U.S. patent application number 13/199553 was filed with the patent office on 2012-05-31 for aluminum alloy sheet for lithographic printing plate, and manufacturing method thereof.
This patent application is currently assigned to Furukawa-Sky Aluminum Corp.. Invention is credited to Kotaro Kitawaki, Shinya Kurokawa, Yusuke Namba, Hirotake Osuga, Hirokazu Sawada, Yoshikazu Suzuki, Akio Uesugi.
Application Number | 20120134875 13/199553 |
Document ID | / |
Family ID | 44674341 |
Filed Date | 2012-05-31 |
United States Patent
Application |
20120134875 |
Kind Code |
A1 |
Namba; Yusuke ; et
al. |
May 31, 2012 |
Aluminum alloy sheet for lithographic printing plate, and
manufacturing method thereof
Abstract
An aluminum alloy sheet for a lithographic printing plate which
has excellent ink stain resistance, with a local defect in a
photosensitive layer after long-term storage being hard to occur,
and excellent the pit uniformity after a roughening and a
manufacturing method thereof are provided. An aluminum alloy sheet
for a lithographic printing plate containing a predetermined
content of Fe, Si, Cu and Ti as well as one type or more selected
from B and C, and composed of remaining Al and inevitable
impurities, in which a concentration of an aluminum carbide present
in the aluminum alloy sheet is not more than 8 ppm, an area
occupancy of aggregation substances present on the aluminum alloy
sheet surface after the roughening treatment with respect to an
arbitrary circle with a radius 5 .mu.m in the aluminum alloy sheet
surface is less than 10%. In a case where the area occupancy is not
less than 10%, the aggregation substances are present at a rate of
1 to 2 pieces/50 cm2.
Inventors: |
Namba; Yusuke; (Shizuoka,
JP) ; Kurokawa; Shinya; (Shizuoka, JP) ;
Sawada; Hirokazu; (Shizuoka, JP) ; Uesugi; Akio;
(Shizuoka, JP) ; Osuga; Hirotake; (Tokyo, JP)
; Suzuki; Yoshikazu; (Tokyo, JP) ; Kitawaki;
Kotaro; (Tokyo, JP) |
Assignee: |
Furukawa-Sky Aluminum Corp.
Tokyo
JP
Fujifilm Corporation
Tokyo
JP
|
Family ID: |
44674341 |
Appl. No.: |
13/199553 |
Filed: |
September 1, 2011 |
Current U.S.
Class: |
420/537 ;
75/10.67; 75/412 |
Current CPC
Class: |
B41N 1/083 20130101;
C22C 1/026 20130101; C22C 1/02 20130101; C22B 21/064 20130101; C22F
1/04 20130101; C22B 21/062 20130101; C22B 21/066 20130101; C22C
21/00 20130101 |
Class at
Publication: |
420/537 ;
75/10.67; 75/412 |
International
Class: |
C22C 21/00 20060101
C22C021/00; C22B 9/02 20060101 C22B009/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 3, 2010 |
JP |
2010-198400 |
Jul 25, 2011 |
JP |
2011-161476 |
Claims
1. An aluminum alloy sheet for a lithographic printing plate
containing about 0.10 to about 0.60 mass % Fe, about 0.01 to about
0.25 mass % Si, about 0.0001 to about 0.05 mass % Cu, about 0.005
to about 0.05 mass % Ti, and one or more types selected from B and
C: about 0.0001 to about 0.0020 mass % of one or more types
selected from B and C, the balance of Al, and unavoidable
impurities, wherein the concentration of an aluminum carbide
present in the aluminum alloy sheet is not more than 8 ppm; and
wherein when an area occupancy ratio of aggregation substances
present on a surface of the aluminum alloy sheet subjected to a
roughening treatment to a circle area with a radius of 5 .mu.m set
on the surface of the aluminum alloy sheet is less than 10%, said
aggregation substances comprising at least one of a Ti--B compound
and a Ti--C compound, and the aluminum carbide.
2. An aluminum alloy sheet for a lithographic printing plate
containing about 0.10 to about 0.60 mass % Fe, about 0.01 to about
0.25 mass % Si, about 0.0001 to about 0.05 mass % Cu, about 0.005
to about 0.05 mass % Ti, and one or more types selected from B and
C: about 0.0001 to about 0.0020 mass % of one or more types
selected from B and C, the balance of Al, and unavoidable
impurities, wherein the concentration of an aluminum carbide
present in the aluminum alloy sheet is not more than 8 ppm; and
wherein when an area occupancy ratio of aggregation substances
present on a surface of the aluminum alloy sheet subjected to a
roughening treatment to a circle area with a radius of 5 .mu.m set
on the surface of the aluminum alloy sheet is not less than 10%,
said aggregation substances are present in an amount of 1 to 2
pieces/50 cm.sup.2.
