JPH06509754A - Two-stage electrolytic graining method, aluminum sheet material produced by the method, and lithographic printing plate made from the aluminum sheet material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates generally to the treatment of aluminum surfaces, and more particularly to the treatment of aluminum sheet materials. of a lithographic printing plate The present invention relates to the processing of aluminum sheet material to make it suitable for use in manufacturing.

More particularly, the present invention provides an alkaline material that enhances its usefulness as a support for lithographic printing plates. electrolytic grain of aluminum or its alloys iB).

Background of the invention The technology of lithographic printing is based on the immiscibility of oil and water; The oil-based substance or ink preferentially stays in the image area and the water or fountain solution The fountain solution preferentially stays in non-image areas. suitable When the newly prepared surface is wetted with water and the ink is applied, the background The print or non-image areas hold water and repel ink, while the image areas receive ink. Repels water. Then apply the second ink to the image area to reproduce the image, such as paper, cloth, etc. transfer onto the surface of the material to be used. Generally, ink is an intermediate layer called blanket. This intermediate material is then transferred to the surface of the material in which the image is to be reproduced. Transfer the keys.

Aluminum has been used as a support for lithographic printing plates for many years. this In order to produce aluminum for such uses, aluminum is subjected to a graining process and subsequent It is typical to apply both the anodization process and the anodization process. Graining process is then applied To improve the adhesion of radiation-sensitive coatings and the background of printing plates. It functions to improve the water-receptive properties of the water-receiving area. Graining depends on the performance of the printing plate and The quality of graining is an important factor in determining the overall quality of the printing plate. This is an important factor. Fine, uniform grain without holes is essentially the highest quality performance.

Both mechanical and electrolytic graining methods are well known and used in the production of lithographic printing plates. Widely used. Best results are obtained by using a regular electrolytic grain chamber. This is known in the art as electrochemical graining or electrochemical roughening. ening), which is used in the manufacture of lithographic printing plates. Different electrolytic graining methods have been proposed. The electrolytic graining method, for example, National Patent No. 3,755.116, National Patent No. 3.887.447, National Patent No. 3.935. 080, 4.087.341, 4.201.836, 4.2 No. 72.342, No. 4.294.672, No. 4, No. 301.229, No. 4.396.468, 4.427.500, 4.468.295 , No. 4.476, 006, No. 4.482.434, No. 4.545.8 No. 75, No. 4, No. 548.683, No. 4.564.429, No. 4.58 1.996, 4.618.405, 4.735.696, 4 ．． No. 897.168 and No. 4.919.774.

In the electrolytic graining method, a current (usually alternating current) is passed from an electrode through an acidic electrolyte. Processing aluminum to increase its surface area by passing it through aluminum to create a specific surface structure. Typically, aluminum is carried through the electrolyte solution The web is in the form of a thin continuous web with a wide width of 2 meters or more.

At the same time, excessive amounts of a sticky reaction by-product, commonly referred to as soot, are produced. It reduces both power consumption and chemical consumption while obtaining an appropriate grain shape without clogging. It is desirable to grain the surface with high efficiency.

The presence of soot necessitates an aggressive etch process following the graining operation; This further modifies the surface to an undesirable state. Therefore, this process requires a minimum amount of A method that allows the formation of It is highly desirable to operate by law.

When performing electrolytic graining of aluminum, nitric acid or hydrochloric acid Typically, nitric or hydrochloric acid mixed with a salt is used. Inside the bath with electrolytic grit chamber Other acids and many other types of chemicals are also known for use in Ru. Electrodes, most commonly formed of graphite, are approximately 1/2 an to It is placed opposite the aluminum web at a distance within a few inches. Single phase or A three-phase alternating current is passed through the electrode to cause a substitution reaction at the interface between the solution and aluminum. chloride or nitric acid that is soluble in the solution, thereby oxidizing the aluminum. Form salt. By removing aluminum using an electric current, certain tables can be A surface structure is obtained. Parameters like temperature, electrolyte concentration, flow rate and electrode gap is important in determining the properties of the surface structure formed.

