JPS597589B2 - Suisei Ink Insatsuhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for giving printed matter made with water-based ink a gloss equal to or higher than that of printed matter made with oil-based ink, and more specifically, when printing using water-based ink, This invention relates to a method of imparting gloss to printed matter by pressing with a roll having a desired surface each time printing is performed.

In recent years, from the perspective of pollution, inks that use water or water and alcohol as solvents (hereinafter simply referred to as water-based inks) have been developed to replace oil-based inks that use petroleum-based or other oil-based solvents as solvents, and are used in gravure printing and flexographic printing. It has come to be used in fields such as screen printing.

However, in reality, these are only used in very few cases, and most of them currently use conventional oil-based inks and require huge investments in pollution prevention equipment and solvent recovery equipment. In particular, when printing on low- or intermediate-quality paper such as non-coated paper, which is prone to heavy penetration, water-based inks are used because printed materials using water-based inks are significantly inferior in quality to those using oil-based inks. has not been considered at all. The reason why water-based ink is not generally used is that it dries slowly and is inferior in quality to printed matter made with oil-based ink. Poor quality is the biggest cause. Various attempts have been made to overcome these deficiencies by improving water-based inks. For example, in place of casein, a water-soluble resin that was used when water-based inks first began to be used, we adopted an alkyd-type water-soluble resin, which has excellent durability and has an advantage in terms of gloss. It is something like that. However, despite these improvements in ink production, there is still a large difference in quality such as gloss and density compared to oil-based inks, and it is difficult to expect significant progress in the quality of printed matter by improving the ink itself.

This difference varies greatly depending on the type of printing material, and the difference becomes even larger in the case of water-absorbing materials such as non-coated paper such as ordinary gravure paper, high/intermediate paper, and rough paper.

One of the characteristics of gravure printing and flexographic printing (particularly gravure printing) is that even these non-coated papers can be printed quickly, in large quantities, and beautifully. However, when printing with water-based inks using conventional methods, these It cannot be expected to exhibit characteristics. The present invention completely solves the inferior quality of printed matter, which is difficult to solve from an ink manufacturing perspective, from the standpoint of printing. It is something that can give quality.

Water, which is the main component of water-based inks (usually accounts for 40 to 50%), has advantages such as being safer and cheaper than common ink solvents such as toluene and xylene, but has many disadvantages in terms of printing.
For example, there are problems such as graininess of the plate and frequent scumming, which are thought to be caused by the resin dissolving ability, but the biggest drawback is the difference in evaporation rate. This not only slows down the drying speed, but also when printing and coating on non-coated porous materials such as gravure paper, the paper itself is extremely hydrophilic, so the penetration speed is extremely fast, but at the same time, once the water gets inside, It is difficult to get out and evaporate to dryness. When printing with water-based ink, it is difficult to dry, so the ink penetrates into the pores of the printing surface and at the same time captures some of the resin and pigment.

This tendency is especially severe on low-grade papers such as uncoated paper, resulting in dull, dull tones and a quality similar to that of an ink painting. Such a reduction in the gloss of the printed matter is shown in Example 2, the glossiness measurement result a by the polishing method of the present invention, the glossiness b by the ordinary printing method using oil-based ink, and the glossiness C by the ordinary printing method using water-based ink. As is clear from FIG. 1, the glossiness C of the normal printing method using water-based ink is also clear because the glossiness of the printed surface becomes lower than the glossiness of unprinted paper. In the case of oil-based ink (b), on the contrary, the gloss tends to increase as the amount of printing ink increases. In the ordinary printing method using water-based ink, the color tone is not only depressed, but also regarding the printing density, the density measurement result d by the polishing method of the present invention in Example 2, the density e by the ordinary printing method using oil-based ink, and the water-based ink. As is clear from FIG. 2, which shows the normal printing method f using water-based ink, the density of the shadow area does not increase with the normal printing method f using water-based ink, resulting in a printed matter with a narrow tone reproduction range as a whole. In addition, there are many other drawbacks that arise from the inherent characteristics of water-based inks, such as the curling of paper in the width direction that sometimes causes the folding machine to stop immediately after printing. The present invention solves these drawbacks and makes it clear that in order to make the quality of printed matter equal to or better than that of printed matter using oil-based ink, it is not possible to improve the printing ink alone since water or water and alcohol are used as the vehicle. From the perspective of a printer, we have achieved an improvement in the quality of printed matter using water-based ink.

In other words, the present invention transfers water-based ink to the printing material by printing, thereby removing water that is unavoidably absorbed and retained by the printing material. After adjusting the moisture content to an appropriate ratio using a dryer or other appropriate means, the printing material is pressed onto a roll having a mirror or other desired surface at an appropriate temperature and pressure to ensure smoothness. Gives the desired shine by raising the
It also has the effect of increasing the apparent print density and correcting paper curls. Next, one embodiment of the present invention will be described in more detail with reference to the drawings.

