JPS6347347A - Aluminum alloy support for lithographic printing plate - Google Patents

Abstract

PURPOSE:To obtain the titled Al alloy support especially suitable for electrochemical surface roughening, making the appearance of a roughened surface uniform and having superior fatigue resistance and printability by providing a compsn. consisting of prescribed percentages of Mg, Si and Cr and the balance Al with inevitable impurities. CONSTITUTION:This Al alloy support for a lithographic printing plate consists of 0.3-0.5wt% Mg, 0.05-0.3wt% Si, 0.01-0.25wt% Cr and the balance Al with inevitable impurities or further contains <=0.50wt% Cu as required. Cu improves the strength and enhances the effect of etching by electrolytic surface roughening. The Al alloy support has the above-mentioned characteristics and hardly causes the staining of the non-image area during printing, so it is used as an extremely superior support for a lithographic printing plate.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to an aluminum alloy support for lithographic printing plates, which is particularly suitable for electrochemical roughening treatment, has a uniform appearance on the roughened surface, and The present invention relates to an aluminum alloy support for lithographic printing plates that has excellent fatigue strength, heat softening resistance, and printability.

Conventional technology Conventionally, lithographic printing plates have been produced by applying a photosensitive substance onto an aluminum alloy base plate that has been subjected to surface treatments such as roughening treatment or anodizing treatment, and then drying it to form a so-called PS plate.
Printing plates obtained by subjecting S plates to plate-making processes such as image exposure, development, and gumming are widely used. In such a lithographic printing plate processing process, the photosensitive layer that remains undissolved during the development process forms an image area, and the area where the photosensitive layer is removed and the surface of the aluminum alloy plate underneath is exposed becomes hydrophilic. Due to its nature, it becomes a water receiving area and forms a non-image area.

As such a support for a lithographic printing plate, an aluminum alloy plate is generally used, which is lightweight and has excellent surface treatment properties, workability, and corrosion resistance. Conventional aluminum alloy materials used for this purpose include JIS A 1050 (A1 alloy with a purity of 99.5% or more), JIS A 110
0 (Al-0.05~0.20 heavy 5% C0 alloy)
, JIS A 3003 (A! -0,05~0
．． Thickness of 20% Cu-1,5% Mn alloy) etc.
, i to o, amm aluminum alloy plates, and the surfaces of these aluminum alloy plates are roughened by one or a combination of mechanical, chemical, and electrochemical methods. It is then used after being anodized.

Specifically, an aluminum lithographic printing plate subjected to mechanical roughening treatment, chemical etching treatment, and anodized film treatment described in JP-A No. 48-49501, or JP-A No. 51-Sho. Aluminum lithographic printing plate subjected to chemical etching treatment and anodic oxidation film treatment described in 61304@ in that order, JP-A-146-1986
Aluminum lithographic printing plates subjected to electrochemical treatment, post-treatment, and anodic oxide film treatment described in No. 234@, electrochemical treatment and chemical etching treatment described in Japanese Patent Publication No. 48-28123. , and an aluminum lithographic printing plate subjected to anodization film treatment in that order,
Or after mechanical roughening treatment
Aluminum lithographic printing plates etc. that have undergone the treatment described in this issue are known.

By providing a suitable photosensitive layer on such a support, it is possible to obtain up to 100,000 sheets of clear printed matter. However, there is a strong desire to obtain more printed matter from a single printing plate, that is, a desire to further improve printing durability. In order to improve printing durability in this way, a PS plate with an aluminum alloy plate as a support is exposed and developed in the usual way, and then heat treated at high temperature (so-called burning treatment) to reduce the image area. An effective method is to strengthen the
-27243@ and Japanese Patent Publication No. 44-27244. The heating temperature and time for such a burning process depend on the type of resin forming the image, but
Usually, the heating time is within the range of 200 to 280°C for 3 to 7 minutes.