Most known electrolytic graining methods use a uniform current density along the web. This includes: However, in U.S. Pat. No. 4.272.342 to Oda et al. is an alternating current applied to aluminum, Qt>Qt>Qco (However, Q, , Q, and Q are the periods of the first 1/3 of the total electrolytic grain chamber time, respectively. per unit area within the period, the middle 1/3 period and the last 1/3 period. A method has been proposed in which an aluminum electrolytic grain chamber is passed through so as to represent the amount of electricity. ing. This method of controlling current density distribution reduces the total amount of electricity required and realizes It is said that this is to improve the quality of the grain structure produced. However, Improved grain structure that is more ideally suited to the requirements of main lithographic printing plates There is a critical need in the art for electrolytic graining methods.

)1 Ausmann U.S. Pat. No. 5.041.198 states that (1) the first stage electric (2) make the current density of the first stage higher than that of the second stage; (3) the residence time of the second stage is longer than that of the first stage; and (4) the current frequency is set to its highest value in the third stage. A three-stage electrolytic grain chamber method for aluminum is described.

In a preferred embodiment of the method described by Hausmann, the three steps Different electrolyte temperatures are used in each case. This method gives a uniform grain However, it is complex, expensive, and requires the ability to adjust the current frequency. Ru.

What the present invention is directed to is more effective control of current distribution and improved grain size. The aim is to provide a new and improved method of obtaining structures.

Disclosure of invention In accordance with the present invention, an improved two-stage method for electrolytic graining of aluminum surfaces is provided. A method (i.e., using first and second stages with different processing conditions) is provided. child In this method, aluminum is exposed to an acidic current while passing an alternating current through it. Immersion in a solute solution and application of alternating current, D, :D, in the range of about 1-1 to about 7=1. t, :t2 is within the range of about 1=2 to about 1:15, and Q is less than Q2. The total current consumption (Q=QI+02) is about 200 to about 5,000. within the range of coulomb/drrf (however, D and D are the first and second stages, respectively) represents the current density in amperes/dn-r at represents the processing time (seconds) in the second stage, and Ql and Q2 represent the processing time (seconds) in the first and second stages, respectively. - ron/drrf).

The invention also includes within its scope electrolytically grained surfaces by this two-step method. aluminum articles such as aluminum sheet materials, as well as sand a support made of polished aluminum sheet material and at least one lithographic plate; It includes a lithographic printing plate consisting of a radiation-sensitive layer capable of forming a printing surface.

In the two-stage method of the invention, the current density is less in the first stage than in the second stage. at least as large, preferably as substantially large, while the time is greater than the first in the second stage. It is longer than in the step. The current density and time at each stage satisfy the ratio specified above. Not only must Qt(D+ and 1+) be (equal to the product of) is smaller than Q, (equal to the product of Dt and t), and the sum of Ql and Q is within the range of about 200 to about 5,000 coulombs/drd. must be chosen so that it becomes

The method of the present invention is provided by the method of U.S. Pat. No. 4,272,342. The present invention provides a more uniform grain than the conventional lithographic printing plate, thereby providing an excellent lithographic printing plate. this is also a two-step method, which is simpler and more easily controlled, whereas , U.S. Pat. No. 4,272,342 and U.S. Pat. It's a method.

Description of preferred embodiments As used herein, the term "aluminum" is used as required by the context. Pure aluminum and aluminum alloys that can be electrolytically grained to shall include both. Suitable aluminum alloys contain small amounts of silicon, iron, copper, and Contains alloys containing magnesium, magnesium, zinc, titanium, chromium, nickel, etc. Ru.

Prior to electrolytic grating, the aluminum surface must be cleaned to remove oil, dirt, and grease. will be excluded from this. Suitable solvents and/or caustic solutions for carrying out such cleaning are Known in the art.

The two-stage electrolytic grain chamber process of the present invention can be carried out in batch, semi-continuous or continuous mode. This is a method that allows you to That is, for example, in batch operations, aluminum Complete step l by immersing the article in a suitable electrolyte solution and applying an alternating current at a suitable current density. Apply for enough time to The current is then controlled by appropriate control of the applied voltage. An appropriate time can be selected to reduce the density and complete stage 2.

