BACKGROUND OF THE INVENTION
[0001] The present invention relates to an aluminum alloy blank for a lithographic printing
plate and an aluminum alloy support for a lithographic printing plate having excellent
electrochemical surface roughening properties, and to manufacturing methods thereof.
[0002] Presensitized plates including supports made of aluminum plates are widely used in
offset printing.
[0003] In general, a flat-rolled plate having a thickness of 0.1 to 0.5 mm has been conventionally
applied to an aluminum alloy blank for use in a support for a lithographic printing
plate.
[0004] JIS 1000 series materials and JIS 3000 series materials are frequently applied to
A1 materials used herein.
[0005] A typical method conventionally used for manufacturing such an aluminum alloy flat-rolled
plate includes the steps of polishing and removing surfaces of an ingot obtained by
semicontinuous casting (direct chill (DC) casting), subjecting the ingot to a homogenization
treatment as appropriate, performing hot rolling at given temperature, performing
a heat treatment called intermediate annealing either after performing the hot rolling
or in mid-course of performing cold rolling, and then performing final cold rolling.
[0006] Generally, a typical method known for manufacturing a presensitized plate includes
the steps of obtaining a support for a lithographic printing plate by subjecting a
surface of a sheet-type or coil-type aluminum plate to a surface roughening treatment
and an anodic oxidation treatment, then forming an image recording layer by coating
a photosensitive solution on this support and drying the photosensitive solution,
and cutting the support into desired sizes as appropriate. After printing an image,
this presensitized plate is subjected to development and formed into a lithographic
printing plate.
[0007] In this method, a surface roughening treatment electrochemically performed in an
acidic solution (hereinafter referred to as an "electrolytic surface roughening treatment"
in this specification) is effective in order to improve adhesion of the image recording
layer to the support. Alternatively, it is also effective to perform a surface treatment
or to coat an undercoating solution after the anodic oxidation treatment.
[0008] When performing the surface roughening treatment including the electrolytic surface
roughening treatment, minute irregularities (pits) are formed on the surface of the
support. It has been conventionally considered that, by rendering diameters of the
pits uniform and large or rendering depths of the pits smaller, adhesion between the
recording layer and the support at an image area was strengthened and the recording
layer was not peeled off even after printing numerous sheets; meanwhile, a non-image
area could hold a large quantity of a fountain solution on a surface and stains hardly
occur. In this way, it has been considered possible to obtain a presensitized plate
which has excellent print quality. Methods for improving shapes and uniformity of
electrolytically surface roughened pits from the above-mentioned viewpoints have been
disclosed in
JP 2000-108534 A,
JP 2000-37965 A and
JP 2000-37964 A, for example.
[0009] However, these methods are studied on materials having high Al purities and are therefore
inapplicable to Al materials having high degrees of alloy components.
[0010] For an application to materials having high degrees of alloy components, Claim 1
of
JP 7-173563 A (corresponding to
EP 0640694 A) discloses an electrolytically surface roughened aluminum alloy blank for a lithographic
printing plate having an excellent electrolytic surface roughening property, which
is a continuously cast flat-rolled aluminum alloy plate containing 0.20 to 0.80 wt%
of Fe, and the balance being aluminum, crystal grain refining elements, and unavoidable
impurity elements. Here, among the impurity elements, a content of Si is equal to
or below 0.3 wt% and a content of Cu is equal to or below 0.05 wt%. Moreover, a solid
solution amount of Fe is equal to or below 250 ppm, a solid solution amount of Si
is equal to or below 150 ppm and a solid solution amount of Cu is equal to or below
120 ppm.
[0011] However, the alloy component elements include those which are solid solved in Al,
those which are deposited as metal components, and those which exist as intermetallic
compounds, and the amounts of the intermetallic compounds must be equal to or below
given amounts. Accordingly, maintaining the low solid solution amounts of Fe, Si,
and Cu as in this technique increases the deposited components and thereby causes
disadvantages such as deterioration in resistance to aggressive ink stains. Further,
it is difficult to maintain the low solid solution amounts while uniformly and finely
crystallizing second phase grains. Here, the "aggressive ink stains" are stains of
dot or annular shapes appearing on a printed sheet and the like, which are attributable
to the ink attached more frequently to a non-image surface area of a lithographic
printing plate as a result of several interruptions in the course of printing.
[0012] Meanwhile, there is other related art which discloses a lithographic printing plate
having excellent handling characteristics in which a direction of rolling of an aluminum
flat-rolled plate can be easily determined (
JP 2002-79770 A).
[0013] Both ends of the lithographic printing plate are bent after the plate making process
for forming the image thereon. Then, the lithographic printing plate is attached mechanically
to a plate cylinder of a press. As the press continues printing with the lithographic
printing plate, the fixing parts may be deformed or broken, and thereby causing printing
defects such as misalignment. Otherwise, the bent portions may crack (hereinafter
referred to as "corner cracks") and preclude printing any longer. Correspondingly,
there has been disclosed a technique for improving resistance of an aluminum plate
to metal fatigue by controlling alloy contents within specified ranges (
JP 3-11635 B). However, an aluminum plate exhibits different strength properties between the rolling
direction and the orthogonal direction thereto. Even though the above-mentioned problem
may be usually avoided by this technique, however, if a lithographic printing plate
made of such an alloy is used in the wrong orientation (i.e., by 90°) in the course
of the plate making process or attachment to the press, the lithographic printing
plate may be bent in the fragile orientation along the rolling direction. The lithographic
printing plate thus attached to the press may crack similarly. Therefore, there is
a demand for a lithographic printing plate which can avoid misrecognition of the orientation
in the course of the plate making process or attachment to the press.
[0014] Meanwhile, numerous methods have been disclosed in order to provide numbers, characters,
patterns, designs, and the like on a surface of a lithographic printing plate on an
opposite side of a surface coated with a photosensitive layer. For example,
JP 7-76800 A and
JP 6-286352 A disclose a method of performing an electrochemical surface roughening treatment on
a surface of a support for a lithographic printing plate without provision of a photosensitive
layer (such a surface will be herein after referred to as a "rear surface", which
may be also applied to a relevant surface of a lithographic printing plate similarly).
JP 7-205563 A discloses a method of performing an alkali etching treatment on the rear surface
of a support for a lithographic printing plate.
JP 6-305271 A and the like disclose a method of performing a press treatment on the rear surface
of a support for a lithographic printing plate by use of a transfer roller. Meanwhile,
JP 6-73478 A discloses a method of providing an aluminum alloy plate with discontinuous patterns
in certain colors by use of an anodic oxidation treatment. Nevertheless, all these
methods entails the treatment process such as the electrochemical surface roughening
treatment, the alkali etching treatment, the press treatment using the transfer roller,
or the anodic oxidation treatment. As a result, fabrication of the lithographic printing
plate provided with provision of the numbers, characters, patterns, designs, and the
like on the rear surface according to any of these methods would incur an unfavorable
process increase.
[0015] According to the related art, it has not been possible to obtain a support for a
lithographic printing plate from an Al plate having high contents of alloy component
elements, which has a uniform electrolytically roughened surface and allows simplification
of manufacturing processes and reduction in manufacturing costs and manufacturing
time.
[0016] EP 0 978 573 A2 relates to an aluminum alloy support for a lithographic printing plate obtainable
by homogenization heat-treating an aluminum alloy cast slab, hot rolling the slab
to form a hot rolled strip, cold rolling the hot rolled strip without intermediate
annealing to form a substrate, graining the substrate, and anodically oxidizing the
substrate. The support comprises 0.10 to 0.40 wt% of Fe, 0.03 to 0.15 wt% of Cu, and
the balance of Al and unavoidable impurities, with up to 30 wt-ppm of precipitated
Si. Any solid solution amounts of iron, silicon or copper are not mentioned in
EP 0 978 573 A2. The aluminum alloy support is stated as being excellent in resistance to ink staining
in the non-image areas during printing and as having proper strength.
[0017] The support for a planographic printing plate described in
EP 0 672 759 A1 is an aluminum alloy plate comprising 0<Fe≤0.20 wt%, 0≤Si≤0.13 wt%, 99.7 wt%≤Al and
the balance of inevitable impurity elements, wherein a solid solution amount of Fe
is 10 ppm to 800 ppm. According to the reference, the planographic printing plate
support is suited for an electrochemical graining treatment and has a small heat softening
property after a burning treatment.
[0018] EP 0 581 321 A2 relates to a method of producing a planographic printing plate support comprising
several steps including the roughening of a surface of an aluminum thin plate, wherein
the Fe content of said plate is selected to be in a range of from 0.4 % to 0.2 %,
the Si content is selected to be in a range of from 0.20 % to 0.05 %, the Cu content
is selected to be in a range of not larger than 0.02 %, and the Al purity is selected
to be not smaller than 99.5 %, and wherein after continuous casting, Fe in a range
of from 20 % to 90 of the Fe total content exists in a grain boundary and the rest
of Fe exists as a solid solution in grains. The aluminum support produced by the method
is stated as having excellent electrolytic roughness.
SUMMARY OF THE INVENTION
[0019] Therefore, an object of the present invention is to provide a continuously cast flat-rolled
aluminum, alloy blank which can achieve a lithographic printing plate having a uniform
electrolytically roughened surface and excellent press life. Another object of the
present invention is to provide an aluminum alloy blank which can simplify manufacturing
processes and reduce manufacturing costs and manufacturing time. Still another object
of the present invention is to provide a support for a lithographic printing plate
which can achieve a lithographic printing plate having excellent press life and stain
resistance.
[0020] Still another object of the present invention is to provide a lithographic printing
plate which is easy to use without misrecognition of an orientation of the plate in
the course of a plate making process or attachment to a press, in addition, capable
of suppressing the number of manufacturing steps.
[0021] The present invention provides the following aluminum alloy blanks which are suitable
for electrolytic surface roughening.
- (1) An aluminum alloy blank for a lithographic printing plate made of a continuously
cast flat-rolled aluminum alloy plate including Fe in a range of 0.20 to 0.80 wt%,
and the balance being aluminum, a crystal grain refining element, and unavoidable
impurity elements. Here, among the impurity elements, a content of Si is in a range
of 0.02 to 0.30 wt% and a content of Cu is equal to or below 0.05 wt%. Moreover, the
solid solution amount of Si is in a range of 150 ppm to 1500 ppm inclusive, the solid
solution amount of Fe is in a range of 250 ppm to 4000 ppm inclusive, and the solid
solution amount of Cu is in a range of 100 ppm to 500 ppm inclusive.
[0022] In an alternative embodiment, the above aluminum alloy blank for a lithographic printing
plate comprises Fe in a range of 0.20 to 0.80 wt%, the balance being aluminum, a crystal
grain refining element and unavoidable impurity elements, wherein the content of silicon
and the content of copper is as defined above (i.e. Si in a range of 0.02 to 0.30
wt% and Cu ≤0.05 wt%), and wherein the solid solution amount of Si is in a range of
300 to 1300 inclusive.
(2) Preferably, the aluminum alloy blank for a lithographic printing plate having
resistivity in a range of 6.5 to 3.5 µΩmm when measured at liquid nitrogen temperature.
[0023] The present invention also provides the following.
(3) A support for a lithographic printing plate formed by performing a surface roughening
treatment including an electrochemical surface roughening on an aluminum alloy blank
for a lithographic printing plate according to (1) or (2) described above.
(4) The support for a lithographic printing plate according to (3) described above,
in which the surface roughening treatment including the electrochemical surface roughening
has processes of performing the electrochemical surface roughening at a current density
of 5 A/dm2 or higher and then chemically dissolving not less than 0.1 g/m2 of Al.
(5) The support for a lithographic printing plate according to (4) described above,
in which the electrochemical surface roughening treatment is a treatment using an
alternating current having a trapezoidal waveform in an electrolytic solution containing
nitric acid.
(6) The support for a lithographic printing plate according to (4) described above,
in which the electrochemical surface roughening treatment is a treatment using an
alternating current having a sinusoidal waveform in an electrolytic solution containing
hydrochloric acid.
(7) The support for a lithographic printing plate according to any one of (3) to (6)
described above, in which the surface roughening treatment including the electrochemical
surface roughening has processes of performing a first electrochemical surface roughening
treatment using a total quantity of electricity in a range of 65 to 500 C/dm2 upon an anodic reaction in an electrolytic solution containing nitric acid, chemically
dissolving not less than 0.1 g/m2 of Al, performing a second electrochemical surface roughening treatment using a total
quantity of electricity in a range of 25 to 100 C/dm2 upon an anodic reaction in an electrolytic solution containing hydrochloric acid,
and then chemically dissolving not less than 0.03 g/m2 of Al.
[0024] The prevent invention also provides the following presensitized plates.
(8) A presensitized plate including a recording layer on one surface of the support
for a lithographic printing plate according to any one of (3) to (7) described above.
(9) A presensitized plate including a recording layer on one surface of the support
for a lithographic printing plate according to any one of (3) to (7) described above,
and any of a woodgrain pattern and a stripe pattern on the other surface thereof.
[0025] Moreover, the present invention provides a lithographic printing plate including
the support for a lithographic printing plate of the aspect (3), in which one surface
of an aluminum flat-rolled plate obtained by twin roll continuous casting and cold
rolling is at least subjected to a surface roughening treatment, and the other surface
thereof is subjected to an alkali etching treatment and a desmutting treatment to
obtain a woodgrain pattern.
[0026] Furthermore, the present invention provides a lithographic printing plate including
the support for a lithographic printing plate of the aspect (3), in which one surface
of an aluminum flat-rolled plate obtained by twin belt continuous casting, hot rolling,
and cold rolling is at least subjected to a surface roughening treatment, and the
other surface thereof is subjected to an alkali etching treatment and a desmutting
treatment to obtain a striped pattern.
[0027] The aluminum alloy blank for a lithographic printing plate of the present invention
achieves a uniform electrolytically roughened surface after undergoing the electrochemical
surface roughening treatment, and an excellent support for a lithographic printing
plate is obtained therefrom. When a presensitized plate is formed by use of this support
for a lithographic printing plate, such a presensitized plate has excellent quality
such as excellent press life.
[0028] Moreover, a method of manufacturing the aluminum alloy blank for a lithographic printing
plate of the present invention which can be formed into such an excellent presensitized
plate has more simplified manufacturing processes as compared to a conventional method
and advantages such as possibilities to reduce manufacturing costs and time. Accordingly,
industrial contribution of the present invention is immense.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029]
Fig. 1 is a graph showing an example of an alternating current waveform chart used
for an electrochemical surface roughening treatment in a method of manufacturing a
support for a lithographic printing plate of the present invention.
Fig. 2 is a side view showing an example of radial type cell for an electrochemical
surface roughening treatment using an alternating current in the method of manufacturing
a support for a lithographic printing plate of the present invention.
Fig. 3 is a schematic diagram of an anodic oxidation apparatus used in an anodic oxidation
treatment in the method of manufacturing a support for a lithographic printing plate
of the present invention.
Fig. 4 is a graph showing an example of a sinusoidal waveform chart used in the electrochemical
surface roughening treatment in the method of manufacturing a support for a lithographic
printing plate of the present invention.
Fig. 5 is a view showing an example of the lithographic printing plate 1 of the present
invention, which includes a woodgrain pattern on the rear surface thereof.
Fig. 6 is a view showing an example of the lithographic printing plate 2 of the present
invention, which includes a striped pattern on the rear surface thereof.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] Now, the present invention will be described below in detail.
(Support for lithographic printing plate)
<Aluminum alloy blank (flat-rolled aluminum)>
[0031] An aluminum alloy blank of the present invention to be described below is used for
a support for a lithographic printing plate of the present invention. Essential alloy
components of the aluminum alloy are Al and Fe. The aluminum alloy may contain Si
and Cu as impurities.
[0032] Si is an element contained by 0.03 to 0.1 wt% as an avoidable impurity in Al bare
metal which is a raw material. A small amount of Si is often added intentionally so
as to avoid unevenness among raw materials. Si exists in aluminum in a state of a
solid solution, or exists as a deposit of an intermetallic compound or Si alone.
[0033] In this specification, the Si amount as the alloy component is in a range of 0.02
to 0.30 wt%, and Si in a specified amount thereof is in the state of a solid solution.
Si influences an electrolytic surface roughening treatment. The inventors of the present
invention focused particularly on the solid solution amount and have found out the
following fact. Specifically, when subjecting an aluminum alloy substrate formed by
continuous casting to electrochemical surface roughening, keeping the solid solution
amount of Si equal to or above a certain amount leads to an excellent effect on stability
of the electrolytic surface roughening. It is possible to stabilize the electrolytic
surface roughening treatment by setting the Si content in the range of 0.02 to 0.30
wt% and the Si solid solution amount in a range of 150 ppm to 1500 ppm inclusive.
[0034] The reason for setting the Si content equal to or below 0.30 wt% is that uniformity
in the electrolytic surface roughening is damaged by excessive Si. Moreover, when
Si is excessive, elemental Si is relatively increased. In such a case, the elemental
Si may cause defects on an anodized film when performing an anodic oxidation treatment
after the surface roughening treatment. Water retentivity is deteriorated in such
defective portions, and paper tends to be stained in the course of printing.
[0035] In the present invention, the Si solid solution amount is in the range of 150 ppm
to 1500 ppm inclusive from the viewpoint of excellent stability of the electrolytic
surface roughening treatment. Preferably, the Si solid solution amount is in a range
of 300 ppm to 1300 ppm inclusive.