3. A method of manufacturing an aluminum alloy sheet for a
lithographic printing plate comprises the steps of: melting an
aluminum alloy containing about 0.10 to about 0.60 mass % Fe, about
0.01 to about 0.25 mass % Si, about 0.0001 to about 0.05 mass % Cu,
about 0.005 to about 0.05 mass % Ti, about 0.0001 to about 0.0020
mass % of at least one of B and C, and the balance of Al and
unavoidable impurities at about 680 to about 780.degree. C.; and
treating the molten metal of the aluminum alloy at about 680 to
about 780.degree. C., wherein said steps of treating includes:
stirring the molten metal of the aluminum alloy over about 5 to
about 60 minutes by mechanical or electromagnetic means; holding
the stirred molten metal over about 10 to about 60 minutes;
performing an in-line degassing treatment for the held molten
metal; filtering the in-line degassing-treated molten metal with an
in-line filter; and stirring the molten metal, to which
grain-refiners are added, over at least 10 minutes.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an aluminum alloy sheet
used for a lithographic printing plate formed by anodizing a
surface of an aluminum alloy sheet subjected to a roughening
treatment and by coating it with a photosensitive substance, and a
method of manufacturing the aluminum alloy sheet. More
specifically, the present invention relates to an aluminum alloy
sheet for a lithographic printing plate which is excellent in pit
uniformity after a roughening treatment, in ink stain resistance in
a non-image area and in fault tolerance of a photosensitive layer
after prolonged storage, and a method of manufacturing the
excellent aluminum alloy sheet.
BACKGROUND OF THE INVENTION
[0002] In general, as a lithographic printing plate, is used a
support which is obtained by subjecting a surface of an aluminum
sheet or an aluminum alloy sheet to surface treatments such as a
roughening treatment, an anodized film treatment, etc., and which
is coated with a photosensitive substance. Among such lithographic
printing plates, a so-called PS (Pre-Sensitized) plate comprising a
support previously coated with the photosensitive substance is
widely used, and thus it can be immediately subjected to an
exposing processing.
[0003] In actual use of such the lithographic printing plate, it
subjected to a variety of plate-making processes such as an
exposure processing, a development processing, a gum coat
processing, etc. An image forming area on the lithographic printing
plate is formed as a lipophilic image forming area for receiving an
ink, which is defined by a part of the photosensitive layer which
is not dissolved in the development processing. On the other hand,
a non-image area on the lithographic printing plate as a
hydrophilic non-image area for receiving a fountain solution, from
which a part of the photosensitive layer is dissolved and removed
in the development processing so that an anodized layer is exposed
therefrom. The printing plate fabricated as above is wound around a
rotatable plate cylinder of a printing machine. Then, the ink is
applied to the image forming area on the wound lithographic
printing plate under the presence of the fountain solution. The
image formed on the printing plate by the ink is transferred to a
rubber blanket, and is then printed on a printing medium.
[0004] Conventionally, aluminum alloys such as JIS1050, JIS1100,
JIS3003, etc. have been used for an aluminum alloy sheet for the
lithographic printing plate. The aluminum alloy sheet is usually
roughened by roughening treatments by one or a combination of two
or more of a mechanical method, a chemical method and an
electrochemical method. The sheet is then subjected to an
anodization treatment and a hydrophilic treatment, if necessary,
and is used as a support for the lithographic printing plate. A
photosensitive coat is applied to a surface of the support for the
lithographic printing plate. The original printing plate is
obtained by subjecting the support to an exposure processing and a
development processing.
[0005] Recently, clearer printing and printing in a larger number
using the same plate are in strong demand. In order to respond to
this demand, it is important that ink stains are not caused in the
non-image area during printing, that is, the ink stain resistance
is excellent. For that purpose, in recent years, a lithographic
printing plate of a CTP (Computer To Plate) type in which an image
is directly written in the photosensitive layer using a laser
writing device and the like has been on an increase.
[0006] The photosensitive layer of the CTP-type lithographic
printing plate is more sensitive to light and heat than the
prior-art lithographic printing plates. Thus, if there is inclusion
such as an intermetallic compound on the surface of the aluminum
alloy sheet, a defect can easily occur in the photosensitive layer.
Particularly, intermetallic compounds such as the single Si and
coarse T--B-based compounds cause ink stains. Here, the single Si
refers to those not forming a solid solution in the alloy but
separated as Si grains in Si contained in the aluminum alloy.
[0007] Patent Document 1 describes that since a defect occurs in an
anodized film by the single Si, which lowers a hydrophilic property
in that portion and causes ink stains, a reduction of the single Si
in the aluminum alloy sheet is effective. Patent Document 2
describes that by adjusting contents of Mg and Mn so as to be
separated as Mg2Si or Al--Mn--Si based compounds, a separation of
the single Si can be suppressed.
[0008] Patent Document 3 describes a method of continuously casting
an aluminum support after removing a coarse Ti--B compound from an
aluminum molten metal through a filter. Patent Document 4 describes
that, in a continuous casting method including a process where an
aluminum molten metal is successively passed through a filtering
means, molten metal flow passages, liquid level control means, and
a molten metal feed nozzle, trap means for separated grains
containing the Ti--B compound present in the molten metal is
provided at one or more spots in the liquid level control means and
the molten metal feed nozzle, and that time during which the molten
metal passes through the molten metal flow passages and a distance
of the molten metal flow passages are regulated. However, with the
methods in Patent Documents 3 and 4, the removal of the Ti--B
aggregation substances is not sufficient, and infusion of coarse
aggregation substances cannot be stably prevented.