Typically, this method involves unrolling aluminum in the form of a continuous web. It is then passed through the first and second stages of the process one after another, followed by additional steps such as an anodizing step. Submit to additional processing. Following other treatments such as anodizing and possibly hydrophilization, aluminum rewind or apply one or more radiation-sensitive layers thereon. It can be subjected to an in-line coating process for coating to produce a lithographic printing plate. but However, in its broadest context, the method of the invention can be used in any shape or form. Aluminum articles may also be subjected to the two-step process described herein in an appropriate manner. It is possible.

The method of the invention preferably uses alternating current. Single-phase AC current or three-phase AC current Any suitable waveform of alternating current can be usefully used. can do. Direct current can also be used if desired, but this is typical gives a less uniform grain.

The two-stage electrolytic graining process described herein provides significantly improved grained surfaces. give. In particular, this gives a fine, uniform grain that is essentially hole-free. Graining Such surfaces are particularly well suited for use as supports for lithographic printing plates.

In the method of the invention, the total current consumption, i.e. the sum of the currents consumed in both stages, The meter has a drrf range of about 200 to about 5,000 corons/treated aluminum surface. preferably within the range of about 1.000 to about 3.000 coulombs/drd. . The current is such that D, :D is in the range of about 1:1 to about 7:1, more preferably about 1.2 :I to about 5:l, most preferably in the range of about 2.1 to about 4=1 ( However, D and D2 are amperes/dm in the second and second stages of this two-stage method, respectively. (represents the current density). The time to process aluminum is tlt, is within the range of about 1=2 to about 1:15, more preferably about 1;3 to about 1:10. The most preferred range is from about 1=4 to about 1=8 (1+ and t are each in this range). represents the processing time in seconds in the first and second stages of the two-stage method. Honmei As used in the specification, the term "processing time" refers to the time at which the aluminum is exposed to the current at the electrode. Refers to the time spent immersed in electrolyte while positioned on the contralateral side. It is the product of D and t. Ql, which represents the current consumption in coulombs/drrl, is the product of D and t, Q2 smaller than

In a preferred method, the first stage uses higher current densities and shorter treatment times. The second stage uses lower current densities and longer treatment times.

In batch processes, the processing time at each stage depends on the aluminum article being processed. It is the time that the electrolyte remains immersed in the electrolytic solution while the electric current is applied. continuous method The time at each stage depends on the length of the stage and the aluminum web or other It depends on the speed at which the aluminum article advances through it. That is, step 10 A 20 m long web moving at a speed of 0 m/min is attached to a processing time of 12 seconds. It will be done.

In the two-stage process of the present invention, the first and second stages may be performed in different vessels or in a single vessel. one electrode or characterizing the stage by separate compartments of can be represented by a band within a single bath of length defined by multiple electrodes. Wear.

The independent variables controlled in the method of the invention are time and current density. Voltage is a dependent variable be. The voltage used (typically in the range of about 5 to about 50 volts) is Resistance depends on factors such as solute composition, electrode gap, degree of agitation, etc. . Typically, the gap between the electrode and the aluminum web is in the range of 1 to 20 mm. Ru. The preferred current density for the first stage is within the range of about 50 to about 100 amps/drrr. , while the preferred current density for the second stage is about 15 to about 40 amps/drrr. be.

The preferred treatment time for the first stage is within the range of about 3 to about 10 seconds, while the preferred treatment time for the second stage is within the range of about 3 to about 10 seconds. Preferred treatment times are in the range of about 20 to about 50 seconds.

The acidic electrolyte solution used in the electrolytic graining method of the present invention is useful in the art. It can be any electrolyte solution known to be effective. A typical solution includes , contains nitric acid mixed with aluminum nitrate and hydrochloric acid mixed with aluminum chloride. It will be done.

In the two-step process of the present invention, the acidic electrolyte solution may be maintained at any suitable temperature. stomach. Typical temperatures range from about 1=2 to about 75°C, more preferably from about 1=2 to about 75°C. It is within a range of about 50°C.