[0036] Fe is scarcely solid dissolved in aluminum, and most of Fe remains as intermetallic
compounds. Fe has an effect to increase mechanical strength of the aluminum alloy
and significantly influences the strength of the support. If the Fe content is too
small, a lithographic printing plate tends to be broken because of its fairly low
mechanical strength when the lithographic printing plate is fitted to a plate cylinder
of a printing machine. Further, the lithographic printing plate tends to be broken
similarly when printing a large number of copies at high speed. On the contrary, when
the Fe content is excessive, the lithographic printing plate has unnecessarily high
strength and lacks a fitness property when the lithographic printing plate is fitted
to the plate cylinder of the printing machine. Accordingly, the lithographic printing
plate tends to be broken in the course of printing. Meanwhile, when the Fe content
exceeds 1.0 wt%, for example, a crack tends to occur in the course of rolling. The
aluminum blank of the present invention has the Fe content in a range of 0.20 to 0.80
wt%.
[0037] Fe also influences the electrolytic surface roughening treatment. The inventors of
the present invention have found out that it is preferable to keep a Fe solid solution
amount equal to or above a certain value as well as to keep the Si solid solution
amount equal to or above a certain value when subjecting the aluminum alloy substrate
formed by continuous casting to the electrochemical surface roughening. It is possible
to stabilize an electrolytic property by setting the Fe content in the range of 0.20
to 0.80 wt% and the Fe solid solution amount in a range of 250 ppm to 4000 ppm inclusive.
[0038] The reason for setting the Fe content equal to or above 0.20 wt% is that, if the
Fe content is too small, the lithographic printing plate tends to be broken because
of its fairly low mechanical strength when the lithographic printing plate is fitted
to the plate cylinder of the printing machine as described above. It is also because
the lithographic printing plate tends to be broken similarly when printing a large
number of copies at high speed. The reason for setting the Fe content equal to or
below 0.80 wt% is that, if the Fe content is excessive, the lithographic printing
plate has unnecessarily high strength and lacks the fitness property when the lithographic
printing plate is fitted to the plate cylinder of the printing machine, and that the
lithographic printing plate tends to be broken in the course of printing. Preferably,
the Fe content is in a range of 0.20 to 0.50 wt%.
[0039] In the present invention, the Fe solid solution amount is in the range of 250 ppm
to 4000 ppm inclusive from the viewpoint of excellent stability of the electrolytic
surface roughening treatment. Preferably, the Fe solid solution amount is in a range
of 300 ppm to 1300 ppm inclusive.
[0040] Cu is an important element in terms of controlling the electrolytic surface roughening
treatment. Cu is the element which is solid dissolved very easily, and a part of the
element is formed into intermetallic compounds. Since Cu has a favorable character
in terms of uniform electrolytic surface roughening, it is preferable to contain not
less than 0.001 wt% of Cu.
[0041] When the Cu content exceeds 0.050 wt%, the diameters of pits formed by an electrolytic
surface roughening treatment in a nitric acid solution become too large and uniformity
of the diameters is reduced at the same time. Accordingly, stain resistance is particularly
deteriorated in such a case.
[0042] Meanwhile, the inventors of the present invention have found out that it was possible
to form uniform pits having diameters equal to or below 0.5 µm by an electrolytic
surface roughening treatment in a hydrochloric acid solution and to maximize a rate
of increase in a surface area of a support surface by setting the Cu content in the
above-mentioned range. A contact area with an image recording layer can be enlarged
by enlarging the rate of increase in the surface area. In this way, adhesion therebetween
is improved, whereby press life and press life after cleaner application become excellent.
Moreover, stain resistance becomes excellent when the aluminum alloy is formed into
the lithographic printing plate. In the present invention, from the viewpoint described
above, the Cu content is equal to or below 0.050 wt%, or preferably in a range of
0.001 to 0.030 wt%.
[0043] The Cu solid solution amount is preferably in a range of 100 ppm to 500 ppm inclusive.
[0044] Crystal grain refining elements may be added as appropriate in order to prevent occurrence
of cracks in the course of casting. For this reason, Ti may be added in an amount
of not more than 0.05 wt% and B may be added in an amount of not more than 0.02 wt%.
[0045] The balance of the aluminum plate includes A1 and unavoidable impurities. The unavoidable
impurities to be contained in the aluminum alloy may be Mg, Mn, Zn, Cr, Zr, V, and
Be, for example. Each of these elements may be contained in an amount of not more
than 0.05 wt%. A major part of the unavoidable impurities are contained in the Al
base metal. The unavoidable impurities do not damage effects of the present invention
as long as the unavoidable impurities are contained in the Al base metal having a
purity of 99.7%, for example. Concerning the unavoidable impurities, impurities may
be contained in amounts disclosed in "Aluminum Alloys: Structure and properties" (L.
F. Moldolfo, 1976) and the like, for example.
[0046] The inventors of the present invention have performed various studies to solve the
above-described problems of the related art and have found out that, by forming an
aluminum alloy blank containing specified amounts of specified alloy elements into
a continuously cast flat-rolled plate and by setting the Si solid solution amount
to a specified value, it was possible to improve uniformity of an electrolytically
roughened surface obtained when this blank was subjected to electrolytic surface roughening.
If the solid solution amount exceeds an upper limit, large pits having diameters greater
than 10 µm tend to be formed on the electrolytically roughened surface. Accordingly,
the blank loses water retentivity and causes ink stains, whereby the press life is
deteriorated upon printing.
[0047] Moreover, the inventors have found out that the above-described effect was preferably
enhanced by setting one of the solid solution amounts of Fe and Cu or both to a specified
value in addition to the Si solid solution amount.
[0048] Furthermore, the inventors have found out that it was possible to obtain appropriate
values for the solid solution amounts of Si, Fe, and Cu in the blank by adjusting
the temperature and time for heat treatment to appropriate values. In the present
invention, it is preferable to apply the continuous casting and rolling method, to
use a specified chemical composition and to set the solid solution amount of Si at
a specified value in order to obtain the aluminum alloy blank suitable for the support
for an electrolytically surface roughened lithographic printing plate.
[0049] A preferable method of manufacturing an aluminum alloy blank of the present invention
will now be described below. However, the present invention is not limited only to
the following method. The continuous casting and rolling can form fine and uniform
crystals due to a high solidification rate on a surface of a cast material and requires
no homogenizing heat treatment of an ingot which is essential in the DC casting method,
and a long-term treatment is not performed. Therefore, the aluminum alloy blank is
a suitable blank for use in the support because of its stable quality.
[0050] When forming the aluminum alloy into a plate member, it is possible to adopt the
following method, for example. Firstly, aluminum alloy molten metal adjusted to given
contents of alloy components is subjected to a cleaning treatment and then cast in
accordance with a conventional method. As for the cleaning treatment, in order to
remove unnecessary gas in the molten metal such as hydrogen, a flux treatment, a degasification
treatment using argon gas, chlorine gas or the like, a filtering treatment using any
of a so-called rigid media filter such as a ceramic tube filter or a ceramic foam
filter, a filter applying alumina flakes or alumina balls as a filtering element,
a glass cloth filter, and the like, or a combined treatment of the degasification
treatment and the filtering treatment is performed.
[0051] It is preferable that these cleaning treatments be carried out to prevent the occurrence
of defects attributable to foreign substance in the molten metal such as non-metal
intermediates or oxides, and defects attributable to gas dissolved in the molten metal.
Techniques related to filtering of molten metal are disclosed in various publications,
namely,
JP 6-57432 A,
JP 3-162530 A,
JP 5-140659 A,
JP 4-231425 A,
JP 4-276031 A,
JP 5-311261 A,
JP 6-136466, and the like. Meanwhile, techniques related to degasification of molten metal are
disclosed in various publications, namely,
JP 5-51659 A,
JP 5-49148 U, and the like. The applicant of the present invention has also proposed a technique
concerning degasification of molten metal in
JP 7-40017 A.
[0052] Subsequently, casting is performed by use of the molten metal subjected to the cleaning
treatment as described above. Casting methods include a method using a fixed mold
as typified by the DC casting method, and a method using a mobile mold as typified
by the continuous casting method. However, in the present invention, it is preferable
to apply the continuous casting method using the mobile mold.
[0053] Industrially practiced continuous casting methods include methods using cooling rolls
as typified by the twin roll method (the Hunter method) and the 3C method, and methods
using cooling belts or cooling blocks as typified by the twin belt method (the Hazelett
method) and the Alusuisse Caster II. When using the continuous casting method, solidification
takes place at a cooling rate in a range of 100 to 1000 °C/sec. In general, the continuous
casting method has a higher cooling rate as compared to the DC casting method, and
therefore has a characteristic that the continuous casting method can increase solid
solubility of alloy components relative to an aluminum matrix. Concerning the continuous
casting method, the applicant of the present invention has proposed techniques as
disclosed in various publications, namely,
JP 3-79798 A,
JP 5-201166 A,
JP 5-156414 A,
JP 6-262203 A,
JP 6-122949 A,
JP 6-210406 A,
JP 6-26308A, and the like.
[0054] In the case of performing the continuous casting, when the method using cooling rolls
such as the Hunter method is applied, for example, various advantages are obtained
such as a possibility to cast a plate in a plate thickness of 1 to 10 mm directly
and continuously and a possibility to omit a hot rolling process. In the meantime,
when the method using cooling belts such as the Hazelett method is applied, it is
possible to cast a plate in a plate thickness of 10 to 50 mm. Generally, it is possible
to obtain a plate in a plate thickness of 1 to 10 mm by arranging a hot rolling mill
immediately after casting to perform rolling continuously.
[0055] These continuously cast flat-rolled plates are finished into a given thickness, such
as a plate thickness of 0.1 to 0.5 mm, through processes such as cold rolling, intermediate
annealing, and the like. An intermediate annealing treatment may be performed before,
after, or in mid-course of the cold rolling. Conditions of the intermediate annealing
treatment may be heating for 2 to 20 hours at 280°C to 600°C or preferably for 2 to
10 hours at 350°C to 500°C by use of a batch annealing furnace, or heating for 6 minutes
or less at 400°C to 600°C or preferably for 2 minutes or less at 450°C to 550°C by
use of a continuous annealing furnace. It is also possible to form fine crystalline
structures by heating at a temperature rising rate of 10 to 200 °C/sec with the continuous
annealing furnace. Concerning the conditions for intermediate annealing and the conditions
for cold rolling when using the continuous casting method, the applicant of the present
invention has proposed techniques as disclosed in various publications, namely,
JP 6-220593 A,
JP 6-210308 A,
JP 7-54111 A, and
JP 8-92709.
[0056] The aluminum plate finished into the given thickness as in the range of 0.1 to 0.5
mm by the above-described processes may be further treated to improve the planarity
by use of a reformation apparatus such as roller leveler or a tension leveler. Although
it is possible to perform the improvement in planarity after cutting the aluminum
plate into sheets, it is preferable to perform the improvement in planarity in a state
of a continuous coil to enhance productivity. It is also possible to feed the aluminum
plate into a slitter line so as to form the aluminum plate into a given plate width.
Moreover, it is possible to provide thin oil films on surfaces of the aluminum plates
to prevent occurrence of scratches due to friction between the aluminum plates. Such
oil films may be volatile or nonvolatile as appropriate.
[0057] It is preferable that the aluminum plate used in the present invention be well-tempered
in accordance with H18 as defined in JIS. When omitting the intermediate annealing,
it is preferable that the aluminum plate be well-tempered in accordance with H19.
[0058] However, in the present invention, the solid solution amounts of the alloy elements
such as Si are preferably adjusted to given values by performing a heat treatment
after the intermediate annealing or final cold rolling. In the present invention,
the Si solid solution amount is adjusted in the range of 150 ppm to 1500 ppm inclusive.
More preferably, the Fe solid solution amount is adjusted in the range of 250 ppm
to 4000 ppm inclusive and the Cu solid solution amount is adjusted in the range of
100 ppm to 500 ppm inclusive.
[0059] An appropriate heat treatment is preferably performed in a temperature range of 300°C
to 600°C. The time for the heat treatment is preferably in a range of 5 hours to 20
hours. By conducting the heat treatment under such conditions, it is possible to adjust
the solid solution amounts of Si, Fe, and Cu to desired values, and thereby to obtain
an aluminum alloy blank for a lithographic printing plate which has uniform pits on
an electrolytically roughened surface thereof..
[0060] The conditions of the heat treatment are preferably set in consideration of appropriate
mechanical strength in an ultimately desired plate thickness. In addition, when cold
rolling brings large distortion prior to the heat treatment, it is preferable to set
the conditions appropriately in consideration of a decline in the Fe solid solution
amount, for example.
[0061] The above-described heat treatment can be performed by use of a batch-type heat treatment
furnace. In this case, a heating rate of a coil is equal to or below 100 °C/hour.
Although retention time at given temperature varies depending on that given temperature,
the retention time becomes longer at lower temperatures and shorter at higher temperatures.
[0062] If the heat treatment is not conducted under appropriate conditions in mid-course
of the cold rolling or after the final cold rolling, an electrolytically roughened
surface fails to provide uniform pits and loses water retentivity. Such an electrolytic
roughened surface causes ink stains and loses press life for printing.
[0063] In the present invention, an aluminum flat-rolled plate obtained by twin roll continuous
casting and cold rolling, or an aluminum flat-rolled plate obtained by twin belt continuous
casting, hot rolling, and cold rolling is preferably used. The surface treatment,
to be described later, is at least performed on one surface of such an aluminum flat-rolled
plate. Meanwhile, the other surface thereof is subjected to an alkali etching treatment
and a desmutting treatment to obtain a woodgrain pattern. As shown in Fig. 5 and Fig.
6, the lithographic printing plate of the present invention includes either the woodgrain
pattern or the striped pattern on the rear surface. Accordingly, it is very easy to
distinguish the rolling direction of the applied aluminum flat-rolled plate based
on a relation between the pattern and the rolling direction. Therefore, it is possible
to eliminate misrecognition of the orientation of the lithographic printing plate
in the course of the plate making process or attachment to the press. Accordingly,
it is possible to avoid occurrence of corner cracks caused by bending the lithographic
printing plate in the fragile orientation when attaching the plate to the press.
[0064] In addition, the present invention is particularly favorable from the viewpoint that
the woodgrain pattern or the striped pattern on the rear surface can be obtained without
a special treatment process but by performing the alkali etching treatment and the
desmutting treatment on the surface provided with the photosensitive layer and on
the rear surface at the same time.
<Mechanical surface roughening treatment>
[0065] In the method of manufacturing a support for a lithographic printing plate of the
present invention, the above-described aluminum alloy blank is subjected to a surface
treatment. In the surface treatment, it is possible to carry out a mechanical surface
roughening treatment by use of a rolling brush and an abrasive to be described below.
Alternatively, it is possible to carry out a treatment for forming irregularities
on the surface by transcription at the end of the cold rolling.
[0066] Now, a brush graining method used as the mechanical surface roughening treatment
will be described.
[0067] Generally, the brush graining method uses a roller brush implanted with numerous
bristles such as synthetic resin bristles made of nylon (trademark), propylene or
polyvinyl chloride resin onto a surface of a cylindrical drum, and the method is performed
by scrubbing one or both surfaces of the aluminum plate while spraying a slurry solution
containing an abrasive onto the rotating roller brush. Instead of the roller brush
and the slurry solution, it is also possible to use an abrasive roller which is a
roller provided with an abrasive layer on a surface thereof.
[0068] When using the roller brush, a bend elastic constant of bristles for use is preferably
in a range of 10,000 to 40,000 kg/cm
2, or more preferably in a range of 15,000 to 35,000 kg/cm
2. In addition, elastic strength of the bristles is preferably equal to or below 500
g, or more preferably equal to or below 400 g. The diameter of each bristle is generally
in a range of 0.2 to 0.9 mm. The length of each bristle can be appropriately determined
in accordance with the outside diameter of the roller brush and the diameter of the
drum. However, the length of each bristle is generally in a range of 10 to 100 mm.
[0069] In the present invention, it is preferable to use a plurality of nylon brushes. To
be more precise, it is preferable to use three or more brushes, and is more preferable
to use four or more brushes. By adjusting the number of brushes, it is possible to
adjust wavelength components of cavities which are formed on the surface of the aluminum
plate.
[0070] Meanwhile, the load of a drive motor for rotating the brush is preferably greater
by at least 1 kW as compared to the load before pushing the brush roller against the
aluminum plate. The difference in load is more preferably equal to or above 2 kW,
and is even more preferably equal to or above 8 kW. By adjusting the load, it is possible
to adjust depths of the cavities formed on the surface of the aluminum plate. The
number of revolution per minute of the brush is preferably not less than 100 or more
preferably not less than 200.
[0071] Publicly known abrasives can be used herein. For example, it is possible to use abrasives
such as pumice stone, silica sand, aluminum hydroxide, alumina powder, silicon carbide,
silicon nitride, volcanic ash, carborundum, or emery; and a combination thereof. Among
these abrasives, pumice stone and silica sand are preferable. Silica sand is excellent
in surface roughening efficiency because silica sand is harder and more durable than
pumice stone. On the other hand, aluminum hydroxide grains crack upon application
of an excessive load. Accordingly, aluminum hydroxide is suitable for preventing generation
of locally deep cavities.
[0072] The median diameter of the abrasive is preferably in a range of 2 to 100 µm, or more
preferably in a range of 20 to 60 µm, in terms of excellent surface roughening efficiency
and a narrow graining pitch capability. By adjusting the median diameter of the abrasive,
it is possible to adjust the depths of the cavities formed on the surface of the aluminum
plate.
