JPS6127476B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical field] The present invention relates to a method for making an offset printing plate,
Specifically, the present invention relates to a novel offset plate-making method using an anodized aluminum plate (plate material) and a specific sealing agent. [Prior Art] Up until now, the plate material for offset printing plates has been zinc plates, but recently aluminum plates have become more popular than zinc plates because they are cheaper, more hydrophilic, and have finer grains. There is. Offset plate making using aluminum plate is
Roughly speaking, a grained aluminum plate is used as a plate material, and a photosensitive liquid is coated on this plate and then exposed.
If necessary (if an aluminum planar intaglio plate is to be obtained), a further step of development corrosion is performed, followed by a desensitizing treatment. However, the number of conventional offset plate-making steps is actually quite large, so plate-making takes a long time, and in addition, the resulting offset printing plates have defects such as a tendency to vary in quality. [Objective] The present invention provides a method for making an offset printing plate that uses an anodized aluminum plate as a plate material and allows easy plate making, unlike the conventional method. [Structure] The offset plate making method according to the present invention uniformly coats the surface of an anodized aluminum plate with an inorganic or organic compound that can be activated by irradiation with irradiation energy, or a complex that is partially liberated and ionized. After being supplied, image irradiation is performed to seal only the irradiated areas, and then the sealed areas are desensitized or an offset printing plate is obtained without desensitization. By the way, the present inventors coated or immersed a specific inorganic or organic compound or complex on the surface of an anodized aluminum plate, and irradiated it with light of a wavelength that activated or ionized it.
It has been confirmed that if the compound or the like is adsorbed to the current-carrying hole to seal it, the sealed area can become a high-quality oil-based ink receiving area. The present invention was completed based on this knowledge. The method of the present invention will be explained in more detail below. As mentioned above, the offset plate making method of the present invention differs from the conventional method in that an aluminum plate (including an aluminum alloy plate) having an anodic oxide film on its surface is used as a plate material. By the way, anodic oxidation is generally employed for surface treatment of aluminum (including its alloys). Depending on the purpose, part or all of the formed porous anodic oxide film is coated with
Sealing treatment is often applied. For example, aluminum or aluminum alloy can be dissolved in an electrolyte such as sulfuric acid, oxalic acid, or chromic acid at a concentration of 1.5 to 2.0
By anodizing at a current density of about A/dm ² , an oxide film is formed, which is a porous γ-l ₂ O ₃ layer having countless micropores with a diameter of about 100 to 150 Å. The pores can be sealed by heating in hot deionized water, by heating in heavy metal salt water such as acetic acid or sulfuric acid, or by performing AC electrolysis treatment to accumulate hydroxides in the micropores. Measures such as sealing the holes are used. Conventionally, such anodic oxidation treatment of aluminum has been carried out for purposes such as protecting the aluminum surface, utilizing its porosity to obtain a base for painting or coloring, and further obtaining electrical insulation properties. The reality is that it is being done. In the method of the present invention, such an anodized aluminum plate is used as a plate material for an offset printing plate, and a specific pore sealing agent is coated or immersed on the surface of the plate, and light is irradiated to change the sealing agent according to its brightness. A method is used to seal the holes. The sealing agent used here is either (1) an inorganic or organic substance that is activated by irradiation with irradiation energy, or (2) a complex that is partially liberated and ionized by irradiation with irradiation energy. .
Specifically, as the former (1), acidic liquids of water-soluble divalent or higher metal salts such as iron, aluminum, nickel,
Mention may be made of nitrates, sulfates, hydrochlorides, chromates or phosphates of cobalt, chromium, copper, cadmium, titanium, manganese, molybdenum, calcium, magnesium, panadium, gold, silver, lead or zinc. On the other hand, the latter (2) includes oxalates, acetates, amino acid salts, citrates, oleates, maleates, malates, tartrates, glutamates, and alginates of divalent metals. In addition to organic acid metal salts, metal salts containing picolinic acid amide and ethylenediamine as constituents can be mentioned. Further, for light irradiation, a light source having a wavelength in the far infrared to electron beam range, preferably in the ultraviolet range is used. Detailed study of why pore sealing is effectively performed by applying light to an anodized aluminum (or aluminum alloy) surface with such a specific pore sealing agent coated or immersed in it. Although it has not been done yet, it is thought that the sealing agent is activated by light energy, which adsorbs to the active layer present in the current-carrying hole and promotes the sealing. FIG. 1 shows an example of an experimental apparatus for sealing the surface of an aluminum plate having an anodic oxide film. In Fig. 1, 1 is an anodized Al plate, 2 is a stainless steel mesh electrode, and 3 is a stainless steel mesh electrode.
is a tank, 4 is a sealing agent [here (NH ₄ ) ₂ Cr ₂ O ₇
5 is a high-pressure mercury lamp, 6 is a DC power supply, 7 is a vibratory capacitance electrometer, 8 is a 1% aqueous solution of