Problems to be Solved by the Invention Recently, in the above-mentioned burning process, it has been desired to perform the burning process at a higher temperature and for a shorter time with the main purpose of shortening the processing time. However, when the conventionally used aluminum alloy plate is heated to a high temperature of 280°C or higher, the aluminum recrystallizes, resulting in an extremely low strength and a loss of stiffness of the printing plate, making it difficult to handle. This becomes very difficult and causes problems such as the inability to set the plate on the printing press or the inability to register the colors of the plate in multicolor printing. Therefore, there is a demand for a stable aluminum alloy plate support that has better heat resistance, especially heat softening resistance, than conventional supports.

On the other hand, as printing speeds have increased due to advances in printing technology, the stress applied to printing plates to mechanically fix them to both ends of the printing press cylinder has become higher. If the strength of the aluminum printing plate is insufficient, this fixed part may become deformed or damaged, causing problems such as printing misalignment, or the plate may break due to repeated stress applied to the folded part of the printing plate (grip breakage), causing printing problems. It is often impossible. Therefore, an aluminum alloy plate support with high strength, particularly high fatigue strength, is desired.

However, conventional JIS A 1050 aluminum alloy plates can be electrochemically roughened to provide a uniform rough surface or appropriate surface roughness, and are less likely to stain non-image areas during printing (printability is better), but
It has the disadvantage of poor fatigue strength and heat softening resistance. On the other hand,
JIS A 3003 Aluminum alloy plate has sufficient fatigue strength and heat softening resistance, but electrochemical roughening treatment does not provide a uniform rough surface or appropriate surface roughness, and furthermore, non-image areas may be damaged during printing. The disadvantage was that it was easy to get dirty.

This invention was made against the background of the above-mentioned circumstances, and has sufficient fatigue resistance and heat softening resistance as a printing plate, and also has a uniform rough surface and an appropriate surface roughness by roughening treatment, especially electrochemical roughening treatment. An object of the present invention is to provide an aluminum alloy support for a lithographic printing plate, which has a surface roughness of 1, and has good printability and is less likely to cause stains in non-image areas during printing.

Means for Solving the Problems The aluminum alloy support for lithographic printing plates of the first invention has the following features:
V1c 10.3% or more and 5% or less, Si 0.05% or more and 0
．． 3% or less, and (::ro, 01% or more 0.25%
It is characterized by containing the following, with the remainder consisting of Al and inevitable impurities.

Further, the aluminum alloy support for lithographic printing plates of the second invention has a MC of 10.3% or more and 5% or less and a Si of 0.05% or more and 0.
．． 3% or less, and Cr 0.01% or more and 0.25% or less, with the remainder consisting of Al and inevitable impurities,
Moreover, the average width of the crystal grains on the surface in the sheet width direction perpendicular to the rolling direction is 40JJffl or less.

Function First, the reasons for limiting the components in the aluminum alloy support for lithographic printing plates of the present invention will be explained.

1ν1g= Mg is an effective element for improving strength, improving handleability, uniformly refining the electrolytically roughened surface, and improving fatigue strength, and if it is less than 0.3%, these effects cannot be sufficiently obtained. do not have. On the other hand, if MQ exceeds 5%, these effects will be saturated, which will be economically wasteful and at the same time various problems will occur in the method of manufacturing rolled plates. Therefore, the content of MO is 0.3% or more,
It was set to 5% or less.

Si: Si is an effective element for uniformly refining the electrolytically roughened surface, and if it is less than 0.05%, the effect cannot be sufficiently obtained. On the other hand, if Sit exceeds 0.3%, the fineness and uniformity of the electrolytically roughened surface will deteriorate, and ink stains will easily occur during printing. Therefore, the Si content is 0.05% or more, 0.05% or more.
It was set to 3% or less.

