JP2614112B2 - Electrolytic treatment of aluminum support for printing plate - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for electrolytically treating an aluminum support for a printing plate that can optimally control the electrolytic reaction when performing electrolytic surface roughening treatment on a metal plate. It is.

[Prior Art] An aluminum plate (including an aluminum alloy plate) is used as an aluminum support for a printing plate, particularly as a support for an offset printing plate.

Generally, in order to use an aluminum plate as a support for an offset printing plate, it is necessary that the aluminum plate has appropriate adhesiveness to a photosensitive material and water retention.

For this purpose, the surface of the aluminum plate must be roughened so as to have a uniform and dense grain. This surface roughening treatment has a significant effect on the printing performance and printing durability of the plate material when offset printing is actually performed after plate making, and its quality is an important factor in plate material production.

As a method of roughening the aluminum support for a printing plate, an AC electrolytic etching method is generally employed, and as the current, a special alternating waveform current such as a normal sine wave AC current or a rectangular wave is used. . The surface of the aluminum plate is roughened by alternating current using a suitable electrode such as graphite as a counter electrode, and is usually performed in a single process, but the pit depth obtained there is generally shallow. And the printing durability was poor. For this reason, various methods have been proposed so as to obtain an aluminum plate suitable as a support for a printing plate having a grain having fine and even pits deeper than the diameter and having uniform pits. As a method,
Roughening method using a special electrolytic power supply waveform (Japanese Unexamined Patent Publication No. Sho 53-6750)
No. 7) Ratio of electricity between anode and cathode during electrolytic surface roughening using alternating current (JP-A-54-65607), power supply waveform (JP-A-55-25381), unit area Combinations of power supply amounts per unit (JP-A-56-29699) are known.

In Japanese Patent Publication No. 61-60797, an alternating waveform voltage having a pause time such that the voltage becomes 0 in at least one of the periods of the anode time and the cathode time is applied to the aluminum plate, and the electric energy at the anode time is applied. It is described that a uniform roughened surface can be obtained by flowing so that is larger than the quantity of electricity at the time of cathode.

However, when a large amount of alloy components such as JIS 3003 is used for the aluminum plate for the printing plate, the shape of the generated grain changes due to variations in the minor components of the alloy components between Al lots. However, the printing performance sometimes fluctuated. As a method for solving this problem, as a countermeasure on the waveform, the present inventors recently, in a method of manufacturing an aluminum support for a printing plate,
Assuming that the anode time per cycle is t _F and the cathode time is t _R , the time to reach the peak value of each current is 0.1% or more and 20% or less of t _F and t _R respectively. An electrolytic treatment method was proposed. A number of attempts have been made to reduce the time required to reach the peak value of the current, such as reducing the inductance component in the power supply, reducing the inductance component of the load, increasing the resistance component of the load, and inserting a resistor in series with the load. Was.

[Problems to be solved by the invention]

However, in order to reduce the inductance component of the power supply or the load, there is a method of reducing the capacity of the power supply or reducing the size of the electrolytic treatment layer of the load. However, there is a problem that it is not suitable for mass production. . In addition, to increase the resistance component of the load, there is a method of inserting a resistor in series with the load, but when the resistance increases, the voltage increases,
There is a drawback that a large power cost is required.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for electrolytically treating an aluminum support for a printing plate, which solves the conventional problems, is suitable for mass production, and achieves uniform surface roughening without excessively increasing power costs. is there.

[Means and actions for solving the problem]

Means for Solving the Problems The present inventors have conducted intensive studies mainly on a power supply that generates an alternating current, and have reached the present invention.

That is, the object of the present invention is to provide an electrolytic treatment method for an aluminum support for a printing plate in which an electrochemical treatment is performed by supplying an alternating current between a material to be treated and a counter electrode in an electrolytic treatment solution containing metal ions. A printing plate characterized in that an inductance component larger than a load inductance component is put in a power supply circuit, an alternating current is generated by a power supply provided in series with a circuit that generates an alternating current by a current inversion control circuit, and an electrolytic process is performed. This is achieved by a method for electrolytically treating an aluminum support for use.

In the present invention, in the electrolytic treatment solution containing metal ions,
By including metal ions mainly composed of a metal to be subjected to the electrolytic treatment in the electrolytic treatment solution from the beginning, in the case of the electrolytic treatment of the aluminum web of the present invention, the concentration of aluminum ions contained is 2 to 20 g /. preferable. This ion concentration has a great influence on the quality of the surface roughening in the case of the electrolytic surface roughening treatment.

