BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates to a method for producing a lithographic printing plate
original plate and a method for roughening a surface of an aluminum support body,
and particularly relates to a method for producing a lithographic printing plate original
plate and a method for roughening a surface of an aluminum support body, wherein diameters
of pits formed when the aluminum support body used for a lithographic printing plate
is electrolytically surface-roughened can be made uniform.
Description of the Related Art
[0002] Conventionally, when a photosensitive composite for coloring, dyeing, coating, or
lithographic printing is prepared on pure aluminum or aluminum alloy (hereinafter
may be referred to as "aluminum") and aluminum on which an anodic oxide film is formed,
roughening of the aluminum support body surface has been generally performed as a
method for increasing adhesion to the aluminum support body.
[0003] The roughening of the aluminum support body surface is carried out by electrolyzing
the aluminum support body and is designated as an electrolytic surface-roughening
treatment.
[0004] The electrolytic surface-roughening treatment is performed by applying an alternating
waveform current such as a sine wave current, a rectangular wave current, or a trapezoid
wave current, or a direct current, to the aluminum support body in an acidic electrolyte.
[0005] The acidic electrolyte used for the electrolytic surface-roughening treatment is
usually nitric acid, sulfuric acid, phosphoric acid, or a mixed solution obtained
by mixing nitric acid, sulfuric acid, and phosphoric acid at a certain ratio.
[0006] In the electrolytic surface-roughening treatment by an alternating current, pits
are formed by an anode reaction, however, an oxide film is also simultaneously formed,
whereby surface resistance is increased and dispersibility of the pits is reduced.
When dispersibility of pits is reduced, pits with uneven diameters are prone to be
formed. Accordingly, a surface area of the aluminum support body does not become so
large, whereby poor adhesion to an upper layer is caused.
[0007] In the electrolytic surface-roughening treatment by a direct current, an anodic oxide
film is formed on the aluminum support body, however, concentration of oxygen which
is dissolved in the acidic electrolyte (hereinafter, referred to as dissolved oxygen)
is not constant, whereby unevenness in quality among products develops.
[0008] As a device for dispersing pits, for example, Japanese Patent No.
2614744 can be mentioned. In the Japanese Patent No.
2614744, preferable is a method for performing a surface-roughening treatment after preparing
an organic film or an inorganic film each of which has electric resistance.
SUMMARY OF THE INVENTION
[0009] However, in the Japanese Patent No.
2614744, there are problems where it is difficult to control thickness of the organic film
or the inorganic film, and an electrolyte is contaminated.
[0010] The present invention has been made in view of such problems and has an object to
provide a method for increasing adhesion to an upper layer by controlling formation
of an oxide film to disperse pits and to uniformize the pits when the aluminum support
body is surface-roughened in the acidic solution by alternating current electrolysis
treatment. The present invention also has an object to provide a method for generating
an anode oxide film with prescribed thickness and characteristic to control qualitative
variation among products when surface-roughening by the anode reaction of the direct
current electrolysis treatment.
[0011] The above-mentioned problems can be solved by the following invention. That is, a
method of producing a lithographic printing plate in the present invention is a method
of producing a lithographic printing plate comprising an electrolytic surface-roughening
treatment step of performing an electrolytic surface-roughening treatment of the aluminum
support body, and is mainly characterized in that, in the electrolytic surface-roughening
treatment step, an electrolysis treatment is performed in an acidic solution with
a dissolved oxygen concentration of 6.0 mg/l or less.
[0012] Furtheremore, a surface-roughening method of a surface of the aluminum support body
in the present invention is mainly characterized in that electrolysis treatment of
the aluminum support body is performed in an acidic solution having a dissolved oxygen
concentration of 6.0 mg/l or less.
[0013] Thus, formation of the oxide film in the anode reaction in the alternating current
electrolysis treatment is kept under control, surface resistance is reduced, and a
current is applied uniformly, whereby pits having a smaller average pit diameter and
being uniform in diameter can be formed with high density. A pit evaluation was performed
by analyzing SEM photographs. Moreover, thickness and characteristics of the anodic
oxide film formed by the anode reaction in the direct current electrolysis treatment
are determined only by oxygen ions generated by water dissociation since an influence
by dissolved oxygen becomes smaller, and therefore product quality can be made uniform.
[0014] In the present invention, the concentration of the dissolved oxygen in the acidic
solution is 6 mg/l or less, and preferably 3 mg/l or less, and more preferably 1 mg/l
or less. A dissolved oxygen analyzer (made by Central Kagaku Corp.) was used for concentration
measurement.
[0015] A method for removing dissolved oxygen is any of film degassing, a nitrogen purge,
and a pressure reduction. Any of these methods is a method for connecting with an
exhaust pipe portion between an electrolytic bath and an electrolyte tank and thereby
circulating a solution in which a concentration of dissolved oxygen becomes a certain
degree or less.
[0016] The pressure reduction is a method for reducing a concentration of dissolved oxygen
in an acid electrolytic solution by exposing the acid electrolytic solution to a pressure-reduced
atmosphere.
[0017] The nitrogen purge is a method for substituting dissolved oxygen by passing nitrogen
gas through an acid electrolytic solution to reduce a concentration of dissolved oxygen.
[0018] The film degassing is, for example, a method for removing oxygen by using a deoxidizing
resin in which a weak-base anion exchange resin holds reducible copper, and a method
by using a film degassing device equipped with a degassing film having a property
of passing through a gas such as oxygen, but preventing liquid permeation.
[0019] According to the present invention, in the surface-roughening treatment by using
electrolysis, pits having a smaller average pit diameter and being uniform in diameter
can be formed with high density.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020]
Fig. 1 is a sectional view showing an example of an electrolytic surface-roughening
treatment apparatus equipped with a radial-type alternating current electrolytic bath
in an embodiment of the present invention.
Fig. 2 is a diagram illustrating an example of an apparatus used for an electrolytic
surface-roughening method according to the present invention.
Fig. 3 is a SEM photograph of a surface of the aluminum support body after the surface-roughening
treatment.
Fig. 4 is another SEM photograph of a surface of the aluminum support body after the
surface-roughening treatment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] Hereinafter, the preferred embodiments of the present invention are described.
[Electrolysis Treatment Method]
[0022] As an acidic solution used by the present invention, a nitric acid solution, a hydrochloric
acid solution, a phosphoric acid solution, and a mixed solution of a nitric acid solution,
a hydrochloric acid solution, and a phosphoric acid solution can be mentioned, however,
a nitric acid solution is preferable. A concentration of the nitric acid solution
is preferably 1 to 20 g/l, and more preferably 5 to 15 g/l. A solution temperature
at the time of the electrolysis treatment is preferably 20 to 60 °C, and more preferably
30 to 50 °C. A current density in alternating current electrolysis is preferably 10
to 60 A/dm
2, and more preferably 25 to 55 A/dm
2. A total quantity of electricity is preferably 10 to 400 C/dm
2, and more preferably 60 to 300 C/dm
2. A distance between aluminum and a carbon electrode is preferably 5 to 50 mm, and
more preferably 10 to 20 mm.
[Production of a support body for a lithographic printing plate and of a lithographic
printing plate original plate]
[0023] Hereinafter, the present embodiment describes an example in which the present invention
is applied to an alternating current roughening treatment performed by using a nitric
acid solution, in a step of producing the aluminum support body for the lithographic
printing plate.
[0024] Fig. 1 illustrates a schematic diagram of a sectional view showing an example of
the electrolytic surface-roughening treatment apparatus which is preferably used for
the present invention and equipped with the radial-type alternating current electrolytic
bath.
[0025] As shown in Fig. 1, an electrolytic surface-roughening treatment apparatus 10 comprises
an electrolytic bath main body 12 inside which an electrolytic bath 12A for storing
an acidic electrolyte is provided; and a feeding roller 14 which is rotatably disposed
around an axis extended horizontally inside the electrolytic bath 12A, and feeds an
aluminum web W in a direction of an arrow a, that is, from right to left in Fig. 1,
the aluminum web W being a continuous belt-like thin plate.
[0026] An interior wall surface of the electrolytic bath 12A is formed substantially cylindrically
so as to surround the feeding roller 14, and on the interior wall surface of the electrolytic
bath 12A, semi-cylindrical electrodes 16A and 16B are provided so as to sandwich the
feeding roller 14. The electrodes 16A and 16B are divided into a plurality of small
electrodes 18A and 18B along a direction of the circumference, respectively, and insulating
layers 20A and 20B are equipped between the small electrodes 18A and 18B, respectively.
