U.S. patent application number 12/890729 was filed with the patent office on 2011-03-31 for method of producing aluminum substrate for planographic printing plate and method of recycling planographic printing plate.
This patent application is currently assigned to FUJIFILM CORPORATION. Invention is credited to Masakazu OSADA, Takeshi SERIKAWA.
Application Number | 20110073272 12/890729 |
Document ID | / |
Family ID | 43234272 |
Filed Date | 2011-03-31 |
United States Patent
Application |
20110073272 |
Kind Code |
A1 |
SERIKAWA; Takeshi ; et
al. |
March 31, 2011 |
METHOD OF PRODUCING ALUMINUM SUBSTRATE FOR PLANOGRAPHIC PRINTING
PLATE AND METHOD OF RECYCLING PLANOGRAPHIC PRINTING PLATE
Abstract
A method of producing an aluminum substrate for a planographic
printing plate is provided in which a recycled material including a
used planographic printing plate having a planographic printing
plate support obtained by treating an aluminum substrate is
prepared, a recycled bare metal is obtained from the recycled
material, and a new aluminum bare metal and a trace-metal master
alloy of necessary amounts are mixed into the recycled bare metal
to produce a new aluminum substrate.
Inventors: |
SERIKAWA; Takeshi;
(Shizuoka-ken, JP) ; OSADA; Masakazu;
(Shizuoka-ken, JP) |
Assignee: |
FUJIFILM CORPORATION
Tokyo
JP
|
Family ID: |
43234272 |
Appl. No.: |
12/890729 |
Filed: |
September 27, 2010 |
Current U.S.
Class: |
164/461 ;
164/463 |
Current CPC
Class: |
C25F 3/04 20130101; C22F
1/04 20130101; Y02P 10/212 20151101; C22B 21/0069 20130101; B41N
3/006 20130101; B41N 1/083 20130101; C22C 21/00 20130101; C25D
11/24 20130101; Y02P 10/20 20151101; C25D 11/16 20130101 |
Class at
Publication: |
164/461 ;
164/463 |
International
Class: |
B22D 11/06 20060101
B22D011/06; C22B 21/00 20060101 C22B021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 28, 2009 |
JP |
2009-222874 |
Sep 30, 2009 |
JP |
2009-227792 |
Claims
1. A method of producing an aluminum substrate for a planographic
printing plate, the method sequentially comprising: preparing a
recycled material including a used planographic printing plate
having a planographic printing plate support obtained by treating
an aluminum substrate; producing a recycled bare metal by
introducing the obtained recycled material into a melting furnace,
melting the recycled material at a temperature of from 680.degree.
C. to 900.degree. C. to obtain a recycled material melt, and
shaping the recycled material melt into a predetermined shape with
a predetermined weight; analyzing the aluminum purity and a trace
metal content of the obtained recycled bare metal; comparing
analysis values of the aluminum purity and the trace metal content
of the obtained recycled bare metal with a desired aluminum purity
and a desired trace metal content predetermined for a planographic
printing plate support in order to calculate differences
therebetween, and determining a mixture ratio of a new aluminum
bare metal and a trace-metal master alloy with a determined purity
with respect to the recycled bare metal on the basis of the
calculated differences; producing a pre-rolling melt by introducing
the recycled bare metal, the new aluminum bare metal, and the
trace-metal master alloy into a pre-rolling melting furnace at
amounts corresponding to the determined mixture ratio, and heating
and melting; and producing a strip-shaped aluminum substrate by
rolling the obtained pre-rolling melt.
2. The method of producing an aluminum substrate for a planographic
printing plate according to claim 1, wherein the planographic
printing plate support is obtained by sequentially performing a
roughening treatment, an anodization treatment, and a
hydrophilizing treatment using an aqueous solution including
polyvinyl phosphonic acid on the aluminum substrate.
3. The method of producing an aluminum substrate for a planographic
printing plate according to claim 2, wherein the recycled material
further includes at least one of cut pieces of the aluminum
substrate or cut pieces of the planographic printing plate, which
are generated during producing the planographic printing plate.
4. The method of producing an aluminum substrate for a planographic
printing plate according to claim 1, wherein the planographic
printing plate support is obtained by sequentially performing a
roughening treatment and an anodization treatment using an
electrolytic solution including phosphoric acid on the aluminum
substrate.
5. The method of producing an aluminum substrate for a planographic
printing plate according to claim 4, wherein the recycled material
further includes at least one of cut pieces of the aluminum
substrate or cut pieces of the planographic printing plate, which
are generated during producing a planographic printing plate
precursor.
6. The method of producing an aluminum substrate for a planographic
printing plate according to claim 4, wherein a content of the
phosphoric acid in the electrolytic solution is in a range of from
10% by mass to 50% by mass.
7. A method of recycling a planographic printing plate, the method
sequentially comprising: producing a planographic printing plate
support obtained by treating an aluminum substrate for the
planographic printing plate; producing a planographic printing
plate precursor by forming an image recording layer on the treated
surface of the planographic printing plate support; processing the
obtained planographic printing plate precursor to obtain a
planographic printing plate and performing a desired printing on
the obtained planographic printing plate; recovering the used
planographic printing plate generated after printing; and recycling
the recovered planographic printing plate by providing the
recovered planographic printing plate as the recycled material of
an aluminum substrate in the method of producing an aluminum
substrate for a planographic printing plate of claim 1.
8. The method of recycling a planographic printing plate according
to claim 7, wherein the planographic printing plate support is
obtained by sequentially performing a roughening treatment, an
anodization treatment, and a hydrophilizing treatment using an
aqueous solution including polyvinyl phosphonic acid on at least
one surface of an aluminum substrate for the planographic printing
plate.
9. The method of recycling a planographic printing plate according
to claim 8, wherein the aluminum substrate for the planographic
printing plate is the aluminum substrate for the planographic
printing plate obtained by the method of producing an aluminum
substrate for a planographic printing plate according to claim
2.
10. The method of recycling a planographic printing plate according
to claim 7, wherein the planographic printing plate support is
obtained by sequentially performing a roughening treatment and an
anodization treatment using an electrolytic solution including
phosphoric acid on at least one surface of an aluminum substrate
for the planographic printing plate.
11. The method of recycling a planographic printing plate according
to claim 10, wherein the aluminum substrate for the planographic
printing plate is the aluminum substrate for the planographic
printing plate obtained by the method of producing an aluminum
substrate for a planographic printing plate according to claim 4.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority under 35 USC 119 from
Japanese Patent Application No. 2009-222874 filed on Sep. 28, 2009,
and No. 2009-227792 filed on Sep. 30, 2009, the disclosures of
which are incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method of producing an
aluminum substrate for a planographic printing plate, and more
particularly, to a method of producing an aluminum substrate for a
planographic printing plate, in which a used planographic printing
plate is efficiently recycling, and a method of recycling a
planographic printing plate using the production method.
[0004] 2. Description of the Related Art
[0005] Planographic printing plates are produced by forming an
image recording layer (for example, a photosensitive layer) on an
aluminum planographic printing plate support. Since such an
aluminum substrate needs to be subjected to a uniform and dense
roughening treatment, that is, a surface treatment such as an
electrochemical roughening treatment, a raw material with high
purity and a strictly-adjusted trace metal content should be used
as the aluminum material of the aluminum substrate.
[0006] On the other hand, energy of 140.9 MJ is theoretically
required for producing 1 kg of new metal aluminum and the amount of
CO.sub.2 generated at the time is 9.22 kg/kg. Accordingly, when it
is intended to produce a planographic printing plate while
suppressing the generation of CO.sub.2 as much as possible, it can
be thought that end materials such as cut pieces generated in a
used planographic printing plate having been used in printing or
during producing a planographic printing plate are recycled as a
recycled aluminum material. However, since the purity or the alloy
composition of the recycled aluminum material does not reach the
level required as the raw material of the planographic printing
plate support, it is difficult to use the aluminum material
recycled from a recovered planographic printing plate as a
planographic printing plate support. The recycled aluminum material
is generally used in applications in which the purity of the
contained metal need not be strictly managed, for example, as a raw
material of a window chassis, a vehicle engine, or a vehicle wheel,
but is not provided for the planographic printing plate.
[0007] However, the production energy for producing 1 kg of a
recycled bare metal containing a used planographic printing plate
or end materials such as cut pieces of a planographic printing
plate is only about 4% of 140.9 MJ. Accordingly, if such materials
can be recycled for a planographic printing plate, it is possible
to effectively reduce the generation of CO.sub.2. For this purpose,
it is important to construct a recycling method of guaranteeing the
quality as an aluminum substrate for the planographic printing
plate and then reducing the energy.
[0008] Recently, recycling used planographic printing plates or the
end materials as a recycled material has been studied. For example,
a method of recycling a used planographic printing plate as a
support by removing impurities from the used planographic printing
plate, adding new aluminum bare metal and master alloy (aluminum
alloy containing several tens of % of the desired metal) thereto,
directly introducing the resultant into a pre-rolling melting
furnace to produce a melt, performing a filtering process thereon,
and rolling the resultant is disclosed (for example, see Japanese
Patent No. 3420817). It is suggested that the production cost of
the aluminum substrate for the planographic printing plate is
lowered by recycling used aluminum material for the aluminum
substrate for the planographic printing plate formed of low-purity
aluminum (for example, see Japanese Patent Application Laid-Open
(JP-A) No. 2002-331767).
[0009] However, in the case of JP-A No. 2002-331767, when the
low-purity aluminum is used as a base material of the substrate,
various other means are necessary for accomplishing the adhesive
strength to an image recording layer formed on the surface of the
support or the hydrophilic property sufficient for serving as a
non-image area.