[0073] The abrasive is suspended in water, for example, and is used as the slurry solution.
In addition to the abrasive, the slurry solution may contain a thickener, a dispersing
agent (such as a surfactant), an antiseptic, and the like. The specific gravity of
the slurry solution is preferably in a range of 0.5 to 2.
[0074] As an apparatus suitable for the mechanical surface roughening treatment, it is possible
to cite an apparatus as disclosed in
JP 50-40047 B, for example.
[0075] Concerning details of the apparatus for performing the mechanical surface roughening
treatment with the brushes and the abrasive, it is possible to use a technique disclosed
by the applicant of the present invention in
JP 2002-211159 A.
[0076] In the present invention, it is possible to use an aluminum plate having a surface
with irregular patterns formed by transcription instead of the mechanical surface
roughening using the brushes and the abrasive. Alternatively, it is also possible
to apply the both surface roughening techniques.
<Surface treatment>
[0077] In the method of manufacturing a support for a lithographic printing plate of the
present invention, the support for a lithographic printing plate is obtained by subjecting
the aluminum plate, which is provided with irregular patterns formed on the surface
as described above, to the surface roughening treatment and an anodic oxidation treatment
(these two treatments will be collectively referred to as the surface treatment in
this present invention).
[0078] In the surface roughening treatment, it is preferable to perform electrochemical
surface roughening treatment twice and to perform etching treatments in alkaline aqueous
solutions in the course of the electrochemical surface roughening treatments. It is
preferable to perform a (first) etching treatment in an alkaline aqueous solution,
a (first) desmutting treatment in an acidic aqueous solution, an electrochemical surface
roughening treatment (a first electrolytic treatment) in an aqueous solution containing
nitric acid or hydrochloric acid, a (second) etching treatment in an alkaline aqueous
solution, a (second) desmutting treatment in an acidic aqueous solution, an electrochemical
surface roughening treatment (a second electrolytic treatment) in an aqueous solution
containing hydrochloric acid, a (third) etching treatment in an alkaline aqueous solution,
a (third) desmutting treatment in an acidic aqueous solution, and an anodic oxidation
treatment in this order. It is also preferable to further perform a hydrophilic treatment
after the anodic oxidation treatment.
[0079] It is more preferable to perform the mechanical surface roughening treatments before
the electrochemical surface roughening treatments.
[0080] The method of manufacturing a support for a lithographic printing plate of the present
invention may include other various processes in addition to the above-described processes.
[0081] Now, the respective processes of the surface treatment will be described in detail.
<First alkaline etching treatment>
[0082] The alkaline etching treatment is a treatment for dissolving a surface layer of the
above-described aluminum plate by allowing the aluminum plate to contact an alkaline
solution.
[0083] The first alkaline etching treatment, which is performed prior to the first electrolytic
treatment, aims at smoothing irregular shapes and to form uniform cavities in the
first electrolytic treatment when the mechanical surface roughening is performed,
or aims at removing rolling oil, stains, a natural oxide film, and the like on the
surface of the aluminum plate (flat-rolled aluminum) when the mechanical surface roughening
is not performed.
[0084] In the first alkaline etching, the etching amount is preferably equal to or above
0.1 g/m
2, more preferably equal to or above 0.5 g/m
2, and even more preferably equal to or above 1 g/m
2. Meanwhile, the etching amount is preferably equal to or below 10 g/m
2, more preferably equal to or below 8 g/m
2, and even more preferably equal to or below 5 g/m
2. When the lower limit of the etching amount remains in the above-described ranges,
it is possible to form uniform pits in the first electrolytic treatment and further
to prevent occurrence of unevenness in the treatment. When the upper limit of the
etching amount remains in the above-described range, the amount of the alkaline aqueous
solution used therein is reduced, and it is therefore economically advantageous.
[0085] The alkali to be used in the alkaline solution may be caustic alkali and alkali metal
salt. To be more precise, the caustic alkali includes caustic soda and caustic potash,
for example. Meanwhile, the alkali metal salt includes, for example: alkali metal
silicate such as sodium metasilicate, sodium silicate, potassium metasilicate, or
a potassium silicate; alkali metal carbonate such as sodium carbonate or potassium
carbonate; alkali metal aluminate such as sodium aluminate or potassium aluminate;
alkali metal aldonate such as sodium gluconate or potassium gluconate; alkali metal
hydrogenphosphate such as sodium secondary phosphate, potassium secondary phosphate,
sodium primary phosphate, or potassium primary phosphate. Among these compounds, a
caustic alkali solution and a solution containing both of caustic alkali and alkali
metal aluminate are preferred in terms of a high etching rate and a low price. A caustic
soda aqueous solution is preferred in particular.
[0086] In the first alkaline etching treatment, the concentration of the alkaline solution
is preferably equal to or above 30 g/L or more preferably equal to or above 300 g/L.
Meanwhile, the concentration of the alkaline solution is preferably equal to or below
500 g/L or more preferably equal to or below 450 g/L.
[0087] Moreover, it is preferable that the alkaline solution contain aluminum ions. The
aluminum ion concentration is preferably equal to or above 1 g/L or more preferably
equal to or above 50 g/L. Meanwhile, the aluminum ion concentration is preferably
equal to or below 200 g/L or more preferably equal to or below 150 g/L. Such an alkaline
solution can be prepared by use of water, a 48-wt% caustic soda aqueous solution,
and sodium aluminate, for example.
[0088] In the first alkaline etching treatment, the temperature of the alkaline solution
is preferably equal to or above 30°C or more preferably equal to or above 50°C. Meanwhile,
the temperature is preferably equal to or below 80°C or more preferably equal to or
below 75°C.
[0089] In the first alkaline etching treatment, the treating time is preferably equal to
or above 1 second or more preferably equal to or above 2 seconds. Meanwhile, the treating
time is preferably equal to or below 30 seconds or more preferably equal to or below
15 seconds.
[0090] When the aluminum plates are continuously subjected to the etching treatment, the
aluminum ion concentration in the alkaline solution is increased and the etching amounts
of the aluminum plates thereby vary. Accordingly, it is preferable to manage compositions
of the etching solution as described below.
[0091] Specifically, either a matrix of conductivity, specific gravity and temperature,
or a matrix of conductivity, propagation velocity of ultrasonic waves and temperature
is formed in advance, each of the matrices corresponding to a matrix of caustic soda
concentration and the aluminum ion concentration. Then, the compositions of the solution
are measured in terms of the conductivity, the specific gravity and the temperature
or in terms of the conductivity, the propagation velocity of ultrasonic waves and
the temperature, and caustic soda and water are added thereto so as to achieve target
control values for the compositions of the solution. Thereafter, the etching solution,
which is increased in volume by adding caustic soda and water, is allowed to overflow
from a circulation tank so as to maintain the constant volume. As for caustic soda
for such addition, it is possible to use one for industrial use which contains 40
to 60 wt% therein.
[0092] A conductivity detector and a gravimeter used therein are preferably temperature
compensated, respectively. Here, it is preferable to use a gravimeter of a differential
pressure type.
[0093] The method of allowing the aluminum plate to contact the alkaline solution includes
a method of allowing the aluminum plate to pass through a tank filled with the alkaline
solution, a method of dipping the aluminum plate in a tank filled with the alkaline
solution, and a method of spraying the alkaline solution on the surface of the aluminum
plate.
[0094] Among these methods, the method of spraying the alkaline solution on the surface
of the aluminum plate is preferred. To be more precise, it is preferable to apply
the method of spraying the etching solution by using a spray tube provided with pores
which have diameters in a range of 2 to 5 mm and are arranged with spaces in a range
of 10 to 50 mm. Here, it is preferable to spray the etching solution in an amount
of 10 to 100 L/min for each spray tube. A plurality of spray tubes are preferably
provided therein.
[0095] After completing the alkaline etching treatment, it is preferable to drain the solution
off with a nip roller, then to perform a water washing treatment for 1 to 10 seconds,
and then to drain the water off with the nip roller.
[0096] The water washing treatment is preferably carried out by using an apparatus configured
to perform a water washing treatment with a liquid film of a free-fall curtain shape,
and then using the spray tubes.
[0097] The apparatus configured to perform a water washing treatment with a liquid film
of a free-fall curtain shape includes a water storage tank for storing water, a water
supply tube for supplying the water storage tank with water, and a flow controller
unit for supplying a liquid film of a free-fall curtain shape from the water storage
tank to the aluminum plate.
[0098] In this apparatus, water is supplied from the water supply tube and the water flow
is controlled by the flow controller unit when the water overflows from the water
storage tank, whereby the liquid film of the free-fall curtain shape is supplied to
the aluminum plate. When using this apparatus, the fluid volume is preferably in a
range of 10 to 100 L/min. Meanwhile, the distance L in which water exists as the liquid
film of the free-fall curtain shape between the flow controller unit and the aluminum
is preferably in a range of 20 to 50 mm. Furthermore, the angle α of the aluminum
plate is preferably in a range of 30° to 80° relative to the horizontal direction.
[0099] By using the apparatus configured to perform a water washing treatment with a liquid
film of a free-fall curtain shape, it is possible to perform the water washing treatment
uniformly on the aluminum plate. Accordingly, it is possible to enhance uniformity
of the treatments which are carried out prior to the water washing treatments.
[0100] The apparatus configured to perform a water washing treatment with a liquid film
of a free-fall curtain shape may be preferably an apparatus disclosed in
JP 2003-96584 A, for example.
[0101] Meanwhile, as the spray tube for use in the water washing treatment, it is possible
to use a spray tube provided with a plurality of spray tips arranged along the width
direction of the aluminum plate, which are configured to fan out injection water.
The distance between the adjacent spray tips is preferably in a range of 20 to 100
mm, and the fluid volume for each spray tip is preferably in a range of 0.5 to 20
L/min. It is preferable to use a plurality of such spray tubes.
<First desmutting treatment>
[0102] After performing the first alkaline etching treatment, it is preferable to perform
acid washing (a first desmutting treatment) in order to remove stains (smuts) remaining
on the surface. The desmutting treatment is carried out by allowing the aluminum plate
to contact an acidic solution.
[0103] Acids used herein include nitric acid, sulfuric acid, phosphoric acid, chromic acid,
hydrofluoric acid, and fluoroboric acid, for example.
[0104] Here, in the first desmutting treatment to be carried out after the first alkaline
etching treatment, if electrolysis in nitric acid is subsequently carried out as the
first electrolytic treatment, then it is preferable to use overflow waste of an electrolytic
solution used in the electrolysis in nitric acid.
[0105] Upon management of compositions of a desmutting solution, it is possible to select
and use any of a method of management by conductivity and temperature corresponding
to a matrix of concentration of the acidic solution and the aluminum ion concentration,
a method of management by conductivity, specific gravity and temperature corresponding
to the same, and a method of management by conductivity, propagation velocity of ultrasonic
waves and temperature corresponding to the same.
[0106] In the first desmutting treatment, it is preferable to use the acidic solution containing
an acid in a range of 1 to 400 g/L and aluminum ions in a range of 0.1 to 5 g/L.
[0107] Temperature of the acidic solution is preferably equal to or above 20°C, or more
preferably equal to or above 30°C. Meanwhile, the temperature is preferably equal
to or below 70°C, or more preferably equal to below 60°C.
[0108] In the first desmutting treatment, the treating time is preferably equal to or above
1 second, or more preferably equal to or above 4 seconds. Meanwhile, the treating
time is preferably equal to or below 60 seconds, or more preferably equal to or below
40 seconds.
[0109] The method of allowing the aluminum plate to contact the acidic solution includes
a method of allowing the aluminum plate to pass through a tank filled with the acidic
solution, a method of dipping the aluminum plate in a tank filled with the acidic
solution, and a method of spraying the acidic solution on the surface of the aluminum
plate.
[0110] Among these methods, the method of spraying the acidic solution on the surface of
the aluminum plate is preferred. To be more precise, it is preferable to apply the
method of spraying the desmutting solution by using a spray tube provided with pores
which have diameters in a range of 2 to 5 mm and are arranged with spaces in a range
of 10 to 50 mm. Here, it is preferable to spray the desmutting solution in an amount
of 10 to 100 L/min for each spray tube. A plurality of spray tubes are preferably
provided therein.
[0111] After completing the desmutting treatment, it is preferable to drain the solution
off with a nip roller, then to perform a water washing treatment for 1 to 10 seconds,
and then to drain the water off with the nip roller.
[0112] The water washing treatment is similar to the water washing treatment which is carried
out after the alkaline etching treatment. However, the fluid volume for each spray
tip is preferably in a range of 1 to 20 L/min.
[0113] Here, in the first desmutting treatment, if the overflow waste of the electrolytic
solution to be used in the subsequent electrolysis in nitric acid is used as the desmutting
solution, then it is preferable to cancel draining with the nip roller and the water
washing treatment after the desmutting treatment. Instead, it is preferable to handle
the aluminum plate until the process of electrolysis in nitric acid while spraying
the desmutting solution as appropriate to prevent the surface of the aluminum plate
from drying.
<First electrolytic treatment>
[0114] The first electrolytic treatment is an electrochemical surface roughening treatment
to be performed in an aqueous solution containing nitric acid or hydrochloric acid.
[0115] According to the present invention, it is possible to form grain shapes of superposition
of highly uniform irregular structures on the surface of the aluminum plate by carrying
out the first electrolytic treatment and the second electrolytic treatment in this
order. In this way, it is possible to achieve excellent stain resistance and press
life.
[0116] Here, average roughness Ra of the surface of the aluminum plate after the first electrolytic
treatment is preferably in a range of 0.2 to 1.0 µm.
(First electrolytic treatment: when performing electrochemical surface roughening
treatment in aqueous solution containing nitric acid)
[0117] By the electrochemical surface roughening treatment in the aqueous solution containing
nitric acid (the electrolysis in nitric acid), it is possible to form favorable irregular
structures on the surface of the aluminum plate. In the present invention, when the
aluminum plate contains relatively a large amount of Cu, relatively large and uniform
cavities are formed by the electrolysis in nitric acid. As a result, a lithographic
printing plate using the support for a lithographic printing plate obtained by the
present invention will have excellent press life.
[0118] The aqueous solution containing nitric acid usable herein may be one applicable to
an electrochemical surface roughening treatment using a normal direct current or a
normal alternating current. Here, it is possible to add at least one of nitrate compounds
having nitrate ions, such as aluminum nitrate, sodium nitrate or ammonium nitrate,
in a range of 1 g/L to a saturation level, to the aqueous solution containing nitric
acid in a concentration of 1 to 100 g/L upon use. Moreover, metal contained in the
aluminum alloy such as iron, copper, manganese, nickel, titanium, magnesium or silica
may be dissolved in the aqueous solution containing nitric acid. It is also possible
to add hypochlorous acid or hydrogen peroxide in an amount of 1 to 100 g/L.
[0119] To be more precise, it is preferable to use the solution prepared by dissolving aluminum
nitrate in the nitric acid aqueous solution having the nitric acid concentration in
a range of 5 to 15 g/L, so as to adjust the aluminum ion concentration to 3 to 7 g/L.
[0120] Temperature of the aqueous solution containing nitric acid is preferably in a range
of 20°C to 55°C inclusive.
[0121] It is possible to form the pits having an average pore size in a range of 1 to 10
µm by means of the electrolysis in nitric acid. Note that an electrolytic reaction
is condensed when a quantity of electricity is relatively higher, and honeycomb pits
exceeding 10 µm are also generated.
[0122] To obtain such grains, a total quantity of electricity contributing to an anodic
reaction of the aluminum plate at the point of termination of the electrolytic reaction
is preferably equal to or above 150 C/dm
2, or more preferably equal to or above 170 C/dm
2. Meanwhile, the total quantity of electricity is preferably equal to or below 600
C/dm
2, or more preferably equal to or below 500 C/dm
2. Current density in this case is preferably in a range of 20 to 100 A/dm
2 in terms of a peak current value when using an alternating current, or in a range
of 20 to 100 A/dm
2 when using a direct current.
(First electrolytic treatment: when performing electrochemical surface roughening
treatment in aqueous solution containing hydrochloric acid)
[0123] The aqueous solution containing hydrochloric acid usable herein may be one applicable
to an electrochemical surface roughening treatment using a normal direct current or
a normal alternating current. Here, it is possible to add at least one of chloride
or nitrate compounds including ones having nitrate ions such as aluminum nitrate,
sodium nitrate or ammonium nitrate, and ones having chlorine ions such as aluminum
chloride, sodium chloride or ammonium chloride in a range of 1 g/L to a saturation
level to the aqueous solution containing hydrochloric acid in a concentration of 1
to 30 g/L or more preferably 2 to 10 g/L upon use. Moreover, it is possible to add
a compound, which forms a complex with copper, in a proportion of 1 to 200 g/L. Metal
contained in the aluminum alloy such as iron, copper, manganese, nickel, titanium,
magnesium or silica may be dissolved in the aqueous solution containing hydrochloric
acid. It is also possible to add hypochlorous acid or hydrogen peroxide in an amount
of 1 to 100 g/L.
[0124] As for the aqueous hydrochloric acid solution, it is particularly preferable to prepare
the aqueous solution by adding aluminum salt (aluminum chloride: AlCl
3•6H
2O) to an aqueous solution containing hydrochloric acid in a concentration of 2 to
10 g/L so as to adjust the aluminum ion concentration preferably in a range of 3 to
7 g/L or more preferably in a range of 4 to 6 g/L. When the electrochemical surface
roughening treatment is carried out by use of the above-described aqueous hydrochloric
acid solution, uniform surface shapes are obtained by the surface roughening treatment.