[0009] As described above, ink stains cannot be sufficiently solved
even by regulating the inclusion such as the intermetallic
compounds.
[0010] It has been found out by recent researches that an aluminum
carbide affects the ink stain resistance, too. Methods of
manufacturing an aluminum alloy sheet for lithographic printing
plate in which the aluminum carbide is decreased have been already
proposed as disclosed in Patent Documents 5 and 6.
[0011] Patent Document 5 describes that an inert gas is blown into
a molten metal after an electrolytic refining of an aluminum oxide,
a holding time in a holding process is regulated, and a filtration
is performed by an in-line degassing treatment and an in-line
filter so as to control the aluminum carbide concentration
contained in an aluminum alloy sheet manufactured from the molten
metal.
[0012] Patent Document 6 describes that amounts of oxides and
carbides are controlled by performing at least one of a melting
process, a holding process, a hydrogen-gas removing process, a
filtering process and a casting process in a protective gas
atmosphere containing a fluoride gas.
[0013] However, with the methods described in Patent Documents 5
and 6, an effect to decrease the aluminum carbide amount is not
sufficient, and it is difficult to stably manufacture an aluminum
alloy sheet in which the aluminum carbide amount is decreased.
Also, an aluminum fluoride indicated in Patent Document 5 and an
aluminum fluoride generated by the reaction between the protective
gas containing a fluoride gas and the molten metal described in
Patent Document 6 are likely to generate a hydrogen fluoride by
heating in the atmosphere. Since the hydrogen fluoride has the
extremely strong toxicity to biological bodies and severe
corrosiveness, they have problems of a bad influence on human
bodies and damage of a furnace.
LIST OF THE PRIOR ART DOCUMENTS
[0014] [Patent Document 1] JPS62-146694A [0015] [Patent Document 2]
JPH05-309964A [0016] [Patent Document 3] JPH10-52740A [0017]
[Patent Document 4] JP2009-006386A [0018] [Patent Document 5]
US2009/0220376A1 [0019] [Patent Document 6] JP2007-167863A
SUMMARY OF THE INVENTION
[0020] The present invention relates to an aluminum alloy for a
lithographic printing plate which is excellent in the pit
uniformity after a roughening treatment, the ink stain resistance
in a non-image area and the fault tolerance of a photosensitive
layer after prolonged storage by decreasing an amount of an
aluminum carbide and preventing an aggregation of at least one of a
Ti--B compound and a Ti--C compound and the aluminum carbide.
[0021] The inventors have found that the aluminum alloy can be
achieved by controlling the conditions in a melting process stage
of an aluminum alloy and in a treating process stage of a molten
metal, and completed the present invention.
[0022] According to one aspect of the present invention, an
aluminum alloy sheet for a lithographic printing plate contains
about 0.10 to about 0.60 mass % Fe, about 0.01 to about 0.25 mass %
Si, about 0.0001 to about 0.05 mass % Cu, about 0.005 to about 0.05
mass % Ti, about 0.0001 to about 0.0020 mass % of one or more types
selected from B and C, the balance of Al, and unavoidable
impurities;
[0023] wherein the concentration of aluminum carbide present in the
aluminum alloy sheet is not more than 8 ppm; and
[0024] wherein when an area occupancy ratio of aggregation
substances present on a surface of the aluminum alloy sheet
subjected to a roughening treatment to a circle area with a radius
of about 5 .mu.m arbitrarily set on the surface of the aluminum
alloy sheet is less than 10%, the aggregation substances comprising
at least one of a Ti--B compound and a Ti--C compound, and aluminum
carbide. In the case where the area occupancy ratio of the
aggregation substances is not less than 10%, the aggregation
substances are present in an amount of 1 to 2 pieces/50
cm.sup.2.
[0025] According to another aspect of the present invention a
method of manufacturing an aluminum alloy sheet for a lithographic
printing plate comprises the steps of:
[0026] melting an aluminum alloy containing about 0.10 to about
0.60 mass % of Fe, about 0.01 to about 0.25 mass % of Si, about
0.0001 to about 0.05 mass % of Cu, about 0.005 to about 0.05 mass %
of Ti, about 0.0001 to about 0.0020 mass % of at least one of B and
C, and the balance of Al and unavoidable impurities at about 680 to
about 780.degree. C.; and
[0027] treating the molten metal of the aluminum alloy at about 680
to about 780.degree. C.,
[0028] wherein said steps of treating includes:
[0029] stirring the molten metal of the aluminum alloy over about 5
to about 60 minutes by mechanical or electromagnetic means;
[0030] holding the stirred molten metal over about 10 to about 60
minutes;
[0031] performing an in-line degassing treatment for the held
molten metal;
[0032] filtering the in-line degassing-treated molten metal with an
in-line filter; and
[0033] stirring the molten metal, to which grain-refiners are
added, over at least 10 minutes.