[0010] In the method described in Japanese Patent No. 3420817,
since a method (hereinafter, referred to as "direct introduction
method") of directly introducing the used planographic printing
plate into a pre-rolling melting furnace for forming a support is
used, it is difficult to avoid the great influence of the
composition of the used aluminum to be introduced on the alloy
composition of the rolled aluminum plate. However, as described
above, when the process of roughening the planographic printing
plate, for example, the roughening treatment using an electrolysis
method, is performed, the alloy composition of the aluminum plate
has a critical influence on the roughened shape. Accordingly, when
it is intended to obtain an aluminum substrate with a higher purity
necessary for the roughening treatment using an electrolysis
method, the amount of used planographic printing plate to be
introduced is limited in view of quality and it is necessary to use
a large amount of aluminum with a high purity. Therefore, the
recycling efficiency is poor and it is not preferable in view of a
reduction in carbon dioxide. It is necessary to measure the
impurity composition in the course of performing the introduction
into the melting furnace and performing the rolling process and the
melting or the composition adjustment requires time, which causes
deterioration in yield.
SUMMARY OF THE INVENTION
[0011] The invention is made in view of the above-mentioned
situation. The present invention provides a method of producing an
aluminum substrate for a planographic printing plate, which can
produce an aluminum substrate for a planographic printing plate
satisfying the quality of aluminum purity or trace-metal content
with a high yield even when a used planographic printing plate is
reused at the time of producing an aluminum substrate for a
planographic printing plate and which can reduce the accompanying
amount of aluminum oxide generated and greatly reduce the
generation of CO.sub.2, a cause of global warming.
[0012] The present invention also provides a method of recycling a
planographic printing plate with high efficiency which can greatly
reduce the generation of CO.sub.2 in processes by using the
above-mentioned method of producing an aluminum substrate for a
planographic printing plate.
[0013] As a result of vigorous study, the inventors have been
discovered that the above-mentioned object could be accomplished by
using a used planographic printing plate including an aluminum
substrate having been subjected to specific surface treatment,
whereby the invention was made.
[0014] That is, according to the invention, there is provided a
method of producing an aluminum substrate for a planographic
printing plate, the method sequentially including:
[0015] preparing a recycled material including a used planographic
printing plate having a planographic printing plate support
obtained by treating an aluminum substrate;
[0016] producing a recycled bare metal by introducing the obtained
recycled material into a melting furnace, melting the recycled
material at a temperature of from 680.degree. C. to 900.degree. C.
to obtain a recycled material melt, and shaping the recycled
material melt into a predetermined shape with a predetermined
weight;
[0017] analyzing the aluminum purity and a trace metal content of
the obtained recycled bare metal;
[0018] comparing analysis values of the aluminum purity and the
trace metal content of the obtained recycled bare metal with a
desired aluminum purity and a desired trace metal content
predetermined for a planographic printing plate support in order to
calculate differences therebetween, and determining a mixture ratio
of a new aluminum bare metal and a trace-metal master alloy with a
determined purity with respect to the recycled bare metal on the
basis of the calculated differences;
[0019] producing a pre-rolling melt by introducing the recycled
bare metal, the new aluminum bare metal, and the trace-metal master
alloy into a pre-rolling melting furnace at amounts corresponding
to the determined mixture ratio, and heating and melting; and
[0020] producing a strip-shaped aluminum substrate by rolling the
obtained pre-rolling melt.
[0021] In the method of producing an aluminum substrate for a
planographic printing plate according to a first embodiment of the
invention, the planographic printing plate support is obtained by
sequentially performing a roughening treatment, an anodization
treatment, and a hydrophilizing treatment using an aqueous solution
containing polyvinyl phosphonic acid on the aluminum substrate.
[0022] Furthermore, as a result of vigorous study, the inventors
have been discovered that the above-mentioned object could be
accomplished by using a used planographic printing plate including
an aluminum substrate formed of aluminum alloy containing a
specific amount of Cu, whereby the invention was made.
[0023] That is, in the method of producing an aluminum substrate
for a planographic printing plate according to a second embodiment
of the invention, the planographic printing plate support is
obtained by sequentially performing a roughening treatment and an
anodization treatment using an electrolytic solution containing
phosphoric acid on the aluminum substrate.
[0024] The recycled material, which is used in the production
method according to the invention, of the aluminum substrate
including a used planographic printing plate is not particularly
limited to the used planographic printing plate, but may include
cut pieces of an aluminum substrate or cut pieces of a planographic
printing plate, which are generated in the course of producing the
planographic printing plate.
[0025] According to a first embodiment of the invention, there is
provided a method of recycling a planographic printing plate, the
method sequentially including:
[0026] producing a planographic printing plate support obtained by
treating an aluminum substrate for the planographic printing
plate;
[0027] producing a planographic printing plate precursor by forming
an image recording layer on the treated surface of the planographic
printing plate support;
[0028] processing the obtained planographic printing plate
precursor to obtain a planographic printing plate and performing a
desired printing on the obtained planographic printing plate;
[0029] recovering the used planographic printing plate generated
after printing; and
[0030] recycling the recovered planographic printing plate by
providing the recovered planographic printing plate as the recycled
material of an aluminum substrate in the method of producing an
aluminum substrate for a planographic printing plate.
[0031] In the method of producing an aluminum substrate for a
planographic printing plate according to a first embodiment of the
invention, the planographic printing plate support is obtained by
sequentially performing a roughening treatment, an anodization
treatment, and a hydrophilizing treatment using an aqueous solution
including polyvinyl phosphonic acid on at least one surface of an
aluminum substrate.
[0032] Further, in the method of producing an aluminum substrate
for a planographic printing plate according to a second embodiment
of the invention, the planographic printing plate support is
obtained by sequentially performing a roughening treatment and an
anodization treatment using an electrolytic solution including
phosphoric acid on at least one surface of an aluminum
substrate.
[0033] Here, the aluminum substrate for the planographic printing
plate may be the recycled aluminum substrate for the planographic
printing plate obtained by the above-mentioned method of producing
an aluminum substrate for a planographic printing plate.
[0034] Although the function of the method according to the first
embodiment of the invention is not clear, it is thought that the
support used in the invention made to be hydrophilic using the
polyvinyl phosphonic acid reduces the amount of aluminum oxide,
which is an oxide material generated by the contact of aluminum
with air at the time of melting aluminum during producing the
recycled bare metal, in comparison with an aluminum substrate not
having been subjected to the above-mentioned treatment, whereby the
loss of the aluminum material is small and the support can be
recycled with high yield.
[0035] Although the function in the method according to the second
embodiment of the invention is not clear, it is assumed as
follows.
[0036] In the aluminum substrate for the planographic printing
plate having been subjected to the anodization treatment using an
electrolytic solution containing phosphoric acid, the pore diameter
of the anodized oxide film formed on the surface of the support is
greater than that of the anodized oxide film formed using an
electrolytic solution containing generally-used sulfuric acid.
Since such a support is rapidly melted due to the large pore
diameter when preparing the melt by heating during production of
the recycled bare metal, the duration of time that the recycled
material contacts air under a high-temperature condition is
shortened in comparison with a support including an anodized oxide
film having plural pores with a small pore diameter. Accordingly,
since the amount of undesired aluminum oxide to be generated is
reduced, it is conceived that the loss of the aluminum material is
small and the support can be recycled with high yield. The ratio of
phosphoric acid in the acid components of the electrolytic solution
used in the invention is not particularly limited, but is
preferably 5% by mass or higher in view of efficiency, and the acid
components in the electrolytic solution may include only phosphoric
acid.
[0037] The invention includes determining the mixture ratio by
analyzing the aluminum purity and the trace-metal content of the
obtained recycled bare metal or the recycled melt, comparing the
analyzed values with a desired aluminum purity and the desired
trace-metal content of a planographic printing plate in order to
calculate differences therebetween, and determining the mixture
ratio of a new aluminum bare metal and trace-metal master alloy on
the basis of the differences, and thus the ratio for mixing the
maximum amount of recycled bare metal is determined, whereby
recycling with high yield is accomplished with reduced loss of raw
material.
[0038] Here, the "desired aluminum purity and the desired
trace-metal content of a planographic printing plate support" means
the "aluminum purity and the trace-metal content" required
depending on the types of the planographic printing plates to be
produced, and the optimal values are determined in advance
depending on the required performance of the respective
planographic printing plates.
[0039] Therefore, according to the invention, since the ratio for
mixing the maximum amount of recycled bare metal can be determined
with high precision on the basis of the set values, it is possible
to greatly reduce the amount of the new aluminum bare metal used,
which consumes great energy in the production thereof, and it is
thus possible to effectively reduce the amount of carbon dioxide in
producing an aluminum substrate for a planographic printing
plate.
[0040] Accordingly, even when a used planographic printing plate is
reused at the time of producing an aluminum substrate for a
planographic printing plate, it is possible to greatly reduce the
loss of energy and of yield.
[0041] The present invention provides a method of producing an
aluminum substrate for a planographic printing plate, which can
produce an aluminum substrate for a planographic printing plate
satisfying the quality of aluminum purity or trace-metal content
with a high yield even when a used planographic printing plate is
reused at the time of producing an aluminum substrate for a
planographic printing plate and which can reduce the accompanying
amount of aluminum oxide generated and greatly reduce the
generation of CO.sub.2, a cause of global warming.
[0042] The present invention also provides a method of recycling a
planographic printing plate with high efficiency which can greatly
reduce the generation of CO.sub.2 in the processes by using the
above-mentioned method of producing an aluminum substrate for a
planographic printing plate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] Exemplary embodiments of the present invention will be
described in detail based on the following figures, wherein:
[0044] FIG. 1 is a schematic diagram illustrating a flow of
closed-loop recycling in a method of recycling a planographic
printing plate;
[0045] FIG. 2 is a schematic diagram illustrating an example of a
recycled bare metal producing apparatus in which recycled bare
metal is produced from a used planographic printing plate;
[0046] FIG. 3A is a plan view illustrating a trapezoidally-shaped
recycled bare metal obtained by the method according to the
invention; and
[0047] FIG. 3B is a side view illustrating a trapezoidally-shaped
recycled bare metal obtained by the method according to the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0048] Hereinbelow, preferable embodiment of a method of producing
an aluminum substrate for a planographic printing plate and a
method of recycling a planographic printing plate according to the
invention is described in detail.