represents a recorder and R represents a resistance.
The distance between the Al plate 1 and the electrode 2 is about 3 cm. In such a device, as the sealing of the surface of the Al plate 1 (porous anodic oxide film) progresses, the resistance value increases, causing a change in potential, which can be read as a voltage drop by the recorder 8. . The results of various experiments using this device were the second
This is shown in Figures 4 to 4. Figure 2 shows the measured values when the bath temperature was maintained at 29°C and light was irradiated (curve a: inventive example) and when no light was irradiated (curve b: comparative example). The graph shows the values measured in the same manner except that the bath temperature was 35°C. These second
As can be seen from FIGS. 3 and 3, at this level of bath temperature, the pores are sealed by the action of light irradiation. However, if light irradiation is omitted and the bath temperature is increased, the temperature will increase as shown in Figure 4 [1% (NH ₄ ) ₂ Cr ₂ O ₇ solution used]
As shown in , sealing progresses at 60°C, making partial sealing impossible. For these reasons, in carrying out the method of the present invention, the bath temperature is preferably 50°C or lower. Further, in this experiment, it was confirmed that the concentration of the sealing agent is 1 to 5%, and that an aqueous solution thereof is suitable. In order to actually seal the aluminum surface image-wise using the plate-making method of the present invention, an aluminum plate (plate material) having an anodized film as shown in Fig. 1 is immersed in a sealing agent. It is more desirable from the standpoint of work and quality of the product to apply a sealing agent onto the plate material and irradiate it with light (image exposure) before it dries. If the amount of light irradiation is increased, sealing will be achieved more quickly. Although it is advantageous to irradiate the light with a negative or positive film in close contact with the surface of the plate material, other means commonly used in offset plate making may be used instead. Furthermore, the inorganic or organic compound may be supplied (coated or immersed) onto the surface of the printing plate by dissolving it in a suitable medium. Thus, the aluminum plate with the anodic oxide film surface that has been partially (image-wise) sealed has a sharp and stable image formation, and the dyed image can be produced using conventional image forming methods such as screen printing. It is much more detailed than what was originally written. Next, when making a printing plate suitable for printing with oil-based ink, a desensitizing treatment liquid is applied to the partially sealed plate to clearly form lipophilic and hydrophilic areas. Offset printing plate (lithography)
is obtained. That is, the pore-sealed area becomes a non-image area with a hydrophilic surface due to the desensitizing treatment liquid, and the other area becomes an ink (oil-based ink) receiving area, making it possible to print. Examples of the desensitizing treatment liquid include gum arabic, carboxymethyl cellulose, dextrin, and malonic acid.
Therefore, the desensitization treatment of the pore-sealing area can be carried out by applying the above-mentioned desensitization treatment liquid to the entire plate surface which has been image-wise sealed using a roller coating method, a brush coating method, or a dipping method. It may be applied by means such as a coating method. In addition, if water-based ink is used, the partially sealed area itself will attract water-based ink and become an image area, and the active anodic oxide film surface will not have any ink attached. It becomes a non-image area, and dry offset printing or direct printing is possible without desensitization treatment. Furthermore, if the pores are immersed in or coated with a corrosive solution prior to desensitization, the corrosive solution will not penetrate into the sealed area and will remain as an image, while the other areas (active areas) will be exposed to aluminum. As a result, a flat intaglio plate having an uneven pattern on the metal surface is obtained. Although many aluminum surface treatment methods have been proposed so far, most of them have been aimed at the entire surface treatment or dyeing of the aluminum surface. The reality is that we have not seen any examples yet. The method of the present invention is applicable not only to the production of offset printing plates, but also to the production of various aluminum products including decorative items. Example An aluminum plate was anodized according to JIS H 9500-1976 to prepare a plate material. A sealing agent (using a 1% aqueous solution of the treatment agent) is applied to this surface, and the image is exposed while it is still wet.The surface is then dyed with 0.1% iron ammonium oxalate, the reflection density of each is measured, and the holes are sealed. The effectiveness of the test was determined. The results were as shown in Table-1.

【table】

〔effect〕

According to the method of the present invention, a high-quality offset printing plate can be obtained with a far fewer number of steps than conventional plate-making methods.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of an experimental apparatus used for carrying out the method of the present invention, and FIGS. 2 to 4 are graphs showing the results of various measurements during the sealing process. .

Claims (1)

[Claims] 1 After uniformly supplying an inorganic or organic compound that can be activated by irradiation energy, or a complex that partially liberates and ionizes, onto the surface of an anodized aluminum plate, image irradiation is performed and only the irradiated area is exposed. 1. A method for making an offset printing plate, which comprises sealing the pores, and then desensitizing the pores without desensitizing the pores or desensitizing the pores.