[0034] The aluminum alloy sheet for a lithographic printing plate
according to the present invention is excellent in pit uniformity
after a roughening treatment, with less ink stains occurred in a
non-image area during printing, that is, excellent in the ink stain
resistance and moreover, less faults of the photosensitive layer
occurred in a photosensitive layer if stored under the atmosphere,
that is, excellent in the fault tolerance of the photosensitive
layer after long-term storage. Also, with the manufacturing method
of an aluminum alloy sheet for a lithographic printing plate
according to the present invention, the above aluminum alloy sheet
for a lithographic printing plate can be obtained reliably and
stably.
DETAILED DESCRIPTION OF THE INVENTION
[0035] The present invention will be described below in more
detail. First, reasons for limiting the aluminum alloy components
used in the present invention will be described.
A. Reasons for Limiting Aluminum Alloy Components
Fe:
[0036] The Fe content affects sizes and number densities of
Al--Fe-based compounds and Al--Fe--Si-based compounds dispersed in
the material, and also largely affects the crystal grain behaviors
during re-crystallization and the pit uniformity generated during a
roughening treatment. When the Fe content is less than 0.10 mass %
(hereinafter referred to simply as "%"), the crystal grain size at
re-crystallization is coarsened and the pits generated by the
roughening treatment become non-uniform. On the other hand, if the
Fe content exceeds 0.60%, coarse Al--Fe-based compounds and
Al--Fe--Si-based compounds are increased, and the pits generated by
the roughening treatment become non-uniform. Thus, the Fe content
should be within a range of about 0.10 to about 0.60%. The
preferable Fe content is within the range of about 0.20 to about
0.40%.
Si:
[0037] When the Si content is less than about 0.01%, after a
roughening treatment, the pits become non-uniform. On the other
hand, if the Si amount exceeds 0.25%, coarse Al--Fe--Si-based
compounds are increased, and pits become non-uniform after the
roughening treatment. Also, a separation of the single Si can
easily occur, which remains in the anodized film and causes film
defects. As a result, these defects become starting points of
stains in the non-image area during printing, and cause stains in
printing. Thus, the Si content should be within a range of 0.01 to
0.25%. The preferable Si content is within the range of 0.07 to
0.15%.
Cu:
[0038] Cu is an element which largely affects the roughening
properties. When the Cu content is less than 0.0001%, pits
generated by a roughening treatment become non-uniform. On the
other hand, if the Cu content exceeds 0.05%, the pits generated by
the roughening treatment also become non-uniform, and the color
tone of the surface becomes too black, which damages
merchantability. Thus, the Cu content should be within a range of
0.0001 to 0.05%. The preferable Cu content is within the range of
about 0.005 to about 0.04%.
Ti:
[0039] Ti is an element which largely affects roughening
properties, and also is an element which largely affects a
structural state of an aluminum alloy ingot. When the Ti content is
less than 0.005%, after a roughening treatment, the pits become
non-uniform. Also, crystal grains of the ingot are not refined, but
become coarse crystal grain structures, and band-shaped stripes are
generated along the rolling direction, and the band-shaped stripes
remain even after the roughening treatment. On the other hand, if
the Ti content exceeds 0.05%, not only the above-described effects
are saturated, but also coarse Al--Ti-based compounds are formed,
and the compounds are distributed in the stripe shape on a rolled
plate. As a result, a defect occurs in the anodized film, which
causes a defect in a photosensitive layer and ink stains during
printing. Thus, the Ti content should be within a range of 0.005 to
0.05%. The preferable Ti content is within the range of about 0.005
to about 0.03%.
Content of One or More Types Selected from B and C:
[0040] In order to refine crystal grain structures, slight amounts
of B and/or C are added in a combination with Ti. When the contents
of one or more types selected from B and C are less than 0.0001%,
the effect of crystal grain refining cannot be obtained, and the
pits become non-uniform after a roughening treatment. On the other
hand, if the contents exceed 0.0020%, not only the crystal grain
refining effect is saturated, but also an aluminum carbide in a
molten metal can easily aggregate with Ti--B-based compounds and
Ti--C-based compounds, and a decrease of the aluminum carbide
amount from the molten metal becomes insufficient. Also, since the
aluminum carbide can be easily separated at a spot where the
Ti--B-based compounds and the Ti--C-based compounds are present,
ink stains and local defects of a photosensitive layer after
long-term storage can easily occur. Also, coarse aggregation
substances of the Ti--B-based compounds and the Ti--C-based
compounds can cause surface defects. Thus, the contents of one or
more types selected from B and C should be within 0.0001 to
0.0020%. The preferable range of the contents is about 0.0003 to
about 0.0012%.
The Other Components:
[0041] Mg is an element most of which is present as a solid
solution in an aluminum alloy and which improves the strength of
the support at normal temperature. Since it plays a role to improve
the thermal softening resistance, in order to obtain the desired
support strength and the thermal softening resistance, it may be
contained in an amount exceeding 0% and not more than 0.5%. In this
range, the characteristics of the aluminum alloy sheet for the
lithographic printing plate are not damaged.