As shown in FIG. 3, printing is carried out on a sheet or rolled printing material 6 using a plate cylinder 1 and an impression cylinder 2, and water-based ink is transferred according to the density of the image.

As a result, the solvent, mainly water, which is difficult to evaporate and easily penetrates, penetrates into the inside of the printing material 6, and the upper part of the printing material 6, mainly the surface layer, is provided with moisture according to the density of the ink.
The ink-applied printing material 6 enters the dryer 3, and the moisture content is adjusted to an appropriate amount for pressing according to the shade of the pattern. The dryer 3 may be a hot air dryer, a far-infrared dryer, a steam drum dryer, or any other suitable dryer, and is not particularly limited. Passing through the dryer 3 is not necessarily necessary. Examples of such cases include, for example, drying at room temperature to the appropriate moisture content after ink transfer and before entering the press, or using a heatable mirror roll to reduce the moisture content in the contact area before entering the press. In some cases, it can be adjusted to make it appropriate. The ink surface of the printing material 6 whose moisture content has been adjusted is pressed between a mirror roll 4 having a desired gloss state and a press roll 5 against the mirror roll.

As the mirror-finished roll 4, a heatable (up to 200° C.) mirror-finished roll such as a chrome-plated surface, a polished cast steel roll, or the like is used. By using the mirror roll 4 with a desired surface shape, it is possible to obtain printed matter with a desired glossy state. As the press roll 5, a roll coated with hard rubber, a cotton roll, a woolen paper roll, an asbestos roll, etc. can be used.

After completing the first color printing and glossing process in this way, the printing material 6 is similarly glossed in the same way as the first color each time the second color and subsequent colors are printed, and finally,
Printed matter can be obtained that has a gloss level equal to or higher than that of printed matter printed with oil-based ink.

In the case of one-color printing, it goes without saying that the first color printing and glossing are completed to produce the final printed matter. As is clear from the graph showing the relationship between moisture content and gloss in Figure 5, the optimum moisture content to produce a glossy effect by pressing is 8 to 2.
501), which is an extremely narrow range. However, this indicates the optimum moisture content, and it varies depending on the heating and pressurizing conditions and the substrate to be printed, and is not limited to this (see Example 3). In the case of alcohol-containing water-based inks, the evaporation rate increases, so the upper limit of the water content increases. Therefore, by setting the area with the largest amount of ink transfer (the shadow area of the pattern) to the maximum effective range of effective moisture content, it is possible to achieve gloss according to density within the effective moisture content range from midtones to highlights. will appear. As the printing material, printing paper such as gravure paper, heavy/medium-quality paper, newsprint, gravure coated paper, manila paper, cardboard, coated paper, etc. can be used. However, the printing material is not limited to these, and any printing material that has even a small amount of permeability and water absorption will be effective. Further, the degree of gloss imparted varies depending on the heating and pressurizing conditions, as shown in FIG.

In Figure 4, G and h are each 58 kg/c! N, 3
Ok/? 12 is a graph showing changes in printed matter when printed with a gravure plate at a plate depth of 25 μm due to changes in specular roll temperature when a press pressure of 25 μm is applied (see Example 4). Therefore, by changing the heating and pressurizing conditions, it is possible to obtain printed matter of any desired gloss. Conventionally, the gloss level of matsutoizoki and glossy inks all depended on the selection of the ink surface, but with this method, gloss can be adjusted during printing, and the moisture content during pressing can be adjusted according to the required degree.
By controlling the press pressure, press temperature, and surface shape of the specular roll, printed matter with the desired gloss can be obtained each time. Among these conditions, controlling the moisture content is particularly effective. Since pressing can produce a glossy effect only when the moisture content is appropriate, it is not possible to give gloss to the entire printed area unless pressing is performed each time a water-based ink is printed. In this method, the gloss effect by pressing does not occur in areas that are not moistened by water-based ink printing, so by printing water-based ink, the areas where the gloss has decreased are restored and improved, and the areas that are not printed are It is possible to use the raw materials as they are.

Therefore, in multicolor printing, it is impossible for the valley colors to completely overlap, so gloss cannot be increased unless pressing is performed after adjusting the moisture content every time the valley color ink is transferred. In this method, as shown in Fig. 3, the ink transfer parts of the printing cylinder 1 and the impression cylinder 2 are directly connected to the drying/pressing part, and before the water in the transferred water-based ink is completely dry, the water is used to create the image. It can easily provide the desired gloss.

Therefore, the most difficult process of the supercalendering process used in the paper manufacturing industry, such as uniform moisture conditioning over the entire surface before calendering, is not performed in this method, and moisture can be added simply through the printing process. Also, unlike the general humidification and humidity control method used in the paper manufacturing industry, the method uses methods such as applying a specific amount of moisture and then heating and drying to adjust the amount of moisture contained, so the degree of heating is changed to adjust the amount of moisture contained. It can be changed subtly by changing the value as appropriate.