A preferred electrolyte solution is a solution consisting of hydrochloric acid and aluminum chloride. Hydrochloric acid standard Typical concentrations range from about 0.1 g/L to about 30 g/L, more preferably about in the range of 1 g/L to about 20 g/L, most preferably about 5 g/L to about 15 g/L. Within range. Typical concentrations of aluminum chloride are from about 1 g/L to about 50 g/L more preferably within the range of about 1=2 to about 35 g/L, most preferably about 1=2 to about 25 g/L.

The type and concentration of electrolyte solution and temperature should be the same in both stages of the method. is advantageous, but not necessary.

As mentioned above, preferred electrolyte solutions for use in the method of the invention are hydrochloric acid and alkaline chloride. This is a solution containing minium. Add boric acid or phosphoric acid or both to this electrolyte solution. Although inclusion is optional, it is preferable. Boric acid and phosphoric acid are both corrosion inhibitors When used in such electrolyte solutions, it gives a finer grain structure. It functions so that

Boric acid is used in an amount of about 0.5 g/L to its saturation point, more preferably about 1=2 to about 13 Advantageously, amounts of about 5 g/L to about 10 g/L are used.

Phosphoric acid is present in an amount of about 1 g/L to about 35 g/L, more preferably about 5 g/L to about 20 g/L. Advantageously in an amount of g/L, most preferably from about 7.5 g/L to about 15 g/L use.

Following the two-step electrolytic graining method of the present invention, aluminum is milled for surface polishing. etching with a cold caustic solution and then treating with a suitable acid such as nitric or sulfuric acid. Soot may be removed by

In the manufacture of lithographic printing plates, the electrolytic graining process is typically followed by the addition of sulfuric or phosphoric acid. The anodizing process is typically followed by an anodizing process using an acid such as Acid oxidation (thermal 5ilation) or electrosilication (ele The process of making the surface hydrophilic, such as the process of Let's go. The anodizing step serves to provide an anodic oxide layer, preferably at least Also controlled to form a layer of 0.3 g/rrr.

Aluminum is anodized to form an anodic oxide film, then the anodized surface The process of making hydrophilic by methods such as silicate formation is very well known in the art. known and need not be further described here.

The two-stage electrolytic graining method of the present invention provides aluminum support for use in lithographic printing plates. It is particularly advantageous for manufacturing bodies. Such a plate consists of a small number of layers laminated on a support. It consists of at least one radiation-sensitive layer.

These may be negative type or positive type.

A wide variety of radiation-sensitive materials suitable for imaging for use in lithographic printing processes are publicly available. It is knowledge. Any radiation-sensitive layer is suitable, which can be exposed to light and subjected to the necessary development and development. After fixing and/or fixing, the area in the imagewise distribution can be used for printing. give.

Useful negative-working compositions include diazo resins, photocrosslinkable polymers and photopolymerizable compositions. Contains. Useful positive-acting compositions include benzoquinone diazides and naphthalenes. Included are aromatic diazooxide compounds such as toquinone diazide.

Radiation-sensitive materials useful in lithographic printing plates include silver halide emulsions; US Pat. No. 141.733 (issued to Guild on February 27, 1979) and Quinonediazides (polymeric and non-polymeric) as described in the cited references ; U.S. Pat. No. 3,511,611 (May 12, 1970 to Rauner et al. photosensitive polycarbonate as described in No. 3,342,601 (September 19, 1967 to Houle et al. diazonium salts and diazonium salts, such as those listed in resins, cinnamalmalonic acid and their functionalities, and others; and U.S. Pat. No. 4,] No. 39.390 (Raune (issued to others) and the citations therein. Includes polyesters, polycarbonates and polysulfonates.