[0049] Method of producing aluminum substrate for planographic
printing plate
[0050] The method of producing an aluminum substrate for a
planographic printing plate according to a first embodiment of the
invention sequentially includes:
[0051] preparing recycled material including a used planographic
printing plate having a planographic printing plate support
obtained by sequentially performing a roughening treatment, an
anodization treatment, and a hydrophilizing treatment using an
aqueous solution containing polyvinyl phosphonic acid on the
aluminum substrate;
[0052] producing a recycled bare metal by introducing the obtained
recycled material into a melting furnace, melting the recycled
material at a temperature of from 680.degree. C. to 900.degree. C.
to obtain a recycled material melt, and shaping the recycled
material melt into a predetermined shape with a predetermined
weight;
[0053] analyzing the aluminum purity and a trace metal content of
the obtained recycled bare metal;
[0054] comparing analysis values of the aluminum purity and the
trace metal content of the obtained recycled bare metal with a
desired aluminum purity and a desired trace metal content
predetermined for a planographic printing plate support in order to
calculate differences therebetween, and determining a mixture ratio
of new aluminum bare metal and a trace-metal master alloy with a
determined purity with respect to the recycled bare metal on the
basis of the calculated differences;
[0055] producing a pre-rolling melt by introducing the recycled
bare metal, the new aluminum bare metal, and the trace-metal master
alloy into a pre-rolling melting furnace at amounts corresponding
to the determined mixture ratio, and heating and melting; and
[0056] producing a strip-shaped aluminum substrate by rolling the
obtained pre-rolling melt.
[0057] The method of producing an aluminum substrate for a
planographic printing plate according to a second embodiment of the
invention sequentially includes:
[0058] preparing a recycled material including a used planographic
printing plate having a planographic printing plate support
obtained by sequentially performing a roughening treatment and an
anodization treatment using an electrolytic solution including
phosphoric acid on the aluminum substrate;
[0059] producing a recycled bare metal by introducing the obtained
recycled material into a melting furnace, melting the recycled
material at a temperature of from 680.degree. C. to 900.degree. C.
to obtain a recycled material melt, and shaping the recycled
material melt into a predetermined shape with a predetermined
weight;
[0060] analyzing the aluminum purity and a trace metal content of
the obtained recycled bare metal;
[0061] comparing analysis values of the aluminum purity and the
trace metal content of the obtained recycled bare metal with a
desired aluminum purity and a desired trace metal content
predetermined for a planographic printing plate support in order to
calculate differences therebetween, and determining a mixture ratio
of a new aluminum bare metal and a trace-metal master alloy with a
determined purity with respect to the recycled bare metal on the
basis of the calculated differences;
[0062] producing a pre-rolling melt by introducing the recycled
bare metal, the new aluminum bare metal, and the trace-metal master
alloy into a pre-rolling melting furnace at amounts corresponding
to the determined mixture ratio, and heating and melting; and
[0063] producing a strip-shaped aluminum substrate by a rolling the
obtained pre-rolling melt.
[0064] Hereinbelow, the present invention is described in
detail.
[0065] Planographic Printing Plate Support
[0066] The support used in the production method according to the
first embodiment of the invention is a planographic printing plate
support obtained by sequentially performing a roughening treatment,
an anodization treatment, and a hydrophilizing treatment using an
aqueous solution containing polyvinyl phosphonic acid on an
aluminum substrate.
[0067] The support used in the production method according to the
second embodiment of the invention is a planographic printing plate
support obtained by sequentially performing a roughening treatment
and an anodization treatment using an electrolytic solution
containing phosphoric acid on an aluminum substrate.
[0068] Aluminum Substrate
[0069] First, an aluminum substrate is prepared.
[0070] As aluminum which is a raw material of the aluminum
substrate used in the invention, a known material such as JIS1050,
JIS1100, JIS3003, JIS3103, or JIS3005 material, which are described
in the fourth version of Aluminum Handbook (1990), Japan Light
Metal Association) can be used. The aluminum substrate used in the
second embodiment of the invention has an aluminum (Al) content of
95% by mass to 99.4% by mass and may further contain a trace metal
such as copper (Cu), iron (Fe), silicon (Si), magnesium (Mg),
manganese (Mn), zinc (Zn), chrome (Cr), or titanium (Ti).
[0071] The Al content in the aluminum alloy as the substrate is
preferably in the range of from 95% by mass to 99.4% by mass. When
the Al content in the aluminum alloy is within the above range, the
high recycling rate of the aluminum substrate can be
accomplished.
[0072] The aluminum substrate used in the invention is produced by
appropriately performing a rolling treatment or a heating treatment
on the resultant that is molded by a conventional method using the
above-mentioned aluminum as a raw material to make the thickness
0.1 nm to 0.7 mm, and performing a remedial leveling treatment if
necessary.
[0073] Examples of the method of molding an aluminum substrate
include a DC casting method, a method in which a soaking treatment
and/or an annealing treatment is omitted from the DC casting
method, and a continuous casting method.
[0074] Roughening Treatment
[0075] The aluminum substrate used in the invention is subjected to
a roughening treatment. Examples of the roughening method include a
chemical etching method, an electrochemical roughening method in
which roughening treatment is electrochemically performed in a
hydrochloric or nitric electrolytic solution, and a mechanical
roughening method using a wire brush grain, a ball grain, and a
brush grain roughening the surface with a nylon brush and an
abrasive compound. The roughening methods may be used singly or in
combination of two or more thereof. Among these, it is useful to
use the electrochemical roughening method in which roughening
treatment is chemically performed in a hydrochloric or nitric
electrolytic solution. The amount of electricity suitable for the
anode is in the range of from 50 C/dm.sup.2 to 400 C/dm.sup.2. More
specifically, it is preferable that the AC and/or DC electrolysis
is performed under the conditions of a temperature of from
20.degree. C. to 80.degree. C., a time of 1 second to 30 minutes,
and a current density of from 100 C/dm.sup.2 to 400 C/dm.sup.2 in
the electrolytic solution containing hydrochloric acid or nitric
acid of 0.1% to 50%.
[0076] The aluminum substrate having been subjected to the
roughening treatment may be chemically etched using acid or alkali.
Preferable examples of an etching agent include sodium hydroxide,
sodium carbonate, sodium aluminate, sodium metasilicate, sodium
phosphate, potassium hydroxide, and lithium hydroxide. The
concentration and the temperature are preferably in the range of
from 1% to 50% and in the range of from 20.degree. C. to
100.degree. C., respectively. To remove the contamination (smut)
remaining on the etched surface, an acid wash is performed.
Examples of the acid include nitric acid, sulfuric acid, phosphoric
acid, chromic acid, fluoric acid, hydrofluoric acid, and
hydrofluoboric acid.
[0077] The methods and conditions of the roughening treatment are
not particularly limited, as long as the center line average
roughness (Ra) of the treated surface is in the range of from 0.2
.mu.m to 0.55 .mu.m.
[0078] Anodization Treatment in First Embodiment
[0079] In the first embodiment of the invention, the roughened
aluminum substrate is subjected to an anodization treatment to form
an oxide film thereon. In the anodization treatment, an aqueous
solution of sulfuric acid, phosphoric acid, oxalic acid or boric
acid/sodium borate is used singly or in combination thereof as a
major component of the electrolytic bath. The conditions of the
anodization treatment is not particularly limited, but the
anodization treatment is preferably performed by DC or AC
electrolysis under the conditions of from 30 g/L to 500 g/L, a
processing solution temperature of from 10.degree. C. to 70.degree.
C., and a current density of from 0.1 A/m.sup.2 to 40 A/m.sup.2.
The thickness of the anodized oxide film is preferably in the range
of from 0.5 .mu.m to 1.5 .mu.m and more preferably in the range of
from 0.5 to 1.0 .mu.m.
[0080] Anodization Treatment in Second Embodiment
[0081] In the second embodiment of the invention, the roughened
aluminum substrate is subjected to the anodization treatment using
an electrolytic solution containing phosphoric acid to form an
oxide film thereon.
[0082] In the second embodiment of the invention, the electrolytic
solution containing phosphoric acid is used for anodization
treatment. The content of phosphoric acid in the electrolytic
solution is not particularly limited, but, in view of effect, the
content of phosphoric acid with respect to the acid component
contained in the electrolytic solution is preferably 5% by mass or
higher, more preferably 70% by mass or higher, and still more
preferably 90% by mass. The acid component may include only
phosphoric acid.
[0083] The content of phosphoric acid in the electrolytic solution
is preferably in the range of from 10% by mass to 50% by mass, and
more preferably in the range of from 20% by mass to 40% by mass.
The electrolytic solution is generally an aqueous solution
containing phosphoric acid as a major component.
[0084] The electrolytic solution used in the second embodiment of
the invention may contain other acid components used in the
anodization treatment, such as sulfuric acid, oxalic acid, or boric
acid/sodium borate, as long as the effect of the invention is not
deteriorated. The electrolytic solution generally is an aqueous
solution of the above-mentioned acid components, and the acid
components including phosphoric acid as a major component thereof
are used singly or in combination.
[0085] The electrolytic solution may contain known additives other
than the acid components containing phosphoric acid.
[0086] In the second embodiment of the invention, the conditions of
the anodization treatment using the electrolytic solution
containing phosphoric acid are not particularly limited, but the
temperature of the processing solution is preferably in the range
of from 10.degree. C. to 70.degree. C., more preferably in the
range of from 10.degree. C. to 50.degree. C., and still more
preferably in the range of from 25.degree. C. to 45.degree. C. The
current density used in the DC or AC electrolysis is in the range
of from 0.1 A/m.sup.2 to 40 A/m.sup.2, preferably in the range of
from 0.2 A/m.sup.2 to 10 A/m.sup.2, more preferably in the range of
from 1 A/m.sup.2 to 7 A/m.sup.2. The process time can be
appropriately selected depending on the thickness of the anodized
oxide film to be formed, is preferably in the range of from 10
seconds to 10 minutes, and more preferably in the range of from 20
seconds to 3 minutes.
[0087] The thickness of the anodized oxide film formed in the
second embodiment of the invention is preferably in the range of
from 0.5 .mu.m to 1.5 .mu.m and more preferably in the range of
from 0.5 .mu.m to 1.0 .mu.m.
