titanium dioxide and the like are commonly used.

In making the base paper, the pulp is beaten, a filler is added, and if necessary, various conventionally known additives such as a sizing agent, a fixing agent, a yield improving agent, and a paper strength enhancer are added and mixed. Paper is made with a Fourdrinier paper machine, a cylinder paper machine, a twin wire paper machine, or the like.

In the base paper of the present invention, a high-filler-containing layer and a plurality of layers including a low-filler-containing layer are separately formed and laminated together, or a multi-layer paper machine is used to temporarily form a layer having a desired filler content. Make paper. <Ink Receiving Layer> Pigments used in the ink receiving layer include synthetic silica (colloidal silica, wet process silica, vapor phase process silica, etc.), alumina and hydrated alumina (alumina sol,
Colloidal alumina, aluminum hydroxide, pseudoboehmite, etc.), silicates such as aluminum silicate, magnesium silicate and calcium silicate, magnesium carbonate, light calcium carbonate, heavy calcium carbonate, clay such as kaolin, talc and calcined clay, calcium sulfate, Not only inorganic pigments such as titanium dioxide, zinc oxide and zinc carbonate, but also organic pigments such as plastic pigments and urea resins can be used. Among these, synthetic silica is preferably used because various products having different properties such as ink absorbency, color developability, and particle size and oil absorption are commercialized.

In the ink receiving layer, a hydrophilic binder is usually used to maintain the properties as a coating film. Examples of the hydrophilic binder include polyvinyl alcohol and its modified products, modified starch such as oxidized starch, etherified starch and hydroxymethylated starch, proteins such as casein, gelatin and soybean protein, methyl cellulose, hydroxymethyl cellulose and carboxymethyl cellulose. The cellulose derivatives, SB latex, NB latex, acrylic latex, vinyl acetate-based latex such as polyvinyl acetate and ethylene vinyl acetate, polyurethane, unsaturated polyester resin and the like can be used. In the present invention, at least one kind of these hydrophilic binders is used, but it is preferable to use polyvinyl alcohol as a main component in terms of affinity with an aqueous inkjet ink, color developability, and surface strength.

The amount of the compounding part is preferably 5 to 60 parts with respect to 100 parts by weight of the above-mentioned pigment. If the blending amount of the binder is small, the surface strength will be insufficient, and if it is too large, the ink absorbency will be insufficient. If necessary, in addition to the pigment and the binder, a sizing agent, a surfactant, a water-proofing agent, a pigment dispersant, a thickener, a defoaming agent, a defoaming agent, a release agent, a foaming agent, a coloring agent. Dyes, color pigments, fluorescent dyes, preservatives, wet paper strength enhancers, water retention agents and the like can be added as appropriate.

As a method for providing the ink receiving layer on the support, various blade coaters which are general coating devices,
Roll coater, air knife coater, bar coater,
Various devices such as a gate roll coater, a curtain coater, a short dwell coater, a gravure coater, a flexo gravure coater, and a size press can be used on-machine or off-machine.

With respect to the coating amount of the ink receiving layer, if the coating amount is small, the initial absorption of ink tends to be insufficient, and it becomes difficult to obtain a uniform coating layer. If the coating amount is large, the strength of the ink receiving layer is high. There is a shortage, and powder drop during cutting tends to be a problem. The coating amount can be determined according to the desired quality in consideration of recording suitability and coating suitability, but usually 3 to 4
Was ^{0g / m 2, 5~20g / m} 2 is more preferable.

Further, after the ink receiving layer is provided, it is possible to carry out the surface treatment with a calendar device such as a machine calendar, a super calendar or a soft calendar.