The small electrodes 18A and 18B can be formed by using, for example, graphite, metal,
etc., and the insulating layers 20A and 20B can be formed by using, for example, polyvinyl
chloride resin, etc. Thickness of the insulating layers 20A and 20B is preferably
1 to 10 mm. In addition, in both of the electrodes 16A and 16B, the small electrodes
18A and 18B are connected to an AC power supply, respectively. Each of the small electrodes
18A and 18B and the insulating layers 20A and 20B as held by an insulating electrode
holder 20C to form the electrodes 16A and 16B, respectively.
[0027] The AC power supply has a function which supplies an alternating waveform current
to the electrodes 16A and 16B. As the AC power supply, there can be mentioned a sine
wave generating circuit in which a sine wave is generated by a current and voltage
regulation of a commercial alternating current, with using an induction regulator
and a transformer; a thyristor circuit in which a trapezoid wave current or a rectangular
wave current is generated from a direct current obtained by rectifying a commercial
alternating current; etc.
[0028] In the upper part of the electrolytic bath 12A, there is formed an opening 12B through
which the aluminum web W, being an example of a metal plate in the embodiment and
being a continuous beltlike aluminum plate, is drawn in and out at the time of the
alternating-current electrolysis surface-roughening treatment. In the vicinity of
the downstream end of the electrode 16B in the opening portion 12B, an acidic electrolyte
replenishment path 22 which replenishes the electrolytic bath 12A with an acidic electrolyte
is provided. As such acidic electrolyte, a nitric acid solution, a hydrochloric acid
solution, etc. can be used.
[0029] In the vicinity of the opening portion 12B in the upper part of the electrolytic
bath 12A, disposed are a group of upstream guide rollers 24A which guide the aluminum
web W to the interior of electrolytic bath 12A; and downstream guide rollers 24B which
guide the aluminum web W, already given electrolytic surface-roughening treatment
inside the electrolytic bath 12A, to the exterior of the electrolytic bath 12A.
[0030] An overflow bath 12C is provided at an upstream side of the electrolytic bath 12A
in the electrolytic bath main body 12. The overflow bath 12C has a function to temporarily
store an acidic electrolyte which overflows the electrolytic bath 12A to maintain
the height of a liquid level of the electrolytic bath 12A.
[0031] In the electrolyte in the vicinity of the entrance portion which guides the aluminum
web W to the interior of electrolytic bath 12A, a direct-current portion 26, which
impresses negative direct-current voltage to the aluminum web W, is provided at a
position of 5 to 15 mm from a surface of the aluminum web W. The direct-current portion
26 has a function to impress negative direct-current voltage to the aluminum web W
to pass a direct current through the aluminum web W, in the entrance inside the electrolytic
bath 12A all the time.
[0032] An auxiliary electrolytic bath 28 is provided at a downstream side of the electrolytic
bath 12A in the electrolytic bath main body 12. The auxiliary electrolytic bath 28
is shallower than the electrolytic bath 12A, and a bottom 28A is formed flat. In addition,
a plurality of cylindrical auxiliary electrodes 29 is provided on the bottom 28A.
[0033] The auxiliary electrode 29 is preferably formed from high corrosion resistance metal
such as platinum, ferrite, etc. and may be formed in a plate form.
[0034] The auxiliary electrodes 29 are connected to a side to which the electrode 16A in
the AC power supply is connected, in parallel to the electrode 16A, and a thyristor
Th1 is connected in-between so that a current could flow in a direction from a side
connected to the electrode 16A in the AC power supply toward the auxiliary electrodes
29 at the time of ignition.
[0035] In addition, the auxiliary electrode 29 is also connected, via a thyristor Th2, to
a side to which the electrode 16B in the AC power supply is connected. The thyristor
Th2 is connected so that a current could flow in a direction from a side connected
to the electrode 16B in the AC power supply toward the auxiliary electrodes 29 at
the time of ignition.
[0036] When either of the thyristors Th1 and Th2 is ignited, an anode current flows into
the auxiliary electrodes 29. Therefore, by carrying out a phase control of the thyristors
Th1 and Th2, a current value of the anode current which flows into the auxiliary electrode
29 can be controlled, and also a ratio Qc/Qa, where Qc is a quantity of electricity
which flows when the aluminum web W is a cathode and Qa is a quantity of electricity
which flows when the aluminum web W is an anode, can be controlled.
[0037] Moreover, the auxiliary electrodes 29 and the direct-current part 26 are connected
through a direct current power supply.
[0038] The frequency of the alternating current is not particularly limited, but preferably
40 to 120 Hz, more preferably 40 to 80 Hz, and still more preferably 50 to 60 Hz.
[0039] For the aluminum web W, the ratio Qc/Qa, where Qc is a quantity of electricity which
flows at the time of a cathode reaction and Qa is a quantity of electricity which
flows at the time of an anode reaction, is preferably 0.9 to 1, and more preferably
0.95 to 0.99. Thus, uniform honeycomb pits can be formed on the surface of the aluminum
web W.
[0040] The duty of the alternating current is not particularly limited, but, from viewpoints
of uniformly providing the surface-roughening treatment to the surface of the aluminum
web W and of manufacturing an power supply unit, preferably 0.33 to 0.66, more preferably
0.4 to 0.6, and most preferably 0.5. In the present embodiment, "duty" means ta/T,
where T is an alternating current period and ta is a time of an anode reaction of
an aluminum alloy plate (anode reaction time).
[0041] TP, which is a time until a current value of an alternating current reaches a positive
or negative peak from zero, is preferably 0.5 to 6 msec, and more preferably 0.6 to
5 msec, in the case of a trapezoid wave current. Thus, more uniform and crater-like
depressed portions can be formed on the surface of the aluminum web W.
[0042] An quantity of electricity which flows from the starting time until the finishing
time of the electrolytic surface-roughening treatment is preferably 10 to 1000 C/dm
2, more preferably 10 to 800 C/dm
2, and still more preferably 40 to 500 C/dm
2, in total when the aluminum web W is an anode.
[0043] Each of I ap, a current at the time of a peak at an anode cycle side of an alternating
current, and I cp, a current at the time of a peak at a cathode cycle side of an alternating
current, is preferably 10 to 100 A/dm
2, more preferably 20 to 80 A/dm
2, and still more preferably 30 to 60 A/dm
2. Moreover, I cp/I ap is preferably 0.9 to 1.5, and more preferably 0.9 to 1.0.
[0044] In the electrolytic surface-roughening treatment, it is preferable that, in one or
two or more electrolytic baths, one or more idle period in which an alternating current
does not flow into the aluminum web W is provided, and a length of the idle period
is 0.001 to 0.6 second, whereby honeycomb pits are uniformly formed on the whole surface
of the aluminum web W.
[0045] As an example where the present invention is applied, a method for producing the
lithographic printing plate original plate is described. Here, the lithographic printing
plate original plate is a plate before producing a lithographic printing plate, and
the lithographic printing plate is produced by image-exposing and developing the plate.
<Aluminum Web (Rolled Aluminum)>
[0046] An aluminum plate used as the aluminum web W in the present embodiment is a metal
including aluminum, which is stable in terms of size, as a major constituent. As mentioned
above, the aluminum alloy plate is also included as the aluminum plate, hereinafter,
these plates are collectively called an aluminum plate.
[0047] As the aluminum plate, a plastic film or paper on which an aluminum alloy is laminated
or vapor-deposited can also be used. Furthermore a complex sheet obtained by bonding
an aluminum sheet onto a polyethylene terephthalate film can also be used. Moreover,
the aluminum plate may also include elements such as Bi and Ni, and inevitable impurities.
[0048] As the aluminum plates, aluminum alloy plates which are conventionally known and
used, such as JIS A1050, JIS A1100, JIS A3003, JIS A3004, JIS A3005, and an international
registration alloy 3103A, can be suitably used.
[0049] A method for producing the aluminum plate may be either of a continuous casting method
and a DC casting method. An aluminum plate produced by omitting intermediate annealing
in the DC casting method and omitting a soaking treatment can also be used. An aluminum
plate having projections and depressions given by pack-rolling, transferring, etc.
can also be used in finish rolling. Moreover, the aluminum plate may be an aluminum
web which is a continuous belt-like sheet material or plate material, or may be a
leaf-like sheet which is cut into a size corresponding to the lithographic printing
plate original plate to be shipped as a product.