Accordingly, unevenness does not occur in the surface roughening treatment regardless
of whether a low-purity aluminum flat-rolled plate or a high-purity aluminum flat-rolled
plate is used. As a result, it is possible to satisfy excellent press life and stain
resistance when such an aluminum flat-rolled plate is formed into a lithographic printing
plate.
[0125] Temperature of the aqueous solution containing hydrochloric acid is preferably equal
to or above 20°C or more preferably equal to or above 30°C. Meanwhile, the temperature
is preferably equal to or below 55°C or more preferably equal to or below 50°C.
[0126] Concerning additives for the aqueous solution containing hydrochloric acid, apparatuses,
power sources, current density, flow rates, and temperature, it is possible to apply
publicly known techniques for use in electrochemical surface roughening. Although
both of an alternating current and a direct current are applicable to the power source
used in electrochemical surface roughening, an alternating current is particularly
preferred.
[0127] Hydrochloric acid itself possesses high aluminum dissolving power. Accordingly, it
is possible to form fine irregularities on the surface only by applying a small current.
Such fine irregularities have an average pore size in a range of 0.01 to 0.4 µm and
are generated uniformly on the entire surface of the aluminum plate.
[0128] When the quantity of electricity is raised further (the total quantity of electricity
(the anodic reaction) in a range of 150 to 2000 C/dm
2), larger pits having an average pore size in a range of 1 to 30 µm provided with
smaller pits having an average pore size in a range of 0.01 to 0.4 µm on the surfaces
of the larger pits are formed. To obtain such grains, the total quantity of electricity
contributing to the anodic reaction of the aluminum plate at the point of termination
of the electrolytic reaction is preferably equal to or above 10 C/dm
2, more preferably equal to or above 50 C/dm
2, or even more preferably equal to or above 100 C/dm
2. Meanwhile, the total quantity of electricity is preferably equal to or below 2000
C/dm
2, or more preferably equal to or below 600 C/dm
2.
[0129] Current density in this case is preferably in a range of 20 to 100 A/dm
2 in terms of a peak current value.
[0130] When the aluminum plate is subjected to the electrolysis in hydrochloric acid while
applying such a large quantity of electricity, it is possible to form large undulation
and fine irregularities at the same time. It is possible to improve stain resistance
by homogenizing the large undulation by the second alkaline etching to be described
later.
[0131] The first electrolytic treatment using the aqueous solution containing nitric acid
or hydrochloric acid can be performed in accordance with electrochemical graining
methods (electrolytic graining methods) as disclosed in
JP 48-28123 B and
GB 896563 B, for example. Although these electrolytic graining methods use an alternating current
having a sinusoidal waveform, it is also possible to use a special waveform as disclosed
in
JP 52-58602 A. It is also possible to use a waveform as disclosed in
JP 3-79799 A. Meanwhile, it is also possible to apply methods disclosed in
JP 55-158298 A,
JP 56-28898 A,
JP 52-58602 A,
JP 52-152302 A,
JP 54-85802 A,
JP 60-190392 A,
JP 58-120531 A,
JP 63-176187 A,
JP 1-5889 A,
JP 1-280590 A,
JP 1-118489 A,
JP 1-148592 A,
JP 1-178496 A,
JP 1-188315 A,
JP 1-154797 A,
JP 2-235794 A,
JP 3-260100 A,
JP 3-253600 A,
JP 4-72079 A,
JP 4-72098 A,
JP 3-267400 A, and
JP 1-141094 A. In addition to the above, it is also possible to perform electrolysis by use of
an alternating current having a special frequency which is disclosed as a method of
manufacturing an electrolytic capacitor. Such a manufacturing method is disclosed
in
US 4276129 and
US 4676879.
[0132] Although various techniques have been disclosed concerning electrolytic tanks and
power sources, it is possible to apply methods disclosed in
US 4203637,
JP 56-123400 A,
JP 57-59770 A,
JP 53-12738 A,
JP 53-32821 A,
JP 53-32822 A,
JP 53-32823 A,
JP 55-122896 A,
JP 55-132884 A,
JP 62-127500 A,
JP 1-52100 A,
JP 1-52098 A,
JP 60-67700 A,
JP 1-230800 A, and
JP 3-257199 A.
[0133] In addition, it is also possible to apply methods disclosed in
JP 52-58602 A,
JP 52-152302 A,
JP 53-12739 A,
JP 53-32833 A,
JP 53-32824 A,
JP 53-32825 A,
JP 54-85802 A,
JP 48-28123 B,
JP 51-7081 B,
JP 52-133838 A,
JP 52-133840 A,
JP 52-133844 A,
JP 52-133845 A,
JP 53-149135 A, and
JP 54-146234 A.
[0134] When the aluminum plates are continuously subjected to the electrolytic surface roughening
treatment, the aluminum ion concentration in the solution is increased and the shapes
of irregularities on the aluminum plate formed by the first electrolytic treatment
thereby vary. Accordingly, it is preferable to manage compositions of a nitric acid
electrolytic solution or a hydrochloric acid electrolytic solution as described below.
[0135] Specifically, either a matrix of conductivity, specific gravity and temperature,
or a matrix of conductivity, propagation velocity of ultrasonic waves and temperature
is formed in advance, each of the matrices corresponding to a matrix of a nitric or
hydrochloric acid concentration and the aluminum ion concentration. Then, the compositions
of the solution are measured in terms of the conductivity, the specific gravity and
the temperature or in terms of the conductivity, the propagation velocity of ultrasonic
waves and the temperature, and nitric or hydrochloric acid and water are added thereto
so as to achieve target control values for the compositions of the solution. Thereafter,
the electrolytic solution, which is increased in volume by adding nitric or hydrochloric
acid and water, is allowed to overflow from a circulation tank so as to maintain the
constant volume. As for nitric acid for such addition, it is possible to use one for
industrial use which contains 30 to 70 wt% therein. As for hydrochloric acid for such
addition, it is possible to use one for industrial purposes which contains 30 to 40
wt% therein.
[0136] A conductivity detector and a gravimeter used therein are preferably temperature
compensated, respectively. Here, it is preferable to use a gravimeter of a differential
pressure type.
[0137] In order to achieve higher accuracy, it is preferable that a sample collected from
the electrolytic solution for measurement of the compositions of the solution be used
for such measurement after controlling the solution to certain temperature (such as
40 ± 0.5°C) with a heat exchanger apart from one for the electrolytic solution.
[0138] The electrolytic current waveform used in the electrochemical surface roughening
treatment is not particularly limited, and a sinusoidal wave, a rectangular wave,
a trapezoidal wave, a triangular wave, and the like are applicable. However, it is
preferable to use any of the sinusoidal wave, the rectangular wave, and the trapezoidal
wave. Among those waves, the trapezoidal wave is particularly preferred. In the case
of the first electrolysis in hydrochloric acid, the sinusoidal wave is particularly
preferred because it is easier to generate uniform pits having an average diameter
equal to or above 1µm. The sinusoidal wave is the one shown in Fig. 4.
[0139] The trapezoidal wave is the one shown in Fig. 1. In terms of this trapezoidal wave,
time (TP) consumed by a current to reach from zero to a peak is preferably in a range
of 0.5 to 3 msec. If the time TP exceeds 3 msec, an aluminum plate becomes susceptible
to minor components in the electrolytic solution typified by ammonium ions which are
spontaneously increased by the electrolytic treatment particularly when using the
aqueous solution containing nitric acid. Accordingly, it is difficult to achieve uniform
graining. As a result, stain resistance tends to be reduced when the aluminum plate
is formed into a lithographic printing plate.
[0140] It is possible to use an alternating current having a duty ratio in a range of 1:2
to 2:1. However, as disclosed in
JP 5-195300 A, it is preferable to apply an alternating current having a duty ratio of 1:1 in an
indirect feeding mode where a conductor roll is not used for aluminum.
[0141] It is possible to use an alternating current having a frequency in a range of 0.1
to 120 Hz. However, in light of facilities, it is preferable to use an alternating
current having a frequency in a range of 50 to 70 Hz. When the frequency is below
50 Hz, a carbon electrode which is a main electrode tends to be dissolved easily.
On the contrary, when the frequency is above 70 Hz, the current condition is susceptible
to inductance components on a power circuit and power costs are thereby increased.
[0142] Fig. 2 is a side view showing an example of radial type cell for the electrochemical
surface roughening treatment using the alternating current in the method of manufacturing
a support for a lithographic printing plate of the present invention.
[0143] One or more alternating current power sources can be connected to an electrolytic
tank. In order to perform uniform graining by controlling the current ratio between
an anode and a cathode of an alternating current applied to an aluminum plate opposed
to main electrodes and in order to dissolve carbon in the main electrodes, it is preferable
to dispose auxiliary anodes as shown in Fig. 2 and to shunt a part of the alternating
current. In Fig. 2, reference numeral 11 denotes an aluminum plate, reference numeral
12 denotes a radial drum roller, reference numerals 13a and 13b denote main electrodes,
reference numeral 14 denotes an electrolytic solution, reference numeral 15 denotes
an electrolytic solution inlet, reference numeral 16 denotes a slit, reference numeral
17 denotes an electrolytic solution passage, reference numeral 18 denotes auxiliary
anodes, reference numerals 19a and 19b denote thyristors, reference numeral 20 denotes
an alternating power source, reference numeral 40 denotes a main electrolytic tank,
and reference numeral 50 denotes an auxiliary anode tank. By shunting a part of a
current as a direct current into the auxiliary anodes provided apart from the two
main electrodes in a different tank through a rectifier or a switching element, it
is possible to control the ratio between a current value contributing to an anodic
reaction acting on the aluminum plate opposed to the main electrodes and a current
value contributing to a cathodic reaction. The ratio of the quantity of electricity
contributing to the anodic reaction and the cathodic reaction (the quantity of electricity
at the cathodic reaction / the quantity of electricity at the anodic reaction) on
the aluminum plate opposed to the main electrodes is preferably in a range of 0.3
to 0.95.
[0144] Any types of publicly known electrolytic tanks applied to surface treatments, such
as a vertical type, a flat type, or a radial type, can be used as the electrolytic
tank. However, a radial type electrolytic tank as disclosed in
JP 5-195300 A is particularly preferred. The electrolytic solution passing through the electrolytic
tank may flow in a parallel direction or in a counter direction relative to a traveling
direction of an aluminum web.
[0145] Meanwhile, in an electrochemical surface roughening treatment applying a direct current,
it is possible to use an electrolytic solution which is used in an electrochemical
surface roughening treatment applying a normal direct current. To be more precise,
it is possible to use an electrolytic solution which is similar to the electrolytic
solution used in the above-described electrochemical surface roughening treatment
applying the alternating current.
[0146] The direct current power source waveform used in the electrochemical surface roughening
treatment is not particularly limited as long as the current does not change polarity,
and a comb-shaped wave, a continuous direct current, a wave obtained by subjecting
a commercial alternating current to full-wave rectification with a thyristor, and
the like are applicable. However, it is preferable to use a smoothed continuous direct
current.
[0147] Although it is possible to perform the electrochemical surface roughening treatment
applying the direct current in accordance with any of the batch method, the semicontinuous
method, and the continuous method. However, it is preferable to adopt the continuous
method.
[0148] An apparatus to be used in the electrochemical surface roughening treatment applying
the direct current is not particularly limited as long as the apparatus is configured
to apply a direct current voltage between anodes and cathodes which are arranged alternately
and to allow an aluminum plate to pass through the anodes and the cathodes while maintaining
the clearance.
[0149] The electrodes are not particularly limited. It is possible to use publicly known
electrodes which are conventionally used in electrochemical surface roughening treatments.
[0150] As for the anode, it is preferable to use: an anode formed by plating or cladding
platinum-group metal on valve metal such as titanium, tantalum or niobium; an anode
formed by coating or sintering a platinum-group metal oxide on the valve metal; aluminum;
stainless steel, for example. Among these anodes, an anode formed by cladding platinum
on the valve metal is preferred. A method such as water cooling by passing water inside
the electrode can further extend the anode life.
[0151] As for the cathode, it is possible to select metal or the like from the Pourbaix
diagram, which is not dissolved when electrode potential is set negative. Among such
substances, carbon is preferred.
[0152] Arrangement of the electrodes can be selected appropriately in accordance with the
wave structure. Moreover, it is possible to adjust the wave structure by changing
lengths of the anode and cathode in the traveling direction of the aluminum plate,
changing passage time of the aluminum plate, or by changing a flow rate, temperature,
compositions or current density of the electrolytic solution. Meanwhile, when using
an apparatus provided with a tank for the anode and a tank for a cathode separately,
it is also possible to change electrolytic conditions of the respective treatment
tanks.
[0153] After completing the first electrolytic treatment, it is preferable to drain the
solution off with a nip roller, then to perform a water washing treatment for 1 to
10 seconds, and then to drain the water off with the nip roller.
[0154] The water washing treatment is preferably carried out by use of spray tubes. As the
spray tube for use in the water washing treatment, it is possible to use a spray tube
provided with a plurality of spray tips arranged along the width direction of the
aluminum plate, which are configured to fan out injection water. The distance between
the adjacent spray tips is preferably in a range of 20 to 100 mm, and a fluid volume
of each spray tip is preferably in a range of 1 to 20 L/min. It is preferable to use
a plurality of such spray tubes.
<Second alkaline etching treatment>
[0155] The second alkaline etching treatment, which is carried out between the first electrolytic
treatment and the second electrolytic treatment, aims at dissolving smuts generated
in the first electrolytic treatment and dissolving edge portions of the pits formed
by the first electrolytic treatment. By applying the second alkaline etching treatment,
the edge portions of the large pits formed by the first electrolytic treatment are
dissolved and the surface is thereby smoothed. As a consequence, ink will not be easily
caught by the edge portions. Accordingly, it is possible to obtain a presensitized
plate having excellent stain resistance.
[0156] The second alkaline etching treatment is basically similar to the first alkaline
etching treatment.
Accordingly, only the difference will be described below.
[0157] In the second alkaline etching treatment, the etching amount is preferably equal
to or above 0.05 g/m
2, or more preferably equal to or above 0.1 g/m
2. Meanwhile, the etching amount is preferably equal to or below 4 g/m
2, or more preferably equal to or below 3.5 g/m
2. When the etching amount is equal to or above 0.05 g/m
2, the edge portions of the pits generated in the first electrolytic treatment are
smoothed in a non-image area of the lithographic printing plate and ink is hardly
caught by the edge portions. Accordingly, it is possible to achieve excellent stain
resistance. In the meantime, when the etching amount is equal to or below 4 g/m
2, the irregularities generated in the first electrolytic treatment are increased in
size. Accordingly, it is possible to achieve excellent press life.
[0158] In the second alkaline etching treatment, the concentration of the alkaline solution
is preferably equal to or above 30 g/L, or more preferably equal to or above 300 g/L.
Meanwhile, the concentration of the alkaline solution is preferably equal to or below
500 g/L, or more preferably equal to or below 450 g/L.
[0159] Moreover, it is preferable that the alkaline solution contains aluminum ions. The
aluminum ion concentration is preferably equal to or above 1 g/L, or more preferably
equal to or above 50 g/L. Meanwhile, the aluminum ion concentration is preferably
equal to or below 200 g/L, or more preferably equal to or below 150 g/L. Such an alkaline
solution can be prepared by use of water, a 48-wt% caustic soda aqueous solution,
and sodium aluminate, for example.
<Second desmutting treatment>
[0160] After performing the second alkaline etching treatment, it is preferable to perform
acid washing (a second desmutting treatment) in order to remove stains (smuts) remaining
on the surface. The second desmutting treatment can be carried out in the same method
as the first desmutting treatment.
[0161] It is preferable to use either nitric acid or sulfuric acid in the second desmutting
treatment.
[0162] In the second desmutting treatment, it is preferable to use an acidic solution containing
an acid in a range of 1 to 400 g/L and aluminum ions in a range of 0.1 to 8 g/L.
[0163] To be more precise, when using sulfuric acid, it is possible to use a solution prepared
by dissolving aluminum sulfate in a sulfuric acid aqueous solution having a sulfuric
acid concentration in a range of 100 to 350 g/L, so as to adjust the aluminum ion
concentration to a range of 0.1 to 5 g/L. Alternatively, it is possible to use overflow
waste of an electrolytic solution used in the anodic oxidation treatment to be described
later.
[0164] In the second desmutting treatment, the treating time is preferably equal to or above
1 second, or more preferably equal to or above 4 seconds. Meanwhile, the treating
time is preferably equal to or below 60 seconds, or more preferably equal to or below
20 seconds.
[0165] In the second desmutting treatment, temperature of the acidic solution is preferably
equal to or above 20°C, or more preferably equal to or above 30°C. Meanwhile, the
temperature is preferably equal to or below 70°C, or more preferably equal to or below
60°C.
<Second electrolytic treatment (second electrolysis in hydrochloric acid)>
[0166] The second electrolytic treatment is an electrochemical surface roughening treatment
to be performed in an aqueous solution containing hydrochloric acid by use of an alternating
or direct current. It is acceptable to carry out only the above-described first electrolytic
treatment in the present invention. However, by combining this second electrolytic
treatment, it is possible to form more complicated irregular structures on the surface
of the aluminum plate and thereby to achieve excellent press life.
[0167] The second electrolysis in hydrochloric acid to be performed after the first electrolytic
treatment is basically similar to those described in terms of the first electrolysis
in hydrochloric acid.