Cr: Or is an element effective in improving strength, handling, improving fatigue resistance, refining crystal grains, and uniformly refining the electrolytically roughened surface. If Crff1 is less than 0.01%, these effects are not sufficient; on the other hand, if Cr is contained in excess of 0.25%, a huge Or compound is formed during manufacturing, which deteriorates the surface quality of the board and the above two performances. decreases. Therefore, the Or content was set to 0.01% or more and 0.25% or less.

In addition to these MCI, Si, and (:r) components, Cu can be contained as needed. That is, Cu is effective for improving strength and enhancing the etching effect by electrolytic surface roughening. However, 0.5 If Cu is contained in excess of %, etching during electrolytic surface roughening will be excessive.
On the contrary, the roughened surface becomes uneven, which is not preferable. Therefore, if Cu is added as necessary, the amount of Cu is 0.
．． It is desirable that it be 5% or less.

Although aluminum alloys usually contain Fe as an unavoidable impurity, it is desirable to limit Fe to 0.50% or less, more preferably 0.30% or less. In other words, Fe is effective in improving strength and fatigue strength, but if it is contained in an amount exceeding 0.50%, Al-F
Since coarse e-(S i )-based crystallized substances are formed, the electrolytically grained surface becomes non-uniform, and stains are likely to occur during printing, a content of 0.50% or less is appropriate. Regarding other impurities other than Fe, there is no problem as long as it is within the range normally contained in commercially available industrial pure aluminum.

Furthermore, when producing an aluminum alloy ingot, T1 or Ti-8 is generally added as a grain refiner, but the aluminum alloy blank of the present invention also contains Ti and/or Ti-8 as a grain refiner. B may be contained. However, Ti is 0.1% or less and B is 0.1% or less.
It is desirable to set it to 0.02% or less.

In particular, the aluminum alloy support for lithographic printing plates according to the second invention not only contains the above-mentioned components as alloy components, but also contains an average width of crystal grains on the surface in the plate width direction perpendicular to the rolling direction. 40JJm or less. This can be achieved by reducing the grain size to 403.1 m or less immediately after intermediate annealing before final cold rolling in the cold rolling process. In this way, by refining the grains immediately after intermediate annealing and making the average width of the grains in the width direction of the final sheet 40 pm or less, the surface roughened by acid or alkali etching or electrochemical etching is uniform. Moreover, it becomes fine and the occurrence of uneven color tone and streaks is suppressed.

That is, the surface roughening processability becomes good, and the surface appearance quality of the base plate for printing plate support becomes good.

Next, the method for manufacturing the aluminum alloy support for lithographic printing plates of the present invention will be described in detail.

First, a molten aluminum alloy containing the above-mentioned components is cast according to a conventional method. Semi-continuous casting is generally used as this casting method, but continuous thin plate casting may also be used to save energy and improve mechanical properties. The obtained ingot is subjected to processes such as homogenization treatment, hot rolling, cold rolling, and intermediate annealing to give a plate thickness of 0.10 to 0.50. Homogenization treatment refines the crystal grains during intermediate annealing and eliminates segregation of Fe, Si, Or, MQ, etc. in the ingot to achieve a uniform distribution, and uniformly roughens the surface during electrochemical roughening. In order to
It is preferable to set it within the range of time. Note that the homogenization treatment and the heat treatment for hot rolling do not need to be divided into two steps, and hot rolling may be performed immediately with one heating step. In either case, the hot rolling start temperature is 400 to 550°
It is preferably within the range of C.