[0050] Thickness of the aluminum plate is usually approximately 0.05 mm to 1 mm, and preferably
0.1 mm to 0.5 mm. The thickness can be suitably changed according to a size of a printing
machine, a size of a printing plate, and a request by a user.
[0051] In the method for producing the lithographic printing plate original plate in the
present embodiment, the lithographic printing plate original plate is obtained by
performing various surface treatments including the electrolytic surface-roughening
treatment in an acidic solution on the above-mentioned aluminum plate. These surface
treatments may further include various kinds of treatments.
[0052] An alkali etching treatment or a desmut treatment is preferably performed before
the electrolytic surface-roughening treatment, and it is also preferable that the
alkali etching treatment and the desmut treatment are performed in this order. In
addition, an alkali etching treatment or a desmut treatment is preferably performed
after the electrolytic surface-roughening treatment, and it is also preferable that
the alkali etching treatment and the desmut treatment are performed in this order.
The alkali etching treatment after the electrolytic surface-roughening treatment may
be omitted. In the present invention, mechanical surface-roughening treatment is also
preferably performed before the alkali etching treatment and the desmut treatment.
The electrolytic surface roughening treatment may be performed twice or more. Subsequently,
an anodizing treatment, a pore-sealing treatment, a hydrophilization treatment, etc.
are also preferably performed.
[0053] Hereafter, each of the mechanical surface-roughening treatment and a first alkali
etching treatment, a first desmut treatment, the electrolytic surface-roughening treatment,
a second alkali etching treatment, a second desmut treatment, the anodizing treatment,
the pore-sealing treatment, and the hydrophilization treatment is described in detail.
It is note that, in the present embodiment, a treatment performed before the electrolytic
surface-roughening treatment may be sometimes called with giving an ordinal number
"first", while a treatment performed after the electrolytic surface-roughening treatment
maybe sometimes called with giving an ordinal number "second".
<Mechanical surface-roughening treatment>
[0054] The mechanical surface-roughening treatment is preferably performed before the electrolytic
surface-roughening treatment. The mechanical surface-roughening treatment is generally
performed by brushing one side or both sides of the surface of the aluminum web by
using a roller-shaped brush with spraying a slurry solution containing an abrasive
on the roller-shaped brush which is rotating, the roller-shaped brush having a cylindrical
body on a surface of which a large amount of brush hair, such as synthetic resin hair
made from synthetic resins such as nylon (registered trademark), propylene, and vinyl
chloride resin, is implanted. Instead of the roller-shaped brush and the slurry solution,
a polishing roller which is a roller having a polishing layer on the surface can also
be used. A length of the brush hair of the roller-shaped brush may be suitably determined
according to an outer diameter and a body diameter of the roller-shaped brush, but
is generally 10 to 100 mm.
[0055] As the abrasive, a known one can be used. For example, an abrasive, such as pumice
stone, silica sand, aluminum hydroxide, alumina powder, volcanic ash, carborundum,
and emery, or a mixture containing those abrasives can be used. Among these, pumice
stone and silica sand are preferable, and particularly silica sand is more preferable
from a viewpoint where silica sand is harder and more durable compared with pumice
stone, thereby is excellent in surface-roughening efficiency. An average particle
diameter of the abrasive is preferably 3 to 50 µm, and more preferably 6 to 45 µm,
since surface-roughening efficiency is excellent and a graining pitch can be narrowed.
When pumice stone is used as the abrasive, the average particle diameter is in particular
preferably 40 to 45 µm, and when silica sand is used as the abrasive, the average
particle diameter is in particular preferably 20 to 25 µm. The abrasive is, for example,
made into a polishing slurry solution by suspending the abrasive in water and then
used. Besides the abrasive, a thickener, a dispersing agent (for example, a surface
active agent), an antiseptic agent, etc. may be contained in the polishing slurry
solution. The average particle diameter means a particle diameter having 50% of a
cumulative percentage in cumulative distribution of a percentage of the abrasive particles
having each particle diameter in proportion to a volume of all the abrasives contained
in the polishing slurry solution.
[0056] Moreover, in the mechanical surface-roughening treatment, a degreasing treatment
for removing rolling oil on the surface of the aluminum web, for example, a degreasing
treatment by using a surface active agent, an organic solvent, an alkaline solution,
etc. may be first performed by request before performing brush-polishing.
<First Alkali Etching Treatment>
[0057] In a first alkali etching treatment, etching is performed by contacting the aluminum
web with an alkali solution. When the mechanical surface-roughening treatment is not
performed yet, the first alkali etching treatment is performed for a purpose of removing
a rolling oil, contamination, and a natural oxidation film on the surface of the aluminum
web (rolled aluminum), while when the mechanical surface-roughening treatment is already
performed, the first alkali etching treatment is performed for a purpose of obtaining
a smooth winding surface by dissolving edge portions with projections and depressions
generated by the mechanical surface-roughening treatment. As the method for contacting
the aluminum web with the alkali solution, for example, a method for making the aluminum
web pass through a bath filled with an alkali solution, a method for soaking the aluminum
web in a bath filled with an alkali solution, a method for spraying an alkali solution
on the surface of the aluminum web, etc. can be mentioned.
[0058] An etching amount is preferably 1 to 15 g/m
2 for a surface to which the electrolytic surface-roughening treatment is given at
a following step, and preferably 0.1 to 5 g/m
2 (approximately 10 to 40% of a surface to which the electrolytic surface-roughening
treatment is given) for the surface to which the electrolytic surface-roughening treatment
is not given.
[0059] As alkali used for the alkali solution, caustic alkali and alkali metal salt can
be mentioned, for example. Specifically, as caustic alkali, caustic soda and caustic
potash can be mentioned, for example. As alkali metal salt, for example, alkali metal
silicates, such as sodium metasilicate, sodium silicate, potassium metasilicate, and
potassium silicate; alkali metal carbonate, such as sodium carbonate and potassium
carbonate; alkali metal aluminate, such as sodium aluminate and potassium aluminate;
alkali metal aldonic acid salt, such as sodium gluconate and potassium gluconate;
and alkali metal hydrogen phosphate, such as secondary sodium phosphate, secondary
potassium phosphate, tertiary sodium phosphate, and tertiary potassium phosphate can
be mentioned. Particularly, a caustic alkali solution and a solution containing both
caustic alkali and alkali metal aluminate are preferable since these solutions exhibit
a high etching speed and are inexpensive. In particular, a caustic sodium solution
is more preferable.
[0060] A concentration of the alkali solution can be determined according to an etching
amount, but is preferably 1 to 50% by mass, and more preferably 10 to 35% by mass.
If aluminum ions are dissolved into the alkali solution, a concentration of the aluminum
ions is preferably 0.01 to 10% by mass, and more preferably 3 to 8% by mass. A temperature
of the alkali solution is preferably 20 to 90 °C. A treatment time is preferably 1
to 120 seconds. An amount of the etching treatment is preferably 1 to 15 g/m
2 dissolution, and more preferably 3 to 12 g/m
2 dissolution. The first alkali etching treatment can be performed by using an etching
bath usually used for the etching treatment for the aluminum web. As the etching bath,
either of a batch-type or a continuous-etching bath can be used. Moreover, when the
first alkali etching treatment is performed by spraying the alkali solution on a surface
of the aluminum web, a spray apparatus can be used.
<First Desmut Treatment>
[0061] A first desmut treatment is performed by, for example, contacting the aluminum web
with an acidic solution of hydrochloric acid, nitric acid, sulfuric acid, etc. with
a concentration of 0.5 to 30% by mass (containing aluminum ions of 0.01 to 5% by mass).
As the method for contacting the aluminum web with the acidic solution, for example,
a method for making the aluminum web pass through a bath filled with an acidic solution,
a method for soaking the aluminum web in a bath filled with an acidic solution, a
method for spraying an acidic solution on a surface of the aluminum web, etc. can
be mentioned. In the first desmut treatment, as the acidic solution, preferably used
are a waste liquid of an aqueous solution containing mainly nitric acid or an aqueous
solution containing mainly hydrochloric acid, the waste liquid being discharged in
the electrolytic surface-roughening treatment mentioned later, or a waste liquid of
an aqueous solution containing mainly sulfuric acid, the waste liquid being discharged
in the anodizing treatment mentioned later. A solution temperature in the first desmut
treatment is preferably 25 to 90 °C. Moreover, a treatment time of the first desmut
treatment is preferably 1 to 180 seconds.