[0018]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. In the examples and comparative examples, parts and% represent important parts of solid content and weight% of solid content. [Example 1] <Base paper><Rear surface layer blending: no filler> Pulp: hardwood bleached kraft pulp, freeness 360 ml 100 parts Filler: unused additive: cationized starch 2 parts, anionized polyacrylamide 0. 3 parts, alkyl ketene dimer emulsion 0.3 parts <Surface layer blend> Pulp: hardwood bleached kraft pulp, 360 ml freeness 100 parts Filler: kaolin clay 20 parts Additive: cationized starch 2 parts <production of base paper> Using a Fourdrinier type multi-layer paper machine, a back layer web and a surface layer web of the above formulation are formed, and a two-layer web in which the back layer web is superposed on the back layer web is dehydrated by a wet press. Then, it was subjected to a two-stage pressure press and then dried to produce a two-layer structure base paper. Then, using a 5% liquid solution of oxidized starch, a dry press was applied with a size press to a dry weight of 3.5 g / m ² , followed by drying and machine calendering to obtain a basis weight of 180.
A base paper of g / m ² was obtained. The filler content of the surface layer of this base paper was 15.3%, and the filler content of the back surface layer was 0.1%. <Compounding of ink receiving layer> Synthetic amorphous silica (Fineseal X-37B: manufactured by Tokuyama Corp.) 40 as a pigment
And 60 parts of synthetic amorphous silica (Cyroid 621: Grace Devison Co., Ltd.), 25 parts of polyvinyl alcohol (PVA-117, made by Kuraray) as a hydrophilic adhesive, ethylene vinyl acetate emulsion (Sumika Flex 74).
00 parts made by Sumitomo Chemical Co., Ltd. and 4 parts of styrene butadiene latex (made by LX438C Nippon Zeon) are mixed, and further 2 parts of styrene acrylic resin (Polymaron 360) as a surface sizing agent, polyamine dye fixing agent (PAS).
-H-10L (manufactured by Nitto Boseki Co., Ltd.) 8 parts, and a color having a solid content of 20% was adjusted by appropriately adding dilution water. <Manufacture of Inkjet Recording Paper> The above-mentioned color was applied on the surface side of the base paper prepared above using a bar blade coater so that the coating amount was 9 g / m ^2, and the moisture content in the paper was 4.5. An inkjet recording paper was obtained by drying until the content became%. [Example 2] A base paper was produced in the same manner as in Example 1 except that the content of the filler in the back surface layer of the base paper was changed to 7%. The filler content in the front surface layer of this base paper was 15.1%, and the filler content in the back surface layer was 4.8%. An ink jet recording paper was prepared in the same manner by using the same color as in Example 1 on the surface layer side of this base paper. [Comparative Example 1] A single layer paper having a basis weight of 180 g / m ² was prepared by making a single layer paper with a Fourdrinier paper machine using the stock composition of the back layer of Example 1 and then treating it in the same manner as in Example 1. I got the base paper. The filler content in this base paper was 0%. An ink jet recording paper of Comparative Example 1 was prepared by applying and drying on the felt side of this base paper in the same manner using the composition of the ink receiving layer used in Example 1. [Comparative Example 2] A single layer paper having a basis weight of 180 g / m ² was prepared by making a single layer paper with a Fourdrinier paper machine using the stock material mixture of the surface layer of Example 1, and then treating in the same manner as in Example 1. I got the base paper. The content of the filler in this base paper was 15.5%. An ink jet recording paper of Comparative Example 2 was prepared by applying the same composition as the ink receiving layer used in Example 1 to the felt side of the base paper and drying it in the same manner. Evaluation method The recording sheets obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were evaluated by the methods described below. In each item,
If it is evaluated as Δ or more, it can be put to practical use. In addition, about inkjet recording evaluation, the commercially available inkjet printer PM-950C (Seiko Epson inkjet printer) was used. Evaluation item <Color development> Solid images of 3 cm on black, cyan, magenta, and yellow were printed and left for one day.
HRD914) and the total value was evaluated. ◯: The total value of the four colors is 6.5 or more. X: The total value of the four colors is less than 6.5. <Ink Absorption> Red and green solid images were printed side by side, and the degree of bleeding at the boundary was evaluated. ◯: The boundary is clear and no bleeding is observed. Δ: The boundary is slightly blurred but no bleeding is observed. ×: The boundary is unclear and bleeding is recognized. The evaluation results are as shown in Table 1. <Printability> 5,000 sheets were printed on a R202 offset printing machine manufactured by Roland Co., and the blanket stain condition was visually evaluated. <Opacity of Inkjet Recording Medium> Whether or not the image printed on the ink receiving layer side by the evaluation of color development can be seen through from the surface opposite to the ink receiving layer was visually evaluated. ○: The image cannot be seen at all. Δ: The image is slightly visible, but it is at a practically acceptable level. X: The image is transparent.