After hot rolling, it is normal to perform first cold rolling, then intermediate annealing, and then rough final cold rolling, but in some cases, intermediate annealing is performed two or more times before cold rolling Rolling may also be performed. In this process, by controlling the average grain size immediately after intermediate annealing before final cold rolling to 40 pm or less, the average width of grains in the width direction of the final cold rolled sheet is reduced to 40 pm or less.
By setting the thickness to 0 μm or less, the electrolytically roughened surface by electrolytic roughening treatment can be made uniform and fine. The appropriate annealing temperature in this intermediate annealing is 300 to 600'C. 300
If the temperature is lower than 600°C, recrystallization will not occur completely, and if the temperature exceeds 600°C, the surface will be severely oxidized, the color of the surface will change, and the recrystallized grains will become coarse, which is not preferable. In addition, this intermediate annealing is normal batch annealing (average heating rate 20 to 50°C/hr)
However, continuous annealing (average heating rate of several °C to several tens of degrees C/S
ec) may be used, but in order to make the average recrystallized grain size before final cold rolling 40 pm or less, it is preferable to apply continuous annealing rather than batch annealing.

In the case of continuous annealing, it is desirable to set the intermediate annealing temperature to 380° C. or higher from the viewpoint of recrystallization. On the other hand, in batch annealing, the higher the soaking temperature, the finer the crystal grains during recrystallization.

Here, in order to make the average recrystallized grain size 40 νm or less, intermediate annealing conditions are also important, but it is also necessary to consider cold rolling reduction ratio conditions before intermediate annealing.

That is, in order to make the average recrystallized grain size 40 JJm or less, it is preferable to perform cold rolling at a reduction rate of 30% or more before intermediate annealing.

The final cold rolling was performed to obtain a yield strength of 15 Kgf in order to obtain the necessary stiffness as an aluminum alloy support for lithographic printing plates.
A cold rolling reduction ratio of /Hi or higher is required. Therefore, the final cold rolling reduction ratio is required to be at least 20%, preferably 40% or more. The final tempering may be either HIn, H2 or H3n as long as a yield strength of 15 directions f/mm or more can be obtained.

Next, a method for processing a printing plate of a lithographic printing support according to the present invention will be explained in detail.

Graining methods in this invention include an electrochemical roughening method in which the surface is electrochemically roughened in a salt or nitric acid electrolyte, a wire brush graining method in which the aluminum surface is scratched with a metal wire, and a polishing ball and polishing method. Mechanical roughening methods such as the pole grain method, which roughens the aluminum surface with an abrasive, and the brush grain method, which roughens the surface with a nylon brush and abrasive, can be used. The oxidation methods can also be used alone or in combination. The electrochemical surface roughening method has the advantage that a uniform roughened surface or an appropriate surface roughness can be obtained, and that non-image areas are less likely to be smudged during printing.

The aluminum thus roughened is chemically etched with acid or alkali.

When an acid is used as an etching agent, it takes too much time to destroy the microstructure, so it is usually preferable to use an alkali as an etching agent.

In this invention, the alkaline agent suitably used for etching includes caustic soda, sodium chloride, sodium aluminate, sodium metasilicate, sodium phosphate, potassium hydroxide, lithium hydroxide, etc., and the preferable range of concentration and temperature is are 1 to 50% and 20 to 100°C, respectively, and it is preferable to apply conditions such that the amount of aluminum dissolved is 5 to 20 g/m.

After etching, dirt (smut) remains on the surface.
It is common to pickle to remove. Examples of acids used for this pickling include nitric acid, sulfuric acid, phosphoric acid, chromic acid, butic acid, and hydrofluoric acid. In particular, for smut removal treatment after electrochemical roughening treatment,
50-90°C as described in No. 3-12739
A method of contacting with 15 to 65% by weight sulfuric acid at a temperature of
It is desirable to apply an alkali etching method as described in Japanese Patent Publication No. 48-28123.

The aluminum alloy plate treated as described above can be used as a support for lithographic printing, but it is preferable to further perform treatments such as anodization treatment and chemical conversion treatment as necessary.

The positive percent tiling process can be performed by a method conventionally used in this field. Basically, it involves passing a direct or alternating current through an aluminum plate in an aqueous or non-aqueous solution such as sulfuric acid, phosphoric acid, chromic acid, oxalic acid, sulfamic acid, benzenesulfonic acid, or a combination of two or more of these. This allows an anodic oxide film to be formed on the surface of the aluminum support.