[0088] When the anodization treatment is performed using the
electrolytic solution containing phosphoric acid, the pore diameter
of the anodized oxide film to be formed increases. The average pore
diameter of the pores in the oxide film is preferably in the range
of from 200 .ANG. to 900 .ANG., more preferably in the range of
from 300 .ANG. to 900 .ANG., and, still more preferably in the
range of from 400 .ANG. to 900 .ANG.. Since the pore diameter of
the anodized oxide film generally formed by the electrolytic
solution containing sulfuric acid is around 100 .ANG., it can be
seen that pores with a greater diameter are formed using the
electrolytic solution containing phosphoric acid. The average pore
density is preferably in the range of from 100/.mu.m.sup.2 to
1000/.mu.m.sup.2, more preferably in the range of from
100/.mu.m.sup.2 to 500/.mu.m.sup.2, and still more preferably in
the range of from 100/.mu.m.sup.2 to 350/.mu.m.sup.2.
[0089] The average pore diameter and pore density of the pores in
the second embodiment of the invention are average values which are
obtained by taking an image of the surface of the anodized oxide
film with an electron microscope and measuring the pore diameter of
the pores and the number of pores in the unit area in the electron
microscopic image to calculate the average pore diameter and
density, and performing these processes on five positions in the
anodized oxide film.
[0090] In the anodization method according to the second embodiment
of the invention, the anodized oxide film having pores with an
average pore diameter of 200 .ANG. or greater and preferably 300
.ANG. or greater is formed. Accordingly, when the planographic
printing plate using such a support is recycled, the used
planographic printing plate is rapidly and efficiently melted at
the time of producing a melt in the production of the recycled bare
metal, thereby reducing the amount of undesirable aluminum oxide
incidentally produced.
[0091] Hydrophilizing Treatment Using Aqueous Solution Containing
Polyvinyl Phosphonic Acid in First Embodiment
[0092] In the first embodiment of the invention, as described
above, the support which has the anodized oxide film formed thereon
and then treated with the aqueous solution containing polyvinyl
phosphonic acid is used.
[0093] Examples of the treatment using the aqueous solution
containing polyvinyl phosphonic acid used in the first embodiment
of the invention include a treatment method using polyvinyl
phosphonic acid described as a hydrophilizing treatment in U.S.
Pat. No. 4,153,461. For example, an aluminum substrate is treated
by immersing it in the below-described aqueous solution. Other than
the immersion, the aqueous solution may be applied with a brush, a
sponge, a spray, a wheel coater, or the like. After the treatment,
washing with water and drying may be performed as necessary.
[0094] The polyvinyl phosphonic acid is vinyl polymer having a
phosphonate group and has preferably a number average molecular
weight of from 10,000 to 25,000. The content of polyvinyl
phosphonic acid is preferably in the range of from 0.1% by mass to
5.0% by mass in the aqueous solution. The processing temperature is
preferably in the range of from 20.degree. C. to 90.degree. C. and
the processing time is preferably in the range of from 10 seconds
to 30 seconds. The aqueous solution may be an aqueous solution
containing a volatile solvent such as ethyl alcohol,
tetrahydrofuran, acetone, or methyl glycol acetate.
[0095] The amount of polyvinyl phosphate acid attached to the
surface of the support having been subjected to the surface
treatment using polyvinyl phosphonic acid is preferably in the
range of from 8 mg/m.sup.2 to 20 mg/m.sup.2 in terms of the content
of the phosphorous element. When the attached amount is small, it
is not sufficient to suppress the production of aluminum oxide. The
attached amount can be measured by the measurement of element
content using fluorescent X ray.
[0096] Hydrophilizing Treatment in Second Embodiment
[0097] In the second embodiment of the invention, the anodized
oxide film is formed as described above and then a hydrophilizing
treatment may be performed on the surface thereof. As the
hydrophilizing treatment, a method using an alkali metal silicate
(for example, aqueous solution of sodium silicate) such as those
described in U.S. Pat. Nos. 2,714,066, 3,181,461, 3,280,734, and
3,902,734 can be preferably used. In this method, the support is
immersed in the aqueous solution of sodium silicate or is
electrolyzed in the aqueous solution of sodium silicate. Preferable
examples of the methods also include processing methods using
potassium fluorozirconate as disclosed in Japanese Examined Patent
Application Publication (JP-B) No. 36-22063, and using polyvinyl
phosphonic acid as disclosed in U.S. Pat. Nos. 3,276,868,
4,153,461, and 4,689,272. Among these, the hydrophilizing treatment
is preferably performed using aqueous solutions of sodium silicate
and polyvinyl phosphonic acid.
[0098] The aluminum substrate produced in the first embodiment or
the second embodiment preferably has a surface roughness (Ra) of
from 0.2 .mu.m to 0.55 .mu.m. When the surface roughness (Ra) is
0.2 .mu.m or more, the incompleteness in graining of the aluminum
substrate can be more effectively suppressed and printing
durability can be improved. When the surface roughness (Ra) is 0.55
.mu.m or less, deterioration in reproducibility of small points and
fine lines due to the difficulty in photo-polymerization at a deep
part of the grained surface can be more effectively suppressed. The
surface roughness (Ra) (roughness of the grained surface) is more
preferably in the range of from 0.25 .mu.m to 0.5 .mu.m, and still
more preferably in the range of from 0.3 .mu.m to 0.45 .mu.m.
[0099] In general, an image recording layer formed of a
photosensitive composition depending on purposes is formed on the
surface of the support, thereby obtaining a planographic printing
plate precursor.
[0100] Preferable examples of the photosensitive composition used
in the invention include a thermal positive photosensitive
composition containing a photothermal material and an
alkali-soluble high-molecular compound, a thermal negative
photosensitive composition containing a photothermal material and a
thermosetting compound, a conventional negative photosensitive
composition containing a diazo resin and an alkali-soluble
high-molecular compound, a conventional positive photosensitive
composition containing an o-quinine di-azide compound and an
alkali-soluble high-molecular compound, and a photosensitive
composition that can be developed in a printer.
[0101] The photosensitive layer of the thermal positive
photosensitive composition contains the alkali-soluble
high-molecular compound such as a novolak resin and the
photothermal material such as a cyanine dye, and preferably further
contains an anti-soluble agent. The photosensitive layer is not
limited to a single layer, but may have a two-layered
structure.
[0102] The photosensitive layer of the thermal negative
photosensitive composition contains the photothermal material and
the thermosetting compound and serves to cure the region irradiated
with an infrared ray to form an image area. This photosensitive
layer may be a polymerization photosensitive layer containing an
infrared absorber such as a cyanine dye, a radical generator such
as an onium salt, a radical polymerized compound, and a binder
polymer, or may be an acid cross-link photosensitive layer
containing an infrared absorber, a thermal acid generator, an acid
crosslinking agent, and an alkali-soluble high-molecular
compound.
[0103] The photopolymerization photosensitive composition contains
a compound having an ethylenically unsaturated bond, a
photo-polymerization initiator, and an alkali-soluble
high-molecular binder. The photo-polymerization initiator can be
appropriately selected depending on the wavelength of a light
source to be used. It is preferable to form an oxygen-blocking
protective layer such as polyvinyl alcohol on the photosensitive
layer.
[0104] The photosensitive layer of the photosensitive composition
that can be developed in a printer may be a thermo-sensitive
thermoplastic fine particle polymer or micro capsule.
[0105] A mechanism for forming an image in the image recording
layer is not limited, and an area to which energy is applied by
exposure or heating is improved in solubility or is cured, whereby
the solubility to developer is altered.
[0106] Examples of the light source of activating rays used in
exposing an image include a mercury lamp, a metal halide lamp, and
a xenon lamp, and examples of the light source for scanning
exposure include a helium neon laser, an argon laser, a KrF excimer
laser, a semiconductor laser, and a YAG laser.
[0107] In the developing process, the non-cured area or the solved
area in the image recording layer is removed, thereby obtaining
planographic printing plate.
[0108] The obtained planographic printing plate is attached to a
printer, and ink and dampening water are supplied thereto, whereby
a printing is carried out.
[0109] The present invention is characterized by the mixture ratio
determination process in which various recycled aluminum materials
together with the above-mentioned support is melted by the use of a
melting furnace other than the pre-rolling melting furnace to
obtain a recycled bare metal with a predetermined shape and weight,
and the mixture ratio of the recycled bare metal, new bare metal,
and trace-metal master alloy to be introduced into the pre-rolling
melting furnace is determined on the basis of the analysis result
of the obtained recycled bare metal (or recycled melt).
[0110] FIG. 1 is a diagram illustrating a closed-loop recycling
flow in the method of recycling a planographic printing plate
according to the invention, in which a planographic printing plate
having a photosensitive image recording layer is exemplified.
[0111] The method of producing an aluminum substrate for a
planographic printing plate according to the invention is included
as a part of the closed-loop recycling flow.
[0112] Preparation of Recycled Material
[0113] In this process, recycled material is prepared. In general,
an unnecessary used planographic printing plate having been
subjected to a printing is recovered and used as the recycled
material.
[0114] The used planographic printing plate may be used as the
recycled material without any change, or may be subjected to a
process of removing printing ink attached to the surface
thereof.
[0115] As shown in FIG. 1, a used planographic printing plate 36
used for printing in a printing company 32 is recovered by the
printing company, and then sent to and processed by a recycling
plant 34.
[0116] In the invention, end materials such as cut pieces of a
planographic printing plate produced in the course of producing the
planographic printing plate may be included as the recycled
material in addition to the used planographic printing plate (the
end material 33 generated in processing a strip-shaped plate
precursor shown in FIG. 1). When a protective sheet or a packing
paper is attached to the recycled material, the protective sheet or
the packing paper is preferably removed. The attached material such
as image recording layer or the ink is preferably removed in
advance from the recycled material before melting the recycled
material. It is more preferable that the attached material such as
the image recording layer or the ink is removed to be 1% by mass or
less.