<Electrolytic Surface-roughening Treatment>
[0062] An acidic solution used in the electrolytic surface-roughening treatment is not particularly
limited, but an aqueous solution containing mainly nitric acid and an aqueous solution
containing mainly hydrochloric acid are preferably used. The aqueous solution containing
mainly nitric acid has a nitric acid concentration of preferably 3 to 20 g/L, and
more preferably 5 to 15 g/L, and has an aluminum ion concentration of preferably 3
to 15g/L, and more preferably 3 to 7 g/L. The aluminum ion concentration in the aqueous
solution containing mainly nitric acid can be adjusted by adding an aluminum nitrate
to a nitric acid solution having the above-mentioned nitric acid concentration. The
aqueous solution containing mainly hydrochloric acid has a hydrochloric acid concentration
of preferably 3 to 15 g/L, and more preferably 5 to 10g/L, and has a aluminum ion
concentration of preferably 3 to 15 g/L, and more preferably 3 to 7 g/L. The aluminum
ion concentration in the aqueous solution containing mainly hydrochloric acid can
be adjusted by adding aluminum chloride to a hydrochloric acid aqueous solution having
the above-mentioned hydrochloric acid concentration.
<Second Alkali Etching Treatment>
[0063] In a second alkali etching treatment, etching is performed by contacting the aluminum
web with an alkali solution. As a kind of alkali, a method for contacting the aluminum
web with an alkali solution, and an apparatus used for the method, the same ones as
used in the first alkali etching treatment can be mentioned. An etching amount is
preferably 0.001 to 5 g/m
2, more preferably 0.01 to 3 g/m
2, and still more preferably 0.05 to 2 g/m
2, for a surface to which the electrolytic surface-roughening treatment is given.
[0064] As alkali used for the alkali solution, the same ones as used in the first alkali
etching treatment can be mentioned. A concentration of the alkali solution can be
determined according to the etching amount, but is preferably 0.01 to 80% by mass,
A temperature of the alkali solution is preferably 20 to 90 °C. A treatment time is
preferably 1 to 60 seconds. If an acidic solution which contains 100 g/L or more of
sulfuric acid and whose temperature is 60 °C or more is used in the second desmut
treatment mentioned later, the second alkali etching treatment may be omitted.
<Second desmut treatment>
[0065] The second desmut treatment is performed by, for example, contacting the aluminum
web with an acidic solution of phosphoric acid, hydrochloric acid, nitric acid, sulfuric
acid, etc. having a concentration of 0.5 to 30% by mass (containing aluminum ions
of 0.01 to 5% by mass). As a method for contacting the aluminum web with the acidic
solution, the same one as used in the first desmut treatment can be mentioned. In
the second desmut treatment, as the acidic solution, a waste liquid of an sulfuric
acid solution which is discharged in the anodizing treatment mentioned later is preferably
used. Moreover, instead of the waste liquid, there may be used a sulfuric acid solution
having a sulfuric acid concentration of 100 to 600 g/L, an aluminum ion concentration
of 1 to 10 g/L, and a solution temperature of 60 to 90 °C. A solution temperature
in the second desmut treatment is preferably 25 to 90 °C. A treatment time of the
second desmut treatment is preferably 1 to 180 seconds. Aluminum and aluminum alloy
components may be dissolved in the acidic solution used for the second desmut treatment.
<Anodizing Treatment>
[0066] It is preferable that the anodizing treatment is additionally performed to the aluminum
web treated as mentioned above. The anodizing treatment can be performed by conventional
methods in this field. Specifically, a direct current, a pulsating current, or an
alternating current is made flow into the aluminum web in an electrolyte of an aqueous
solution or a nonaqueous solution, the aqueous solution or the nonaqueous solution
being obtained by using, alone or in combination of two or more kinds, sulfuric acid,
phosphoric acid, chromic acid, oxalic acid, sulfamic acid, benzenesulfonic acid, amidosulfonic
acid, etc., whereby an anodic oxide film can be formed on the surface of the aluminum
web.
[0067] In particular, a sulfuric acid solution is preferably used as the electrolyte. In
the electrolyte, a sulfuric acid concentration is preferably 10 to 300 g/L (1 to 30%
by mass), and an aluminum ion concentration is preferably 1 to 25 g/L (0.1 to 2.5%
by mass), and more preferably 2 to 10 g/L (0.2 to 1 % by mass). Such electrolyte can
be prepared by, for example, adding aluminum to dilute sulfuric acid having a sulfuric
acid concentration of 50 to 200 g/L.
[0068] When the anodizing treatment is performed in the electrolyte containing sulfuric
acid, a direct current may be applied to the aluminum web and an alternating current
may be applied thereto. When a direct current is applied to the aluminum web, a current
density is preferably 1 to 60 A/dm
2, and more preferably 5 to 40 A/dm
2. When the anodizing treatment is performed continuously, it is preferable that a
current is made to flow with a low current density of 5 to 10 A/dm
2 at the beginning of the anodizing treatment, and then, as the anodizing treatment
proceeds, the current density is increased to be 30 to 50 A/dm
2 or more, so that what is called "burning" due to concentrating a current on a part
of the aluminum web would not be caused. When the anodizing treatment is performed
continuously, it is preferable that the treatment is performed by an electrolyte power
supply method for supplying electric power to the aluminum web via the electrolyte.
[0069] As an electrode which supplies electric power to the aluminum web, an electrode formed
of lead, iridium oxide, platinum, ferrite, etc. can be used. Particularly, an electrode
which is formed of mainly iridium oxide and an electrode in which a surface of a base
material is covered with iridium oxide are preferable. As such base material, it is
preferable to use what is called valve metal, such as titanium, tantalum, niobium,
and zirconium, and particularly titanium and niobium are more preferable among the
valve metals. Since electric resistance of the valve metal is comparatively higher,
the base material may be formed by cladding the valve metal on the surface of a core
material made from copper. When the valve metal is clad on the surface of the core
material made from copper, it is hard to produce a base material having a complicated
shape, therefore the valve metal is clad to a core material configured by dividing
the base material by parts, and then the base material may be assembled by combining
each of the parts.
[0070] A condition of the anodizing treatment changes variously according to an electrolyte
to be used, thereby cannot be determined as a whole, but generally an electrolyte
concentration of 1 to 80% by mass, a solution temperature of 5 to 70 °C, a current
density of 1 to 60 A/dm
2, a voltage of 1 to 100V, and an electrolysis time of 10 to 300 seconds are suitable.
From a viewpoint of rigidity of the lithographic printing plate, the anodizing treatment
is preferably performed so that an amount of the anodic oxide film would become 1
to 5 g/m
2. Moreover, the anodizing treatment is preferably performed so that difference of
an anodic oxide film amount between in a central part of the aluminum web and in the
vicinity of the edge of the aluminum web would be 1 g/m
2 or less.
<Pore-sealing Treatment>
[0071] The pore-sealing treatment is preferably performed, wherein small pores (micropores)
formed by the anodizing treatment are sealed by contacting an aluminum alloy plate
in which an anodic oxide film is formed, with boiling water, hot water, or steam.
<Hydrophilization Treatment>
[0072] After the anodizing treatment or the pore-sealing treatment, the hydrophilization
treatment is preferably performed by a method for soaking in an aqueous solution of
alkali metal silicate, such as sodium silicate or potassium silicate, a method for
forming a hydrophilic undercoat layer by applying a hydrophilic vinyl polymer or a
hydrophilic compound, etc. As the hydrophilic vinyl polymer used for the method, there
can be mentioned, for example, a copolymer of a vinyl polymer compound containing
sulfonic acid group, such as polyvinyl sulfonic acid and p-styrene sulfonic acid having
a sulfonic acid group, and an ordinal vinyl polymer compound, such as (meta)acrylic
acid alkyl ester. Moreover, as the hydrophilic compound used for the method, there
can be mentioned, for example, a compound having at least one selected from a group
including a -NH
2 group, a -COOH group, and a sulfo group.
[Formation of Intermediate Layer and Photosensitive Layer]
<Intermediate Layer>
[0073] A photosensitive layer may be provided directly on the support for lithographic printing
plates to which the hydrophilization treatment is given or a support for lithographic
printing plates to which the acidic solution treatment is additionally given after
the hydrophilization treatment, and also, as necessary, an intermediate layer may
be provided on each of the above-mentioned supports and then a photosensitive layer
may be provided on the intermediate layer.