[0168] The total quantity of electricity received by the aluminum plate in the anodic reaction
in the course of electrochemical surface roughening in the aqueous solution containing
hydrochloric acid used in the second electrolysis in hydrochloric acid can be selected
in a range of 10 to 200 C/dm
2 at a point of completion of the electrochemical surface roughening treatment. In
order not to significantly damage the roughened surface formed in the first electrolytic
treatment, the total quantity of electricity is preferably in a range of 10 to 100
C/dm
2, or more preferably in a range of 50 to 80 C/dm
2.
<First alkaline etching treatment - first electrolytic (surface roughening) treatment
in nitric acid - second alkaline etching treatment - second electrolytic (surface
roughening) treatment in hydrochloric acid>
[0169] When performing the above-described combination of treatments, it is preferable to
carry out the first electrochemical surface roughening treatment in the electrolytic
solution containing nitric acid while applying the total quantity of electricity in
the anodic reaction in a range of 65 to 500 dm
2, to chemically dissolve Al in an amount of not less than 0.1 g/m
2, to carry out the second electrochemical surface roughening treatment in the electrolytic
solution containing hydrochloric acid while applying the total quantity of electricity
in the anodic reaction in a range of 25 to 100 dm
2, and then to chemically dissolve Al in an amount of not less than 0.03 g/m
2. By subjecting the aluminum alloy blank of the present invention to the surface roughening
treatments according to the above-described combination, it is possible to obtain
the support for a lithographic printing plate which has excellent stain resistance
and press life.
<Third alkaline etching treatment>
[0170] The third alkaline etching treatment, which is performed after the second electrolytic
treatment, aims at dissolving the smuts generated in second electrolytic treatment
and at dissolving edge portions of the pits which are formed in the second electrolytic
treatment. The third alkaline etching treatment is basically similar to the first
alkaline etching treatment. Accordingly, only the difference will be described below.
[0171] In the third alkaline etching treatment, the etching amount is preferably equal to
or above 0.05 g/m
2, or more preferably equal to or above 0.1 g/m
2. Meanwhile, the etching amount is preferably equal to or below 0.3 g/m
2, or more preferably equal to or below 0.25 g/m
2. When the etching amount is equal to or above 0.05 g/m
2, the edge portions of the pits generated in the second electrolytic treatment in
hydrochloric acid are smoothed in a non-image area of the lithographic printing plate
and ink is hardly caught by the edge portions. Accordingly, it is possible to achieve
excellent stain resistance. In the meantime, when the etching amount is equal to or
below 0.3 g/m
2, the irregularities generated in the first electrolytic treatment in hydrochloric
acid and the second electrolytic treatment in hydrochloric acid are increased in size.
Accordingly, it is possible to achieve excellent press life.
[0172] In the third alkaline etching treatment, the concentration of the alkaline solution
is preferably equal to or above 30 g/L. Meanwhile, in order not to excessively reduce
the sizes of the irregularities generated in the precedent alternating current electrolyses
in hydrochloric acid, the concentration of the alkaline solution is preferably equal
to or below 100 g/L, or more preferably equal to or below 70 g/L.
[0173] Moreover, it is preferable that the alkaline solution contain aluminum ions. The
aluminum ion concentration is preferably equal to or above 1 g/L, or more preferably
equal to or above 3 g/L. Meanwhile, the aluminum ion concentration is preferably equal
to or below 50 g/L, or more preferably equal to or below 8 g/L. Such an alkaline solution
can be prepared by use of water, a 48-wt% caustic soda aqueous solution, and sodium
aluminate, for example.
[0174] In the third alkaline etching treatment, the temperature of the alkaline solution
is preferably equal to or above 25°C, or more preferably equal to or above 30°C. Meanwhile,
the temperature is preferably equal to or below 60°C, or more preferably equal to
or below 50°C.
[0175] In the third alkaline etching treatment, the treating time is preferably equal to
or above 1 second or more preferably equal to or above 2 seconds. Meanwhile, the treating
time is preferably equal to or below 30 seconds, or more preferably equal to or below
10 seconds.
<Third desmutting treatment>
[0176] After performing the third alkaline etching treatment, it is preferable to perform
acid washing (a third desmutting treatment) in order to remove stains (smuts) remaining
on the surface. The third desmutting treatment is basically similar to the first desmutting
treatment. Accordingly, only the difference will be described below.
[0177] In the third desmutting treatment, it is preferable to use the acidic solution containing
an acid in a range of 5 to 400 g/L and aluminum ions in a range of 0.5 to 8 g/L. To
be more precise, when using sulfuric acid, it is preferable to use the solution prepared
by dissolving aluminum sulfate in a sulfuric acid aqueous solution having the sulfuric
acid concentration in a range of 100 to 350 g/L, so as to adjust the aluminum ion
concentration to a range of 1 to 5 g/L.
[0178] In the third desmutting treatment, the treating time is preferably equal to or above
1 second, or more preferably equal to or above 4 seconds. Meanwhile, the treating
time is preferably equal to or below 60 seconds, or more preferably equal to or below
15 seconds.
[0179] In the third desmutting treatment, when the same type of solution as the electrolytic
solution to be used in the subsequent anodic oxidation treatment is used as a desmutting
solution, it is possible to omit draining and a water washing treatment by use of
a nip roller after the desmutting treatment.
<Anodic oxidation treatment>
[0180] The aluminum plate after the above-described treatments is further subjected to the
anodic oxidation treatment. The anodic oxidation treatment can be carried out in accordance
with a method conventionally practiced in this field. In this case, it is possible
to form an anodized film by applying electricity to the aluminum plate as the anode
in a solution having the sulfuric acid concentration in a range of 50 to 300 g/L and
the aluminum ion concentration equal to or below 5 wt%. As for the solution used in
the anodic oxidation treatment, it is possible to use any one of or a combination
of sulfuric acid, phosphoric acid, chromic acid, oxalic acid, sulfamic acid, benzensulfonic
acid, amidosulfonic acid, and the like.
[0181] At this time, at least any components normally contained in the aluminum plate, the
electrodes, tap water, underground water, and the like may be contained in the electrolytic
solution. Further, second and third components may be added thereto. The second and
third components cited herein may be: metal ions of Na, K, Mg, Li, Ca, Ti, Al, V,
Cr, Mn, Fe, Co, Ni, Cu, Zn, and the like; positive ions such as ammonium ions; and
negative ions such as nitrate ions, carbonate ions, chloride ions, phosphate ions,
fluoride ions, sulfite ions, titanate ions, silicate ions, or borate ions, for example.
Such components may be contained in a concentration of about 0 to 10000 ppm.
[0182] Conditions of the anodic oxidation treatment vary depending on the electrolytic solution
to be used and therefore cannot be determined universally. However, in general, it
is preferable to use the concentration of the electrolytic solution in a range of
1 to 80 wt%, the temperature of the solution in a range of 5°C to 70°C, the current
density in a range of 0.5 to 60 A/dm
2, the voltage in a range of 1 to 100 V, and the time for electrolysis in a range of
15 seconds to 50 minutes. These conditions are appropriately adjusted to form a desired
amount of the anodized film.
[0183] Meanwhile, it is also possible to apply methods disclosed in
JP 54-81133 A,
JP 57-47894 A,
JP 57-51289 A,
JP 57-51290 A,
JP 57-54300A,
JP 57-136596 A,
JP 58-107498 A,
JP 60-200256 A,
JP 62-136596 A,
JP 63-176494 A,
JP 4-176897 A,
JP 4-280997 A,
JP 6-207299 A,
JP 5-24377 A,
JP 5-32083 A,
JP 5-125597 A, and
JP 5-195291 A.
[0184] Among these methods, as disclosed in
JP 54-12853 A and in
JP 48-45303 A, it is preferable to use a sulfuric acid solution as the electrolytic solution. The
sulfuric acid concentration in the electrolytic solution is preferably in a range
of 10 to 300 g/L (1 to 30 wt%), or more preferably in a range of 50 to 200 g/L (5
to 20 wt%). Meanwhile, the aluminum ion concentration is preferably in a range of
1 to 25 g/L (0.1 to 2.5 wt%), or more preferably in a range of 2 to 10 g/L (0.2 to
1 wt%). Such an electrolytic solution can be prepared by adding aluminum sulfate or
the like to dilute sulfuric acid having a concentration in a range of 50 to 200 g/L,
for example.
[0185] The compositions of the electrolytic solution are preferably managed by conductivity,
specific gravity and temperature, or, by conductivity, propagation velocity of ultrasonic
waves and temperature corresponding to a matrix of the sulfuric acid concentration
and the aluminum ion concentration, by using a method similar to the above-described
electrolysis in nitric acid.
[0186] The temperature of the electrolytic solution is preferably in a range of 25°C to
55°C, or more preferably in a range of 30°C to 50°C.
[0187] When performing the anodic oxidation treatment in the electrolytic solution containing
sulfuric acid, a direct or alternating current may be applied between the aluminum
plate and the counter electrodes.
[0188] When a direct current is applied to the aluminum plate, the current density is preferably
in a range of 1 to 60 A/dm
2, or more preferably in a range of 5 to 40 A/dm
2.
[0189] When performing the anodic oxidation treatment continuously, it is preferable to
apply a current at low current density in a range of 5 to 10 A/dm
2 in the beginning of the anodic oxidation treatment and then to raise the current
density up to a range of 30 to 50 A/dm
2 or even higher along with the progress of the anodic oxidation treatment, so as not
to cause so-called "burning" (by which the film becomes thicker than surrounding portions)
owing to the current which is focused on a part of the aluminum plate.
[0190] To be more precise, it is preferable to distribute currents from a direct current
power source such that a current from the direct current power source on a downstream
side is equal to or higher than a current from the direct current power source on
an upstream side. By adopting such current distribution, generation of a socalled
burn is suppressed. As a consequence, it is possible to perform the anodic oxidation
treatment at a high rate.
[0191] When performing the anodic oxidation treatment continuously, it is preferable to
carry out a liquid power supply method configured to supply electricity to the aluminum
plate through the electrolytic solution.
[0192] A porous film provided with numerous holes called pores (micropores) is obtained
by performing the anodic oxidation treatment under the conditions described above.
Normally, the average pore diameter thereof is in a range of about 5 to 50 nm, and
the average pore density thereof is in a range of about 300 to 800 pcs/µm
2.
[0193] The quantity of the anodized film is preferably in a range of 1 to 5 g/m
2. The plate easily causes flaws when the quantity is below 1 g/m
2. On the contrary, when the quantity exceeds 5 g/m
2, a large amount of electricity is required for manufacturing and it is therefore
economically disadvantageous. The quantity of the anodized film is more preferably
in a range of 1.5 to 4 g/m
2. Moreover, it is preferable to perform the anodic oxidation treatment such that a
difference in quantity of the anodized film between the central portion and the vicinity
of edge portions of the aluminum plate is equal to or below 1 g/m
2.
[0195] Among these techniques, an apparatus shown in Fig. 3 is preferably used. Fig. 3 is
a schematic diagram showing an example of an apparatus configured to perform an anodic
oxidation treatment on a surface of an aluminum plate.
[0196] In an anodic oxidation apparatus 410 shown in Fig. 3, a power supply tank 412 is
disposed on an upstream side in a traveling direction of an aluminum plate 416 and
an anodic oxidation treatment tank 414 is disposed on a downstream side in order to
supply electricity to the aluminum plate 416 through an electrolytic solution. The
aluminum plate 416 is conveyed as indicated by arrows in Fig. 3 by way of path rollers
422 and 428. Anodes 420 which are connected to positive terminals of direct current
power sources 434 are disposed in the power supply tank 412 to which the aluminum
plate 416 is firstly introduced. Here, the aluminum plate 416 constitutes a cathode.
Accordingly, a cathodic reaction takes place on the aluminum plate 416.
[0197] Cathodes 430 which are connected to negative terminals of the direct current power
sources 434 are disposed in the anodic oxidation treatment tank 414 to which the aluminum
plate 416 is subsequently introduced. Here, the aluminum plate 416 constitutes an
anode. Accordingly, an anodic reaction takes place on the aluminum plate 416, and
the anodized film is formed on the surface of the aluminum plate 416.
[0198] Clearance between the aluminum plate 416 and the cathodes 430 is preferably in a
range of 50 to 200 mm. Aluminum is used for the cathodes 430. In order to allow hydrogen
gas generated in the anodic reaction to escape easily from the system, it is preferable
to form the anodes 430 not as electrodes having large areas but as electrodes which
are split into multiple pieces along with the traveling direction of the aluminum
plate 416.
[0199] As shown in Fig. 3, between the power supply tank 412 and the anodic oxidation treatment
tank 414, it is preferable to provide a tank called an intermediate tank 413 which
drains off an electrolytic solution. By providing the intermediate tank 413, it is
possible to suppress bypassing of the current from the anodes 420 to the cathodes
430 instead of passing through the aluminum plate 416. It is preferable to provide
nip rollers 424 in the intermediate tank 413 for draining so as to minimize the bypass
current. The electrolytic solution removed by draining is discharged from a solution
outlet 442 to the outside of the anodic oxidation apparatus 410.
[0200] To reduce voltage losses, an electrolytic solution 418 to be stored in the power
supply tank 412 has a higher temperature and/or a higher concentration than an electrolytic
solution 426 to be stored in the anodic oxidation treatment tank 414. Moreover, compositions,
temperatures, and the like of the electrolytic solutions 418 and 426 are determined
based on efficiency of formation of the anodized film, shapes of the micropores on
the anodized film, hardness of the anodized film, voltages, costs of the electrolytic
solutions, and the like.
[0201] The electrolytic solutions are supplied to the power supply tank 412 and the anodic
oxidation treatment tank 414 by squirting the electrolytic solutions from solution
supply nozzles 436 and 438. In order to distribute the electrolytic solution constantly
and to prevent local current constriction on the aluminum plate 416 in the anodic
oxidation treatment tank 414, the solution supply nozzles 436 and 438 are provided
with slits and are thereby configured to stabilize the squirted solutions in the width
direction.
[0202] In the anodic oxidation treatment tank 414, a shielding plate 440 is provided on
an opposite side of the cathodes 430 across the aluminum plate 416. The shielding
plate 440 suppresses the current to flow on an opposite side to the surface on which
the anodized film is to be formed. Clearance between the aluminum plate 416 and the
shielding plate 440 is preferably in a range of 5 to 30 mm. It is preferable to use
a plurality of direct current power sources 434 while connecting the positive terminals
together. In this way, it is possible to control the current distribution in the anodic
oxidation treatment tank 414.
<Sealing treatment>
[0203] In the present invention, it is possible to carry out a sealing treatment for sealing
the micropores which exist on the anodized film when appropriate. The sealing treatment
can be carried out in accordance with publicly known methods such as a boiling water
treatment, a hot water treatment, a steam treatment, a sodium silicate treatment,
a nitrite treatment, or an ammonium acetate treatment. For example, it is possible
to carry out the sealing treatment by use of apparatuses and methods disclosed in
JP 56-12518 B,
JP 4-4194 A,
JP 5-202496 A,
JP 5-179482 A, and the like.
<Hydrophilic treatment>
[0204] A hydrophilic treatment may be carried out after the anodic oxidation treatment or
the sealing treatment. The hydrophilic treatment may be a potassium fluorozirconate
treatment disclosed in
US 2946638 A, a phosphomolybdate treatment disclosed in
US 3201247 A, an alkyl titanate treatment disclosed in
GB 1108559 B, a polyacrylic acid treatment disclosed in
DE 1091433 B, a polyvinyl phosphonic acid treatment disclosed in
DE 1134093 B and in
GB 1230447 B, a phosphonic acid treatment disclosed in
JP 44-6409 B, a phytic acid treatment disclosed in
US 3307951, a treatment using a lipophilic polymer compound and a bivalent metal salt disclosed
in
JP 58-16893 and
JP 58-18291, a treatment of providing an undercoating layer of hydrophilic cellulose (such as
carboxymethylcellulose) containing a water-soluble metal salt (such as zinc acetate)
as disclosed in
US 3860426, and a treatment of undercoating a water-soluble polymer having a sulfo group disclosed
in
JP 59-101651 A.
[0205] It is also possible to perform an undercoating treatment using any of a phosphate
disclosed in
JP 62-019494 A, a water-soluble epoxy compound disclosed in
JP 62-033692 A, phosphate-modified starch disclosed in
JP 62-097892 A, a diamine compound disclosed in
JP 63-056498 A, an inorganic or organic amino acid disclosed in
JP 63-130391 A, an organic phosphonic acid containing a carboxy group or a hydroxyl group disclosed
in
JP 63-145092 A, a compound having an amino group and a phosphonic acid group disclosed in
JP 63-165183 A,
a specific carbonic acid derivative disclosed in
JP 2-316290 A, a phosphate ester disclosed in
JP 3-215095 A, a compound having one amino group and one phosphorous oxyacid group disclosed in
JP 3-261592 A, an aliphatic or aromatic phosphonic acid such as phenylphosphonic acid disclosed
in
JP 5-246171 A, a compound having a S atom such as thiosalicylic acid disclosed in
JP 1-307745 A, a compound having a phosphorous oxyacid group disclosed in
JP 4-282637 A, and the like.
[0206] In addition, it is also possible to perform coloring by use of an acidic dye disclosed
in
JP 60-64352 A.