[0019]

[Table 1]

As is apparent from Table 1, Examples 1 and 2
The ink jet recording paper manufactured in 1. has improved printability without lowering print density and ink absorbency. The ink absorption of the inkjet recording paper manufactured in Comparative Example 1 is poor. Further, in Comparative Example 2, the result was that the blanket was soiled and so-called printability was poor. Further, when the inkjet recording surface was viewed from the offset printing surface after inkjet recording, the inkjet recording paper of Example 1 had high opacity and no inkjet recording was visible. In Example 2, the color of the ink jet recording surface was slightly sensed as compared with the paper of Example 1, but it was not possible to recognize at all that the ink jet recording was on the back surface by seeing only the color. In Comparative Example 1, the opacity was low because there was no filler at all, and the color of the inkjet recording surface could be seen through from the offset printing surface side, which was not practical. Since Comparative Example 2 was a single-layer base paper with a high filler content, there was no see-through from the opposite side of ink jet recording.

[0021]

As described above, according to the present invention, a base paper comprising a plurality of layers having a high filler content layer on the front side and a low filler content layer on the back side, and an ink receiving layer on the high filler content layer side of the base paper are provided. By using an inkjet recording paper, it was possible to obtain an inkjet recording paper excellent in offset printing suitability on the back surface without deteriorating the print density and ink absorbability. Further, it was possible to obtain an excellent ink jet recording paper having high opacity and no see-through of ink jet recording. When this inkjet recording paper is used as a postcard, offset printing such as a postal code can be performed without any problem, and at the same time, high-definition inkjet recording can be performed on the opposite surface.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenbun Tanaka             5-21-1 Oji, Kita-ku, Tokyo Nippon Paper Industries             Product Research Institute Co., Ltd. (72) Inventor Koichi Yanagiuchi             5-21-1 Oji, Kita-ku, Tokyo Nippon Paper Industries             Product Research Institute Co., Ltd. (72) Inventor Yoshihide Kimura             5-21-1 Oji, Kita-ku, Tokyo Nippon Paper Industries             Product Research Institute Co., Ltd. (72) Inventor Jun Unaka             4-1-1 Imai, Fuji City, Shizuoka Prefecture             Paper Manufacturing Co., Ltd. (72) Inventor Park Ikuta             4-1-1 Imai, Fuji City, Shizuoka Prefecture             Paper Manufacturing Co., Ltd. F-term (reference) 2C056 EA13 FC06                 2H086 BA15 BA21 BA32 BA34

Claims (4)

[Claims] 1. A base paper for ink jet recording paper, which comprises pulp and a filler as main raw materials, wherein the base paper has a multilayer structure of at least two layers, and the content of the filler in the surface layer is larger than the content of the filler in the back layer and the surface layer is A base paper for ink jet recording paper, which comprises a high-filler layer sufficient to satisfy desired ink receptivity and a backing layer having a low-filler layer sufficient to satisfy desired surface strength. 2. The surface layer has a filler content of 5 to 40% by weight based on the solid weight of the pulp, and the back layer has a filler content of 0.
The base paper for ink jet recording paper according to claim 1, wherein the base paper is 10% by weight. 3. The method for producing a base paper for inkjet recording paper according to claim 1, wherein the multilayer structure is produced by a multilayer paper machine. 4. An ink jet recording paper, characterized in that an ink receiving layer containing a filler and an adhesive as a main component is provided on the surface layer of the base paper according to claim 1 or 2.