The conditions for anodizing treatment vary depending on the electrolytic solution used, so it cannot be generalized, but in terms of -a, the concentration of the electrolytic solution is 1 to 80%, the solution temperature is 5 to 70%, and the C1 current density is 0.5. ~
60 ampere/-1 voltage 1~1oov, electrolysis time 10~
A range of 100 seconds is appropriate.

Among these anodic oxidation coating treatments, the British Patent No. 1
, 412.768 @, and the method of oxidizing the oxidation at high current density in sulfuric acid, and U.S. Pat. No. 3,511,
The method of anodizing using phosphoric acid as an electrolytic bath as described in No. 661 is preferred.

@Polar oxidized aluminum alloy plate is also US Patent No. 2
．． No. 714.066 and U.S. Pat. No. 3,181,461, by methods such as immersion in an aqueous solution of aluminum metal silicates, e.g. sodium silicate; A subbing layer of hydrophilic cellulose (such as carbodimethyl cellulose) containing a water-soluble metal salt (such as zinc acetate) as described may also be provided.

On the aluminum alloy support for lithographic printing plates according to the present invention, a photosensitive layer conventionally known as a photosensitive layer of a PS plate can be provided to obtain a photosensitive lithographic printing plate, which is subjected to plate-making processing. The obtained lithographic printing plate has excellent performance.

The composition of the above-mentioned photosensitive layer includes the following.

(1) Photosensitive layer consisting of diazo resin and binder U.S. Pat. Nos. 2.063.631 and 1, 867, 41
The condensation product of diphenylamine-p-diazonium salt and formaldehyde, which is the reaction product of the diazonium salt disclosed in No. 5 and an organic condensation agent containing a reactive carbonyl group such as aldol or acecool (so-called diazo resin) is preferably used. Other useful condensed diazo compounds are JP-A-49-48001 and JP-A-49-48001;
It is disclosed in No. 9-45322, No. 49-45323, etc.

These types of photosensitive diazo compounds are usually obtained in the form of water-soluble inorganic salts and can therefore be applied in aqueous solutions. Or these water-soluble diazo compounds
1167 with an aromatic or aliphatic compound having one or more phenolic hydroxyl groups, sulfonic acid groups, or both, and the reaction product is a substantially water-insoluble photosensitive compound. Polymeric diazo resins can also be used. Also, JP-A-56-12103
Hexafluorophosphoric acid j2i as described in No. 1
Alternatively, it can also be used as a reaction product with a tetrafluoroTWII salt. Other British Patents No. 1 and 31
Also preferred are the diazo resins described in No. 2.925.

(2) Photosensitivity consisting of O=quinonediazide compound Particularly preferred O-quinonediazide compound is O-naphthoquinonediazide compound, for example as described in US Pat. No. 2,788.
No. 118, No. 2.767, No. 092, No. 2,772
, No. 972, No. 2.859.112, No. 2,90
No. 7,665, No. 3,046,110, No. 3,0
46.111@, same No. 3.046.115, same No. 3,
046, No. 118, No. 3.046.119, No. 3
, 046,120, 3.046.121@, 3.046.122, 3.046.123, 3,061,430, 3.102,809 ,
3.106', 465, 3,635, 70
9@, No. 3.647.443M, and many other publications, all of which can be suitably used.

(3) Photosensitive layer consisting of an azide compound and a binder (polymer compound), for example, British Patent Nos. 1,235,281 and 1,49
No. 5.861, JP 51-32331@, JP 51-3
In addition to compositions consisting of an azide compound and a water-soluble or alkali-soluble polymer compound described in 8128@,
JP-A-50-5102, JP-A No. 50-84302, JP-A No. 5
Included are compositions comprising a polymer containing an azide group and a polymer compound as a binder, as described in No. 0-84303 and No. 53-12984.