[0207] Moreover, it is preferable to perform the hydrophilic treatment in accordance with
a method of dipping the aluminum plate in an aqueous solution of an alkali metal silicate
such as sodium silicate or potassium silicate, a method of forming a hydrophilic undercoating
layer by coating either a hydrophilic vinyl polymer or a hydrophilic compound, or
the like.
[0208] The hydrophilic treatment using an aqueous solution of an alkali metal silicate such
as sodium silicate or potassium silicate can be performed in accordance with methods
and procedures disclosed in
US 2714066 and
US 3181461.
[0209] The alkali metal silicate may be sodium silicate, potassium silicate, and lithium
silicate, for example. The aqueous solution of the alkali metal silicate may contain
an appropriate amount of sodium hydroxide, potassium hydroxide, lithium hydroxide,
and the like.
[0210] Meanwhile, the aqueous solution of the alkali metal silicate may contain an alkali
earth metal salt or a Group 4 (Group IVA) metal salt. The alkali earth metal salt
may be: a nitrate such as calcium nitrate, strontium nitrate, magnesium nitrate, barium
nitrate; a sulfate; a hydrochloride; a phosphate; an acetate; an oxalate; a borate,
for example. The Group 4 (Group IVA) metal salt may be titanium tetrachloride, titanium
trichloride, potassium fluorotitanate, potassium titanium oxalate, titanium sulfate,
titanium tetraiodide, zirconium oxychloride, zirconium dioxide, and zirconium tetrachloride,
for example. These alkali earth metal salts and the Group 4 (Group IVA) metal salts
are used either singly or in a combination of two or more types.
[0211] The Si amount adsorbed by the alkali metal silicate treatment can be measured by
use of an x-ray fluorescence spectrometer, and such an adsorption amount is preferably
in a range of about 1.0 to 15.0 mg/m
2.
[0212] By performing the alkali metal silicate treatment, it is possible to obtain an effect
of improving dissolution resistance of the surface of the support for a lithographic
printing plate to an alkaline developer, and to suppress dissolution of the aluminum
component in the developer. Accordingly, it is possible to reduce generation of development
scum attributable to fatigue of the developer.
[0213] Meanwhile, the hydrophilic treatment by forming the hydrophilic undercoating layer
can be performed in accordance with conditions and procedures disclosed in
JP 59-101651 A and
JP 60-149491 A.
[0214] The hydrophilic vinyl polymer to be used in this method may be polyvinylsulfonic
acid, and a copolymer compound of a vinyl polymer compound having a sulfo group such
as p-styrene sulfonic acid and a normal vinyl polymer compound such as (meta)acrylate
alkyl ester, for example. Meanwhile, the hydrophilic compound to be used in this method
may be a compound including at least any one of the group consisting of a -NH
2 group, a -COOH group, and a sulfo group, for example.
<Drying>
[0215] After the support for a lithographic printing plate is obtained as described above,
it is preferable to dry the surface of the support for a lithographic printing plate
before providing the image recording layer. It is preferable to perform drying after
completing the final process of the surface treatment, the water washing treatment,
and draining with the nip roller.
[0216] Temperature for drying is preferably equal to or above 70°C, or more preferably equal
to or above 80°C. Meanwhile, the temperature is preferably equal to or below 110°C,
or more preferably equal to or below 100°C.
[0217] The drying time is preferably equal to or above 1 second or more preferably equal
to or above 2 seconds. Meanwhile, the drying time is preferably equal to or below
20 seconds, or more preferably equal to or below 15 seconds.
<Management of compositions of solutions>
[0218] In the present invention, the compositions of the respective treatment solutions
used in the above-described surface treatment are preferably managed by a method disclosed
in
JP 2001-121837 A. It is preferable to prepare multiple samples of the treatment solutions in various
concentrations in advance, to measure the propagation velocity of ultrasonic waves
regarding two levels of temperature of the respective solutions, and to produce a
matrix data table. Moreover, during the treatments, it is preferable to measure the
temperature of the solutions and the propagation velocity of ultrasonic waves in real
time, and to control the concentrations based on the measurement results. Particularly,
when the electrolytic solution having the sulfuric acid concentration equal to or
above 250 g/L is used in the desmutting treatment, it is preferable to control the
concentration according to the above-described method.
[0219] Here, it is preferable that the respective electrolytic solutions used in the electrolytic
surface roughening treatments and in the anodic oxidation treatment have a Cu concentration
equal to or below 100 ppm. When the Cu content is too high, Cu is deposited on the
aluminum plate when a production line is stopped. In this case, the deposited Cu is
transferred to the path rollers when the production line is restarted and may cause
uneven treatments.
(Presensitized plate)
[0220] The support for a lithographic printing plate obtained by the present invention can
be formed into a presensitized plate of the present invention by providing the image
recording layer. A photosensitive composition is used in the image recording layer.
[0221] The photosensitive composition suitable for use in the present invention may be a
thermal positive photosensitive composition containing an alkali-soluble polymer compound
and a photothermal conversion material (this composition and an image recording layer
using this composition will be hereinafter referred to as a "thermal positive type"),
a thermal negative photosensitive composition containing a setting compound and a
photothermal conversion material (hereinafter similarly referred to as a "thermal
negative type"), a photopolymerization type photosensitive composition (hereinafter
similarly referred to as a "photopolymer type"), a negative photosensitive composition
containing diazo resin or a photocrosslinkable resin (hereinafter similarly referred
to as a "conventional negative type"), a positive photosensitive composition containing
a quinone diazide compound (hereinafter similarly referred to as a "conventional positive
type"), and a photosensitive composition which does not require a special developing
process (hereinafter similarly referred to as a "non-treatment type"), for example.
Now, these suitable photosensitive compositions will be described below.
<Thermal positive type>
<Photosensitive layer>
[0222] The thermal positive type photosensitive composition contains an alkali-soluble polymer
compound and a photothermal conversion material. On the image recording layer of the
thermal positive type, the photothermal conversion material converts light energy
as from an infrared laser into heat, and the heat efficiently cancels an interaction
which is reducing alkali solubility of the alkali-soluble polymer compound.
[0223] The alkali-soluble polymer compound may be resin having an acidic group in the molecule
thereof, and a mixture of two or more types of such resin, for example. Particularly,
it is preferable to use resin having an acidic group such as a phenolic hydroxy group,
a sulfonamide group (-SO
2NH-R (R in the formula represents a hydrocarbon group)), or an active imino group
(-SO
2NHCOR, - SO
2NHSO
2R, or -CONHSO
2R (R in the respective formulae is as defined above)), for example, in light of solubility
to the alkaline developer.
[0224] Among these materials, the resin having a phenolic hydroxy group is preferred in
light of excellent image formation property by exposure to the light as from an infrared
laser. The suitable resin having a phenolic hydroxy group may be novolac resin such
as phenol formaldehyde resin, m-cresol formaldehyde resin, p-cresol formaldehyde resin,
or m-/p-mixed cresol formaldehyde resin, phenol/cresol-mixed (any of m-, p-, and m-/p-mixed
types are acceptable) formaldehyde resin (phenol-cresol-formaldehyde cocondensed resin).
[0225] In addition, a polymer compound disclosed in
JP 2001-305722 A (paragraph numbers from [0023] to [0042], in particular), a polymer compound disclosed
in
JP 2001-215693 A which has a repeating unit expressed by a general formula (1), and a polymer compound
disclosed in
JP 2002-311570 A (paragraph number [0107], in particular)are also suitable.
[0226] In light of recording sensitivity, the suitable examples of the photothermal conversion
material include pigments and dyes having a light absorption range in the infrared
wavelength range of 700 to 1200 nm. The preferable dyes may include a azo dye, a metal
complex salt azo dye, a pyrazolone azo dye, a naphthoquinone dye, an anthraquinone
dye, a phthalocyanine dye, a carbonium dye, a quinoneimine dye, a methine dye, a cyanine
dye, a squalirium dye, a pyrilium salt, and a metal thiolate complex (such as nickel
thiolate complex). Among these materials, a cyanine dye is particularly preferred.
More specifically, a cyanine dye expressed by a general formula (I) in
JP 2001-305722 A is preferred.
[0227] The thermal positive type photosensitive composition may contain a dissolution blocker.
The preferable dissolution blockers may include those disclosed in paragraph numbers
from [0053] to [0055] in
JP 2001-305722 A, for example.
[0228] Moreover, it is preferable that the thermal positive type photosensitive composition
contain additives including a sensitivity adjuster, a printing agent for obtaining
a visible image immediately after heating by light exposure, a compound such as a
dye as an image coloring agent, and a surfactant for improving a coating property
and treatment stability. As for these additives, compounds disclosed in paragraph
numbers from [0056] to [0060] in
JP 2001-305722 A are preferred.
[0229] The photosensitive compositions described in detail in
JP 2001-305722 A are preferably used for other purposes as well.
[0230] Moreover, the image recording layer of the thermal positive type is not limited to
a single layer type, and a two-layer type structure is also applicable.
[0231] A preferable image recording layer of a two-layer structure (a duplex type image
recording layer) is a type in which a lower layer having excellent press life and
solvent resistance (hereinafter referred to a "layer A") is provided on a side close
to the support and a layer having an excellent positive image formation property (hereinafter
referred to as a "layer B") is provided thereon. This type has high sensitivity and
can therefore achieve wide development latitude. The layer B generally includes a
photothermal conversion material. The aforementioned dyes are suitable for the photothermal
conversion material.
[0232] As for the resin to be used in the layer A, a polymer containing a monomer having
a sulfonamide group, an active imino group, a phenol hydroxy group or the like as
a copolymer component is preferred in terms of excellent press life and solvent resistance.
As for the resin to be used in the layer B, a resin soluble to an alkaline aqueous
solution and having a phenolic hydroxy group is preferred.
[0233] In addition to the above-described resin, the compositions used in the layer A and
the layer B may contain other various additives when appropriate. To be more precise,
various additives disclosed in paragraph numbers from [0062] to [0085] in
JP 2000-3233769 A are preferably used. Moreover, the above-described additives disclosed in the paragraph
numbers from [0053] to [0060] in
JP 2001-305722 A are preferably used as well.
[0234] The respective components constituting the layer A and the layer B, and the contents
thereof are preferably controlled as disclosed in
JP 11-218914 A.
<Intermediate layer>
[0235] It is preferable to provide an intermediate layer between the image recording layer
of the thermal positive type and the support. As the components to be contained in
the intermediate layer, it is preferable to use various organic compounds disclosed
in paragraph number [0068] in
JP 2001-305722 A.
<Others>
[0236] As a method of manufacturing the image recording layer of the thermal positive type
and a plate making method, it is possible to use methods described in detail in
JP 2001-305722 A.
<Thermal negative type>
[0237] The thermal negative type photosensitive composition contains a setting compound
and a photothermal conversion material. The image recording layer of the thermal negative
type is a negative photosensitive layer in which a portion irradiated with light such
as infrared laser light is cured to form an image area.
<Polymerization layer>
[0238] One preferable image recording layer of the thermal negative type is a polymerization
type image recording layer (a polymerization layer). The polymerization layer contains
the photothermal conversion material, a radical generator, a radical polymerizable
compound which is a setting compound, and a binder polymer. In the polymerization
layer, the photothermal conversion material converts the absorbed infrared rays into
heat, then the heat decomposes the radical generator to generate a radical, and the
radical polymerizable compound is put into a chain reaction by the generated radical
and is thereby cured.
[0239] The photothermal conversion material may be the photothermal conversion material
to be used in the above-described thermal positive type, for example. Particularly
preferable examples of the cyanine dyes are disclosed in paragraph numbers from [0017]
to [0019] in
JP 2001-133969 A.
[0240] Onium salt is preferred as the radical generator. Particularly, onium salt disclosed
in paragraph numbers from [0030] to [0033] in
JP 2001-133969 A are preferred.
[0241] The radical polymerizable compound may be a compound having at least one or preferably
two or more terminal ethylenically unsaturated bonds.
[0242] Linear organic polymers are preferred as the binder polymer. Specifically, linear
organic polymers having solubility or a swelling property with respect to water or
a weakly alkaline water are preferred. Among such polymers, (meta)acrylic resin with
a side chain having either an unsaturated group typified by an allyl group and an
acryloyl group or a benzyl group, and, a carboxy group, is preferred in light of an
excellent balance between film strength, sensitivity, and a development property.
[0243] Concerning the radical polymerizable compound and the binder polymer, it is possible
to use materials described in detail in paragraph numbers from [0036] to [0060] in
JP 2001-133969 A.
[0244] It is preferable that the thermal negative type photosensitive composition contain
additives (such as a surfactant for improving a coating property) disclosed in paragraph
numbers from [0061] to [0068] in
JP 2001-133969 A.
[0245] As a method of manufacturing the polymerization layer and a plate making method,
it is possible to use methods described in detail in
JP 2001-133969 A.
<Acid crosslink layer>
[0246] Moreover, an acid crosslink type image recording layer (an acid cross link layer)
is also preferred as another image recording layer of the thermal negative type. The
acid crosslink layer contains a photothermal conversion material, a thermal acid generator,
an acid-crosslinkable compound (a crosslinking agent) which is a setting compound,
and an alkali-soluble polymer compound which can react with the crosslinking agent
in the presence of acid. In the acid crosslink layer, the photothermal conversion
material converts the absorbed infrared rays into heat, then the heat decomposes the
thermal acid generator to generate an acid, and the generated acid causes a reaction
between the crosslinking agent and the alkali-soluble polymer compound for curing.
[0247] Those materials used in the polymerization layer may be used for the photothermal
conversion material.
[0248] The thermal acid generator may be a thermal decomposition compound such as a photoinitiator
for photopolymerization, a color-turning agent for pigments, or an acid generator
used for micro resist.
[0249] The crosslinking agent may be: an aromatic compound substituted by a hydroxymethyl
group or an alkoxymethyl group; a compound having an N-hydroxymethyl group, an N-alkoxymethyl
group or an N-acyloxymethyl group; and an epoxy compound, for example.
[0250] The alkali-soluble polymer compound may be novolac resin or a polymer with a side
chain having a hydroxyaryl group, for example.
<Photopolymer type>
[0251] The photopolymerization type photosensitive composition includes an addition polymerizable
compound, a photopolymerization initiator, and a high molecular weight binder.
[0252] The preferable addition polymerizable compound may be an ethylenically unsaturated
bond-containing compound which is addition polymerizable. The ethylenically unsaturated
bond-containing compound is a compound having a terminal ethylenically unsaturated
bond. To be more precise, the ethylenically unsaturated bond-containing compound has
various chemical aspects such as a monomer, a prepolymer, and a mixture thereof, for
example. The monomer may be an ester of an unsaturated carboxylic acid (such as acrylic
acid, methacrylic acid, itaconic acid or maleic acid) and an aliphatic polyvalent
amine compound, and an amide of an unsaturated carboxylic acid and an aliphatic polyvalent
amine compound.
[0253] Moreover, a urethane addition polymerizable compound is also preferred as the addition
polymerizable compound.
[0254] The photopolymerization initiator can be selected from among various photopolymerization
initiators or a combined system of two or more photopolymerization initiators (a photopolymerization
initiating system) as appropriate depending on a wavelength of a light source used.
For example, initiating systems disclosed in paragraph numbers from [0021] to [0023]
in
JP 2001-22079 A are preferred.
[0255] The high molecular weight binder is supposed not only to function as a film forming
agent for the photopolymerization type photosensitive composition but also to dissolve
the image recording layer in the alkaline developer. Accordingly, an organic high
molecular weight polymer having solubility or a swelling property with respect to
an alkaline water is used therein. As the organic high molecular weight polymer, materials
disclosed in paragraph numbers from [0036] to [0063] in
JP 2001-22079 A are preferred.
[0256] It is preferable that the photopolymerization type photosensitive composition of
the photopolymer type contain additives (including a surfactant for improving a coating
property, a colorant, a plasticizer, and a thermal polymerization inhibitor, for example)
disclosed in paragraph numbers from [0079] to [0088] in
JP 2001-22079.
[0257] Moreover, it is preferable to provide an oxygen impermeable protection layer on the
image recording layer of the photopolymer type in order to prevent a polymerization
inhibition effect of oxygen. A polymer to be contained in the oxygen impermeable protection
layer may be polyvinyl alcohol and a copolymer thereof, for example.
[0258] In addition, it is also preferable to provide an intermediate layer or an adhesive
layer as disclosed in paragraph numbers from [0124] to [0165] in
JP 2001-228608.
<Conventional negative type>
[0259] The photosensitive composition of the conventional negative type contains diazo resin
or photocrosslinkable resin. In particular, a photosensitive composition containing
diazo resin and a polymer (a binder) having solubility or a swelling property with
respect to an alkali is preferred.
[0260] The diazo resin may be: a condensate of an aromatic diazonium salt and an active
carbonyl group-containing compound such as formaldehyde; and an organic solvent-soluble
diazo resin inorganic salt which is a reaction product between a condensate of a p-diazophenylamine
and formaldehyde, and, any of a hexafluorophosphate salt or a tetrafluoroborate salt,
for example. Particularly, a high molecular weight diazo compound containing not less
than 20 mol% of a hexamer or larger as disclosed in
JP 59-78340 A is preferred.
[0261] The binder may be a copolymer which contains any of acrylic acid, methacrylic acid,
crotonic acid, and maleic acid as an essential component, for example. To be more
precise, the binder may be a multi-copolymer of monomers such as 2-hydroxyethyl (meta)acrylate,
(meta)acrylonitrile or (meta)acrylic acid as disclosed in
JP 50-118802 A, or a multi-copolymer including alkyl acrylate, (meta)acrylonitrile, and an unsaturated
carboxylic acid as disclosed in
JP 56-4144 A.