(Intermediate Layer of Macromolecular Compound having Acid Radical and Onium Group)
[0074] As a macromolecular compound used for the intermediate layer formation, more preferably
used is a macromolecular compound which has an acid radical or has a component with
an acid radical and a component with an onium group. The acid radical of the component
of the macromolecular compound is preferably an acid radical having an acid dissociation
index (pKa) of 7 or less, more preferably -COOH, -SO
3H, -OSO
3H, and -PO
3H
2, -OPO
3H
2, -CONHSO
2, and -SO
2NHSO
2-, and still more preferably -COOH. A component having a suitable acid radical is
a polymerizable compound expressed by general formulas (1) and (2) below.

[0075] In the formulas, A represents a divalent linking group. B represents an aromatic
group or a substituted aromatic group. Each of D and E independently represents a
divalent linking group. G represents a trivalent linking group. Each of X and X' independently
represents an acid radical of 7 or less pKa or its alkali metal salt, or an ammonium
salt. R1 represents a hydrogen atom, an alkyl group, or a halogen atom. Each of a,
b, d, and e independently represents 0 or 1. Moreover, t represents an integer of
1 to 3. Among the components having the acid radical, it is more preferable that A
represents -COO- or CONH-, B represents a phenylene group or a substituted phenylene
group, and its substituent group is a hydroxyl group, a halogen atom, or an alkyl
group. Each of D and E independently represents an alkylene group, or a divalent linking
group expressed by a molecular formula of C
nH
2nO, C
nH
2nS, or C
nH
2n+1N. G represents a trivalent linking group expressed by a molecular formula CnH
2N-1, CnH
2n-10, CnH
2n-1S, or C
nH
2nN. Here, n represents an integer of 1 to 12. Each of X and X' independently represents
carboxylic acid, sulfonic acid, phosphonic acid, sulfuric acid monoester, or phosphoric
acid monoester. R1 represents a hydrogen atom or an alkyl group. Each of a, b, d,
and e independently represents 0 or 1, but a and b are not 0 simultaneously. Among
the components having the acid radicals, a compound expressed by a general formula
(1) is still more preferable, where B represents a phenylene group or a substituted
phenylene group, and its substituent is a hydroxyl group or an alkyl group having
a carbon number of 1 to 3. Each of D and E independently represents an alkylene group
having a carbon number of 1 to 2 or an alkylene group having a carbon number of I
to 2 and linked with an oxygen atom. R1 represents a hydrogen atom or a methyl group.
X represents a carboxylic acid group. Moreover, a is 0, and b is 1.
[0077] One kind or two or more kinds of the above-mentioned components having the acid radicals
may be used alone or in combination.
(Intermediate Layer of Macromolecular Compound having Onium group)
[0078] As an onium group of a component of a macromolecular compound used for forming the
intermediate layer, preferable is an onium group including an atom of the fifth or
sixth group of the periodic system, more preferable is an onium group including a
nitrogen atom, a phosphorus atom, or a sulfur atom, and still more preferable is an
onium group including a nitrogen atom. Moreover, as the macromolecular compound, preferable
is a vinyl polymer having a backbone structure such as acrylate resin, methacrylic
resin, and polystyrene, urethane resin, polyester, or a polymer being polyamide. In
particular, more preferable is the vinyl polymer having a backbone structure such
as acrylate resin, methacrylic resin, or polystyrene. As the macromolecular compound,
still more preferable is a polymer being a polymerizable compound in which a component
having an onium group is expressed by a general formula (3), a general formula (4),
or a general formula (5), shown below.

[0079] In the formulas, J represents a divalent linking group. K represents an aromatic
group or a substituted aromatic group. M independently represents a divalent linking
group. Y1 represents an atom of the fifth group of the periodic system, and Y2 represents
an atom of the sixth group of the periodic system. Z- represents a counter anion.
R2 represents a hydrogen atom, an alkyl group, or a halogen atom. Each of R3, R4,
R5, and R7 independently represents a hydrogen atom, or, as necessary, an alkyl group,
an aromatic group, and an aralkyl group to each of which a substituent may be linked,
and R6 represents an alkylidyne group or a substituted alkylidyne group. R3 and R4,
or R6 and R7 may be bound each other to form a ring. Each of j, k, and m independently
represents 0 or 1. And, u represents an integer of 1 to 3. Among the components having
an onium group, it is more preferable that J represents -COO- or CONH-, K represents
a phenylene group or a substituted phenylene group, and its substituent is a hydroxyl
group, a halogen atom, or an alkyl group. M represents an alkylene group, or a divalent
linking group expressed by a molecular formula of C
nH
2nO, C
nH
2nS, or C
nH
2n+1N. Here, n represents an integer of 1 to 12. Y1 represents a nitrogen atom or a phosphorus
atom, and Y2 represents a sulfur atom. Z
- represents a halogen ion, PF
6-, BF
4-, or R
8SO
3-. R2 represents a hydrogen atom or an alkyl group. Each of R3, R4, R5, and R7 independently
represents a hydrogen atom, or, as necessary, an alkyl group, an aromatic group, or
an aralkyl group each of which having a carbon number of 1 to 10 and to which a substituent
may be linked, and R6 represents an alkylidyne group or a substituted alkylidyne group
each of which having a carbon number of 1 to 10. R3 and R4, or R6 and R7 may be bound
each other to form a ring. Each of j, k, and m independently represents 0 or 1, but
j and k are not 0 simultaneously. Among the components having the onium group, it
is still more preferable that K represents a phenylene group or a substituted phenylene
group, and its substituent is a hydroxyl group or an alkyl group having a carbon number
of 1 to 3. M represents an alkylene group having a carbon number of 1 to 2, or an
alkylene group having a carbon number of 1 to 2 and linked to an oxygen atom. Z
- represents a chlorine ion or R
8SO
3-. R2 represents a hydrogen atom or a methyl group. Moreover, j is 0, and k is 1.
<Photosensitive layer>
[0080] A lithographic printing plate original plate can be obtained by providing a photosensitive
layer to a lithographic printing plate support before forming of the intermediate
layer, or to a lithographic printing plate support in which the intermediate layer
is formed.
[0081] The photosensitive layer is not particularly limited, but, for example, there can
be mentioned a visible light exposure type platemaking layer which is exposed by ordinary
visible light, and a laser exposure type platemaking layer which is exposed by laser
light such as infrared laser light. Hereinafter, the visible light exposure type platemaking
layer and the laser exposure type platemaking layer will be described.
(1) Visible Light Exposure Type Platemaking Layer
[0082] The visible light exposure type platemaking layer can be formed with a photopolymer,
and as needed, a composite containing a colorant, etc. As the photopolymer, there
can be mentioned a positive type photopolymer which dissolves in a developing solution
when exposed to light, and a negative type photopolymer which does not dissolve in
a developing solution when exposed to light. As the positive type photopolymer, there
can be mentioned, for example, a combination of a diazide compound, such as a quinone
diazide compound and a naphthoquinone diazide compound, and a phenol resin, such as
a phenol novolak resin and a cresol novolak resin. As the negative type photopolymer,
there can be mentioned, for example, a combination of: a diazo compound, such as a
diazo resin (for example, a condensate of aromatic diazonium salt and aldehyde such
as formaldehyde), an inorganic acid salt of the diazo resin, and an organic acid salt
of the diazo resin; and a binder, such as a (meta)acrylate resin, a polyamide resin,
and a polyurethane resin, and a combination of: a vinyl polymer, such as a (meta)acrylate
resin and a polystyrene resin; a vinyl polymer compound, such as (meta)acrylic ester
and styrene; and a photopolymerization initiator, such as a benzoin derivative, a
benzophenone derivative, and a thioxanthone derivative.
[0083] As the colorant, besides a ordinal coloring matter, there can be used an exposure
color-development coloring matter which is color-developed by exposure, and an exposure
color-disappearing coloring matter which becomes almost or completely colorless by
exposure. As the exposure color-development coloring matter, a leuco coloring matter
can be mentioned, for example. As the exposure color-disappearing coloring matter,
for example, a triphenylmethane coloring matter, a diphenylmethane coloring matter,
an oxazin coloring matter, a xanthene coloring matter, an imino-naphthoquinone coloring
matter, an azomethene coloring matter, and an anthraquinone coloring matter can be
mentioned.