[0042] The pit uniformity after a roughening treatment is
considered as the so-called electrolytic graining properties. In
order to obtain the further refined pit uniformity by means of an
electrolytic operation having a lower current density, one or two
or more types of 0.001 to 0.05% In, 0.001 to 0.05% Sn, 0.0001 to
0.01% Be, 0.001 to 0.05% Pb, and 0.001 to 0.05% Ni may be
contained.
Inevitable Impurities:
[0043] The characteristics of the aluminum alloy sheet for the
lithographic printing plate are not damaged by an impurity amount
corresponding to JIS1050, that is, at most 0.05% Mn, at most 0.05%
Zn, at most 0.05% Zr, at most 0.05% Cr and approximately at most
0.05% in total of the other components.
[0044] Subsequently, the aluminum carbide present in the aluminum
alloy sheet will be described.
B. Aluminum Carbide
[0045] In general, aluminum carbide is inevitably present in an
aluminum metal. This is because, during electrolytic refining such
as by three-layer electrolysis, a graphite used as an electrode is
dissolved in an aluminum molten metal, and as the molten metal
temperature is lowered during transfer or casting, an oversaturated
carbon is separated as the aluminum carbide in the aluminum molten
metal. Also, an amount of the aluminum carbide in the metal is
largely fluctuated depending on metal manufacturers and metal
manufacturing conditions. When an aluminum alloy containing a large
amount of the aluminum carbide is used for a lithographic printing
plate, an anodized film is not properly formed at a spot where the
aluminum carbide is present. If the aluminum carbide is in contact
with a fountain solution for a long time, the aluminum carbide is
oxidized. And, it was found out that, since the hydrophilic nature
is lowered in that portion, ink adheres thereto, and thus an ink
stain occurs in a non-image area. Also, in the case of long-term
storage in a state in which the aluminum carbide is present on the
surface of the aluminum alloy sheet after a roughening treatment,
the aluminum carbide is oxidized by the reaction with moisture in
the atmosphere. As a result, an aluminum hydroxide and CH.sub.4 gas
generated by the reaction cause the lower adhesiveness with the
photosensitive layer, and can easily cause a local defect in the
photosensitive layer.
[0046] When a concentration of the aluminum carbide present in the
aluminum alloy sheet exceeds 8 ppm, an ink stain caused by the
aluminum carbide and a local defect of the photosensitive layer
after long-term storage can easily occur. Thus, the aluminum
carbide concentration should be at most 8 ppm. Also, it is
preferable that an amount of aluminum carbide is low as possible,
and the concentration of aluminum carbide is preferably at most
about 5 ppm or more preferably at most about 3 ppm.
[0047] Subsequently, a distribution of aggregation substances
present on the surface of the aluminum alloy sheet after the
roughing treatment will be described.
C. Distribution of Aggregation Substances Present on Surface of
Aluminum Alloy Sheet after Roughening Treatment:
[0048] Since aluminum carbide has extremely low wettability with
aluminum molten metal, it has the property that of easily existing
on a solid-liquid interface between a solid such as a furnace wall,
a hearth, a dross mainly composed of aluminum oxide and the like,
and on the molten metal and a gas-liquid interface between a gas
blown into the molten metal for hydrogen gas removal and the molten
metal. When aluminum carbide is present in the aluminum molten
metal as a single body, aluminum carbide is discharged from
aluminum molten metal, and an amount of the aluminum carbide in the
molten metal is decreased. However, when one or more types of the
Ti--B-based compounds and the Ti--C-based compounds are present in
the molten metal, the aluminum carbide forms aggregation substances
with these compounds. These aggregation substances contain three
types, the aggregation substance composed of aluminum carbide and
T--B-based compound, the aggregation substance composed of aluminum
carbide and the T--C-based compound, and the aggregation substance
composed of aluminum carbide, the T--B-based compound, and the
T--C-based compound. These aggregation substances have high
wettability with the aluminum molten metal, and are hardly
discharged from the molten metal. Also, an oversaturated carbon
dissolved in the aluminum molten metal is separated as aluminum
carbide due to a lowered molten metal temperature. As described
above, when the T--B-based compounds and the T--C-based compounds
are present in the molten metal, the aluminum carbide is easily
separated using these compounds as a starting point.
[0049] The above aggregation substance becomes a defect portion of
the anodized film and causes an ink stain or a surface defect.
Therefore, not only the control of the aluminum carbide
concentration in the molten metal but also the control of the Ti
content, the B content, and the C content are also required, and
thus it is important to control the distribution state of the
aggregation substances of the aluminum carbide and the above
compounds on the surface of the aluminum alloy sheet.