A particularly important type of negative-working lithographic printing plates is based on the use of diazo resins. It is something. The radiation-sensitive layer typically comprises a diazo resin, a polymeric binder and an adhesive. It consists of components such as colorants, stabilizers, exposure indicators, surfactants, etc. especially Useful diazo resins include, for example, p-diazodiphenylamine and paraformal Condensation product with dehyde, 3-methoxy-4-diazodiphenylamine and barafor Condensation products with maldehyde as well as U.S. Pat. 849.392 and 3.867, 147. this Particularly useful polymeric binders for use with diazo resins such as National Patent No. 4.652.604, National Patent No. 4.741.985 and National Patent No. 4.940 ．． 646.

A second particularly important type of negative-working lithographic printing plate is a radiation-sensitive photocurable polymer. It is based on the use of . light that is particularly useful for this purpose The curable polymer has a photosensitive group -CH=CH-C as an essential part of the polymer backbone. O-containing, especially p-phenylene diacrylate polyesters.

These polymers are described, for example, in U.S. Pat. ．． No. 320, No. 3, 702.765 and No. 3.929.489. It is. A typical example of such a photocrosslinkable polymer is of the formula.

Diethyl p-phenylene diacrylate and 1,4-bi-diacrylate consisting of repeating units of It is a polyester produced from (β-hydroxyethoxy)cyclohexane. Ru. Other particularly useful polymers of this type include dimethyl-3,3'-[(sodioimide). ) disulfonyl] dibenzoate and dimethyl-5-sodiosulfoisophthalene It contains ionic units derived from monomers such as salts. this Examples of such polymers include poly[l,4-cyclohexylene-bis(oxyethylene) Ren)-p-phenylene diacrylate co-3゜3'-[(sodioimino) disulfonyl] dibenzoate and poly(1,4-cyclohexylene-bis(o) xyethylene)-p-phenylene diacrylate co-co-3,3'-[(sodio imino)disulfonyl]dibenzoate co-3-hydroxyisophthalate included.

A third particularly important type of negative-working lithographic printing plates are the so-called "double layer" plates.

In this type of lithographic printing plate, the radiation-sensitive layer containing diazo resin is anodized. a radiation-sensitive material coated on an aluminum support and containing a photocrosslinkable polymer. A layer is applied over the layer containing diazo resin. Such a double layer version is, for example, It is described in British Patent No. 12714017. These include diazo resins The radiation-sensitive layer contains a photocrosslinkable polymer on a mostly anodized support. This is a good thing because the bond is much stronger than that of the photosensitive layer. In other words, the optical rack The increased performance provided by the crosslinkable polymer provides superior adhesion of diazo resin compositions. Gain without sacrificing sex.

The invention is further illustrated by the following examples of its implementation. In these examples, there are three differences. types of aluminum, namely 1050 alloy, 3103 alloy and 5XXX alloy. used gold. 1050 alloy contains a minimum of 99.50% aluminum as well as a small amount Contains silicon, iron, copper, manganese, magnesium, zinc and titanium. 31 03 alloy contains approximately 96.5% aluminum and small amounts of silicon, iron, copper, and manganese. , magnesium, chromium and zinc. For example, the 5XXχ alloy includes: As described in U.S. Pat. No. 4,818,300, about 98.5% Contains aluminum and small amounts of silicon, iron, copper and magnesium.

The purpose of the invention is to create an aluminum surface with a fine and uniform grain without holes. That is. To characterize this surface, we performed measurements on the following parameters: It was. All of these parameters are based on the ANSI/ASME standard for surface texture. Defined in Standard 846.1-1985.

R1, which is the mean of the roughness and is known as the arithmetic mean of the center line, is the sampling The arithmetic mean of the absolute values of the measured side height deviations taken within the length and measured from the screen center line. be.

root-mean-square roughness ), R9 is the root mean square deviation from the center line (root-mean-sq uare deviation).

R8, which is 10 points high, is relative to the center line. The 5 highest peaks within the sampling length measured from parallel, non-crossing lines and the five deepest valleys.

For lithographic printing plates, the above parameters characterizing the grained aluminum surface All of the data are important. The smaller the value of R1, the finer the grains. R1 The smaller the value of , the greater the non-existence of holes. Generally speaking, from 0.5 R1 values less than 6 and R1 values less than 6 give excellent ink/water balance. It is an index of the three-dimensional structure. Ideally, the value of R,/R1 should be 1.

