JPH0235673B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a recording sheet that records using ink, and in particular, the sheet has high density images and characters recorded on the sheet, clear color tone, fast ink absorption speed, and little ink bleeding.
The present invention relates to an inkjet recording sheet suitable for multicolor recording. In recent years, the inkjet recording method is characterized by high speed, low noise, easy multicolor printing, great flexibility in recording patterns, and no need for development or fixing. It has rapidly become popular in various applications. Furthermore, the images formed by the multicolor inkjet recording method are comparable to those produced by normal multicolor printing, and when the number of copies to be produced is small, the inkjet recording method is preferred over the multicolor printing method because it is cheaper than the normal plate making method. Attempts are being made to apply it to the field of color photography and printing. It is commonly used as a base for high-quality paper, coated paper, and photographic paper used for printing. So-called baryta paper has extremely poor ink absorbency, so when used for inkjet recording, ink may remain on the surface for a long time, touching parts of the device or being touched by the operator, or sheets that are continuously ejected. If the inks overlap and the recording surface is rubbed, the residual ink will stain the image. In addition, when ink dots of three or four colors overlap in the same place in high-density image areas or multicolor recording, there is a problem that the amount of ink is large and the ink mixes without being absorbed or flows out. It's not practical. In other words, the recording sheet can produce images with high density and clear tones, and in addition, it absorbs ink quickly and does not run out, and it does not stain even if touched immediately after printing. At the same time, it is required to suppress the lateral diffusion of the inkjet on the surface of the recording sheet and to obtain a high-resolution image without bleeding. Several proposals have been made to solve these problems. For example, JP-A-52-
No. 53012 discloses an inkjet recording paper made by moistening a low-sized base paper with a paint for surface treatment. Also, in JP-A No. 53-49113,
An inkjet recording paper is disclosed in which a sheet containing urea-formalin resin powder is impregnated with a water-soluble polymer. Further, JP-A-55-5830 discloses an inkjet recording paper in which an ink-absorbing coating layer is provided on the surface of the support;
No. 51583 discloses an example in which non-colloidal silica is used as a pigment in the coating layer, and JP-A-55-146786 discloses an inkjet recording paper provided with a water-soluble polymer coating layer. Furthermore, Japanese Patent Application Publication No. 55-11829
This issue has a layer structure of two or more layers, the outermost layer has an ink absorbency of 1.5 to 5.5 mm/min, and the second
Ink absorbency of layer 5.5~60.0mm/
A method is disclosed for adjusting the spread of ink dots and absorption speed by adjusting the amount of ink. However, the technical idea as typified by JP-A No. 52-58012 attempts to obtain resolution by sacrificing ink absorption to some extent, and the technical idea typified by JP-A-53-49113 is to sacrifice ink absorption to some extent to obtain resolution. Although such a technical idea provides a certain level of ink absorption and resolution, it has the drawback that ink penetrates deeply into the paper layer, making it difficult to obtain ink density, and both are unsatisfactory as multicolor inkjet recording paper. Therefore, as a method to improve these drawbacks, an inkjet recording paper coated with non-cohesive silica powder was disclosed in JP-A-55-51583;
-790 discloses an optically readable barcode printing paper coated with finely divided silicic acid. By providing a layer of non-colloidal silica or the like on the surface in this way, the resolution, color density (chromaticity), absorbency, roundness, etc. suitable for inkjet can be greatly improved. When silicic acid, that is, synthetic amorphous silica referred to in the present invention, is incorporated into a paper layer as a filler by the usual method, good suitability for inkjet cannot be obtained, unlike when it is provided as a layer on the surface. . Bands, retention agents, etc. used in the normal papermaking process have no effect at all when a large amount of synthetic amorphous silica is added to papermaking, and the synthetic amorphous silica that barely remains in the paper layer is composed of fine particles. It was found that the inkjet suitability could not be improved because the ink was scattered all over the fiber surface and a large amount of voids were not formed in the paper layer. As a result of intensive research on how to retain synthetic amorphous silica, the present inventors found that by adding a specific cationic resin to a fibrous material slurry containing a large amount of synthetic amorphous silica, the zeta potential of fines could be increased. By controlling it around zero and agglomerating and fixing it with an anionic retention agent, it is possible to successfully keep synthetic amorphous silica in the paper layer as agglomerates of an appropriate size, and to obtain good suitability for inkjet. The present invention has been made based on this discovery. The present invention will be explained in detail below. Although the fibrous material used in the present invention is mainly wood pulp, it is also possible to use synthetic pulp, synthetic fibers, etc. in combination, if necessary. The synthetic amorphous silica used in the present invention is 93% or more of SiO ₂ , about 1% or less of Al ₂ O ₃ , and Na ₂ O on a dry basis.