[0050] The distribution of the aggregation substances composed of
one or more types of compounds selected from the T--B-based
compounds and the T--C-based compounds and the aluminum carbide is
specified by (1) an area occupancy ratio of the aggregation
substance on the surface of the aluminum alloy sheet to an area of
an arbitrary circle having a radius of 5 .mu.m; and by (2) the
number of the aggregation substances present in an arbitrary area
of 50 cm.sup.2 on the surface of the aluminum alloy sheet. When the
area occupancy ratio is less than 10%, there is no problem with
occurrence of an ink stain or a defect of a photosensitive layer
after long-term storage. On the other hand, when the area occupancy
ratio is not less than 10%, and when the number of the aggregation
substances present in the area of 50 cm.sup.2 is not more than 2,
there is no problem with occurrence of the ink stain or the defect
of the photosensitive layer after long-term storage. Also, when the
number of the aggregation substances present in the area of 50
cm.sup.2 is 3 or more, the ink stain and the photosensitive layer
defect after long-term storage occur. Therefore, the distribution
of the aggregation substances should be specified that the area
occupancy ration is less than 10%, or that the number of the
aggregation substances present in the area of 50 cm.sup.2 is not
more than 2, that is, 2 or 1, if the area occupancy ratio is not
less than 10%. Here, a circle having a radius of 5 .mu.m was
provided around the aggregation substances as the center. The area
occupancy ratio was obtained by dividing a value of an area
occupied by the aggregation substances by an area of the circle.
The area occupancy ratio of the aggregation substances and their
number are measured by surface observation and qualitative analysis
of the aluminum alloy sheet using an electronic probe microanalyzer
(JXA-8200 by JEOL Ltd.). Here, the size of the aggregation
substances to be a problem is a radius of not more than 5 .mu.m in
equivalent circle diameter. When the radius is larger than 5 .mu.m,
the area of the aggregation substances is too large and it is not a
target of the present invention, and the ink stain and the
photosensitive layer defect after long-term storage may occur
substantially.
[0051] Subsequently, a manufacturing method of an aluminum alloy
sheet for a lithographic printing plate according to the present
invention will be described.
D. Manufacturing Method of Aluminum Alloy Sheet
[0052] A method of manufacturing an aluminum alloy sheet for a
lithographic printing plate according to the present invention is
basically constituted by a melting step, a treatment step, a
casting step, a homogenization step, a hot rolling step, an
annealing step, a cold rolling step, and a surface treatment step.
Since the amounts and the aggregation state of the aluminum
carbide, the T--B-based compounds, and the T--C-based compounds are
determined particularly by the melting step of the aluminum metal
and the subsequent treatment step, the steps of melting and
treatment are important in the present invention.
Aluminum Molten Metal Temperature at Steps of Melting and Treating
Molten Metal:
[0053] When the aluminum molten metal temperature at the steps of
melting an aluminum metal and treating the molten metal is less
than about 680.degree. C., aluminum metals and various master
alloys for component adjustment are not fully melted. Also, since
the molten metal temperature is further lowered in an in-line
degassing treatment process and a filtration treatment process
using an in-line filter, which will be described later which is
included in the above treatment step, the aluminum alloy sheets
cannot be stably produced. On the other hand, when the molten metal
temperature exceeds about 780.degree. C., the reaction between the
aluminum molten metal and soot caused by imperfect combustion of
fuel, carbon-containing compounds and the like in the treatment
step is promoted, and the aluminum carbide is caused by the
reaction. Also, when the molten metal temperature exceeds about
780.degree. C., an amount of carbon melted in the oversaturated
state is increased, and the large amount of aluminum carbide is
separated due to a lowered molten metal temperature in a stirring
process, a retaining process, an in-line degassing process, and a
filtration treatment process using an in-line filter, which are
included in the treatment step. As a result, the aluminum carbide
cannot be sufficiently removed. Thus, the aluminum molten metal
temperature at the stages of melting and treating should be about
680 to about 780.degree. C. The preferable molten metal temperature
is about 680 to about 750.degree. C.
Melting Step of Aluminum Metal:
[0054] In an aluminum molten metal obtained by electrolytic
refining of bauxite, the melted carbon and the separated aluminum
carbide are present as described above, and, in the aluminum metal
prepared from this aluminum molten metal, a large amount of the
separated aluminum carbide is contained. By melting this aluminum
metal so as to bring the contained aluminum carbide into contact
with the atmosphere, the aluminum carbide is oxidized and this
aluminum oxide is separated from the aluminum molten metal as dross
so that the aluminum carbide can be reduced.
[0055] In the treatment step subsequent to the melting step, a
stirring process, a retaining process, an in-line degassing
treatment process, a filtration treatment process using an in-line
filter, and a process of adding and stirring of a crystal grain
refining agent are included in this order.
Stirring Process:
[0056] The molten metal subjected to the melting process is stirred
by mechanical means or electromagnetic means over about 5 to about
60 minutes. Since a difference in the specific gravity between the
aluminum carbide and the aluminum molten metal is small, a
separation of the aluminum carbide from the aluminum molten metal
takes a long time. Thus, by forcedly stirring the molten metal, the
separation of the aluminum carbide from the aluminum molten metal
is promoted. By this stirring process, the aluminum carbide
separated from the aluminum molten metal is brought into contact
with the atmosphere so as to be oxidized, resulting in generation
of an aluminum oxide, and, by removing it from the aluminum molten
metal, the aluminum carbide is removed. Also, since the aluminum
carbide can easily exist in a solid-liquid interface, the aluminum
carbide can be also removed from the aluminum molten metal by
bringing the aluminum carbide into contact with the dross on the
surface of the aluminum molten metal, a furnace wall and a furnace
hearth.