This is because this represents a completely uniform surface. However, this ideal is unattainable, and for the lithographic printing plate support, R, / of l, 30 or less It is believed that the value of R, gives excellent performance.

All other factors, e.g. electrolyte type and concentration, bath temperature, electrode gap, etc., are the same. When a smaller value of R,/R, and therefore a more uniform grain, Dt,D t, t+, t2, Q+ and Q2 meet the relationships specified herein.

In the examples below, optical density was measured with a reflection densitometer device. light The density value is a measure of the amount of soot on the grained surface. optical density is low The amount of soot on the grained surface is reduced. White surfaces typically have a density of about 0. 1 or 0.2, while dark gray or black surfaces have an optical density of about 1.3. will have.

Examples 1-30 An aluminum web having a thickness of 0.20 mm was processed using a continuous two-stage electric current according to the present invention. The sand removal method was applied. In each of Examples 1 to 30, unless otherwise indicated, aluminum The alloy was 1050 alloy. The electrolyte solution contains hydrochloric acid and Contains aluminum chloride.

In performing this method, aluminum is immersed in a caustic solution to remove oil and oil from its surface. Remove any debris, rinse, treat with acid to remove any metal salts on the surface, and reapply. Rinsed and then sanded. In this two-stage graining method, the Dt listed in Table 1 is , Dt, t+, tt, Q+ and Q2. I used the flow. In Table 1, D, and are ampere/drrf, and tl and t2 are seconds, Q, and Q2 and Q are coulombs/drd.

The values for optical density and surface properties obtained in Examples 1 to 30 are shown in Table 2. On the table where the values for R1, R, and R are in μm.

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Preparation of lithographic printing plates from electrolytically grained aluminum prepared in Examples 1 to 30 Suitable procedures and compositions are described, for example, in U.S. Pat. These examples are described in 4.865.951 and 4.983.497. , as in Examples 1-30, except that in step l of the method, power was applied with varying frequencies. I did it in the same way as when I was there. On each side, the electrolyte solution contains 11.5 g/L H Contains CI and 5 g/L AlCl, temperature is 25 °C, tl is 6.8 seconds and t was 33.9 seconds.

The results obtained are shown in Table ■. In Table 3, the frequency is 7 seconds per cycle. Dl and The vibration is in amperes/drrr and Qt, Qt and Q are in coulombs/dttf. , and R, , R, and R1 are μm.

dl χ more! ! Base::6:6:::Basis I:Itsumoto=l i:P': Revised Seventy Seven Keimon I Keikoshi Keishichi. 1　llI屡■■I韮韮吋李g W　u　Wcal　::　u　: :: u u u u u u u w As shown by the data listed in 8. Good results were obtained under all conditions. Higher than standard 50 or 60 cycles Although it is not necessary for the present invention to use higher frequencies, gives improved uniformity in grain structure when using very high current densities. can be used, and very high current densities allow short processing times to be used. , thereby making it easier to achieve high throughput.

The two-step method of the present invention typically has a also gives a small R1 value. A value smaller than 0.5 for R is very fine sand. It is an indicator of eye structure. This also gives low R,/R1 values of less than about 1.5. , this value is an indicator of uniform grain formation. Provides optimal performance in lithographic printing plates. A very high degree of grain structure uniformity is desirable when the R,/R value is equal to 1.3 or obtained when it is smaller than that.

The two-stage method of the present invention is compared to the prior art electrolytic graining method for aluminum. It offers many important benefits. Particularly for subsequently applied radiation-sensitive coatings. Very fine grain, giving excellent adhesion and good resolution during the printing process structure and a very large surface area can be obtained. The uniformity of the grain structure is remarkable. Ru. In contrast to the results obtained with prior art electrolytic graining methods, the grain structure is virtually non-existent. It's a direction. A grained surface with low soot levels is produced; It is only bonded tightly and is easily removed, so there is little etching. This reduces the chance that the grain structure will be adversely affected by the harsh etching process.