[0117] The recycled material may be cut into pieces, for example,
using the method described JP-A-2000-12718 so as to improve its
melting efficiency.
[0118] Production of Recycled Bare Metal
[0119] FIG. 2 shows an example of a recycled ingot producing
apparatus 38, in which a recycled material 40 containing the used
planographic printing plate 36 generated in the printing company 32
and the end material 33 with a side of 1 cm to 60 cm generated in
the production plant 18 of a planographic printing plate are
processed to produce a recycled melt, and a recycled bare metal is
produced.
[0120] The recycled ingot producing apparatus 38 includes a melting
furnace 42 melting the recycled material 40 to produce a melt 44, a
casting mold solidifying the melt 44 to form a recycled ingot 74,
and a receiver receiving the recycled ingot 74 from the lower
side.
[0121] The top of the melting furnace 42 is covered with a ceiling
wall 46, a partition wall vertically extends to a bottom wall from
the ceiling wall 46, and an introduction port 48 is disposed in a
side wall. A burner 50 is disposed in the other side wall opposed
to the introduction port 48 and serves to heat and melt the
recycled material 40 introduced from the introduction port. In the
second embodiment of the invention, when the recycled material 40
starts to be partially melted by the heating from the outside, the
recycled material partially changed to a liquid phase rapidly
reaches a deep part of the anodized oxide film through relatively
large pores formed in the anodized oxide film, whereby the
high-temperature melt diffuses and infiltrates and the recycled
material is rapidly melted into a liquid phase.
[0122] When the melting furnace 42 is a dedicated melting furnace
exclusively melting the recycled material 40, the variation in
component purity (aluminum purity or trace metal content) of the
obtained recycled melt 44 can be suppressed as much as possible. In
view of improvement in purity of the recycled bare metal, it is
preferable that the melting furnace 42 performs melting pure
aluminum with an aluminum content of 99.5% or more and the inside
is washed before melting the recycled material 40. It is also
preferable that the melting furnace 42 is filled in advance with a
melt up to about 1/3 to 1/2 the furnace capacity before introducing
the recycled material 40 thereto. Therefore, in the first stage of
recycling, a melt of pure aluminum exists in advance by the
above-mentioned amount.
[0123] In the melting step according to the invention, it is
possible to enhance the melting speed and to shorten the tact time
until obtaining the recycled melt 44, by melting the recycled
material in the melting furnace 42 at a temperature range of from
680.degree. C. to 900.degree. C.
[0124] In general, in the recycled melt producing apparatus, since
the recycled material 40 and the melt 44 come in direct contact
with air, aluminum oxide is inevitably produced at the time of
heating and melting aluminum metal. Since the melted aluminum oxide
is lighter than pure aluminum, the melted aluminum oxide exists in
the vicinity of the surface of the melt.
[0125] In the first embodiment of the invention, since the surface
of the aluminum substrate for the planographic printing plate used
as the recycled material is treated by polyvinyl phosphonic acid,
the production of aluminum oxide is reduced at the time of heating
and melting the aluminum substrate in the recycled melt producing
apparatus.
[0126] In the second embodiment of the invention, since the
anodized oxide film on the surface of the aluminum substrate for
the planographic printing plate used as the recycled material has
pores with relatively large diameters, the aluminum substrate is
efficiently liquefied for a short time as described above.
Accordingly, since the duration of time that the solid state brings
into contact with air (oxygen) under a high-temperature environment
is shortened, the amount of non-desired aluminum oxide produced by
the contact of the recycled material with air under the
high-temperature environment is reduced.
[0127] When a predetermined amount of recycled material is
introduced into and melted in the melting furnace 42, it is
preferable that a small amount of melt is extracted from the melt
44 for analysis in this stage.
[0128] The melt 44 from which a small amount of melt for analysis
has been extracted is supplied to a casting mold 54 having a
trapezoid shape through a pipe 52. In this case, the total amount
of melt 44 is not supplied, but it is preferable that 1/3 to 1/2 of
the total amount of melt is left in the melting furnace 42 so as to
use the remaining melt as a preliminary melt of the next melt
treatment.
[0129] The melt in the casting mold 54 is cooled by water or air
and is shaped into recycled bare metal (ingot) 74 of a trapezoid
shape with 10 Kg to 1200 Kg. A possible shape of the recycled ingot
is shown in FIGS. 3A and 3B. FIG. 3A is a plan view illustrating an
example of the trapezoid shape of the recycled bare metal and FIG.
3B is a side view thereof
[0130] Analysis
[0131] In the aluminum recycling plant 34, the components of the
extracted recycled melt is analyzed. In some cases, an analysis
sample may be extracted from the recycled bare metal 74. In the
first embodiment of the invention, the aluminum purity and the
content of the trace metal (such as Si, Fe, Cu, or Mn) is analyzed
and Mg, Zn, Ti, and Cr can be preferably analyzed. In the second
embodiment of the invention, the aluminum purity and the content of
the trace metal (such as Cu, Si, Fe, or Mn) is analyzed and Mg, Zn,
Ti, and Cr can be preferably analyzed. The analysis data is also
sent when the recycled bare metal is delivered to the aluminum
rolling plant 14. When the analysis is performed using the recycled
bare metal 74, the analysis step may be performed in the aluminum
rolling plant 14.
[0132] Determination of Mixture Ratio
[0133] The recycled bare metal 74 produced in the production plant
34 is carried to the aluminum rolling plant 14, and is recycled
therein. In the aluminum rolling plant 14, the values of the
aluminum purity and the trace metal content obtained as the result
in the above-mentioned analysis process are compared with a desired
aluminum purity and a desired trace metal content of an aluminum
substrate for a desired planographic printing plate in order to
calculate differences therebetween, and the mixture ratio of a new
bare metal with a determined aluminum purity and a trace-metal
master alloy (aluminum alloy) with a determined trace-metal content
with respect to the recycled bare metal is determined on the basis
of the calculated difference. By this process, the maximum mixture
ratio of the recycled bare metal for accomplishing desired aluminum
purity and a desired trace metal content in the desired aluminum
substrate for a planographic printing plate can be known, and the
best recycling efficiency depending on the composition of the
recycled bare metal can be achieved.
[0134] Production of Pre-rolling Melt
[0135] The recycled bare metal, the new aluminum bare metal, and
the trace-metal master alloy are introduced into the pre-rolling
melting furnace with the mixture ratio determined in the mixture
ratio determination process, and are heated and melted, thereby
obtaining an aluminum melt used for producing a support. The
pre-rolling melting furnace is generally much greater in capacity
than the recycling melting furnace 42 and has a scale of 100 t.
[0136] The aluminum purity of the pre-rolling melt obtained in this
process is preferably 99.0% or higher and more preferably 99.5% or
higher. The aluminum plate with aluminum purity of 99.5% or higher
can be preferably used for the electrolytic roughening treatment as
described later. When the aluminum purity is less than 99.0%, a
problem with cracks or the like can be easily caused at the time of
rolling an aluminum plate in a rolling treatment. The trace metal
content is selected depending on a target physical property of the
aluminum substrate for the planographic printing plate. In the
second embodiment of the invention, the Cu content should be in the
above-mentioned range.
[0137] The melting condition may be the same as the melt producing
condition in the recycled bare metal producing process or may be
properly controlled depending on the rolling condition of the
support.
[0138] Production of Aluminum Substrate
[0139] An impurity removing treatment using flux, gas, or filter is
performed on the resultant aluminum melt to remove non-metal
impurities or combustion gas of the non-metal impurities, oxides,
and the like and to remove H.sub.2 gas or Na melted in the melt.
The melt is processed preferably in two steps of a method using gas
and a method using filter. The processed aluminum melt is cast
preferably on the basis of a DC casting method using a twin-roll
continuous caster or a fixed casting mold. The resultant is rolled
in the above-mentioned process into a predetermined thickness and
subjected to an annealing process as needed, whereby a strip-shaped
aluminum substrate is produced. In general, the produced aluminum
substrate 16 is stored and carried as an aluminum coil wound in a
coil shape. The resultant aluminum substrate 16 is sent to the
planographic printing plate producing plant 18 in the aluminum coil
state. The recycled aluminum substrate 16 is provided to produce a
planographic printing plate precursor.
[0140] According to the invention, it is possible to efficiently
recycle and produce an aluminum substrate for a planographic
printing plate.
[0141] Production of Planographic Printing Plate Precursor
[0142] The resultant aluminum substrate for a planographic printing
plate is used for producing a planographic printing plate
precursor. In this way, the planographic printing plate is recycled
according to the invention.
[0143] Hereinafter, a method of producing a planographic printing
plate precursor using the resultant aluminum substrate for a
planographic printing plate is described.
[0144] Production of Support
[0145] In the first embodiment of the invention, the aluminum
substrate 16 obtained by the above-mentioned production method is
first subjected to a roughening treatment required for a
planographic printing plate support. Here, one surface or both
surfaces of the aluminum substrate 16 are roughened.
[0146] In the second embodiment of the invention, the aluminum
substrate 16 formed of the aluminum alloy containing a specific
amount of Cu and obtained by the above-mentioned production method
is subjected to a roughening treatment required for a planographic
printing plate support. Here, one surface or both surfaces of the
aluminum substrate 16 are roughened.
[0147] The roughening treatment is not particularly limited, but
the electrochemical roughening treatment can be preferably used.
The electrochemical roughening treatment is performed by performing
an etching in an acid aqueous solution of hydrochloric acid or
nitric acid using AC current as electrolysis current. The acid
concentration is preferably in the range of from 3 g/L to 150 g/L
and the aluminum ion concentration in the solution is preferably
adjusted to the range of from 2 g/L to 7 g/L. The amount of
electricity to be applied is preferably in the range of from 20
C/dm.sup.2 to 500 C/dm.sup.2. It is preferable to use
rectangular-wave current or trapezoid-wave current as the AC
current, and it is more preferable to use the trapezoid-wave
current.