In general, an inductance component that is larger than the inductance component of a load in the DC line of the present invention is inserted into a DC line by using a reactor.

In the present invention, a power supply having an AC inversion control circuit for supplying an alternating current from the AC line side is provided with inversion elements on four sides of the bridge circuit, and two pairs of the inversion elements on opposite sides are alternately arranged. Turning on / off by a gate signal means to cause the middle side to generate AC. The gate turn-off thyristor (GT
O) is generally used.

Next, the present invention will be described in detail with reference to the drawings. FIG. 1 shows a basic circuit diagram of a power supply used in the electrolytic treatment method of the present invention. In FIG. 1, the reactor 1 is an inductance component inserted in a DC line, and it is necessary that the inductance component is larger than the inductance component of the load, and it is desirable that the inductance be 1.2 times or more the inductance of the load. By doing so, the time until the peak current of the anode and the cathode reaches the peak value can be remarkably reduced.
Reference numeral 2 denotes an inversion element, which uses a gate turn-off thyristor (GTO element) having a large withstand voltage due to a surge voltage, but is not limited to this. Each inverting device the four sides of the bridge circuit _{(GTO) 2 1, 2 2} , 2 3, 2 4 to provided inverting element opposing sides _{(GTO) 2 1, 2 3} , and inverting element (GT
As O) versus the 2 _2, 2 ₄ is to generate an AC to medium side (counter electrode) by turning on and off by the gate signal two pairs alternately.

FIG. 2 is a schematic side view of one embodiment of the electrolytic treatment apparatus of the present invention. In FIG. 1, reference numeral 11 denotes an aluminum web, 12 denotes a drum roll for maintaining a clearance between the electrode and the aluminum web, and 13 denotes a drum roll. The pass roll 14 is an electrolytic solution. When roughening an aluminum web as a lithographic printing plate support, an electrolytic solution mainly composed of nitric acid or hydrochloric acid is used as the electrolytic solution 14. Reference numeral 15 denotes an electrolytic solution discharge port, which keeps the liquid level in the electrolytic treatment tank 20 constant by maintaining the liquid level here. Reference numeral 16 denotes a main counter electrode, and a graphite electrode is generally used. In order to prevent the deterioration of the electrodes, it is preferable to attach a main counter electrode and an auxiliary counter electrode 22 (not shown) connected in parallel to the power supply. The auxiliary counter electrode 22 is of various types such as platinum and lead, but is preferably a ferrite electrode. Reference numeral 17 denotes a pump for sending a liquid to the electrolytic treatment tank of the main counter electrode, which is not shown in the present embodiment, but is a device for measuring physical properties, a controller for temperature control,
A filter for removing foreign substances may be attached to the pipe after the pump. Numeral 18 denotes a power source (see FIGS. 1 and 2), and the reactor 1 is inserted into the DC line as an inductance component larger than the inductance component 3 of the load (the main counter electrode 16 of the electrolytic treatment tank and the bus). Inverting control circuit (inverting elements 2 ₁ , 2 ₂ , 2 ₃ , 2 ₄
Is generated by a power supply 18 containing a bridge circuit including The frequency can be changed depending on the quality required, but in roughening the aluminum surface of a lithographic printing plate support,
15HZ or more is desirable. Reference numeral 19 denotes an electrolyte stock tank, to which an electrolyte 14 is supplied from an electrolyte supply port 21 via a pump 17.

The electrolytic solution used in the present invention is a solution mainly composed of nitric acid or hydrochloric acid.In the case of nitric acid, the nitric acid concentration is 5 to 50 g /, and the concentration of aluminum ions in the electrolytic bath at that time is 2 to 20 g /.
In the case of hydrochloric acid, the hydrochloric acid concentration is preferably 5 to 100 g /, and the aluminum ion concentration at that time is preferably 2 to 30 g /. Further, it is preferable that the current density of the electrolytic current is 10 to 80 A / dm ² and the electrolytic bath temperature is 30 ° C. or more for uniform graining.

Next, embodiments of the electrolytic treatment method for an aluminum support for a printing plate of the present invention will be described in more detail. The aluminum support is first alkali-etched before the electrolytic treatment of the present invention. Preferred alkaline agents are caustic soda,
Caustic potash, sodium metasilicate, sodium carbonate, sodium aluminate, sodium gluconate and the like. It is appropriate that the concentration is selected from the range of 0.01 to 20%, the temperature is 20 to 90 ° C., and the time is 5 seconds to 5 minutes.
It is a 01~5g / m ^2.