The three-dimensional grain structure produced by this two-step method is desirable for high-quality printing. The optimum ink/water balance can be created by This two-step sand graining method The method also provides good power while still achieving the grain shape that is important in lithographic printing methods. Leading to efficiency and low chemical consumption. The result of this graining method is Advantageous features of many of these are table tops that contribute to good press durability and operating tolerances. It contributes to giving a face.

The novel two-step process of the present invention is based on aluminum film used as a support for lithographic printing plates. It is particularly advantageous for graining of sheet materials, and this specification specifically focuses on such applications. However, if one wishes to provide a surface with a fine, uniform grain, This novel two-step method can be used whenever It can also be used for graining aluminum articles such as. for example , this method is used to produce decorative architectural aluminum and aluminum for electrolytic capacitors. It is advantageous for the production of aluminum foil.

Angyu Tagami Angyu Continuation of front page (81) Designated countries EP (AT, BE, CH, DE.

DK, ES, FR, GB, GR, IT, LU, MC, NL, SE), CA, J P

Claims (10)

[Claims] 1. Two-stage electrolytic graining of the surface of articles made of aluminum or aluminum alloys A method for obtaining a fine, uniform grain essentially without holes, comprising: The article is immersed in an acidic electrolyte solution while passing an electric current through the article in the first and second stages. and controlling the applied current such that D1:D2 is within a range of about 1:1 to about 7:1; t1:t2 is within the range of about 1:2 to about 1:15, Q1 is smaller than Q2, and the total current consumption is within the range of about 200 to about 5,000 coulombs/dm2. (where D1 and D2 are the currents in amperes/dm2 in the first and second stages, respectively) t1 and t2 represent the processing time in seconds in the first and second stages, respectively. , and Q1 and Q2 are the electric currents in coulombs/dm2 in the first stage and the second stage, respectively. 2. A method characterized in that the method is characterized in that: 2. D1:D2 is within the range of about 2:1 to about 4:1, and t1:t2 is about 1:4 to in the range of about 1:8, and the total current consumption is about 1,000 to about 3,000 cycles. 2. A two-stage process according to claim 1, wherein the temperature range is within the range of -lon/dm2. 3. The current density in the first stage is in the range of about 50 to about 100 amperes/dm2. A two-stage method according to claim 1 or 2. 4. The current density in the second stage is within the range of about 15 to about 40 amperes/dm2. The two-stage method according to any one of Items 1 to 3. 5. Claims 1 to 4, wherein the electrolyte solution comprises hydrochloric acid and aluminum chloride. The two-step method according to any one of the preceding paragraphs. 6. Electrolytically grained by the method according to any one of claims 1 to 5. Aluminum article with a polished surface. 7. Electrolytically grained by the method according to any one of claims 1 to 5. and roughness average R■ less than 0.5 and R■/R less than 1.3 A support for a lithographic printing plate having a value of (where R is the root mean square roughness) Aluminum sheet material adopted for use as. 8. made of aluminum or its alloys, with at least one lithographic printing surface thereon; consisting of a grained support having a radiation-sensitive layer capable of forming a surface; The body is electrolytically grained by the method according to any one of claims 1 to 5. lithographic printing plate. 9. made of aluminum or its alloys, with at least one lithographic printing surface thereon; consisting of a grained support having a radiation-sensitive layer capable of forming a surface; The body is electrolytically grained by the method according to any one of claims 1 to 5. and roughness average R■ less than 0.5 and R■/R■ less than 1.3 (where R is the root mean square roughness), and the radiation-sensitive layer has a A lithographic printing plate made of a photocrosslinkable polymer. 10. made of aluminum or its alloys, with at least one lithographic printing thereon consisting of a grained support having a radiation-sensitive layer capable of forming a surface; The carrier is electrolytically grained by the method according to any one of claims 1 to 5. Roughness average R■ less than 0.5 and R■/R less than 1.3 (where R is the root mean square roughness), and the radiation-sensitive layer has a A lithographic printing plate made of diazo resin and polymer binder.