[0148] In the electrochemical roughening treatment using the
electrolysis method, the aluminum purity or the trace metal content
of the aluminum substrate 16 has an influence on the uniformity of
a produced pit, thereby affecting printing durability,
contamination resistance, and exposure stability. Accordingly, the
aluminum purity of the aluminum substrate is preferably 99.9% or
higher, and more preferably 99.5% or higher. Among the trace metals
contained in the aluminum substrate 16, the Cu content is
preferably in the range of 0.001% by mass to 0.050% by mass, more
preferably in the range of from 0.002% by mass to 0.040% by mass,
and still more preferably in the range of from 0.008% by mass to
0.035% by mass. It is preferable that the Si content is in the
range of from 0.05% by mass to 0.50% by mass, the Fe content is in
the range of from 0.15% by mass to 0.7% by mass, the Mn content is
in the range of from 0.002% by mass to 0.15% by mass, the Mg
content is in the range of from 0.001% by mass to 1.5% by mass, the
Zn content is in the range of from 0.001% by mass to 0.25% by mass,
the Ti content is in the range of from 0.001% by mass to 0.10% by
mass, the Cr content is in the range of from 0.001% by mass to
0.10% by mass.
[0149] Since smut or inter-metal compound exists in the surface of
the aluminum substrate 16 having been subjected to the roughening
treatment using the above-mentioned electrolysis method, the
surface is preferably processed with alkali and is then subjected
to a cleaning treatment using an acid solution containing sulfuric
acid as a major component.
[0150] In the first embodiment of the invention, the anodization
treatment is performed on the roughened aluminum substrate 16 to
form an anodized oxide film. In the anodization treatment, an
aqueous solution of sulfuric acid, phosphoric acid, oxalic acid, or
boric acid/sodium borate is used as a major component of the
electrolytic solution singly or in combination. The conditions for
forming the anodized oxide film is as described above. The
thickness of the anodized oxide film is preferably in the range of
from 0.5 .mu.m to 1.5 .mu.m and can be properly selected from this
range.
[0151] Various conditions of the hydrophilizing treatment to be
performed thereafter can be selected as needed. When the obtained
planographic printing plate precursor is used and then recycled
again, it is preferable in view of recycling efficiency that the
hydrophilizing treatment is performed using the polyvinyl
phosphonic acid.
[0152] The hydrophilizing treatment is not limited to this method,
but a known hydrophilizing treatment such as a hydrophilizing
treatment using a sodium silicate solution may be properly
performed. In this way, the planographic printing plate support 16A
of which the surface has been subjected to the hydrophilizing
treatment is obtained.
[0153] In the second embodiment of the invention, the anodization
treatment is performed on the roughened aluminum substrate 16 to
form an anodized oxide film. The anodization treatment can be
performed as described above, and an aqueous solution of sulfuric
acid, phosphoric acid, oxalic acid, or boric acid/sodium borate is
used as the major component of the electrolytic solution singly or
in combination. It is preferable in view of recycling efficiency of
the aluminum substrate that the electrolytic solution containing
phosphoric acid as a major component is used as described above.
The conditions for forming the anodized oxide film is as described
above. The thickness of the anodized oxide film is preferably in
the range of from 0.5 .mu.m to 1.5 .mu.m and can be properly
selected from this range.
[0154] Various conditions of the hydrophilizing treatment to be
performed thereafter can be selected as needed.
[0155] A known hydrophilizing treatment such as a hydrophilizing
treatment using a sodium silicate solution or a hydrophilizing
treatment using a polyvinyl phosphonic acid solution may be
properly performed. In this way, the planographic printing plate
support 16A of which the surface has been subjected to the
hydrophilizing treatment is obtained.
[0156] Formation of Image Recording Layer
[0157] Then, an image recording layer is formed on the obtained
support, whereby the planographic printing plate precursor is
produced. In the image recording layer forming process, a coating
solution for the image recording layer formed of a photosensitive
composition is applied to the roughened surface of the support 16A
and the image recording layer is dried in the drying process.
[0158] Examples of the photosensitive compositions suitably used to
form the image recording layer according to the invention include a
thermal positive photosensitive composition containing a
photothermal material and an alkali-soluble high-molecular
compound, a thermal negative photosensitive composition containing
a photothermal material and a thermosetting compound, a
photopolymerization photosensitive composition, a negative
photosensitive composition containing a diazo resin and a
photo-crosslink resin, a positive resin photosensitive composition
containing a quinine di-azide compound, and a photosensitive
composition that does not require a specific developing step.
[0159] In this manner, a strip-shaped plate precursor of a
planographic printing plate is produced, and the strip-shaped plate
precursor is cut into rectangular sheets with a predetermined size
in a state in which a laminated paper is superposed on the
strip-shaped plate precursor, thereby producing a planographic
printing plate precursor 30 having a laminated paper attached
thereto (see FIG. 1).
[0160] Plural produced planographic printing plate precursors 30
each having a laminated paper attached thereto are stacked, packed,
and sent to the printing company 32. Since the laminated paper is
placed between the planographic printing plate precursors 30 at the
time of stacking the planographic printing plate precursors 30,
damages on the image recording layer of the planographic printing
plate precursors 30 at the time of carrying and storing the plates
are effectively suppressed. The laminated paper is removed before
forming an image on the image recording layer.
[0161] The planographic printing plate precursor is made up through
a writing process (image forming step) by exposure or heating and
optionally performing the development, thereby obtaining a
planographic printing plate.
[0162] The obtained planographic printing plate is supplied with
print ink and dampening water, and is then printed to a printing
process.
[0163] In the method of recycling a planographic printing plate
according to the invention, a "new bare metal 100% route" 90
sending the aluminum substrate 16 of 100% new bare metal from the
aluminum rolling plant 14 to the planographic printing plate
producing plant 18 is carried out only at the first time, a
"recycling route" 92 sending an aluminum substrate 88 containing a
recycled material, which is obtained by the method of producing an
aluminum substrate for a planographic printing plate according to
the invention, from the aluminum rolling plant 14 to the
planographic printing plate producing plant 18 is carried out at
the second time or later.
[0164] In the method according to the invention, it is possible to
construct a complete closed-loop recycling flow for recycling
aluminum scraps generated in the field of planographic printing
plate industry. As a result, it is possible to greatly reduce the
generation of CO.sub.2, compared with the case in which an aluminum
substrate for a planographic printing plate is produced using only
the new aluminum bare metal 12 produced by an aluminum refining
plant 10.
[0165] Therefore, in the method according to the invention, it is
possible to guarantee the quality of the aluminum purity and the
trace metal content in the obtained aluminum substrate for a
planographic printing plate, to improve the energy loss and the
yield loss markedly, and to greatly reduce the generation of
CO.sub.2 in production of the planographic printing plate
precursor.
EXAMPLES
[0166] Hereinafter, examples of the invention is described, but the
invention is not limited to the examples.
Examples 1-1 and 1-2 and Comparative Example 1-1
[0167] 1. Production of Aluminum Substrate
[0168] A melt was produced using aluminum alloy containing 0.073%
by mass of Si, 0.270% by mass of Fe, 0.028% by mass of Cu, 0.001%
by mass of Mn, 0.001% by mass of Cr, 0.003% by mass of Zn, 0.020%
by mass of Ti and the balance of Al and inevitable impurities, and
an aluminum substrate used in Example 1-1 was produced as
follows.
[0169] First, a melt process including degassing and filtering was
performed to the aluminum alloy melt and a cast ingot with a
thickness of 500 mm was produced using a DC casting method. The
surface of the obtained cast ingot was face-milled by 10 mm, the
cast ingot was heated, the hot rolling was started at 400.degree.
C. without soaking the cast ingot, and then the resultant was
rolled up to the thickness of 4 mm. Then, the resultant was
cold-rolled up to the thickness of 1.5 mm, process annealing was
carried out thereon, the resultant was cold-rolled up to 0.24 mm,
and the flatness was corrected, thereby obtaining an aluminum plate
(aluminum substrate).
[0170] 2. Production of Planographic Printing Plate Support
(Surface Treatment of Aluminum Substrate)
[0171] The obtained aluminum plate was subjected to the surface
treatment in the following process. After the surface treatment and
the water washing, liquid-cutting was carried out with a nip
roller. The water washing was carried out by ejecting water from a
spray tube.
[0172] 2-1. Mechanical Roughening Treatment
[0173] First, a mechanical roughening treatment was carried out
using a brush roller with a rotating nylon brush formed of
6,10-nylon and having a hair length of 50 mm, and a hair diameter
of 0.48 mm while supplying a suspension of silica (abrading agent,
average particle diameter of 25 .mu.m) with a specific gravity of
1.12 and water as a grinding slurry to the surface of the aluminum
plate.
[0174] 2-2. Chemical Roughening Treatment
[0175] Subsequently, an aqueous solution with a temperature of
70.degree. C. containing 27% by mass of NaOH and 6.5% by mass of
aluminum ions was ejected to the aluminum plate to perform an
alkali etching process. The amount of melted aluminum plate was 8
g/m.sup.2. An aqueous solution of nitric acid with a temperature of
35.degree. C. was sprayed to the aluminum plate to perform a
desmutting treatment for 10 seconds.
[0176] 2-3. Electrochemical Roughening Treatment
[0177] An electrochemical roughening treatment was carried out
using trapezoid-wave AC current and using an aqueous solution of
nitric acid containing 1% by mass of nitric acid (which contains
0.5% by mass of aluminum ions and 0.007% by mass of ammonium ions
at a temperature of 50.degree. C.). The current density at the peak
of the AC current was 50 A/dm.sup.2 when the aluminum plate was
used as an anode and a cathode, the ratio of the amount of
electricity of the AC current as the cathode to the amount of
electricity as the anode was 0.95, the duty ratio was 0.50, the
frequency was 60 Hz, and the total amount of electricity as the
anode was 180 C/dm.sup.2.
[0178] Thereafter, the water washing was carried out. Subsequently,
an aqueous solution with a temperature of 45.degree. C. containing
26% by mass of NaOH and 6.5% by mass of aluminum ions was ejected
to the aluminum plate by a spray to perform an alkali etching
process. The amount of melted aluminum plate was 3 g/m.sup.2. Then,
a sulfuric acid solution (with a sulfuric acid concentration of 300
g/L and an aluminum ion concentration of 15 g/L) was ejected to the
aluminum plate from a spray tube at 80.degree. C. for 7 seconds to
perform an acid etching process. Thereafter, the water washing was
carried out.