[0084] The visible light exposure type platemaking layer can be formed by for example applying
a photopolymer solution obtained by mixing the photopolymer and the colorant with
a solvent, and then drying. As the solvent used for the photopolymer solution, there
can be mentioned a solvent which is able to dissolve the photopolymer and has a certain
degree of volatility at room temperature. Specifically, there can be mentioned, for
example, an alcohol solvent, a ketone solvent, an ester solvent, an ether solvent,
a glycol ether solvent, an amide solvent, and a carbonate solvent. As the alcohol
solvent, there can be mentioned, for example, ethanol, propanol, and butanol. As the
ketone solvent, there can be mentioned, for example, acetone, methyl ethyl ketone,
methyl propyl ketone, methyl isopropyl ketone, and diethyl ketone. As the ester solvent,
there can be mentioned, for example, ethyl acetate, propyl acetate, methyl formate,
and ethyl formate. As the ether solvent, there can be mentioned, for example, tetrahydrofuran,
and dioxane. As the glycol ether solvent, there can be mentioned, for example, ethyl
cellosolve, methyl cellosolve, and butyl cellosolve. As the amide solvent, there can
be mentioned, for example, dimethylformamide, and dimethylacetamide. As the carbonate
solvent, there can be mentioned, for example, ethylene carbonate, propylene carbonate,
diethyl carbonate, and dibutyl carbonate.
[0085] A method for applying the photopolymer solution is not particularly limited, and
conventionally well-known methods, such as a rotation application method, a wire bar
application method, a dip application method, an air knife application method, a roll
coating method, and a blade application method, can be used.
(2) Laser Exposure Type Platemaking Layer
[0086] As the laser exposure type platemaking layer, there can be mainly mentioned, for
example, a negative type laser platemaking layer in which a portion irradiated with
laser light remains, a positive type laser platemaking layer from which a portion
irradiated with laser light is removed, and a photopolymerization type laser platemaking
layer which is photopolymerized when irradiated with laser light.
[0087] The negative type laser platemaking layer can be formed by using a solution for forming
the negative type laser platemaking layer, the solution obtained by dissolving or
suspending, in a suitable solvent, (A) an acid precursor which is decomposed by heat
or light to generate acid, (B) an acid-crosslinking compound which is crosslinked
by the acid generated by decomposition of the acid precursor (A), (C) an alkali soluble
resin, (D) an infrared absorber, and (E) a phenolic hydroxyl-containing compound.
[0088] As the acid precursor (A), there can be mentioned, for example, like an imino phosphate
compound, a compound which is decomposed by ultraviolet light, visible light, or heat,
thereby generates sulfonic acid. In addition, a compound generally used as a photo-cationic
polymerization initiator, a photo-radical polymerization initiator, a photol alterant,
etc. also can be used as the acid precursor (A). As the acid-crosslinking compound
(B), there can be mentioned, for example, an aromatic compound having at least any
one of an alkoxy methyl group and an hydroxyl group, a compound having an N-hydroxymethyl
group, an N-alkoxy methyl group, or an N-acyloxy methyl group, and an epoxy compound.
As the alkali soluble resin (C), there can be mentioned, for example, a novolak resin,
a polymer having a hydroxy aryl group as a side chain of poly(hydroxy styrene), etc.
[0089] As the infrared absorber (D), there can be mentioned, for example, a dye and a pigment
which absorb infrared rays with a wavelength of 760 to 1200 nm. Specifically, there
can be mentioned, for example, a black pigment, a red pigment, a metallic powder pigment,
a phthalocyanine pigment; an azo dye which absorbs infrared rays having the above-mentioned
wavelength, an anthraquinone dye, a phthalocyanine dye, and a cyanine dye. As the
phenolic hydroxyl-containing compound (E), there can be mentioned, for example, a
compound expressed by a general formula (R1-X
n-Ar-(OH)
m (In the formula, R1 is an alkyl group or an alkenyl group having a carbon number
of 6 to 32, X is a single bond, O, S, COO, or CONCH, Ar is an aromatic hydrocarbon
group, a cycloaliphatic hydrocarbon group, or a heterocycle group, and each of n and
m is independently a natural number of 1 to 8.). As such compound, for example, alkylphenols,
such as nonylphenol, can be mentioned. For the solution for forming the negative type
laser platemaking layer, besides the above-mentioned each component, a plasticizer
etc. may also be mixed.
[0090] The positive type laser platemaking layer can be formed by using a solution for forming
the positive type laser platemaking layer, the solution obtained by dissolving or
suspending (F) an alkali-soluble macromolecule, (G) an alkali-dissolution inhibitor,
and (H) a infrared absorber, in a suitable solvent. As the alkali-soluble macromolecule
(F), there can be mentioned, for example, a phenol polymer having a phenolic hydroxyl
group, such as a phenol resin, a cresol resin, a novolak resin, a pyrogallol resin,
and a poly(hydroxystyrene); a sulfonamide group-containing polymer being a polymer
in which at least a part of monomeric units has sulfonamide groups; and an active
imido group-containing polymer obtained by homopolymerization or copolymerization
of monomers having an active imido group, such as an N-(p-toluenesulfonyl) (meta)acrylamide
group.
[0091] As the alkali-dissolution inhibitor (G), there can be mentioned, for example, a compound
which reacts with the alkali-soluble macromolecule (F) by heating etc. to reduce alkali
solubility of the alkali-soluble macromolecule (F). Specifically, for example, a sulfone
compound, an ammonium salt, a sulfonium salt, and an amide compound can be mentioned.
As a combination of the alkali-soluble macromolecule (F) and the alkali-dissolution
inhibitor (G), there can be preferably mentioned a combination of a novolak resin
as the alkali soluble macromolecule (F) and a cyanine dye, a kind of a sulfone compound,
as the alkali-dissolution inhibitor (G). As the infrared absorber (H), there can be
mentioned, for example, a coloring matter, a dye, and a pigment which have an absorption
region in an infrared region with a wavelength range of 750 to 1200 nm and have a
light-heat conversion ability, such as a squarylium coloring matter, a pyrylium coloring
matter, a carbon black, an insoluble azo dye, and an anthraquinone dye.
[0092] The photopolymerization type laser platemaking layer can be formed by using a solution
for forming the photopolymerization type laser platemaking layer, the solution containing
(I) a vinyl polymer compound having an ethylene unsaturated bond at a molecular end.
For the solution for forming the photopolymerization type laser platemaking layer,
(J) a photopolymerization initiator, (K) a sensitizer, etc. can be mixed, as needed.
As the vinyl polymer compound (I), there can be mentioned, for example, an ethylene
unsaturated carboxylic acid polyvalent ester which is an ester of an ethylene unsaturated
carboxylic acid, such as (meta)acrylic acid, itaconic acid, and maleic acid, and an
aliphatic polyhydric alcohol; a methylenebis(meta)acrylamide composed of the ethylene
unsaturated carboxylic acid and a polyvalent amine; and an ethylene unsaturated carboxylic
acid polyvalent amide, such as a xylylene(meta)acrylamide. As the vinyl polymer compound
(I), there can be further mentioned, an aromatic vinyl compound, such as a styrene
and an α-methylstyrene; and an ethylene unsaturated carboxylic-acid monoester, such
as methyl (meta)acrylate and ethyl (meta)acrylate. As the photopolymerization initiator
(J), a photopolymerization initiator which is usually used for photopolymerization
of vinyl monomers can be used. As the sensitizer (K), there can be mentioned, for
example, a titanocene compound, a triazine compound, a benzophenone compound, a benzimidazole
compound, a cyanine dye, a merocyanine dye, a xanthene dye, and a coumarin dye.
[0093] The solvent and the applying method which are mentioned above for the photopolymer
solution can be employed for solvents to be used for the solution for forming the
negative type laser platemaking layer, the solution for forming the positive type
laser platemaking layer, and the solution for forming the photopolymerization type
laser platemaking layer, and applying methods of the solution for forming the negative
type laser platemaking layer, the solution for forming the positive type laser platemaking
layer, and the solution for forming the photopolymerization type laser platemaking
layer. Note that, when the photopolymerization type laser platemaking layer is formed,
it is preferable that, by using a silicone compound having a reactant functional group,
such as a partially decomposed type silane compound obtained by partially decomposing
a silane compound by water, alcohol, or carboxylic acid, a treatment is in advance
provided to a surface-roughening treatment surface of the support for lithographic
printing plates, since adhesiveness of the support and the photopolymerization type
laser platemaking layer is improved.