[0057] As the mechanical means or the electromagnetic stirring
means, the means for stirring the aluminum molten metal by
operating a forklift, a crane and the like equipped with a stirring
jig, or an electromagnetic stirring means using an electromagnetic
stirring device and the like. When the stirring time is less than 5
minutes, the above-described stirring effect is not sufficient. On
the other hand, when the stirring time exceeds about 60 minutes,
not only the stirring effect is saturated, inclusion such as oxides
might be included easily, which can easily cause linear defects or
ink stains derived from the inclusion. Here, as the oxides,
reference may be made to an aluminum oxide generated by the
reaction with oxygen in the atmosphere, an aluminum hydroxide
generated by the reaction with moisture in the atmosphere, an
aluminum oxide containing water and the like. Thus, the stirring
time should be about 5 to about 60 minutes. The preferable stirring
time is about 10 to about 50 minutes.
[0058] Apart from the in-line degassing treatment, which will be
described later, a hydrogen gas removing process may be carried out
by blowing an argon gas, a chlorine gas or a mixed gas of them into
the aluminum molten metal in the furnace. The stirring effect can
be also obtained from this treatment. That is because inclusions
such as the aluminum carbide is adsorbed by gas bubbles, and the
gas bubbles float in that state so that the inclusions are
separated from the aluminum molten metal as the dross.
Holding Process:
[0059] After the above stirring process, the aluminum molten metal
is subjected to the holding process. Since the aluminum carbide is
poor in the wettability with the aluminum molten metal, the
aluminum carbide settles down, or floats by fluidization of the
molten metal by the holding process. By this settling or floating,
the aluminum carbide can be separated. The separation using a
difference in the specific gravity between the inclusion such as
the aluminum oxide and the aluminum molten metal is also possible.
When the holding time is less than about 10 minutes, the
above-described separation effect is not sufficient. On the other
hand, when the holding time exceeds about 60 minutes, the effect is
saturated, which is not preferable economically. Thus, the holding
time should be about 10 to about 60 minutes. The preferable holding
time is about 20 to about 60 minutes.
In-Line Degassing Treatment Process:
[0060] After the above holding process, the molten metal is
subjected to the in-line degassing treatment process. As an in-line
degassing treating device, those sold in the market with the
trademarks such as SNIF or ALPUR can be used. In these devices,
while an argon gas or a mixed gas of argon and chlorine is blown
into the molten metal, a rotary body with a blade is rotated at a
high speed so as to supply the gas in fine bubbles into the molten
metal. Removal of hydrogen gas and inclusions can be performed
in-line in a short time. By this treatment process, the above
stirring effect can be obtained, and the aluminum carbide in the
molten metal can be further decreased. When the in-line degassing
treatment process is not carried out, removal of hydrogen gas or
inclusions such as the aluminum carbide is not sufficient, and a
surface defect, ink stains or a defect in the photosensitive layer
after long-term storage caused by the aluminum carbide occurs.
Filtration Treatment Process by In-Line Filter:
[0061] After the above in-line degassing treatment process, the
aluminum molten metal is filtered by an in-line filter. As the
in-line filter, a ceramic tube filter, a ceramic foam filter, an
alumina ball filter or the like may be used so as to remove
inclusions by a cake filtration mechanism or a filter element
filtration mechanism. By filtering the aluminum molten metal by the
filtration mechanism using a filter, not only the aluminum carbide
but also inclusions such oxides including the aluminum oxide can be
removed. When the filtration treatment process by the in-line
filter is not carried out, removal of inclusions such as the
aluminum carbide, oxides and the like is insufficient, ink stains
or a defect in the photosensitive layer after long-term storage
caused by the aluminum carbide can easily occur, and linear defects
of the inclusions or ink stains can be caused.
Process of Addition and Stirring of Crystal Grain Refining
Agent:
[0062] In order to refine crystal grains of an ingot structure, as
a crystal grain refining agent, massive or linear Ti-based aluminum
alloys, T--B-based aluminum alloys, T--C-based aluminum alloys and
the like are added. As described above, an added amount as content
of one or more types selected from B and C is within a range of
0.0001 to 0.0020%. The T--B-based aluminum alloys and the
T--C-based aluminum alloys have the greater crystal grain refining
effect than the Ti-based aluminum alloys, but they also have a
defect that surface defects caused by the aggregation substances of
the T--B-based compounds or the T--C-based compounds contained in
these aluminum alloys can easily occur.