[0179] 2-4. Anodization Treatment
[0180] Subsequently, an anodization treatment was carried out on
the aluminum plate under the conditions of a current density of 25
A/dm.sup.2, a temperature of 50.degree. C., and a time of 30
seconds, by using an aqueous solution with a sulfuric acid
concentration of 100 g/L (containing 0.5% by mass of aluminum ions)
as an anodizing solution and using a DC voltage, whereby an oxide
film with a thickness of 1.5 .mu.m was formed. Thereafter, the
water washing was carried out by the use of a spray.
[0181] 2-5. Hydrophilizing Treatment Using Aqueous Solution of
Polyvinyl Phosphonic Acid
[0182] The resultant aluminum substrate was immersed in an aqueous
solution of 0.6% polyvinyl phosphonic acid (an aqueous solution
produced using well water) at a solution temperature of 60.degree.
C. for 30 seconds. In this way, an aluminum substrate (1) of a
planographic printing plate was obtained. The amount of attached
material measured using a fluorescent X ray was 18.8 mg/m.sup.2 in
terms of an amount of phosphorous element.
[0183] 3. Production of Planographic Printing Plate Precursor
(Formation of Image Recording Layer) 3-1. Undercoating
[0184] A 3% methanol solution of copolymer of p-vinyl benzoate acid
and vinylbenzyl triethylammonium chloride (copolymerization mole
ratio of 85/15, Mw 28,000) was applied to the processed surface of
the support by the use of a bar coater to form an undercoating
layer so that the coating amount after drying is 18 mg/m.sup.2.
[0185] 3-2. Formation of Recording Layer (Intermediate Layer)
[0186] The following lower layer coating solution was applied to
the aluminum substrate having the undercoating layer formed thereon
by the use of the bar coater so that the coating amount after
drying is 0.85 g/m.sup.2, and was then dried at 160.degree. C. for
44 seconds, thereby forming a lower layer. Thereafter, the
following upper layer coating solution was applied thereto by the
use of the bar coater so that the coating amount after drying is
0.22 g/m.sup.2, and was then dried at 148.degree. C. for 25
seconds, thereby forming a planographic printing plate
precursor.
[0187] Lower Layer Coating Solution
TABLE-US-00001 N-(4-aminosulfonylphenyl)
methacrylamide/acrylonitrile/methyl methacrylate (36/34/30: Mw
60,000) 1.73 g m,p-cresol novolak (m/p ratio = 6/4, Mw 4,500) 0.192
g Cyanine dye A (below structure) 0.134 g 3-methoxy-4-diazodiphenyl
amine hexafluorophosphate 0.032 g Ethyl violet 0.0781 g Polymer 1
(below structure) 0.035 g Methyl ethyl ketone 25.41 g
1-methoxy-2-propanol 12.97 g .gamma.-butyrolactone 13.18 g Cyanine
dye A ##STR00001## Polymer 1 ##STR00002##
[0188] Upper Layer Coating Solution
TABLE-US-00002 m,p-cresol novolak (m/p ratio = 6/4, Mw 4,500)
0.3479 g Cyanine dye A (above structure) 0.0192 g Polymer 1 (above
structure) 0.015 g Quaternary ammonium salt (below structure)
0.0043 g Methyl ethyl ketone 6.79 g 1-methoxy-2-propanol 13.07 g
Quaternary ammonium salt ##STR00003##
[0189] 3-3. Production of Planographic Printing Plate and
Printing
[0190] A test pattern was formed as an image on the planographic
printing plate precursor with TRENDSETTER (trade name, manufactured
by Creo).
[0191] Thereafter, a developing process was carried out at a
developing temperature of 30.degree. C. for a developing time of 12
seconds by the use of PS processor LP940H (trade name, manufactured
by Fujifilm Corporation) and provided with developer DT-2 (trade
name, manufactured by Fujifilm Corporation). After the development,
the resultant plate was provided to continuous printing using
printer RISURON (trade name, manufactured by Komori
Corporation).
[0192] 4. Preparation of Recycled Material
[0193] The print ink attached to the surface of the planographic
printing plate having been subjected to the printing was removed
with a petroleum cleanser and the plate was detached from the
printer. The used planographic printing plate was cut into small
pieces with the greatest length of 5 mm to 50 mm using an
electrical cutter. Foreign substances are separated from the raw
material cut into small pieces using a suction separation method
and then using a magnetic separation method. The recycled material
obtained from the planographic printing plate support is called
recycled material (1).
[0194] 5. Production of Recycled Bare Metal
[0195] In the recycling plant, first, 1.5 t of aluminum melt with a
purity of 100% was melted in the melting furnace 42 of the recycled
ingot producing apparatus 38 shown in FIG. 2. 1.5 t of the recycled
material (1) was introduced thereto and was heated and melted at
720.degree. C., thereby obtaining melt (1). Then, analysis samples
were extracted from the melt.
[0196] Thereafter, the melt was made to flow into the casting mold
54 through a pipe 52, and was cooled and solidified so as to have
the size shown in FIGS. 3A and 3B, whereby recycled bare metal
(ingot) was obtained.
[0197] Aluminum oxide slab floated over the melt surface was
removed, the mass thereof was measured, and the corresponding
weight of aluminum was subtracted from an ideal amount of aluminum
when it is assumed that no oxidation is occurred, whereby the
recycled bare metal yield was calculated.
[0198] The aluminum purity and the trace metal content of the
analysis sample were analyzed. As a result, the melt (1) contained
Si of 0.070%, Fe of 0.300%, Cu of 0.015%, and Mg of 0.010%.
[0199] The analysis result was sent to the aluminum rolling plant
14 along with the bare metal.
[0200] 6. Production of Aluminum Substrate for Planographic
Printing Plate
[0201] In the aluminum rolling plant, an aluminum substrate for a
planographic printing plate is produced in accordance with the
order given from the planographic printing plate producing plant,
and the order includes the alloy composition in addition to the
thickness, size, and amount of the aluminum substrate.
[0202] Therefore, when the aluminum rolling plant 14 produces the
aluminum substrate for a planographic printing plate using the
delivered recycled bare metal, the alloy composition included in
the order is sets as a target, the alloy composition is compared
with the analysis values sent along with the recycled bare metal to
calculate the differences therebetween, and the amounts of recycled
bare metal, trace-metal master alloy, and pure aluminum to be mixed
with the target value of the alloy composition and a predetermined
amount of aluminum melt in the pre-rolling melting furnace are
arithmetically calculated. By this step, the maximum mixture ratio
of the recycled bare metal can be known, thereby obtaining the best
recycling efficiency depending on the composition of the recycled
bare metal.
[0203] For example, when the target values are Si of 0.07%, Fe of
0.25%, Cu of 0.025%, and Mg equal to or less than 0.01%, the
capacity of the pre-rolling melting furnace is 100 t and when the
recycled bare metal with the composition of the present embodiment
is used, it is possible to obtain the target alloy composition by
mixing 83 t of the recycled bare metal and 17 t of the pure
aluminum bare metal and adjusting the contents of Si and Cu by the
addition of master alloys.
[0204] Therefore, the recycled bare metal, the new aluminum bare
metal, and the trace-metal master alloy were introduced into the
pre-rolling melting furnace in accordance with the mixture ratio
determined in the mixture ratio determination process, and the
resultant was heated and melted, thereby obtaining a pre-rolling
aluminum melt.
[0205] The degassing process and the filtering treatment were
performed on the aluminum melt to remove impurities, and then an
aluminum substrate was produced using the same DC casting method as
described in "1. Production of Aluminum substrate" above.
[0206] A planographic printing plate support was produced similarly
to "2. Production of planographic printing plate support" above,
except that the above-obtained aluminum substrate is used as a raw
material in place of using the new aluminum.
[0207] When 50 t of a new planographic printing plate was produced
using the used planographic printing plate (PS plate) obtained by
the method of producing an aluminum substrate for a planographic
printing plate as a raw material and when 50 t of a planographic
printing plate (PS plate) was produced using 100% of the raw
material (new bare metal) of the aluminum substrate used in Example
1 (Control 1-1), the amounts of CO.sub.2 generated were measured in
the aluminum refining process, the recycled bare metal producing
process, the aluminum substrate producing process, and the
planographic printing plate producing process, and the measurement
results were shown in Table 1. The recycled bare metal yield was
also shown in Table 1.
Example 1-2
[0208] A planographic printing plate precursor of Example 1-2 was
produced similarly to Example 1-1, except that the polyvinyl
phosphonate solution treatment in the step of 2-5 of Example 1-1 is
replaced with the immersion treatment in 0.5% of polyvinyl
phosphonate solution at a solution temperature 40.degree. C. for 30
seconds. The amount of phosphorous element measured using a
fluorescent X ray was 9.8 mg/m.sup.2. The planographic printing
plate precursor was used in printing, and was then recycled in the
same way to produce a new planographic printing plate precursor,
which was evaluated in the same way as Example 1-1.
Comparative Example 1-1
[0209] A planographic printing plate precursor of Comparative
Example 1-1 was produced similarly to Example 1-1, except that the
polyvinyl phosphonate solution treatment is not performed. The
produced planographic printing plate was used in printing, and was
then recycled in the same way to produce a new planographic
printing plate precursor, which was evaluated in the same way as
Example 1-1. The evaluation result is also shown in Table 1.
TABLE-US-00003 TABLE 1 Example Example Comparative Control 1-1 1-2
Example 1-1 1-1 Yield of recycled bare 95.2 94.8 93 -- metal (%)
Amount of carbon 1.5 1.5 1.51 10.41 dioxide generated in producing
aluminum substrate (t/1t)
[0210] The amount of CO.sub.2 generated in the recycled bare metal
producing process was calculated from the energy and the yield at
the time of melting the recycled material. Data appearing on the
website of the Japan Aluminum Association was used as the amounts
of CO.sub.2 generated in the aluminum refining process and the
rolling process.