Humidification using only humidification may result in water droplets, uneven humidification, etc., and supercalendar methods require extremely sophisticated techniques. In this method, humidity is controlled not only by humidification, but also by heating and drying (of course, humidity may be controlled by humidification alone), and does not require particularly sophisticated technology. Particularly in tone pattern printing using halftone dots, one of the features of this method is that uneven gloss does not occur at all because some unevenness is absorbed into the individual halftone dots. In addition, since printing and glossing can be performed within the same mechanism, the printing machine, processes such as rewinding, storage, and uniform humidity control over the entire surface can be omitted, and the gloss condition can be constantly monitored along with printing operations.

Therefore, it is very different from the supercalender method used by paper manufacturers or the method of applying a second coat after printing and drying to make it glossy. Most gravure printing machines and flexo printing machines have a mirror-finished steam drum with a chrome plated surface for each color ink printing section, and when using this method, a press roll is placed on the appropriate drum. Just by attaching one piece, you can apply the appropriate press pressure.

Therefore, by simply adding a press roll to a conventional printing machine, it is possible to give printed matter made with water-based ink a higher gloss than printed matter printed with oil-based ink.

Furthermore, when using this method, the surface layer (approximately 10 to 20% of the total thickness) of the printing material is compressed, so that the pigment and resin components dispersed on the surface are densified, and the printing density is also increased. Generally, partial supply of moisture causes the paper to wrinkle or curl after it is completely dry; however, in this method, since the paper is pressed in a semi-dry state, curling and paper wrinkles can be prevented. As described in detail above, according to the method of the present invention, it is possible to give prints made with water-based ink a gloss equal to or higher than that of prints made with oil-based ink, and it is also possible to increase the density, resulting in high-quality prints. be able to.

Therefore, water-based ink, which has not been used much because it does not produce high-quality printed matter, should be used in the same way as oil-based ink, even though it has various advantages in terms of work hygiene, danger, pollution, etc. The practical benefits are enormous. Next, examples will be shown.

<Example 1> Aqua Color Pros (Ki,
Each time a valley color plate is printed using a 1501/inch net gravure plate on coated gravure paper Henry S manufactured by Daishowa Paper Co., Ltd. at a printing speed of 150 m/Wrjt. 5kW, temperature adjustable
The moisture content was adjusted using a dryer equipped with three infrared drying lamps, a steam drum heater with a surface temperature of 120°C was used as a mirror roll, and a cotton roll was used as a press roll and pressed at a linear pressure of 62 kg. Prints were obtained that had the same level of gloss and quality as those printed with ink.

Example 2 AquaIn, a water-based ink manufactured by Toyo Ink Manufacturing Co., Ltd.
ksB-169AQ Sumi (no alcohol added) to Oji Paper Co., Ltd. Y special gravure paper Hokuto 1501/Inch
After printing at a printing speed of 100 m/- using a gray scaled complimentary gravure plate, the moisture content was adjusted using the same dryer as in Example 1, and then the same mirror roll and press roll as in Example 1 were used. When pressed at a linear pressure of 58 kg, printed matter having gloss and density as shown in FIGS. 1 and 2 was obtained (a and d in the figures).

For comparison, normal printing was carried out using the same water-based ink (c and f in the figure) and conventional oil-based ink (book rotogravure ink 0GB manufactured by Toyo Ink Mfg. Co., Ltd.).
The results of normal printing in I) (b and e in the figure) are shown at the same time.

<Example 3> Using the same ink and printing paper as in Example 2, printing was performed on a 1501/inch solid plate (25μ) at the same printing speed as in Example 2, and then drying was performed in the same manner as in Example 1. After varying the water content in the machine, Example 2
Press glossing was carried out under the same conditions as above, and a printed paper having the glossiness shown in FIG. 5 was obtained.

Example 4 After printing under the same conditions as Example 3, the moisture content was adjusted to 13%, and the press pressure was 30 kg/CTn and the press pressure was 5.
When the glossiness was measured as a result of the mirror roll temperature change in each case of 8k9/Cm, the results shown in FIG. 4 were obtained.

The gloss in each of the above examples was measured at a total gloss of 75 using a gloss meter manufactured by Nippon Denshoku Kogyo Co., Ltd.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the glossiness of Example 2, FIG. 2 is a graph showing the density of Example 2, FIG. 3 is an explanatory diagram showing one embodiment of the present invention, and FIG. 4 is a graph showing the density of Example 2. FIG. 5 is a graph showing changes in glossiness due to changes in press pressure and specular roll temperature according to Example 4, and FIG. 5 is a graph showing changes in glossiness due to changes in water content according to Example 3. 1...Print cylinder, 2...Impression cylinder, 3...
...Dryer, 4...Mirror roll, 5...
・Press roll, 6...Printing material.

Claims (1)

[Claims] 1. A water-based ink that, when printing is performed using a water-based ink, gives gloss to the printed material by pressing it with a roll having a desired surface each time each color is printed on the printed material. Printing method.