[0262] It is preferable that the photosensitive composition of the conventional negative
type contain compounds disclosed in paragraph numbers from [0014] to [0015] in
JP 7-281425 A such as a printing agent, a dye, a plasticizer for providing the coating with flexibility
and abrasion resistance or a development accelerator, and a surfactant for improving
a coating property, as additives.
[0263] Below the photosensitive layer of the conventional negative type, it is preferable
to provide an intermediate layer disclosed in
JP 2000-105462 A, which contains a polymer compound including a constituent having an acid radical
and a constituent having an onium group.
<Conventional positive type>
[0264] The photosensitive composition of the conventional positive type contains a quinone
diazide compound. In particular, a photosensitive composition containing an o-quinone
diazide compound and an alkali-soluble polymer compound is preferred.
[0265] The o-quinone diazide compound may be an ester of 1,2-naphtoquinone-2-diazide-5-sulfonyl
chloride and any of phenol-formaldehyde resin and cresol-formaldehyde resin, or an
ester of 1,2-naphtoquinone-2-diazide-5-sulfonyl chloride and pyrogallol-acetone resin
disclosed in
US 3635709, for example.
[0266] The alkali-soluble polymer compound may be phenol-formaldehyde resin, cresol-formaldehyde
resin, phenolcresol-formaldehyde cocondensed resin, polyhydroxystyrene, an N-(4-hydroxyphenyl)methacrylamide
copolymer, a carboxy group-containing polymer disclosed in
JP 7-36184 A, phenolic hydroxy group-containing acrylic resin disclosed in
JP 51-34711 A, sulfonamide group-containing acrylic resin disclosed in
JP 2-866 A, or urethane resin, for example.
[0267] It is preferable that the photosensitive composition of the conventional positive
type contain compounds disclosed in paragraph numbers from [0024] to [0027] in
JP 7-92660 A such as a sensitivity adjuster, a printing agent or a dye, and a surfactant disclosed
in paragraph number [0031] in
JP 7-92660 A for improving a coating property, as additives.
[0268] Below the photosensitive layer of the conventional positive type, it is preferable
to provide an intermediate layer which is similar to the above-described intermediate
layer preferably used in the conventional negative type.
<Non-treatment type>
[0269] The photosensitive composition of the non-treatment type includes thermoplastic fine-particle
polymer type, a microcapsule type, a sulfonic acid generating polymer containing type.
All of these are included in the thermosensitive type containing the photothermal
conversion material. It is preferable that the photothermal conversion material be
a dye similar to the one used in the above-described thermal positive type.
[0270] The photosensitive composition of the thermoplastic fine-particle polymer type is
formed by dispersing a hydrophobic and thermofusible fine-particle polymer in a hydrophilic
polymer matrix. On an image recording layer of the thermoplastic fine-particle polymer
type, hydrophobic polymer fine particles are fused by heat generated through light
exposure and bond together to form a hydrophobic area, namely, the image area.
[0271] As for the fine particle polymer, it is preferable that the fine particles be fused
by heat to cohere and have a hydrophilic surface so that the polymer can be disposed
in a hydrophilic component such as a fountain solution. To be more precise, thermoplastic
fine-particle polymers disclosed in Research Disclosure No. 33303 (January 1992),
JP 9-123387 A,
JP 9-131850 A,
JP 9-171249 A,
JP 9-171250 A,
EP 931647 A, and the like are preferred. Among these polymers, polystyrene and methyl polymethacrylate
are preferred. The fine-particle polymer having the hydrophilic surface may be: a
polymer which is hydrophilic by nature; a fine-particle polymer modified to be hydrophilic
by attaching a hydrophilic compound such as polyvinyl alcohol or polyethylene glycol
onto a surface thereof, for example.
[0272] It is preferable that the fine-particle polymer has a reactive functional group.
[0273] Preferable photosensitive compositions of the microcapsule type include a composition
as disclosed in
JP 2000-118160 A and a composition of the microcapsule type that includes a compound having a heat-reactive
functional group as disclosed in
JP 2001-277740 A.
[0274] The sulfonic acid generating polymer used in the photosensitive composition of the
sulfonic acid generating polymer containing type may be a polymer with a side chain
having any of a sulfonic ester group, disulfone group, and sec- or tert-sulfonamide
group as disclosed in
JP 10-282672 A, for example.
[0275] By combining hydrophilic resin with the photosensitive composition of the non-treatment
type, the development property on a printing machine is improved; and moreover, film
strength of the photosensitive layer is also enhanced. As for the hydrophilic resin,
it is preferable to use resin having a hydrophilic group such as a hydroxy group,
a carboxy group, hydroxyethyl group, a hydroxypropyl group, an amino group, an aminoethyl
group, an aminopropyl group or a carboxymethyl group, or sol-gel conversion binder
resin, for example.
[0276] The image recording layer of the non-treatment type can be developed on a printing
machine without requiring a special developing process. As a method of manufacturing
the image recording layer of the non-treatment type and a plate making method, it
is possible to use methods described in detail in
JP 2002-178655 A.
<Back coating>
[0277] It is possible to provide a covering layer made of an organic polymer on a rear surface
of the presensitized plate of the present invention obtained by providing a variety
of image recording layers on the support for a lithographic printing plate of the
present invention as appropriate, in order to prevent scratches on the image recording
layer which may be caused by stacking.
(Plate making method (method of manufacturing lithographic printing plate))
[0278] The presensitized plate using the support for a lithographic printing plate obtained
by the present invention will be further formed into a lithographic printing plate
in accordance with various treatment methods depending on the image recording layer.
[0279] A light source for an active light beam for use in image exposure may be a mercury
lamp, a metal halide lamp, a xenon lamp, or a chemical lamp, for example. A laser
beam may be a helium-neon laser (a He-Ne laser), an argon laser, a krypton laser,
a helium-cadmium laser, a KrF excimer laser, a semiconductor laser, an yttrium-aluminum-garnet
(YAG) laser, or an yttrium-aluminum-garnet second-harmonic-generation (YAG-SHG) laser,
for example.
[0280] When the image recording layer is any of the thermal positive type, the thermal negative
type, the conventional negative type, the conventional positive type, and the photopolymer
type, it is preferable to obtain the lithographic printing plate by developing the
image recording layer using a developer after the light exposure.
[0281] The developer is preferably an alkaline developer or more preferably an alkaline
aqueous solution which substantially contains no organic solvent.
[0282] Moreover, a developer which substantially contains no alkali metal silicate is also
preferred. As a developing method using a developer substantially containing no alkali
metal silicate, it is possible to use a method described in detail in
JP 11-109637.
[0283] It is also possible to use a developer which contains an alkali metal silicate.
EXAMPLES
[0284] The present invention will be described in further detail by the following examples.
(Examples 1 to 12, Comparative Examples 1 to 3)
(1) (Relation between solid solution amounts of alloy elements and electrolytically
roughened surfaces)
[0285] Aluminum materials having compositions shown in Table 1 were subjected to heat treatments
shown respectively in Tables 2, 3, and 4 to adjust solid solution amounts of Fe, Si,
and Cu. Alloy blanks of the present invention and alloy blanks of Comparative Examples
were manufactured. Then, the alloy blanks were subjected to the following surface
treatments to obtain aluminum supports for a lithographic printing plate. Thereafter,
uniformity of an electrolytically roughened surface of every alloy plate was evaluated.
[0286] Table 1 shows chemical compositions of various alloys of the present invention and
various alloys for comparison used in this test.
Table 1
Composition |
Si
(wt%) |
Fe
(wt%) |
Cu
(wt%) |
Ti
(wt%) |
Others
total
(wt%) |
Balance |
Al-1 |
0.09 |
0.3 |
0.001 |
0.005 |
0.05 |
Al |
Al-2 |
0.04 |
0.3 |
0.010 |
0.005 |
0.05 |
Al |
Al-3 |
0.04 |
0.8 |
0.010 |
0.005 |
0.05 |
Al |
Al-4 |
0.04 |
1.0 |
0.010 |
0.005 |
0.05 |
Al |
Al-5 |
0.03 |
0.3 |
0.005 |
0.01 |
0.05 |
Al |
Al-6 |
0.03 |
0.3 |
0.015 |
0.01 |
0.05 |
Al |
Al-7 |
0.03 |
0.3 |
0.027 |
0.01 |
0.05 |
Al |
Al-8 |
0.03 |
0.3 |
0.05 |
0.01 |
0.05 |
Al |
Al-9 |
0.03 |
0.3 |
0.06 |
0.01 |
0.05 |
Al |
Al-10 |
0.06 |
0.3 |
0.002 |
0.015 |
0.05 |
Al |
Al-11 |
0.10 |
0.3 |
0.010 |
0.015 |
0.05 |
Al |
Al-12 |
0.08 |
0.3 |
0.025 |
0.015 |
0.05 |
Al |
<Surface treatment: when performing electrolytic surface roughening under electrolytic
surface roughening condition I>
(a) Alkaline etching
[0287] An etching treatment was carried out by spraying an aqueous solution adjusted to
a caustic soda concentration of 25 wt%, an aluminum ion concentration of 100 g/L,
and temperature of 60°C from the spray tubes onto the aluminum plate. An etching amount
on a surface of the aluminum plate to be subjected to an electrochemical surface roughening
treatment was 5 g/m
2.
(b) Desmutting treatment
[0288] A desmutting treatment was carried out by spraying 1-wt% nitric acid aqueous solution
at temperature of 35°C from the spray tubes for 5 seconds.
(c) Electrolytic surface roughening treatment under electrolytic surface roughening
condition I Electrochemical surface roughening treatment using alternating current
in nitric acid aqueous solution (first electrolytic treatment)
[0289] Then, an electrochemical surface roughening treatment was continuously carried out
by use of an electrolytic solution (temperature at 50°C) adjusted to the aluminum
ion concentration of 4.5 g/L by dissolving aluminum nitrate in the 1-wt% nitric acid
aqueous solution, and by use of an alternating current voltage at 60 Hz. The electrolytic
current waveform is shown in Fig. 1, in which the time (TP) consumed by the current
value to reach from zero to a peak was 0.8 msec., and the duty ratio (ta/T, a ratio
of anodic reaction time in one cycle) was 0.5. A carbon electrode was used as a counter
electrode. Ferrite was used for the auxiliary anodes. Two tanks were used as the electrolytic
tanks as shown in Fig. 2.
[0290] In the electrochemical surface roughening treatment, current density of the aluminum
plate in the course of the anodic reaction at the peak of the alternating current
was 60 A/dm
2. A ratio between a total quantity of electricity at the anodic reaction and a total
quantity of electricity at the cathodic reaction of the aluminum plate was 0.95. The
total quantity of electricity at the anodic reaction of the aluminum plate was 190
C/dm
2. 5% of the current flowing from the power source was shunted to the auxiliary anodes.
A relative velocity between the aluminum plate and the electrolytic solution was 1.5
m/sec on an average inside the electrolytic tanks.
(d) Alkaline etching
[0291] An etching treatment was carried out by spraying an aqueous solution adjusted to
a caustic soda concentration of 5 wt%, an aluminum ion concentration of 5 g/L, and
temperature of 35°C from the spray tubes onto the aluminum plate. An etching amount
on the surface of the aluminum plate subjected to the electrochemical surface roughening
treatment was 0.1 g/m
2.
(e) Desmutting treatment
[0292] A desmutting treatment was carried out by spraying an aqueous solution having a sulfuric
acid concentration of 300 g/L, an aluminum ion concentration of 5 g/L, and temperature
of 35°C from the spray tubes for 5 seconds.
(f) The water washing treatment was carried out between the above-described respective
treatments.
[0293] The solid solution amounts and uniformity of the electrolytically roughened surfaces
of the obtained supports were measured in accordance with the conditions described
below. Results are shown in Tables 2, 3, and 4.
<Evaluation of the uniformity of the electrolytically roughened surfaces>
[0294] The surfaces after the electrolytic surface roughening treatments were observed (at
2000-fold magnification) with a scanning electron microscope (SEM: 5500 made by JEOL
Ltd.) to evaluate graining uniformity. Results are shown in Tables 2 to 6 and 8.
- A: round pits accounted for 90% or above
- B: round pits accounted for a range equal to or above 50% but below 90%
- C: round pits accounted for a range equal to or above 10% but below 50%
- D: round pits accounted for less than 10%
<Measurement of solid solution amounts and uniformity>
[0295] Relations between the solid solution amounts of the alloy elements and the uniformity
of the electrolytically roughened surfaces were compared between the alloy blanks
of the present invention and the alloy blanks of the comparative examples as obtained
by the above-described processes.
<Measurement of solid solution amounts of Fe, Si, and Cu>
[0296] The solid solution amounts were measured in accordance with the phenol dissolution
and extraction method. Samples were dissolved in heated phenol and then benzyl alcohol
was added thereto. Intermetallic compound residues were filtered out from the samples
by use of a polytetrafluoroethylene filter. After dilution with benzyl alcohol, Fe,
Si, and Cu contained in the solution were extracted and the solid solution amounts
thereof were measured by the standard addition inductively coupled plasma (ICP) emission
spectrometry.
<Surface treatment: when performing electrolytic surface roughening under electrolytic
surface roughening condition II>
[0297] The blanks obtained in the same manner were subjected to brush graining in slurry
of pumice stone (grain size 30 µm (median diameter) / water (specific gravity 1.5),
and then to (a) the alkaline etching (amount of aluminum dissolved: 0.3 g/m
2) and (b) the desmutting treatment (1% nitric acid solution, 30°C, 10 seconds). Thereafter,
the electrolytic surface roughening treatment was carried out in the 1% nitric acid
by use of a power source having a polarity-alternating electrolytic waveform so that
the amount of electricity at the anodic reaction can be 190 c/dm
2. After washing in sulfuric acid (sulfuric acid concentration 300 g/L, 60°C, 3 seconds),
the uniformity of electrolytically roughened surfaces were measured in the same manner.
<Evaluation of uniformity of electrolytically roughened surfaces>
[0298] The uniformity of the electrolytically roughened surfaces were evaluated in the same
method as that applied to the supports obtained by the surface treatment when performing
the electrolytic surface roughening under the electrolytic surface roughening condition
I. Results are shown in Tables 2 to 4. In the Tables, a column Condition I shows the
case in which the surface treatment including the electrolytic surface roughening
treatment I is performed, and a column Condition II shows the case in which the surface
treatment including the electrolytic surface roughening treatment II is performed.
Table 2
|
Al
composition |
Si solid solution amount
(ppm) |
Uniformity of electrolytically roughened surface |
Heat treatment condition |
Condition I |
Condition II |
Example 1 |
Al-1 |
150 |
C |
C |
330°C × 10 hr. |
Example 2 |
Al-1 |
200 |
B, C |
B, C |
400°C × 10 hr. |
Example 3 |
Al-1 |
800 |
B |
B |
550°C × 10 hr. |
Comparative
Example 1 |
Al-1 |
100 |
D |
D |
280°C × 10 hr. |
Table 3
|
Al
composition |
Fe solid solution amount
(ppm) |
Si solid solution amount
(ppm) |
Uniformity of electrolytically roughened surface |
Heat treatment condition |
Condition I |
Condition II |
Example 4* |
Al-2 |
200 |
150 |
C |
C |
350°C × 10 hr. |
Example 5 |
Al-2 |
300 |
150 |
B |
8 |
400°C × 10 hr. |
Example 6 |
Al-2 |
500 |
150 |
B |
B |
450°C × 10 hr. |
Example 7 |
Al-3 |
1300 |
150 |
B |
B |
500*C × 10 hr. |
Example 8 |
Al-3 |
4000 |
150 |
C |
C |
550°C × 20 hr. |
Comparative
Example 2 |
Al-4 |
5000 |
150 |
D |
D |
550°C × 20 hr. |
* Reference Example, outside the scope of invention |
Table 4
|
Al
composition |
Cu solid solution amount
(ppm) |
Si solid solution amount
(ppm) |
Uniformity of electrolytically roughened surface |
Heat treatment condition |
Condition I |
Condition II |
Example 9* |
Al-5 |
50 |
150 |
C |
C |
400°C × 10 hr. |
Example 10 |
Al-6 |
120 |
150 |
B |
B |
400°C × 10 hr. |
Example 11 |
Al-7 |
250 |
150 |
B |
B |
400°C × 10 hr. |
Example 12 |
Al-8 |
450 |
150 |
C |
C |
400°C × 10 hr. |
Comparative
Example 3 |
Al-9 |
550 |
150 |
D |
D |
400°C × 10 hr. |
* Reference Example, outside the scope of invention |
(Examples 13 to 17, Comparative Examples 4 and 5)
(2) (Relation between specific resistance and electrolytically roughened surfaces)
[0299] The aluminum materials having the composition Al-10 shown in Table 1 were subjected
to heat treatments shown in Table 5 to adjust the Si solid solution amounts. Then,
aluminum supports for a lithographic printing plate were obtained by carrying out
the surface treatment including the above-described electrolytic surface roughening
treatment I. Thereafter, specific resistance and uniformity of the electrolytically
roughened surfaces were evaluated as shown in Table 5.
Measurement condition of specific resistance
[0300] Specific resistance of each sample of the aluminum support for a lithographic printing
plate subjected to the surface treatment was measured under liquid nitrogen condition.