[0211] As can be seen from Table 1, in Example 1-1 and Example 1-2
in which the planographic printing plate was produced using the
production method according to the invention, the amount of
CO.sub.2 can be reduced up to about 1/4 of the amount of CO.sub.2
generated in the case (Control 1-1) in which new bare metal was
used at an amount of 100% (that is, a 75% reduction can be
achieved). On the other hand, in Comparative Example 1-1 using the
support not subjected to the polyvinyl phosphonate treatment, the
aluminum purity obtained after the recycled bare metal producing
process was lower than that in Examples 1-1 and 1-2.
[0212] As can be seen from Table 1, in Example 1-1 and Example 1-2
in which the planographic printing plate was produced using the
production method according to the invention, the amount of
CO.sub.2 can be reduced up to about 15% of the amount of CO.sub.2
generated in the case (Control 1-1) in which new bare metal was
used at an mount of 100% (that is, a 85% reduction can be
achieved). On the other hand, in Comparative Example 1-1 using the
support not subjected to the polyvinyl phosphonate process, the
yield of the recycled bare metal was lower than that in Examples
1-1 and 1-2.
Examples 2-1 and 2-2 and Comparative Example 2-1
[0213] 1. Production of Aluminum Substrate
[0214] A melt was produced using aluminum alloy containing 0.073%
by mass of Si, 0.270% by mass of Fe, 0.028% by mass of Cu, 0.001%
by mass of Mn, 0.001% by mass of Cr, 0.003% by mass of Zn, 0.020%
by mass of Ti and the balance of Al and inevitable impurities, and
an aluminum substrate used in Example 2-1 was produced as
follows.
[0215] First, a melt process including degassing and filtering was
performed to the aluminum alloy melt and a cast ingot with a
thickness of 500 mm was produced using a DC casting method. The
surface of the obtained cast ingot was face-milled by 10 mm, the
cast ingot was heated, the hot rolling was started at 400.degree.
C. without soaking the cast ingot, and then the resultant was
rolled up to the thickness of 4 mm. Then, the resultant was
cold-rolled up to the thickness of 1.5 mm, process annealing was
carried out thereon, the resultant was cold-rolled up to 0.24 mm,
and the flatness was corrected, thereby obtaining an aluminum plate
(aluminum substrate).
[0216] 2. Production of Planographic Printing Plate Support
(Surface Treatment of Aluminum Substrate)
[0217] The obtained aluminum plate was subjected to the surface
treatment in the following process. After the surface treatment and
the water washing, liquid-cutting was carried out with a nip
roller. The water washing was carried out by ejecting water from a
spray tube.
[0218] 2-1. Electrochemical Roughening Treatment
[0219] An electrochemical roughening treatment was performed on the
obtained aluminum plate in a hydrochloric acid bath of a
hydrochloric acid solution (17 g/L) using trapezoid-wave AC
current. The current density at the peak of the AC current was 50
A/dm.sup.2 when the aluminum plate was used as an anode and a
cathode, the ratio of the amount of electricity of the AC current
as the cathode to the amount of electricity as the anode was 0.95,
the duty ratio was 0.50, the frequency was 60 Hz, and the total
amount of electricity as the anode was 180 C/dm.sup.2.
[0220] Thereafter, the water washing was carried out. The maximum
surface roughness of the aluminum plate was 4 .mu.m.
[0221] 2-2. Anodization Treatment
[0222] Subsequently, an anodization treatment was carried out on
the aluminum plate under the conditions of a current density of 4
A/dm.sup.2, a temperature of 40.degree. C., and a time of 30
seconds, by using an aqueous solution with a phosphoric acid
concentration of 40% by mass (containing 0.5% by mass of aluminum
ions) as an anodizing solution and using a DC voltage, whereby an
oxide film was formed. Thereafter, the water washing was carried
out by the use of a spray. The formed anodized oxide film was
analyzed with an electron microscope. As a result, pores with an
average pore diameter of 750 A were found by 175/m.sup.2.
[0223] 2-3. Hydrophilizing Treatment
[0224] The resultant aluminum substrate was immersed in an aqueous
solution of 0.6% polyvinyl phosphonic acid (an aqueous solution
produced using well water) at a solution temperature of 60.degree.
C. for 30 seconds. In this way, an aluminum substrate (2) of a
planographic printing plate was obtained. The amount of attached
material measured using a fluorescent X ray was 18.8 mg/m.sup.2 in
terms of an amount of phosphorous element.
[0225] Similarly to "3. Production of planographic printing plate
precursor (Formation of image recording layer)", a planographic
printing plate precursor was produced using the obtained
support.
[0226] Similarly to "4. Preparation of recycled material", the
recycled material was obtained using the planographic printing
plate used in printing.
[0227] Similarly to "5. Production of recycled bare metal", the
recycled material was obtained and the yield of the recycled bare
metal was calculated using the obtained recycled material.
[0228] The aluminum purity and the trace metal content of the
analysis sample were analyzed. As a result, the obtained melt (2)
contained Si of 0.070%, Fe of 0.300%, Cu of 0.015%, and Mg of
0.010%.
[0229] The analysis result was sent to the aluminum rolling plant
14 along with the recycled bare metal.
[0230] Similarly to "6. Production of aluminum substrate for
planographic printing plate", the aluminum substrate was cast.
[0231] A planographic printing plate support was produced similarly
to "2. Production of planographic printing plate support" using the
above-obtained aluminum substrate as a raw material and using new
aluminum.
[0232] When 50 t of a new planographic printing plate was produced
using the used planographic printing plate (PS plate) obtained by
the method of producing an aluminum substrate for a planographic
printing plate as a raw material and when 50 t of a planographic
printing plate (PS plate) was produced using 100% of the raw
material (new bare metal) of the aluminum substrate used in Example
2-1 (Control 2-1), the amounts of CO.sub.2 generated were measured
in the aluminum refining process, the recycled bare metal producing
process, the aluminum substrate producing process, and the
planographic printing plate producing process, and the measurement
results were shown in Table 2. The recycled bare metal yield was
also shown in Table 2.
Example 2-2
[0233] A planographic printing plate precursor of Example 2-2 was
produced similarly to Example 2-1, except that the conditions of
the aluminum substrate anodizing process are changed as follows.
The planographic printing plate precursor was used in printing and
was then recycled in the same way to produce a new planographic
printing plate precursor, which was evaluated in the same way as
Example 2-1.
[0234] Condition of Anodization Treatment
[0235] An anodization treatment was carried out on the aluminum
plate under the conditions of a current density of 4 A/dm.sup.2, a
temperature of 40.degree. C., and a time of 30 seconds, by using an
aqueous solution with a phosphoric acid concentration of 30% by
mass and a sulfuric acid concentration of 10% by mass (containing
0.5% by mass of aluminum ions) as an anodizing solution and using a
DC voltage, whereby an oxide film was formed. Thereafter, the water
washing was carried out by the use of a spray. The formed anodized
oxide film was analyzed with an electron microscope. As a result,
pores with an average pore diameter of 500 .ANG. were found by
200/.mu.m.sup.2.
Comparative Example 2-1
[0236] A planographic printing plate precursor was produced
similarly to Example 2-1, except that the conditions of the
aluminum substrate anodizing process are changed as follows. The
planographic printing plate precursor was used in printing and was
then recycled in the same way to produce a new planographic
printing plate precursor, which was estimated in the same way as
Example 2-1.
[0237] Condition of Anodization Treatment
[0238] An anodization treatment was carried out on the aluminum
plate under the conditions of a current density of 6 A/dm.sup.2, a
temperature of 30.degree. C., and a time of 30 seconds, by using an
aqueous solution with a sulfuric acid concentration of 30% by mass
(containing 0.5% by mass of aluminum ions) as an anodizing solution
and using a DC voltage, whereby an oxide film was formed.
Thereafter, water washing was carried out by the use of a spray.
The formed anodized oxide film was analyzed with an electron
microscope. As a result, pores with an average pore diameter of 130
.ANG. were found by 1000/.mu.m.sup.2 or more.
TABLE-US-00004 TABLE 2 Example Example Comparative Control 2-1 2-2
Example 2-1 2-1 Yield of recycled bare 95.5 94.3 92.8 -- metal (%)
Amount of carbon 1.50 1.50 1.51 10.41 dioxide generated in
producing aluminum substrate (t/1t)
[0239] The amount of CO.sub.2 generated in the recycled bare metal
producing process was calculated from the energy and the yield at
the time of melting the recycled material. Data appearing on the
website of the Japan Aluminum Association was used as the amounts
of CO.sub.2 generated in the aluminum refining process and the
rolling process.
[0240] As can be seen from Table 2, in Example 2-1 and Example 2-2
in which the planographic printing plate was produced using the
production method according to the invention, the amount of
CO.sub.2 can be reduced up to about 1/4 of the amount of CO.sub.2
generated in the case (Control 2-1) in which new bare metal was
used at an amount of 100% (that is, a 75% reduction can be
achieved). On the other hand, in Comparative Example 2-1 using a
support in which the Cu content in the aluminum alloy as a raw
material of the aluminum substrate departs from the range according
to the invention, the aluminum purity obtained after the recycled
bare metal producing process was lower than that in Examples 2-1
and 2-2.
[0241] As can be seen from Table 2, in Example 2-1 and Example 2-2
in which the planographic printing plate was produced using the
production method according to the invention, the amount of
CO.sub.2 can be reduced up to about 15% of the amount of CO.sub.2
generated in the case (Control 2-1) in which new bare metal was
used at an amount of 100% (that is, a 85% reduction can be
achieved). On the other hand, in Comparative Example 2-1 using a
support formed of aluminum alloy in which the Cu content departs
from the range according to the invention, the yield of the
recycled bare metal was lower than that in Examples 2-1 and
2-2.
[0242] All publications, patent applications, and technical
standards mentioned in this specification are herein incorporated
by reference to the same extent as if each individual publication,
patent application, or technical standard was specifically and
individually indicated to be incorporated by reference.
* * * * *