These include fine powder silica of about 5% or less produced by a wet method, so-called white carbon or silica gel, and ultrafine powder silica produced by a dry method. This synthetic amorphous silica is sometimes used as a filler to prevent ink bleed through printing paper, but the addition rate in this case is only a few percent by weight as ash in the paper, and is usually 1 to 2. %. In the present invention, the synthetic amorphous silica has an ash content of 10% by weight or more, preferably 15 to 15% by weight.
It is necessary to set it at 30%, more preferably between 18 and 25%. Furthermore, in the present invention, it is necessary to add a dicyandiamide formalin condensate. Dicyandiamide formalin condensate is known as a wastewater treatment agent and dye mordant, and it is added to a pulp slurry containing a large amount of synthetic amorphous silica in an amount of 0.2 to 2% by weight, preferably 0.4 to 1% by weight based on the dry weight of the pulp. By adding % by weight, the zeta potential of synthetic amorphous silica can be brought to around zero,
This is to control the cohesive force of the filler so that it remains in the paper layer as agglomerates of appropriate size. In this case, there is nothing wrong with using cationic starch or an anionic retention improver in addition to the dicyandiamide formalin condensate, and depending on the case, the suitability for inkjet can be further improved. However, polyamide epichlorohydrin resin, polyethyleneimine, and tertiary and quaternary modified polyacrylamide resins, which are so-called wet strength agents other than cationic starch, have the ability to reduce the zeta potential to near zero, but they cannot be used in inkjet recording. Some of the ink dyes used may reduce the light resistance, which is not preferable. As mentioned above, a conventional fourdrinier paper machine is made from a slurry containing a fibrous material, synthetic amorphous silica, dicyandiamide formalin condensation resin, and, if necessary, a paper strength improver, a retention improver, a coloring agent, etc. It is also possible to produce paper by adding oxidized starch, polyvinyl alcohol, etc., using a size press or the like normally used in paper making.
The recording paper according to the present invention produced in this manner suppresses the spreading of ink dots by a large amount of synthetic amorphous silica which is formed into appropriate aggregates by the dicyandiamide formalin condensation resin and remains in the paper layer. Furthermore, sufficient ink absorption ability can be provided. Further, the dicyandiamide formalin condensation resin can impart water resistance without significantly reducing the light resistance of the dye, making it possible to obtain excellent inkjet recording paper. The present invention will be described below with reference to examples, but it is not limited to these examples. In addition, parts and percentages shown in the examples mean parts by weight and percentages by weight. Methods for measuring various physical property values in Examples are shown below. (1) Dot diameter Draw a test pattern using an inkjet printer R-180 (manufactured by Konishiroku), measure the dot area using a dot area measuring device (Beauback 75 manufactured by Nippon Regulator), and calculate the perfect circle. The average dot diameter was calculated based on this assumption. (μm) (2) Color Density Four colors of magenta, cyan, yellow, and black were printed solidly using a color inkjet printer, and the color density was measured using a Macbeth densitometer RD514. (3) Water resistance A portion of the same sample used to measure color density was
The color density before and after immersion was measured using a Macbeth densitometer RD514, and the percentage obtained by dividing the density after immersion by the density before immersion was used as a measure of water resistance. The higher the value, the better the water resistance. (4) Lightfastness A portion of the same sample used to measure color density was measured using a xenon long-life fade meter FAL.
-25X-HCL (manufactured by Suga Test Instruments), the color density before and after the test was measured, and the percentage obtained by dividing the density after the test by the density before the test was used as a measure of light resistance. The higher the value, the better the light resistance. Example 1 70 parts of LBKP with a water content of 350 ml and a water content of 400 ml
Synthetic amorphous silica (Nipseal LP manufactured by Nippon Silica) was added to the pulp slurry consisting of 30 parts of NBKP.
40 parts, 0.5 parts of dicyandiamide formalin condensation resin (Nicafloc D1000 manufactured by Nippon Carbide), and 0.001 part of an anionic retention agent were added to produce paper with a basis weight of 70 g/m ² as usual on a Fourdrinier paper machine. was made into paper. In the size press installed in the middle of the paper machine, oxidized starch with a concentration of 2% (Nihon Shokuhin Co., Ltd.,
MS3800) was attached. The ash content of the manufactured inkjet recording paper is
It was 20.6%. For comparison, the above synthetic amorphous silica was used as light calcium carbonate (PC manufactured by Shiraishi Kogyo), synthetic zeolite (Zeolex 17S manufactured by Huber),
Heavy calcium carbonate (Escalon #200 manufactured by Sankyo Seifun), clay (SX manufactured by Sieglite Industries), synthetic organic filler (manufactured by Ciba Geigy, Pergopack M2)
A comparative paper was prepared in exactly the same manner as in Example 1, except that the paper was replaced with calcined kaolin (Ansilex, manufactured by Engelhard). Table 1 shows the results of measuring the ink jet suitability of these papers. As can be seen from Table 1, the recording paper in which the synthetic amorphous silica of the example was made had a small dot diameter, and all the color densities showed the highest values. On the other hand, in comparison examples in which the filler was replaced with other fillers, those in which synthetic zeolite with relatively small dot diameters, synthetic organic pigments, and calcined kaolin were added had poor (low) color density; Good ones have large dot diameters (resolution deteriorates) and are good for inkjet paper.
Inappropriate.