(4) Other photosensitive resin layers, such as polyester compounds disclosed in JP-A-52-96896, British Patent No. 112.277@, British Patent No. 1
, 313.30'J@, U.S. Pat. No. 1,341,004, U.S. Pat. No. 1.377, 747, etc.;
, No. 072.527, etc., are included.

The skewness of the photosensitive layer formed on the support is in the range of about 0.1 to about 79 per inch, preferably 0.5 to 43 per inch.

After the PS plate is exposed to light, a resin image is formed by processing including development using conventional methods. For example, in the case of a PS plate having the photosensitive layer (1) made of a diazo resin and a binder, after image exposure, the unexposed portions of the photosensitive layer are removed by development to obtain a lithographic printing plate. Further, the photosensitive layer (2
) In the case of a PS plate having a lithographic printing plate, the unexposed portions are removed by developing with an alkaline aqueous solution after development and exposure, and a lithographic printing plate is obtained.

(Example 1) Alloys A-G shown in Table 1 were cast by a normal method,
Thickness 500m, width 1000m, length 35m with both sides facing up
The ingot was made into a 00m ingot. 530'CX for that ingot
A homogenization treatment was performed for 4 hours. Thereafter, it was heated to 480°C and hot rolled to form a 4# thick plate. It was roughly cold rolled to a thickness of 1.5#. Intermediate annealing was performed on the plate having this thickness. Two intermediate annealing conditions were selected: 450'C annealing by continuous annealing or 350'CX 2 by batch annealing (heating rate 40'C/hr).
Annealing was performed for hr. Next, cold rolling is performed to obtain a 0.
An aluminum alloy plate with a thickness of 3 m was created. These aluminum alloy plates were evaluated for electrolytic etching properties, roughened surface appearance characteristics, fatigue strength, heat softening resistance, and printability using the following methods. The results are shown in Table 2.

(1) Electrolytic etching properties The surface condition was observed with a scanning electron microscope and the uniformity of pits was evaluated. Excellent results were marked with a Q mark, good ones with a Δ mark, and poor ones with an X mark.

(2) Surface appearance characteristics of roughened surface The surface appearance of an aluminum alloy support for a lithographic printing plate that had been subjected to the anodized coating 11W treatment by the method (5) below was visually judged for streaks and color tone unevenness.

Streaks are striped patterns along the rolling direction, and are generated due to non-uniform etching during chemical etching or electrolytic etching, or due to non-uniformity in the metal fitting assembly. Those with good streaks are marked with an ○ mark, and those with poor streaks are marked with an X mark. In addition, when the color tone of the roughened surface is not uniform, it is called uneven, and
A uniform case is considered good and is indicated by an O mark. The presence of both streaks and unevenness is unfavorable in terms of appearance as an aluminum alloy support for lithographic printing plates.

(3) A tensile load of 5 to 3/- was repeatedly applied at 25 Hz to one end of a specimen bent at 90 degrees at a corner with a fatigue strength of 2MR, and the number of load repetitions until breakage was measured. The number of load repetitions is
Practically speaking, 80,000 times or more is desirable.

(4) Heat-resistant softening properties The sample was heated at 270°C for 17 minutes in a Burning Processor 1300 (Fuji Photo Film (Tai-made Burning Processor) having a heat source of 12 kW. The heat-resistant softening properties were evaluated based on the yield strength after cooling.

(5) Printing suitability The printing plate processed by the following method is printed on the offset printing machine KOR.
The degree of contamination in the non-image area was evaluated.

The printed version was prepared as follows.

