JPH04124300A - Production of aluminum substrate for printing plate - Google Patents

Abstract

PURPOSE:To produce an Al substrate for a printing plate with uniform pits by regulating the alternating wave-form of electric current used in an acidic electrolytic soln. so that the electric current fluctuates within a specified range of the peak current for a time left by subtracting the time elapsed until the peak current is attained from each of anode time and cathode time per one cycle. CONSTITUTION:When the surface of an Al sheet is electrochemically roughened with electric current having alternating wave-form in an acidic electrolytic soln., the wave-form is regulated so that the electric current fluctuates within 1-20% range of the peak current for a time tF-tPF-tPF', and a time tR-tPR-tPR' (where tF is anode time per one cycle, tR is cathode time, each of tPF and tPR is the time elapsed until the peak current is attained and each of tPF' and tPR' is the time elapsed until the peak current returns to zero). In the wave-form, a part A (tF-tPF-tPF') satisfies 0.01IFP<=iP<=0.3IFP', a part B (tR-tPR-tPR') satisfies 0.01IRP<=iR<=0.3IRP and frequency P is equal to 1/T=1/(tF+tR).

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for manufacturing an aluminum support for printing plates, and in particular to a method for producing an aluminum support for printing plates made of a roughened aluminum plate suitable for offset printing plates. The present invention relates to a method for manufacturing an aluminum support.

[Conventional technology]

Aluminum plates (including aluminum alloy plates) are used as aluminum supports for printing plates, particularly as supports for offset printing plates.

Generally, aluminum plate is used as offset printing plate material (support)
In order to be used as a photosensitive material, it is necessary to have appropriate adhesion to the photosensitive material and water retention.

For this purpose, the surface of the aluminum plate must be roughened to have uniform and dense grains. 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, so its quality is an important factor in the production of the plate material.

In the manufacturing process of aluminum supports for printing plates, alternating current electrolytic etching is generally used as a method to roughen the surface of aluminum plates. Waveform current is used. Then, the surface of the aluminum plate is roughened using an alternating current using a suitable electrode such as graphite as a counter electrode.

The depth of the print was shallow overall, and the printing durability was poor.

For this reason, a number of methods have been proposed to obtain an aluminum plate suitable for use as a support for a printing plate, which has a uniform and dense grain in which bits are deep compared to its diameter.

The methods include a surface roughening treatment method using a special electrolytic power supply waveform (Japanese Patent Application Laid-Open No. 53-67507), and a ratio of the amount of electricity at the anode and cathode in electrolytic surface roughening treatment using alternating current (Japanese Patent Laid-Open No. 53-67507). Publication No. 54-65607), ii source waveform (JP-A-55-
25381 (Japanese Patent Application Laid-open No. 5,629,699).

Further, in Japanese Patent Publication No. 61-60797, an alternating waveform voltage is applied to an aluminum plate with a pause time such that the voltage becomes zero within each period of at least one of the anode waiting time and the cathode waiting time, It is stated that a uniform rough surface can be obtained by passing a current so that the anode specific electricity amount is larger than the cathode specific electricity amount.

[Problems to be Solved by the Invention] However, when a large amount of material with a large alloy component, such as J, iS 3003 material, is used for the printing aluminum plate, the trace amount of the alloy component between AN lots is Due to variations, the shape of the grains that are generated changes,
Printing performance may vary. Also, although the above patent is an unusual method for obtaining uniform focus,
In recent years, there has been a demand for lithographic printing plates with even better stain resistance, and it has become necessary to further reduce the variation in bit size.

[Means for Solving the Problem] The present inventors focused on the current waveform, and made it possible to more uniformly and
The present invention aims to provide an electrolytic treatment method in which variations in printing performance (variations in bits) are small compared to variations in alloy components of materials.

As a result of intensive research, the present inventors discovered the following electrolytic treatment method.

That is, in a method of electrochemically roughening an aluminum plate using an alternating waveform current in an acidic electrolyte, the anode time per cycle is 2. Cathode time t*
r Time to reach each peak current tPFI
L PF The time from pH1 peak current to return to zero
'+L Fil', tF-t□~tPF1, -1. at the anode and cathode, respectively. , −1□′, the surface of an aluminum plate is electrochemically roughened using an alternating waveform current in which the current variation within a time period of 1□′ is within the range of 1% to 20% of the peak current value. This is an electrolytic treatment method.