Table 5
|
Al
composition |
Si solid solution amount
(ppm) |
Specific resistance
(µΩmm) |
Uniformity of electrolytically roughened surface |
Heat treatment condition |
Example 13 |
Al-10 |
150 |
3.5 |
C |
300°C × 10 hr. |
Example 14 |
Al-10 |
150 |
4.0 |
B, C |
400°C × 10 hr. |
Example 15 |
Al-10 |
150 |
5.0 |
B |
480°C × 10 hr. |
Example 16 |
Al-10 |
200 |
6.0 |
B |
520°C × 10 hr. |
Example 17 |
Al-10 |
800 |
6.5 |
C |
560°C × 10 hr. |
Comparative
Example 4 |
Al-10 |
120 |
3.0 |
D |
280°C × 10 hr. |
Comparative
Example 5 |
Al-10 |
100 |
7.0 |
D |
600°C × 5 hr. |
(Example 18, Comparative Example 6)
(3) (Solid solution amounts of alloy elements and visibility of woodgrain patterns
on rear surfaces)
[0301] The aluminum materials having the composition Al-1 shown in Table 1 were subjected
to heat treatments shown in Table 6 to adjust the Si solid solution amounts. Then,
aluminum supports for a lithographic printing plate were obtained by carrying out
the surface treatment described below. Thereafter, the Si solid solution amounts,
uniformity of the electrolytically roughened surfaces, and visibility of woodgrain
patterns on rear surfaces were evaluated as shown in Table 6.
<Surface treatment>
[0302] The surface treatment including the above-described electrolytic surface roughening
treatment II was repeated except that (g) alkaline etching of the rear surface under
the following conditions was carried out between (a) the alkaline etching and (b)
the desmutting treatment.
(g) Alkaline etching of rear surface
[0303] An etching treatment was carried out by spraying an aqueous solution adjusted to
a caustic soda concentration of 25 wt%, an aluminum ion concentration of 100 g/L,
and temperature of 60°C from the spray tubes onto the rear surface of the aluminum
plate. An etching amount on the surface was 3 g/m
2.
Evaluation of visibility of woodgrain patterns on rear surfaces
[0304]
- A: fine (patterns visible)
- B: faint (acceptable)
- C: none (patterns not visible)
Table 6
|
Al
composition |
Si solid solution amount
(ppm) |
Uniformity of electrolytically roughened surface |
Visibility of woodgrain patterns on rear surface |
Heat treatment condition |
Example 18 |
Al-1 |
800 |
A |
A |
550°C × 10 hr. |
Comparative
Example 6 |
Al-1 |
100 |
C |
B |
280°C × 10 hr. |
(Examples 19 to 24, Comparative Examples 7 to 12)
(4) (Solid solution amounts of alloy elements, electrolytic surface roughening conditions,
and evaluation of printing performances)
[0305] The aluminum materials having the composition Al-11 shown in Table 1 were respectively
subjected to heat treatments and the solid solution amounts were adjusted and measured.
Then, aluminum supports for a lithographic printing plate were obtained by carrying
out the surface treatment described below. Thereafter, the thermal positive type image
recording layer described below was coated under the following conditions to form
the presensitized plates. After exposure, development, and printing, printing performances
(stain resistance) were evaluated as shown in Table 7.
<Surface treatment>
(a) Alkaline etching
[0306] An etching treatment was carried out by spraying an aqueous solution adjusted to
a caustic soda concentration of 25 wt%, an aluminum ion concentration of 100 g/L,
and temperature of 60°C from the spray tubes onto the aluminum plate. An etching amount
on a surface of the aluminum plate to be subjected to an electrochemical surface roughening
treatment was 6 g/m
2.
(b) Desmutting treatment
[0307] A desmutting treatment was carried out by spraying 1-wt% nitric acid aqueous solution
at temperature of 35°C from the spray tubes for 5 seconds.
(c) Electrolytic surface roughening treatment
[0308] An electrochemical surface roughening treatment was continuously carried out by use
of an electrolytic solution (temperature at 50°C) adjusted to the aluminum ion concentration
of 4.5 g/L by dissolving aluminum nitrate in the 1-wt% nitric acid aqueous solution,
and by use of an alternating current voltage at 60 Hz. The electrolytic current waveform
is shown in Fig. 1, in which the time (TP) consumed by the current value to reach
from zero to a peak was set to 0.8 msec., and the duty ratio (ta/T) was set to 0.5.
A carbon electrode was used as a counter electrode. Ferrite was used for the auxiliary
anodes. Two tanks were used as the electrolytic tanks as shown in Fig. 2.
[0309] In the electrochemical surface roughening treatment, current density of the aluminum
plate in the course of the anodic reaction at the peak of the alternating current
was varied as shown in Fig. 7. A ratio between a total quantity of electricity at
the anodic reaction and a total quantity of electricity at the cathodic reaction of
the aluminum plate was 0.95. The total quantity of electricity at the anodic reaction
of the aluminum plate was 250 C/dm
2. 5% of the current flowing from the power source was shunted to the auxiliary anodes.
A relative velocity between the aluminum plate and the electrolytic solution was 1.5
m/sec on an average inside the electrolytic tanks.
(d) Alkaline etching
[0310] An etching treatment was carried out by spraying an aqueous solution adjusted to
a caustic soda concentration of 5 wt%, an aluminum ion concentration of 5 g/L, and
temperature of 35°C from the spray tubes onto the aluminum plate. An etching amount
on the surface of the aluminum plate subjected to the electrochemical surface roughening
treatment was varied as shown in Fig. 7.
(e) Desmutting treatment
[0311] A desmutting treatment was carried out by spraying an aqueous solution having a sulfuric
acid concentration of 15 wt%, an aluminum ion concentration of 5 g/L, and temperature
of 35°C from the spray tubes for 5 seconds.
(h) Anodic oxidation treatment
[0312] An anodic oxidation treatment was carried out by use of the anodic oxidation apparatus
shown in Fig. 3.
[0313] An electrolytic solution (temperature at 33°C) adjusted to an aluminum ion concentration
of 5 g/L by dissolving aluminum sulfate in a 170-g/L sulfuric acid aqueous solution
was used. The anodic oxidation treatment was performed so as to obtain an average
current density of 15 A/dm
2 during the anodic reaction (about 16 seconds) of the aluminum plate. A final amount
of an oxide film was 2.4 g/m
2. Here, the time consumed for the anodic reaction of the aluminum plate was 16 seconds.
(i) Silicate treatment (hydrophilic treatment)
[0314] The aluminum plate was dipped in a 1-wt% No.3 sodium silicate aqueous solution (temperature
at 20°C) for 10 seconds. A Si amount on the surface of the aluminum plate was 3.5
mg/m
2 when measured by an x-ray fluorescence analyzer.
(f) The water washing treatment was carried out between the above-described respective
treatments.
<Production of presensitized plate>
[0315] An image recording layer of the thermal positive type described below was provided
to each support obtained by the foregoing processes to obtain a presensitized plate.
Here, an undercoating layer described below was provided before providing the image
recording layer.
[0316] The support for a lithographic printing plate was coated with an undercoating solution
having the following composition, which was then dried at 80 °C for 15 seconds to
form a coating film of the undercoating layer. A coverage amount of the coating film
after drying was 15 mg/m
2.
<Composition of undercoating solution>
[0317]
*polymer compound to be described below |
0.3 g |
|
*methanol |
100 g |
*water |
1 g |
[0318] Further, a heat-sensitive layer coating solution of the composition to be described
below was prepared. The support for a lithographic printing plate provided with the
undercoating layer was coated with the heat-sensitive coating solution so as to obtain
a coating amount (a heat-sensitive layer coating amount) of 1.8 g/m
2 after drying. The coating solution was then dried to from the heat-sensitive layer
(the image recording layer of the thermal positive type), and the presensitized plate
was thereby obtained.
<Composition of heat-sensitive layer coating solution>
[0319]
*novolac resin (m-cresol : p-cresol = 60 : 40, weight-average molecular weight 7000,
0.05 wt% unreacted cresol contained) |
0.90 g |
*ethyl metacrylate - isobutyl methacrylate - methacrylic acid copolymer (mole ratio
35 : 35 : 30) |
0.10 g |
*a cyanine dye A expressed by the following structural formula |
0.1 g |
|
|
*tetrahydrophthalic anhydride |
0.05 g |
*p-toluene sulfonic acid |
0.002 g |
*ethyl violet modified by replacing a counter ion with 6-hydroxy-β-naphthalene sulfonic
acid |
0.02 g |
*a fluorine-based surfactant (Defensa F-780F, made by Dainippon Ink and Chemicals,
solid content 30 wt%) |
0.0045 g (in solid content) |
*a fluorine-based surfactant (Defensa F-781F, made by Dainippon Ink and Chemicals,
solid content 100 wt%) |
0.035 g |
*methylethylketone |
12 g |
[0320] Images were formed on the obtained presensitized plates by use of Trendsetter made
by Creo Inc. under the conditions of a drum rotation speed of 150 rpm and a beam intensity
of 10 W.
[0321] Thereafter, the presensitized plates were developed for 20 seconds by PS Processor
940H available from Fuji Photo Film Co., Ltd. containing an alkaline developer having
the following composition while maintaining the developer at 30°C. Lithographic printing
plates were thus obtained.
<Composition of alkaline developer>
[0322]
*D-sorbit |
2.5 wt% |
*sodium hydroxide |
0.85 wt% |
*polyethyleneglycol lauryl ether (weight-average molecular weight 1000) |
0.5 wt% |
*water |
96.15 wt% |
Evaluation of printing performance (stain resistance)
[0323] The obtained lithographic printing plates were set on Mitsubishi DAIYA F2 Press (available
from Mitsubishi Heavy Industries, Ltd.) for printing by use of red ink DIC-GEOS (s).
After printing 10000 sheets, stains on each blanket were evaluated visually.
[0324] Results are shown in Table 7. Evaluation was based on the following criteria.
- A: no stains on the blanket
- B: very few stains on the blanket
- C: a few stains on the blanket
- D: the blanket is stained but is still acceptable
- E: the blanket is stained and a printed sheet is apparently stained
- F: considerable stains on the blanket
- G: serious stains on the blanket
Table 7
|
Al
composition |
Si solid solution amount
(ppm) |
Current density
(A/dm2) |
Alkaline etching amount
(g/m2) |
Stain resistance |
Heat treatment condition |
Example 19 |
Al-11 |
600 |
5 |
0.1 |
D |
500°C × 10 hr. |
Example 20 |
Al-11 |
600 |
7 |
0.1 |
B |
500°C × 10 hr. |
Example 21 |
Al-11 |
600 |
20 |
0.1 |
A |
500°C × 10 hr. |
Example 22 |
Al-11 |
600 |
5 |
0.2 |
C |
500°C × 10 hr. |
Example 23 |
Al-11 |
600 |
7 |
0.2 |
B |
500°C × 10 hr. |
Example 24 |
Al-11 |
600 |
20 |
0.2 |
A |
500°C × 10 hr. |
Comparative
Example 7 |
Al-11 |
600 |
5 |
0 |
E |
500°C × 10 hr. |
Comparative
Example 8 |
Al-11 |
600 |
7 |
0 |
E |
500°C × 10 hr. |
Comparative
Example 9 |
Al-11 |
600 |
20 |
0 |
E |
500°C × 10 hr. |
Comparative
Example 10 |
Al-11 |
140 |
5 |
0.1 |
G |
300°C × 10 hr. |
Comparative
Example 11 |
Al-11 |
140 |
7 |
0.1 |
G |
300°C × 10 hr. |
Comparative
Example 12 |
Al-11 |
140 |
20 |
0.1 |
F |
300°C × 10 hr. |
(Examples 25 to 28)
(5) (Solid solution amounts of alloy elements, electrolytic surface roughening conditions,
and evaluation of printing performances)
[0325] The aluminum materials having the composition Al-12 shown in Table 1 were respectively
subjected to heat treatments and the solid solution amounts were adjusted and measured.
Then, aluminum supports for a lithographic printing plate were obtained by carrying
out the surface treatment described below. Thereafter, the thermal positive type image
recording layer similar to the one used in the previous evaluation of printing performances
was formed under the same conditions to obtain the presensitized plates. After exposure,
development, and printing in the same manner, printing performances (stain resistance)
were evaluated as shown in Table 8.
<Surface treatment>
[0326] The surface treatment processes (a) to (f) in the test (4) were repeated except that
the following conditions were applied to (c) the electrolytic surface roughening treatment
and (d) the alkaline etching.
(c) Electrolytic surface roughening treatment
[0327] The electrolytic surface roughening treatment was carried out as described in the
process (c) in the previous test (4), except that the current density was 20 A/dm
2, that a 1-wt% nitric acid aqueous solution or a 1-wt% hydrochloric acid aqueous solution
was used as the electrolytic solution as shown in Table 8, and that a trapezoidal
wave or a sinusoidal wave was selected as the electrolytic current waveform as shown
in Table 8.
(d) Alkaline etching
[0328] The etching treatment was carried out by spraying the aqueous solution adjusted to
the caustic soda concentration of 5 wt%, the aluminum ion concentration of 5 g/L,
and the temperature of 35°C from the spray tubes onto the aluminum plate. The etching
amount on the surface of the aluminum plate subjected to the electrochemical surface
roughening treatment was 0.2 g/m
2.
Table 8
|
Al
composition |
Si solid solution amount*
(ppm) |
Electrolytic solution |
Electrolytic current waveform |
Quantity of electricity
(C/dm2) |
Uniformity of electrolytically roughened surface |
Stain resistance |
Example 25 |
Al-12 |
150 |
1-wt% nitric acid |
trapezoidal |
250 |
A |
A |
Example 26 |
Al-12 |
150 |
1-wt% nitric acid |
sinusoidal |
250 |
C |
D |
Example 27 |
Al-12 |
150 |
1-wt% hydrochloric acid |
trapezoidal |
250 |
B |
B |
Example 28 |
Al-12 |
150 |
1-wt% hydrochloric acid |
sinusoidal |
250 |
A |
A |
* Heat treatment condition: the solid solution amounts were adjusted under the condition
of 450°C × 5 hr. |
(Examples 29 to 31)
(6) (Solid solution amounts of alloy elements, electrolytic surface roughening conditions,
and evaluation of printing performances)
[0329] The aluminum materials having the composition Al-12 shown in Table 1 were respectively
subjected to heat treatments to adjust the solid solution amounts. Then, aluminum
supports for a lithographic printing plate were obtained by carrying out the surface
treatment described below. Thereafter, the thermal positive type image recording layer
similar to the one used in the previous evaluation of printing performances was formed
under the same conditions to obtain the presensitized plates. After exposure, development,
and printing in the same manner, printing performances (stain resistance) were evaluated
as shown in Table 9.
<Surface treatment>
[0330] The surface treatments in the test (4) were repeated except that (j) a brush graining
treatment was first carried out under the following conditions, and that the following
conditions were applied to (c) the electrolytic surface roughening treatment and (d)
the alkaline etching.
(j) Brush graining treatment
[0331] Mechanical surface roughening was carried out by use of slurry obtained by suspending
pumice stone (median diameter: 30 µm) having the specific gravity of 1.13 in water
as polishing slurry, and by use of a laminated brush roll having a bristle diameter
of 0.3 mm, so as to obtain Ra after the subsequent alkaline etching of 0.45 um.
(c) Electrolytic surface roughening treatment
[0332] In Examples 29 and 30, only (c) first electrolytic surface roughening was carried
out as shown in Fig. 9. Then, (d) the alkaline etching was subsequently carried out.
[0333] In Example 31, (c)-2 second electrolytic surface roughening was carried out after
the alkaline etching following (c) the first electrolytic surface roughening. Then,
(d) the alkaline etching was carried out again. This is as shown in Fig. 9.
Evaluation of press life
[0334] The obtained presensitized plates were used in the test (4). Thereafter, images were
formed in the same manner.
[0335] Then, the presensitized plates were developed in a similar processor containing a
similar developer under similar conditions, and lithographic printing plates were
thereby obtained.
[0336] The obtained lithographic printing plates were set on Lithrone Press (available from
Komori Corporation) for printing by use of black ink DIC-GEOS (N) (available from
Dainippon Ink and Chemicals). Press life was evaluated by the number of printed sheets
at the point in time when it was visually detected that a solid image started fading.
The number of the printed sheets representing press life was 50000 sheets in Example
29 and Example 31. Accordingly, 50000 sheets were redefined as 100, and the press
life was indicated by relative values. Results are shown in Table 9.
Table 9
|
Al
composition |
Si solid solution amount*
(ppm) |
(c) First electrolytic surface roughening |
(d)-2
Alkaline etching |
(c)-2 Second electrolytic surface roughening |
(d)
Alkaline etching |
Stain resistance |
Press like |
Example 29 |
Al-12 |
700 |
1-wt% nitric acid
quantity of electricity 250 C/dm2 |
no |
no |
amount of Al
dissolved: 0.1 g/m2 |
C |
100 |
Example 30 |
Al-12 |
700 |
1-wt%
hydrochloric acid
quantity of electricity 250 C/dm2 |
no |
no |
amount of Al
dissolved: 0.1 g/m2 |
B |
80 |
Example 31 |
Al-12 |
700 |
1-wt% nitric acid
quantity of electricity 200 C/dm2 |
amount of Al
dissolved: 3 g/m2 |
0.5-wt%
hydrochloric acid
quantity of electricity 63 C/dm2 |
amount of Al
dissolved: 0.1 g/m2 |
A |
100 |
* The solid solution amounts were adjusted under the heat treatment condition of 550°C
10 hr. |