<Mat layer>
[0094] A mat layer may be provided on the surface of the thus-provided photosensitive layer
in order to shorten the vacuuming time at the time of contact exposure by using a
vacuum printing frame and to prevent halation. Specifically, the methods of providing
a mat layer, and the method of thermal deposition of solid powders can be mentioned.
<Back coat layer>
[0095] For the lithographic printing plate original plate obtained as mentioned above, a
coating layer comprising an organic macromolecular compound (hereinafter, referred
to as "back coat layer") may be prepared as necessary on the back side of the lithographic
printing plate original plate (a side on which the photosensitive layer is not provided)
so that the photosensitive layer is not damaged even if the lithographic printing
plate original plates are piled up. As a principal component of the back coat layer,
it is preferable to use at least one kind of resin having a glass transition point
of 20 °C or more and chosen from a group including saturated copolymerization polyester
resin, phenoxy resin, polyvinyl acetal resin, and vinylidene chloride copolymerization
resin.
[0096] The saturated copolymerization polyester resin is composed of a dicarboxylic acid
unit and a diol unit. As the dicarboxylic acid unit, there can be mentioned, for example,
aromatic dicarboxylic acid such as phthalic acid, terephthalic acid, isophthalic acid,
tetrabromophthalic acid, and tetrachlorophthalic acid; and saturated aliphatic dicarboxylic
acid such as adipic acid, azelaic acid, succinic acid, oxalic acid, suberic acid,
sebacic acid, malonic acid, and 1,4-cyclohexanedicarboxylic acid.
[0097] Furthermore, the back coat layer may suitably include a dye and a pigment for coloring,
a silane coupling agent for improving adhesion to the support, a diazo resin comprising
a diazonium salt, an organic phosphonic acid, an organic phosphorus acid, a cationic
polymer, a wax usually used as a sliding agent, a higher fatty acid, a higher fatty
acid amide, a silicone compound comprising dimethyl siloxane, a denatured dimethyl
siloxane, polyethylene powders, etc.
[0098] It is only necessary that a thickness of the back coat layer has a degree where the
photosensitive layer cannot be easily damaged even without a backing board, and preferably
0.01 to 8 µm. If the thickness is less than 0.01 µm, it is difficult to prevent a
scratch of the photosensitive layer when the lithographic printing plate original
plates are piled up and handled. Meanwhile, if the thickness is more than 8 µm, due
to medicine used around the lithographic printing plate, sometimes the back coat layer
swells to change the thickness during printing and thereby printing pressure changes
to degrade a printing characteristics.
[0099] Various methods can be used as methods of providing the back coat layer in the back
side of the lithographic printing plate original plate. There can be mentioned, for
example, a method where the above-mentioned components for the back coat layer are
dissolved in a suitable solvent to make a solution and applied, or to make into an
emulsification dispersion solution and applied, and then dried; a method where what
is beforehand formed in a film form and the lithographic printing plate original plate
are pasted together with adhesive or heat; and a method where a molten coat is formed
with a melting extruder and stuck to the lithographic printing plate original plate.
A most preferable method for ensuring a preferable thickness is the method where the
components for the back coat layer is dissolved in a suitable solvent to make a solution
and applied, then dried.
[0100] In the production of the lithographic printing plate original plate, either the back
coat layer on the back side and the photosensitive layer on the front side maybe provided
first on the support, and both the layers may also be provided simultaneously,
[0101] The lithographic printing plate is obtained by, as necessary, cutting the thus-obtained
lithographic printing plate original plate in a suitable size, and then exposing,
developing, and photoengraving the original plate. In the case of the lithographic
printing plate original plate in which the visible light exposure type platemaking
layer (photosensitive platemaking layer) is provided, the lithographic printing plate
original plate is exposed by layering transparent films in which printing pictures
are formed and irradiating ordinary visible light, and subsequently is developed,
thereby can be photoengraved. In the case of the lithographic printing plate original
plate in which the laser exposure type platemaking layer is provided, the lithographic
printing plate original plate is exposed by irradiating various laser lights to write
a printing image directly, and subsequently is developed, thereby can be photoengraved.
[0102] As mentioned above, the example to apply the present invention to the production
method for producing the support for lithographic printing plates was explained, and
the present invention is also applicable to other technical fields including a process
in which the electrolytic surface-roughening treatment is performed to the surface
of a metal plate.
[Example]
[0103] Next, the present invention will be explained in more detail by Examples, but should
not be limited to the following Examples.
[0104] With reference to Fig. 2, an explanation is given. Fig. 2 is a diagram showing an
example of an apparatus which is used for the electrolytic surface-roughening method
according to the present invention. An electrolytic surface-roughening treatment by
an alternating current with using a nitric acid solution was carried out in a container
200 having a size of 100 × 100 × 100 mm.
[0105] In the apparatus shown in Fig. 2, a concentration of a nitric acid solution 210 was
set to 10 g/l, and a solution temperature was set to 35 °C, then a nitrogen purge
was performed by injecting nitrogen gas 220 into a nitric acid solution 210. A concentration
of dissolved oxygen in the nitric acid solution 210 was adjusted by the nitrogen purge.
The concentration of dissolved oxygen was measured by a dissolved oxygen analyzer
(made by Central Kagaku Corp).
[0106] An aluminum support body 230 and a carbon electrode 240 were disposed such that each
plane would face each other in the nitric acid solution 210. Each of the aluminum
support body 230 and the carbon electrode 240 was connected to an alternating-current
power supply 250. A distance between the aluminum support body 230 and the carbon
electrode 240 was set to 10 mm. Moreover, for the aluminum support body 230, A1050
is used as an aluminum material.
[0107] With a state where 1% of the nitric acid solution 210 is stationary, an electrolytic
surface-roughening treatment of the aluminum support body 230 was carried out. A current
density in alternating current electrolysis was set to 35 A/dm
2, and a total quantity of electricity was set to 240 C/dm
2. At this time, the electrolytic surface-roughening treatment was performed with changing
the concentration of the dissolved oxygen in the nitric acid solution 210 as a parameter.
The change in dissolved oxygen was performed by the nitrogen purge as mentioned above.
[0108] Uniformity of pits was evaluated by performing SEM photography of a surface-roughened
surface of the aluminum support body 230 to observe the surface. The evaluation results
are shown in Table 1. Fig. 3 and Fig. 4 show SEM photographs taken at this time. Fig.
3 shows a SEM photograph of a surface of the aluminum support body to which the electrolytic
surface-roughening treatment was given without removing dissolved oxygen in the nitric
acid solution 210. Fig. 4 shows a SEM photograph of a surface of the aluminum support
body to which the electrolytic surface-roughening treatment was given at a dissolved
oxygen concentration of 3 mg/l, with removing dissolved oxygen in the nitric acid
solution 21 fl.
[Table 1]
|
Removal of Dissolved Oxygen |
Concentration of Dissolved Oxygen (mg/l) |
Average Diameter of Pits (µm) |
Pit Density (10,000 pits/mm2) |
Pit Uniformity |
Comparative Example |
w/o |
8 |
5.6 |
1.5 |
B |
Example 1 |
w/ |
1 or less |
3.0 |
2.0 |
A |
Example 2 |
w/ |
3 |
3.4 |
1.8 |
A-AB |
Example 3 |
w/ |
6 |
3.9 |
1.6 |
AB- B |
[0109] The pit average diameter and the pit density were calculated by analyzing the 174
× 254 µm SEM photographs. As an evaluation level of the pit uniformity, a following
four-grade evaluation on the basis of Comparative Example was applied.
A: Excellent in pit uniformity
A - AB: Good in pit uniformity
AB - B: Satisfactory in pit uniformity
B: Fair in pit uniformity
[0110] As shown in Table 1, it is preferable that electrolytic surface-roughening treatment
is performed in the nitric acid solution with a dissolved oxygen concentration of
6 mg/l or less. Thereby, an aluminum support body having a smaller average diameter
of pits, a higher pit density, and a better uniformity of pits can be manufactured.
[0111] Moreover, it is more preferable that the electrolytic surface-roughening treatment
is performed in the nitric acid solution with a dissolved oxygen concentration of
3 mg/l or less, and it is most preferable that the electrolytic surface-roughening
treatment is performed in the nitric acid solution with a dissolved oxygen concentration
of 1 mg/l or less. Thereby, an aluminum support body having a smaller average diameter
of pits, a still higher pit density, and a still better uniformity of pits can be
manufactured.