The acidic electrolyte used in the present invention is a liquid mainly composed of nitric acid or hydrochloric acid, and has a nitric acid concentration of 5 to 50 g/I! ,, concentration of aluminum in the electrolytic bath 2-20 g, #, concentration of hydrochloric acid 5-1. OOg/l, aluminum concentration 2-30 g
/f! is desirable. Also, electrolytic current density 10~B OA/
d m”, and the electrolytic bath temperature is preferably 30°C or higher to uniformly form a grain pattern.The concentration of aluminum in the electrolyte is the same as that of the aluminum plate dissolved in the anode reaction, and in some cases, The solution is prepared in advance with aluminum nitrate, etc.

Furthermore, the frequency of the electrolytic current used in the present invention is IO~1
00Hz is preferable for mass production.

The present invention will be explained in detail below. The aluminum plate is first alkali etched. Preferred alkaline agents are caustic soda, caustic potash, sodium metasilicate, soda carbonate, sodium aluminate, sodium gluconate, and the like. Concentration is 0.01-20%, temperature is 20-90℃, time is 5 seconds ~
The etching time is suitably selected from the range of 5 minutes, and the preferred etching amount is 0.01 to 5 g/m''.

Especially in the case of aluminum plates with many impurities such as manganese,
A suitable etching amount is 0.01 to Ig/+d.

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

The pretreatment is as described above, but is followed by electrochemical roughening in an acidic electrolyte using an alternating waveform current.

The acidic electrolyte used in the present invention is a liquid mainly composed of nitric acid or hydrochloric acid, with a nitric acid concentration of 3 to 150 g/I! , more preferably 5 to 50 g/I! ,, concentration of aluminum 50
g/l or less, more preferably 2 to 20 g/j
It is 2. The concentration of hydrochloric acid is 2 to 250 g/l, more preferably 5 to 100 g/l! , concentration of aluminum 50 g
/l or less, more preferably 2 to 30 g/P. Additives such as ammonium ions may be added to the nitric acid and hydrochloric acid, but in the case of mass production, it becomes difficult to control the concentration of the liquid.

In addition, the current density of the electrolytic current is suitably 5 to 100 A/dm2, but more preferably 10 to B0 A/dm. In addition, these conditions depend on the amount of electricity, the desired quality, and the composition of the aluminum plate used. etc. are selected at any time.

Further, the current waveform is determined by inductance components of the power supply, bus bar, electrolytic cell, etc., but it is necessary that the current fluctuation is within 30% of the peak current value.

The current waveform will be explained below using FIG.

As the current waveform, an alternating waveform as shown in FIG. 1 is used.

As shown in Fig. 1, part A (up t□-Lprl 0.011rr< ip≦0.31rp part B (tF--
tP, l-L□') 0.01. IIP≦il≦0.31. .

T　　　tF−+ Needless to say, it is.

Preferably, the roughened aluminum plate is subsequently treated with an acid or alkaline solution.

Specifically, in addition to the sulfuric acid described in Japanese Patent Publication No. 56-11316, phosphoric acid or a mixture of phosphoric acid and chromic acid is used. Further, smut adhering to the surface is removed by lightly etching with an alkaline solution such as caustic soda as described in Japanese Patent Publication No. 48-28123. When removing attached smut with an alkaline solution, the surface of the aluminum plate is etched, so alkali-insoluble components remain. Therefore, it is necessary to desmut again with an acidic solution (sulfuric acid, phosphoric acid, chromic acid, etc.).

The anodizing treatment is 0.1 to 10 g/bo, more preferably 0
．． 3~5g/n? It is best to form it on the surface. It is preferable to perform alkali etching and desmant treatment before anodizing.

The processing conditions for anodic oxidation vary depending on the electrolyte used, so they cannot be determined in general terms, but in general, the electrolyte concentration is 1 to 80% by weight, the solution temperature is 5 to 70°C, and the current density is Appropriate ranges are 0.5 to 60 A/dm'', voltage 1 to 100 Å, and electrolysis time 1 second to 5 minutes.

The grained aluminum plate with the anodic oxide film obtained from camphor is itself stable and has excellent hydrophilic properties, so a photosensitive coating can be immediately applied on top, but if necessary, the surface can be further coated. Can be processed. For example, a silicate layer made of the alkali metal silicate described above or an undercoat layer made of a hydrophilic polymer compound can be provided.