[Table] Example 2 70 parts of LBKP with a water content of 350 ml and a water content of 400 ml
In the pulp slurry consisting of 30 parts of NBKP, synthetic amorphous silica (Nippusil NS manufactured by Nippon Silica) was added.
5 to 80 parts cationic starch (manufactured by Oji Nacional)
Add 1 part of CatoF) and 0.5 part of dicyandiamide formalin condensate (Cetramin manufactured by Hamano Industries),
Paper was made with a fourdrinier paper machine using a conventional method to a basis weight of 60 g/ ^m2 ,
2% polyvinyl alcohol (PVA117, manufactured by Kuraray) was applied using a size press to obtain seven types of recording paper containing synthetic amorphous silica with an ash content in the paper. As a comparative example, a paper was made in the same manner without adding any filler. Table 2 shows the results of measuring the inkjet suitability of these papers. As is clear from Table 2, it is recognized that the higher the ash content in the synthetic amorphous silica paper, the smaller the dot diameter, that is, the better the resolution, and the less decrease in color density is practical. If it exceeds 30%, the suitability for inkjet is good, but the paper strength is extremely reduced and the disadvantages of high filler cost become noticeable.

[Table] Example 3 80 parts of LBKP with a water content of 350ml, a water content of 400ml
Pulp slurry consisting of 20 parts of NBKP was mixed with synthetic amorphous silica (Zeoseal manufactured by Coflan Chemical).
1000V) 40 parts, dicyandiamide formalin condensate (Nippon Carbide, Nika Clocks D1000)
Add 0.1 to 3 parts, make paper using a Fourdrinier paper machine using a conventional method to have a basis weight of 70 g/ ^m2 , and apply a 3% concentration solution of oxidized starch (MS3800, manufactured by Nippon Shokuhin) using a size press machine. A recording sheet was obtained. For comparison, instead of dicyandiamide formalin condensate, polyamide epichlorohydrin resin (manufactured by Deitz Hercules, Kymen
557), polyethyleneimine (manufactured by BASF, Polymin P) was added to one part of each, and one part was not added at all.Other than that, comparative papers were prepared in exactly the same manner as in Example 3. Table 3 shows the results of measuring the inkjet recording suitability of these papers. As is clear from Table 3, in the examples in which synthetic amorphous silica and dicyandiamide formalin condensate were used together, the ash content in the paper was high, the dot diameter was small, and the light resistance, which is important for inkjet paper, was significantly reduced. It can be seen that the water resistance has been sufficiently improved without any deterioration. On the other hand, it can be seen that if the dicyandiamide formalin condensate is not added, the water resistance is poor, and when the wet strength agent is added, the water resistance improving effect is inferior and the light resistance is extremely poor. Therefore, only a system using a combination of synthetic amorphous silica and dicyandiamide formalin condensate can comprehensively improve ink jet suitability and provide extremely excellent recording paper.

【table】

Claims (1)

[Scope of Claims] 1. An inkjet recording paper comprising a fibrous substance and a filler, wherein the filler is synthetic amorphous silica and the recording paper contains a dicyandiamide formalin condensate. 2 Synthetic amorphous silica is added to the recording paper by weight%.
An inkjet recording paper according to claim 1 containing 10% or more.