[0112] Here, Fig. 3 and Fig. 4 are compared. Fig. 3 shows a SEM photograph of a surface
of the aluminum support body manufactured under conditions of Comparative Example
in Table 1, and Fig. 4 shows a SEM photograph of a surface of the aluminum support
body manufactured under conditions of Example 2 in Table 1.
[0113] From Fig. 3 and Fig. 4, it is apparent that the aluminum support body manufactured
under the conditions of Example 2 has a smaller average diameter of pits, a higher
pit density, and a better uniformity of pits than the aluminum support body manufactured
under the conditions of Comparative Example.
[Application as Support for Lithographic Printing Plate]
(Desmut Treatment in Acidic Solution)
[0114] The desmut treatment was performed for 5 seconds by spraying an aqueous solution
with a sulfuric acid concentration of 170 g/L, an aluminum ion concentration of 5
g/L, and a temperature of 50 °C, from a spray pipe, on an aluminum plate obtained
by the surface-roughening treatment. As the sulfuric acid solution, a waste in the
anodizing treatment step mentioned later was used.
[0115] Then, the solution was drained off by a nip roller. After draining off the solution,
the anodizing treatment step was applied without performing a water-washing treatment.
(Anodizing Treatment)
[0116] As the electrolyte, used was an electrolyte (a solution temperature of 50 °C) in
which aluminum sulfate was dissolved in a 170 g/L sulfuric acid solution so that an
aluminum ion concentration was 5g/L. Anodizing treatment was performed so that an
average current density during an anode reaction of the aluminum plate would become
15 A/dm
2, and a final amount of an oxide film was 2.7 g/m
2.
[0117] Then, the solution was drained off by a nip roller, and a water-washing treatment
is carried out for 5 seconds by using a spray pipe having a spray tip from which injection
water was spread fan-like, and furthermore the solution was drained off by a nip roller.
(Hydrophilization Treatment)
[0118] The aluminum plate was soaked in a sodium silicate solution of 1% by mass (a solution
temperature of 20 °C) for 10 seconds. An amount of Si on a surface of the aluminum
plate measured by a fluorescent X-ray analysis apparatus was 3.5 mg/m
2. Then, the solution was drained off by a nip roller, and a water-washing treatment
was carried out for 5 seconds by using a spray pipe having a spray tip from which
injection water was spread fan-like, and furthermore the solution was drained off
by a nip roller. Furthermore, by drying by blowing an air flow of 90 °C for 10 seconds,
a support for lithographic printing plates was obtained.
Production of Lithographic Printing Plate Original Plate
[0119] A thermal positive type image recording layer was provided to each support of the
above-obtained lithographic printing plates as follows to obtain a lithographic printing
plate original plate. It is note that, before providing the image recording layer,
an undercoating layer was provided as described later.
[0120] An undercoating solution having the following composition was applied on the support
for lithographic printing plates and then dried at 80 °C for 15 seconds to form a
coating film of the undercoating layer. After drying, a coating amount of the coating
film was 15 mg/m
2.
<Composition of Undercoating Solution>
[0121]
- Macromolecular Compound below: 0.3 g
- Methanol: 100g
- Water: 1g

[0122] Furthermore, an application solution for thermal layers having a following composition
was prepared, then the application solution for thermal layers was applied to the
support for lithographic printing plates to which the undercoating layer had been
prepared so that an application amount after drying (an application amount for a thermal
layer) would be 1.8 g/m
2, and then dried to form a thermal layer (the thermal positive type image recording
layer), whereby the lithographic printing plate original plate was obtained.
<Composition of Application Solution for Thermal Layer>
[0123]
- Novolak resin (m-cresol/p-cresol = 60/40, weight average molecular weight: 7,000,
containing unreacted cresol of 0.5% by mass): 0.90 g
- Copolymer of ethyl methacrylate/isobutyl methacrylate/methacrylic acid (molar ratio
35/35/30): 0.10 g
- Cyanine dye A represented by a following structural formula: 0.1 g
- Tetrahydrophthalic anhydride: 0.05 g
- ρ-toluenesulfonic acid: 0.002 g
- Ethyl Violet having 6-hydroxy-β-naphthalenesulfonic acid as a counter ion: 0.02 g
- Fluorine surface active agent (Megafac F-780F, produced by Dainippon Ink and Chemicals
Inc., a solid content of 30% by mass): 0.0045 g (solid content conversion)
- Fluorine surface active agent (Megafac F-781F, produced by Dainippon Ink and Chemicals
Inc., a solid content of 100% by mass): 0.035 g
- Methyl ethyl ketone: 12 g

Evaluation of Lithographic Printing Plate Original Plate
[0124] Sensitivity of exposure and development and adhesion to an upper layer were evaluated
for the obtained lithographic printing plate original plate.
(1) Evaluation of Sensitivity of Exposure and Development
[0125] Writing was performed in image form with respect to the obtained lithographic printing
plate original plate at a drum rotation speed of 150 rpm and a beam intensity of 10
W, using TrendSetter manufactured by Creo Inc.. Then, by using PS processor 940H manufactured
by Fuji Photo Film Co., Ltd. in which an alkaline development solution with a following
composition had been prepared, a development was performed for a developing time of
20 seconds with maintaining a solution temperature at 30 °C, whereby a lithographic
printing plate was obtained.
[0126] As a result, sensitivity of the lithographic printing plate original plate produced
under any of conditions of the above Examples 1 to 3 and the above Comparative Example
in Table 1 was good.
[0127] Composition of the alkaline development solution which was used for the sensitivity
evaluation of exposure and development is shown below.
<Composition of Akaline Development Solution>
[0128]
- D-sorbitol: 2.5% by mass
- Sodium hydroxide: 0.85% by mass
- Polyethylene glycol lauryl ether (weight average molecular weight: 1.000): 0.5% by
mass
- Water: 96.15% by mass
(2) Evaluation of Adhesion to Upper Layer (Evaluation of Printing Durability)
[0129] Next, an evaluation of adhesion to an upper layer was performed. Here, the evaluation
of adhesion to an upper layer is to evaluate adhesion of a surface of the aluminum
support body, on which pits were formed, to a layer which is formed on the surface
of the aluminum support body. Here, the adhesion to the upper layer was decided by
evaluating printing durability. An evaluation of the printing durability was performed
by evaluating the printable number of layers under each condition (Examples 1 to 3
and Comparative Example in Table 1), and was expressed by an index when the printable
number in Comparative Example was made 100%.
[Printing Durability Test Condition]
[0130] Printing was performed with respect to the obtained lithographic printing plate,
by using a LITHRONE printing machine manufactured by KOMORI Corporation and a black
ink, DIC-GEOS (N) made by Dainippon Ink and Chemicals Inc., and then a usual printing
durability was evaluated by the number of printed layers at a time when it was recognized
by visual inspection that a solid image density began to become lighter.
[Test Result]
[0131] Table 2 shows test results (the number of printable layers in the case where the
dissolved oxygen treatment was not performed was made an index of 100). Each of Examples
1 to 3 and Comparative Example in this table is a sample to which electrolytic surface-roughening
treatment is given under the same conditions as in each of Examples 1 to 3 and Comparative
Example in Table 1.
[Table 2]
|
Removal of Dissolved Oxygen |
Concentration of Dissolved Oxygen (mg/l) |
Pit Uniformity |
Printing Durability |
Comparative Example |
w/o |
8 |
B |
100% |
Example 1 |
w/ |
1 or less |
A |
116% |
Example 2 |
w/ |
3 |
A-AB |
110% |
Example 3 |
w/ |
6 |
AB- B |
103% |
[0132] As shown in Table 2, printing durability in each of Examples 1 to 3 was more improved
than that in Comparative Example. It is presumed that uniformity of the pits was improved
by reducing a dissolved oxygen concentration in a nitric acid solution, and accordingly
adhesion to an upper layer became better, whereby printing durability was improved.
Thereby, it was proved that, with conveying an aluminum web W into an acidic electrolyte,
the alternating current electrolysis treatment is continuously performed by a frequency
wave current, whereby pits which are uniform in diameter can be formed, thus, printing
durability can be effectively improved.
[0133] Particularly, as seen from results of Examples 1 to 3, a dissolved oxygen concentration
of 1 mg/l or less is most effective. Therefore, it is proved that removal of dissolved
oxygen in the nitric acid solution contributes to uniformity of the pits, in other
words, printing durability.
[0134] On the other hand, it was proved that, in Comparative Example in which dissolved
oxygen was not removed, printing durability decreases.