The coating amount of the undercoat layer is preferably 5 to 150 mg/rrf.

Next, a photosensitive coating film is provided on the aluminum support treated in this way, imagewise exposed, developed and made into a plate, and then set in a printing machine and printed.

[Example] Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples.

(Example-1) An aluminum plate made of JTS3], 03 material was immersed in a 10% caustic soda aqueous solution heated to 60°C, etched so that the amount of aluminum dissolved was 3 g/a, and then smut was removed. It was removed and washed with water. Next, using an electrolytic solution in which 9 g/l of nitric acid solution was mixed with 3 g/j2 of aluminum ions, the temperature of the electrolytic treatment bath was set to 60°C, and the conditions for flowing an alternating waveform were as specified in the attached No. 1. In the figure 1. =1.
, anode electricity [20
0c/dn(with ip"i++"0.051FF=
The aluminum plate was electrolytically roughened by setting it to 0.05111P to obtain a sample (A). As a result of observation using an electron microscope photograph, a uniform focus of 2 to 4 μm was generated.

(Comparative Example-1) Under the conditions of Example-1, i, = i*=0.251FF=
It was set to be 0.257++p, and was designated as sample CB). After desmutting, an electron microscope photograph revealed that pits of 10 to 20 microns were formed and were non-uniform.

(Example-2) Sample (A) and sample (B) were coated with an anodized film of 2.5 g/nf in 20% sulfuric acid, washed with water, and dried. These will be referred to as substrates [A] and (B).

A photosensitive layer was provided on the substrate (Al-(B)) thus prepared by applying the following composition so that the coating weight after drying was 2.5 g/polymer.

Photosensitive liquid composition Ester compound of naphthoquinone-1,2-diazido-5-sulfonyl chloride, pyrogallol, and acetone resin (described in Example 1 of U.S. Pat. No. 3,635.709) -------0,75g Talesol Novolank resin----1--・-1----
--2, OOg Oil Blue 1603 (Orient Chemical) 0.04g ethylene dichloride --m---
−・−−−−−−−−−−−16g 2-Methoxyethyl acetate−−−−1・−12g The photosensitive lithographic printing plate thus prepared was placed in a vacuum printing frame with a transparent positive After performing a 50-second exposure with a 3kW metal halide lamp from a distance of 1m through the film, the Si
5 of sodium silicate with a molar ratio of O□/Na, 1.74
．． After developing with a 26% aqueous solution (pH=117), printing was carried out in a conventional manner. Sample (A) was a sample that was not easily stained, but sample CB) was a sample that was very easily stained.

〔Effect of the invention〕

When an aluminum plate is placed in an acidic electrolyte, the current fluctuation in the time period excluding the time to reach the peak current and the time to return to zero from the anode time and cathode time per cycle is 1% of the peak current value. Aluminum supports for printing plates with uniform bits are obtained by electrochemical roughening using alternating waveform currents with Al1 nodes within 20% of A printing plate that is difficult to produce is obtained.

[Brief explanation of the drawing]

The attached FIG. 1 is a diagram showing one cycle of the current and time relationship of the alternating waveform current used in the present invention. In the figure, ■□=...-Peak current value at anode lff1P-...-Peak current value at cathode i,...
・・Peak current fluctuation value at anode time it・−・・・Peak current fluctuation value at cathode time t v −−−−・・Anode time t
, ----1・Cathode time tF--・・--・-・Time to reach the peak current at anode tpH・--・--Time to reach the peak current at cathode tPF'--1・--・-Anode time to return to zero from peak current tpm' - 1 - time to return to zero from peak current at anode part A Dr-t□-tpr')
-Anode peak time part B (t++ t++++ t
r*I...-cathode peak time T--cycle. (3 idiots)

Claims (1)

[Claims] In a method of electrochemically roughening an aluminum plate using an alternating waveform current in an acidic electrolyte, the anode time per cycle is t_F, the cathode time is t_R, and the time to reach each peak current. t_P_F, t_P
_R, time to return from peak current to zero t_P_F', t
_P_R', t_ at anode and cathode respectively.
F-t_P_F-t_P_F', t_R-t_P_R-
The current fluctuation within the time t_P_R' is 1 of the peak current value.
% to 20%.