After roughening the aluminum alloy plate with a rotating nylon brush in a suspension of bumiston and water, it was treated with caustic soda 2
Etching was performed using a 0% aqueous solution so that the amount of aluminum dissolved was 89/m. After washing thoroughly with running water,
25% full! 1 acid aqueous solution and washed with water. This substrate was subjected to AC electrolytic treatment at a current density of 20 A/- or more in an electrolytic bath containing 0.5 to 2.5% nitric acid as described in JP-A-54-146234@. successively 1
After cleaning the surface by immersing it in a 5% sulfuric acid solution at 50°C* for 3 minutes, it was anodized to 39/'rIi in an electrolytic solution containing 20% sulfuric acid as a main component at a bath temperature of 30°C. A film was applied.

The following photosensitive layer was provided on the sample prepared in this way so that the coating weight when dry was 2.5 g/bottom.

Ester compound of naphthoquinone-1,2-diazido-5-sulfonyl chloride and pyrogallol acetone resin (as described in Example 1 of U.S. Pat. No. 3,635,709) 0.759 Talesol Novolac resin...2.007 oil blue +603
(Orient Chemistry Exhibition) ...0.04 g
Ethylene dichloride... 1632-
Methoxyethyl acetate... 12g The thus obtained photosensitive planographic printing plate was imaged with a metal halide lamp for 60 seconds from a distance of 1 TrL, and SiO2
/Na2O molar ratio is 1.2 and SiO2 content is 1.5
% sodium silicate aqueous solution, washed with water, dried, and then gummed.

As shown in Table 2, alloys A, B, and C1D of the present invention all have high fatigue strength regardless of the intermediate annealing conditions, excellent heat softening resistance, and good electrolytic etching properties and surface appearance. It was found to have good characteristics and printability. On the other hand, it was found that Comparative Alloy E was inferior in fatigue strength and heat softening resistance, and Comparative Alloys F and G were inferior in electrolytic etching properties, surface appearance characteristics, and printability.

(Example 2) Using an ingot of Alloy B shown in Table 1 and using aluminum alloy plates with a thickness of 0 and 3# with various crystal grain sizes by changing the manufacturing process conditions, Example 1 and Similarly, electrolytic etching properties, surface appearance properties, fatigue strength, heat softening properties, and printability were evaluated. Table 3 shows each manufacturing process and the average width of crystal grains in the board width direction on the surface of the final board, and Table 4 shows the evaluation results.

As is clear from Tables 3 and 4, the plate obtained under manufacturing process condition 1, in which the average width of crystal grains in the plate width direction on the surface of the final plate is 40 JJm or less, has high fatigue strength and It has excellent heat softening properties, as well as good electrolytic etching properties, surface appearance properties, and printability. On the other hand, the plate processed by 1q according to manufacturing process condition 2.3 has a small cold rolling reduction before intermediate annealing (process conditions 2 and 3).
) and the high intermediate annealing temperature (process condition 2), it was found that the width of the crystal grains was large and the surface appearance characteristics were poor.

Effects of the Invention As is clear from the above examples, the aluminum alloy support for lithographic printing plates of the present invention has sufficient fatigue strength and heat softening resistance as a printing plate, as well as good electrolytic etching properties and rough etching properties. Surface treatment, especially electrochemical roughening treatment, can provide a uniform rough surface and appropriate surface roughness, and it also has excellent printing permeability, making it difficult for non-image areas to become smudged during printing. Therefore, it is extremely suitable for use as a plate support for lithography.

Claims (2)

[Claims] (1) Mg 0.3% (weight %, same hereinafter) or more and 5% or less, Si 0.05% or more and 0.3% or less, and Cr 0.0
An aluminum alloy support for a lithographic printing plate, characterized in that the aluminum alloy support contains 1% or more and 0.25% or less, with the remainder consisting of Al and inevitable impurities. (2) Contains 0.3% to 5% of Mg, 0.05% to 0.3% of Si, and 0.01% to 0.25% of Cr, with the balance consisting of Al and inevitable impurities, and the surface An aluminum alloy support for a lithographic printing plate, characterized in that the average width of crystal grains in the plate width direction perpendicular to the rolling direction is 40 μm or less.