JP3335584B2 - Humidifier for offset printing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a humidifier suitable for offset printing.

[0002]

2. Description of the Related Art In offset printing, an image portion of a printing plate (plate plate, the same applies hereinafter) is made lipophilic and a non-image portion is made hydrophilic. This is a printing method for transferring. Generally, a printing machine used for offset printing is provided with a plate cylinder, a blanket cylinder, and an impression cylinder, and a printing plate on which an image is formed is wound around the plate cylinder, and water is supplied thereto. Is supplied together with the ink. The ink is applied to the image portion, the ink portion is transferred to a blanket cylinder, and the transferred ink portion is transferred to a printing paper sandwiched between the blanket cylinder and the impression cylinder.

On the other hand, there are various types of printing plates used for offset printing. For example, PS plates using metal as a support, so-called master paper using paper as a base material and applying a pigment to the surface thereof, silver halide Plates and the like using emulsions are widely used. In recent years, a high resolution has been required in many cases, and in order to meet such a demand, a printing plate of a type in which image information from a computer is directly transferred by a laser beam has been used. Plates of this type include, for example, silver digiplate plates (product names,
Mitsubishi Paper Mills, hereinafter the same).
No. 80976). Since the image forming method differs depending on the type of the printing plate, a humidifying liquid, a desensitizing agent and the like are devised according to the type of the printing plate. In some cases, when it is necessary to simultaneously use a plurality of types of printing plates to obtain one printed matter, there is no need to use a plurality of types of humidifying solutions at the same time. JP-A-5-286280
And the like, which are contributing to the improvement of printing characteristics and printing efficiency.

[0004]

In order to obtain a good printed matter by offset printing, it is preferable that the ink supplied to the printing plate is easily transferred to each body of the printing press. Conversely, it is not preferable that the supplied water easily transfer each body. The reason is that, in offset printing, an image is formed by water repelling ink on a printing plate, so that the ink portion (image portion) is transferred from the printing drum on which the printing plate is wound to each body of the printing press. If the water easily transfers along with the transfer (transfer), the water on the plate will be insufficient and the ink will not be repelled sufficiently, and the background stain on the non-image area will occur. This is because a problem such as occurrence of such a problem occurs.

[0005] Further, as the moisture is transferred, it is eventually absorbed by the printing paper, so that it becomes necessary to supply the absorbed moisture. However, especially in a small printing press, it is often not designed to be able to supply water continuously, and it is often difficult to newly design. Further, the type of printing plate used also has a large effect on the ease of water transfer. For example, a printing plate having a hydrophilic gelatin layer and having a low water retention capacity tends to release moisture from the printing plate and transfer moisture easily. In such a printing plate, the water retention capacity of the printing plate itself is weak, and the moisture is transferred to the body as the printing is continued. Such plate plates include, for example, the above-mentioned silver digit plate plate and some PS plates (for which aluminum or the like is used). The reason why some PS plates are used here is that there are various types of PS plates, some of which have a sufficient water retention capacity.

As described above, when the water on the printing plate is insufficient, if the humidifying liquid is gradually supplied from the humidifying liquid tank in accordance with the amount of the lost water, the printing plate is always supplied with the water, and the water is constantly distributed over the printing plate for a long time. Good image formation can be maintained, and there is no need to stop the printing press to add humidifier. However, in the past, there was a tendency for excess humidifying liquid exceeding the amount of water lost to be supplied to the printing plate at a time, and the amount of stock of humidifying liquid decreased quickly, so that mass printing could be performed while maintaining good images. It was inconvenient to perform it continuously for a long time.

The present invention has been made to solve such a problem, and an object of the present invention is to gradually apply a printing method to a printing plate, particularly when performing offset printing using a printing plate having a low water retention capacity. It is an object of the present invention to provide a humidifying liquid that can supply water and suppresses easy transfer of water from a printing plate to obtain a suitable printed matter.

[0008]

To solve the above problems, the following means are employed. That is, the moisturizing liquid for offset printing according to the present invention is a mixture of water, alcohols, silica and a viscous substance, wherein the silica is colloidal silica, the viscous substance is glycerin, and the colloidal silica and the glycerin are used. Is not more than 5 milliliters per liter of the water.

Generally, the alcohols are used as a surfactant for lowering the surface tension of water so as to evenly supply the water to the entire printing plate, and the silica is used for improving printing characteristics by its water retention ability. . The humidifying solution of the present invention is intended to suppress easy transfer of the humidifying solution by mixing glycerin as a viscous substance in addition to these components. Since glycerin is a kind of alcohol, it also exerts the above-mentioned function of lowering the surface tension of water. However, in the present invention, glycerin is not used in order to exert only this function.

In the present invention, attention is paid to the fact that glycerin is a viscous substance (a sticky substance) and has a function of effectively suppressing the movement and evaporation of water. Use as hydropower. The fact that glycerin has the above-mentioned function and has the water retention ability is supported by the fact that glycerin is generally used frequently as a drug for moisturizing and absorbing moisture. That is, in the humidifying solution of the present invention, the humidifying solution itself is provided with the water retention ability by mixing glycerin, so that the transfer of water can be appropriately suppressed.