Particularly, in the case of an aluminum support having a large amount of impurities such as manganese, the amount of etching is suitably 0.01 to 1 g / m ² .

Subsequently, since a substance (smut) insoluble in alkali remains on the surface of the alkali-etched aluminum plate, desmutting may be performed as necessary.

The pretreatment is as described above, but in the present invention, the surface is electrochemically roughened using an alternating waveform current in an electrolytic solution containing metal ions.

The electrolytic solution containing metal ions used in the present invention is a solution mainly containing nitric acid or hydrochloric acid, and has a concentration of 3 to 15 in the case of nitric acid.
0 g / more preferably 5 to 50 g /, and the concentration of aluminum ions contained therein is 50 g / or less, more preferably 2 to 20 g /. The concentration for hydrochloric acid is 2-250 g
/, More preferably 5 to 100 g /, and the aluminum ion concentration at that time is 50 g /, more preferably 2 to 30 g /. Additives such as ammonium ions may be added to the nitric acid or hydrochloric acid, but in the case of mass production, it becomes difficult to control the liquid concentration.

The current density of the electrolysis current is 5~100A / dm ² but is appropriate, 10~80A / dm ² is more preferable. Such conditions are selected as needed depending on the quantity of electricity, the quality required, the components of the aluminum support used, and the like.

〔Example〕

Example 1 A JIS1050 aluminum plate was roughened using an electrolytic treatment tank as shown in FIG. 2 and a power supply as shown in FIG. An electrolytic solution having a nitric acid concentration of 10 g /, an aluminum ion concentration in the electrolytic solution of 7 g /, and a temperature of 55 ° C. was prepared and sent to the electrolytic treatment tank 20 via the pump 17. When the inductance component was measured by supplying electricity to the electrolytic treatment tank 20, the inductance component was 3.8 μH.
As H, electrolytic surface roughening treatment was performed.

40HZ by setting the amount of electricity at the anode to be 500 coulombs
The surface was roughened at the following frequency. Observation of the waveform immediately before the electrolytic treatment tank with an oscilloscope revealed that the peak current reached 0.3 msec. When the pits after the surface roughening were observed with an electron microscope, uniform pits were formed.

Comparative Example 1 Using the same electrolytic treatment tank and electrolytic solution as in Example 1, the inductance component of the reactor of the power supply was set to 2 μH, and the surface was roughened under the same conditions as in the Example. When the waveform was observed with an oscilloscope, the peak current was reached in 3.2 msec.
When the pits after roughening were observed with an electron microscope,
Uneven pits of 20μ were formed.

〔The invention's effect〕

As described above, the electrolytic treatment method for an aluminum support for a printing plate of the present invention does not reduce the capacity of the power supply nor increase the voltage more than necessary,
The time required to reach the peak value of the current is shortened, so that the electrolytic surface roughening treatment can be performed under a suitable pit condition under an appropriate condition of an electric power cost suitable for mass production.

[Brief description of the drawings]

FIG. 1 is a basic circuit diagram of a power supply used in the electrolytic treatment method of the present invention, and FIG. 2 is a schematic side view of an electrolytic treatment tank in one embodiment of the electrolytic surface roughening treatment method of the present invention. 1… Reactor 2,2 ₂ , 2 ₃ , 2 ₄ … Inverting element 3… Load inductance component A, B… Output terminal 11… Aluminum web 12… Electrode 13… Pass roll 14… Electrolysis Electrolyte 15 Electrolyte outlet 16 Main counter electrode 17 Pump 18 Power supply 19 Electrolyte stock tank 20 Electrolytic treatment tank 21 Electrolyte supply port 22 Auxiliary counter electrode

Claims (1)

(57) [Claims] A method for electrolytically treating an aluminum support for a printing plate, wherein an alternating current is supplied between an object to be treated and a counter electrode in an electrolytic solution containing metal ions to perform an electrochemical treatment.
An alternating current is generated by a power supply provided in series with a circuit that generates an alternating current by a current reversal control circuit using an inductance component larger than a load inductance component in a power supply circuit, and electrolytic surface roughening is performed. An electrolytic treatment method for an aluminum support for a printing plate.