Furthermore, glycerin is less toxic and less irritating to the skin, so there is no danger in handling it. In recent years, many substances are subject to use restrictions due to environmental problems, but glycerin has no problem from this viewpoint and is suitable. Further, the amount of the glycerin is more preferably equal to the amount of the colloidal silica. In particular, it is preferable to use a plate having a low water retention capacity, such as a silver digit plate.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, generally, silica is mixed in a humidifying liquid to sufficiently retain the moisture when the humidifying liquid is supplied onto a printing plate. In the present invention, colloidal silica is employed as the silica.
Specifically, Snowtex-O (trade name, manufactured by Nissan Chemical)
However, the present invention is not limited to this.

Further, as the alcohols in the present invention,
Although IPA (isopropyl alcohol) and ethyl alcohol were used, the present invention is not limited to these, and any alcohol that is effective as a surfactant can be used. Next, glycerin is mixed as a viscous substance to give the humidifying liquid a certain degree of stickiness and to have a water retaining ability. As a result, the initially set humidification liquid gradually transfers, so that the humidification liquid is dispensed.
Therefore, even if it is necessary to replenish the humidifying liquid, the number of times can be reduced, and printing can be performed for a long time without stopping the operation of the printing press. The stickiness can also prevent evaporation of water.

Glycerin is particularly adopted as a viscous substance because it has a stickiness suitable for suppressing easy transfer of moisture (humidifying liquid) to each body, and can be mixed with a humidifying liquid to produce printed matter. It has no adverse effect. Before adopting glycerin, an attempt was made to mix other gums such as gum arabic, CMC, and viscous commercially available surfactants.

However, when gum arabic or a commercially available surfactant was used, the humidifying solution was fired, resulting in an adverse effect on printed matter. Antifoaming agents such as silicone resin were added to suppress firing, but these antifoaming agents emulsified the ink and further deteriorated the printing characteristics. Further, CMC and the like were insufficient to effectively suppress the transfer of water.

As a result of the various trials and errors described above,
It was found that glycerin is the most suitable viscous substance which gives the humidifier a suitable viscosity and does not affect the printing characteristics. Further, as described above, there is an advantage that not only is the toxicity to the human body and the environment low, but also it is easy to obtain and handle, and the compatibility with water is satisfactory. The glycerin used was mainly purified glycerin manufactured by Shin Nippon Rika Co., Ltd., but is not limited thereto.

In the present invention, the amounts of colloidal silica and glycerin (per liter of water, hereinafter the same) are preferably 5 milliliters (ml, hereinafter the same), and particularly preferably 3 to 5 ml. The reason why the amount is preferably 5 ml or less is that if the amount exceeds 5 ml, the ink is emulsified and adversely affects printed matter. Especially 3-5m
The reason why 1 is preferable is that it is particularly suitable when a plate having low water retention such as a silver digital plate is used.

It is more preferable that the amounts of colloidal silica and glycerin are equal. If they are equal,
This is because it is less affected by various printing conditions such as printing paper, printing temperature, the number of printed sheets, and type of printing plate. In particular, for a plate having a low water retention capacity such as the above-mentioned silver digiplate plate, the amount of the colloidal silica and the amount of the glycerin are preferably 4 to 5 ml each, and more preferably 4 ml each.

In the case of a plate having no particular problem with respect to the water holding capacity, for example, a PS plate (the above-mentioned type having a sufficient water holding capacity, the same applies hereinafter) and the like, even if the amounts of colloidal silica and glycerin are 3 ml or less, respectively. Sufficient printing characteristics can be maintained. Next, the moisturizing liquid according to the present invention was actually prepared, and printing was actually performed by an offset printing machine, and the state of the printed matter was observed (Experiment 1). The printing plate used is a silver digital plate version.

Examples 1 to 5 in which the amounts of colloidal silica and glycerin were within a predetermined range were prepared and compared with the results of Comparative Examples 1 to 3 in which the amounts were outside the predetermined range. Table 1 shows the results. Although not described in Table 1, Example 1
In Comparative Examples 1 to 5, IPA and ethyl alcohol are mixed in an appropriate amount as alcohols.

[0021]

[Table 1]

The printing result was evaluated by visually observing the obtained printed matter. In Comparative Examples 1 to 3, the ink was emulsified, and the resulting printed matter was not suitable for use. On the other hand, in Examples 1 to 5, products usable as printed matter were obtained. Each example was evaluated in the following four stages. A: It is most suitable as a printed matter without occurrence of background stain and emulsification of ink. B: Suitable as printed matter. C: Suitable as printed matter, but printing in large quantities may emulsify the ink. D: Although it can be used as a printed matter, there may be a case where some background stains occur.

In Example 1, some printed matter was partially stained, but most of the printed matter was within the allowable range usable as printed matter. In addition, the results are for the Silver Digiplate version, and other types of plates (PS version,
When printing was performed using silver master paper), good printing characteristics could be maintained even with the humidifying solution of Example 1. From Examples 2 and 3, it can be seen that a suitable printed matter can be obtained if the blending amounts of colloidal silica and glycerin are 4 to 5 ml each and the blending amounts of both are equal. In other words, it can be seen that the mixing amount is suitable for a plate having a low water retention capacity (especially a silver digiplate plate), and it is particularly preferable to mix 4 ml each (Example 2).

As in Examples 4 and 5, even if the blending amounts are not equal, there is no change in obtaining a suitable printed matter as long as the blending amounts are within the proper range. 5ml
If the amount exceeds 5 ml, ink emulsification occurs (Comparative Example 1), and also, if one of colloidal silica and glycerin exceeds 5 ml, ink emulsification occurs (Comparative Examples 2 and 3). .

To explain the printing results in detail, in the case of Comparative Example 2, the ink was emulsified after printing about 4,000 sheets, and horizontal lines appeared on the printed matter. After printing about 6,000 sheets, the emulsification further progressed, and the printing of photographs became considerably thin. In the case of Comparative Example 3, the ink was emulsified after printing about 3,000 sheets, and the solid portion of the printed matter appeared to have tints, resulting in a printed matter that felt thin in appearance.

Next, the conventionally used humidifying liquid (conventional humidifying liquid, hereinafter the same) and the humidifying liquid of the above-mentioned Example 2, which is an optimum combination example of the present invention (Example 2, the same hereinafter) Were prepared, and the printed matter obtained by using each for offset printing was compared (Experiment 2). The plate used here is also a silver digiplate plate. As the above-mentioned conventional humidifier, adopt the humidifier specified in the Silver Digiplate version,
Diluted at the specified dilution rate and used (trade name: SLM-
OD / PSIII, manufactured by Mitsubishi Paper Mills, dilution ratio is 1-3%).
In addition, the said humidification liquid was employ | adopted as an example of the conventional humidification liquid, and was not used for the purpose of improving only the said humidification liquid.

Various printings (1) to (3) shown in Table 2 were performed, and the printing characteristics when using the conventional humidifying liquid and when using Example 2 were compared.

[0028]

[Table 2]

In Table 2, (1) is printing using normal printing paper, (2) is printing using Japanese paper, which absorbs moisture more easily than normal printing paper, and is liable to cause background contamination, and (3) is printing. This is the case of gold and silver printing in which metal powder is mixed with ink. Example 2
In the case of (1) using ordinary printing paper, a large amount (approximately 50,000 sheets) of suitable printed matter was obtained from a single plate without the occurrence of background stain or emulsification of ink. . The Japanese paper printing of (2) is a printing method in which the humidifying liquid tends to be supplied excessively at a time because the Japanese paper absorbs moisture more easily than the normal printing paper, and the background is easily stained. When Example 2 was used, a good printed matter free of background stain could be obtained.

In the case of (3) using an ink mixed with a metal powder, the ink and the metal powder are hardly mixed in a state suitable for image transfer even if the amount of water is too large or too small.
Although it was difficult to maintain a good image, the transfer of the humidifier was adjusted appropriately by glycerin. As a result, the ink and the metal powder were mixed appropriately, and a printed matter better than before was obtained.

[0031]

According to the humidifying liquid of the present invention, the humidifying liquid, which is reduced by the absorption by the printing paper or the like, is gradually supplied to the plate to suppress the easy transfer to each body. Therefore, an appropriate amount of water is always held on the printing plate, and the ink is sufficiently repelled to obtain a good printed matter without background contamination.
Therefore, the humidifying liquid of the present invention can contribute to the improvement of the water holding power of the printing plate, and is particularly effective for a printing plate having a low water holding power.

Since the humidifying water once set is gradually supplied as described above, it is possible to cope with long-time printing, and it is difficult to change the design for adjusting the amount of humidifying water. It is possible to perform mass printing even with a printing machine or a small printing machine. Specifically, according to the printing result in the case of (1) in Table 2 described above, the printing durability per plate has been reduced from about 20,000 in the past to about 50,000. It could be raised.

Further, in the humidifying solution of the present invention, the amount of colloidal silica and glycerin in water is very small,
These are rarely factors that cause emulsification of the ink. Therefore, the types of printing paper and ink that can be used are not limited, and are preferable from this viewpoint.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41N 3/08 101

Claims (2)

(57) [Claims] 1. A humidifying liquid for offset printing in which an alcohol, silica and a viscous substance are mixed in water, wherein the silica is colloidal silica and the viscous substance is glycerin, and the compounding amount of the colloidal silica and the glycerin is A humidifying liquid for offset printing, wherein the humidifying liquid is not more than 5 ml per 1 liter of the water. 2. The wet printing liquid for offset printing according to claim 1, wherein the compounding amount of the silica and the compounding amount of the glycerin are equal.