[0063] In the present invention, the aggregation of the T--B-based
compounds or the T--C-based compounds is prevented by controlling
the added amount of the crystal grain refining agent or the B
amount and the C amount, and by performing a molten metal treatment
in which the aggregation is not caused. Specifically, by setting
the time during which the crystal grain refining agent is added to
the molten metal, and is stirred within 10 minutes, the aggregation
by stirring is prevented. Here, as the stirring, there are the
above mechanical or electromagnetic stirring process, a bubbling
for hydrogen gas removal, and an in-line degassing treatment
process. When the aluminum molten metal to which the crystal grain
refining agent is added is stirred over more than about 10 minutes,
the aggregation of the T--B-based compound and the T--C-based
compound occurs, and linear defects can easily occur. Also, since
the T--B-based compound and the T--C-based compound are present as
solid in the aluminum molten metal, the aluminum carbide is
adsorbed by this solid-liquid interface, which makes the separation
from the aluminum molten metal difficult. The aggregation
substances of the aluminum carbide and the T--B-based compound and
the aggregation substances of the aluminum carbide and the
T--C-based compound can cause ink stains and a photosensitive layer
defect after long-term storage easily. The preferable stirring time
is within 5 minutes.
Casting:
[0064] The molten metal having subjected to the melting and
treatment steps as above is cast to an ingot in accordance with a
common procedure by a DC casting method and the like. Instead, it
may be cast by a continuous casting method using a driving casting
mold.
[0065] An ingot obtained as above is subjected to the
homogenization treatment step, the hot rolling step, the annealing
step, the cold rolling step and the like in accordance with a usual
procedure as described below, and is finally molded into a rolled
sheet having the desired sheet thickness.
Homogenization Treatment Step:
[0066] The ingot is usually subjected to the homogenization
treatment step at about 450 to about 620.degree. C. As a result,
impurity elements are diffused, and thus the pit generation in an
electrolytic graining is further uniform. Also, crystal grains in
an intermediate annealing can be refined more easily. The holding
time of the homogenization treatment step can be suitably
determined depending on a size of the ingot or the like, but it is
usually about 0.5 to about 20 hours. If the time is less than about
0.5 hours, the sufficient homogenization effect cannot be obtained
in some cases. On the other hand, when the time exceeds about 20
hours, each of the above effects is saturated, which is not
preferable economically. Here, after the homogenization treatment
step, the ingot may be subjected to a heating treatment process for
the hot rolling step after the ingot is once cooled to a room
temperature, or the hot rolling step may be performed after the
ingot is cooled to about 350 to about 500.degree. C. after the
homogenization treatment step.
Hot Rolling Step:
[0067] The hot rolling is preferably started at the temperature of
about 350 to about 500.degree. C. If the hot rolling start
temperature is less than about 350.degree. C., re-crystallization
is not realized during the hot rolling step, and crystal grains of
the ingot still remain in the hot rolled plate. Thus, when the
final hot rolled plate is subjected to an electrolytic graining
treatment process, a band-like or stripe-like appearance unevenness
(streaks) may occur, which makes the surface appearance of the
printing plate non-uniform. On the other hand, if the hot rolling
start temperature exceeds about 500.degree. C., re-crystallized
grains are made coarse during the hot rolling step, the streaks
occur in the surface of the sheet after the electrolytic roughening
treatment process, which may make the surface appearance
non-uniform.
[0068] When the hot rolling end temperature is set at about 300 to
about 350.degree. C., the self-re-crystallization can be realized
by utilizing heat derived from the hot rolling step. As a result,
the entire plate after the hot rolling step can be made a refined
re-crystallization structure. Due to the self-re-crystallization,
the annealing step after the hot rolling step is no longer needed,
and a reduction of a manufacturing cost can be expected. When the
end temperature is less than about 300.degree. C., the surface of
the hot rolled plate is partially re-crystallized, and the
appearance after the roughening treatment process may become
non-uniform. Also, when only the surface layer region of the plate
is re-crystallized, the central region in the plate-thickness is
re-crystallized partially, and a fiber structure partially remains.
Thus, mass production of an aluminum alloy sheet having the stable
strength may become difficult. On the other hand, when the end
temperature exceeds about 350.degree. C., the sufficient
dislocation is not introduced, and crystal grains on the surface
region of the hot rolled plate become coarse. Thus, the appearance
after the roughing treatment process may become non-uniform.
[0069] By performing the annealing step after the end of the hot
rolling step and before the end of the cold rolling step with the
hot rolling end temperature at about 200 to about 300.degree. C.,
crystal grains may be further refined as compared with the
above-described self-crystallization process material so as to
increase uniformity of the appearance after the roughening
treatment process. In this case, when the hot rolling end
temperature is less than about 200.degree. C., rolling oil is not
fully evaporated, but remains on the surface of the final hot
rolled plate and might cause surface stains or corrosion. On the
other hand, when the end temperature exceeds about 300.degree. C.,
since the accumulated dislocation is not sufficient, the crystal
grains are not refined by the annealing step, and the appearance
after the roughening treatment process may become non-uniform.
Annealing Step:
[0070] In the above annealing step, by treating the rolled plate at
about 400 to about 550.degree. C. in a continuous annealing furnace
for 0 to about 60 seconds or at about 300 to about 500.degree. C.
in a batch furnace for about 1 to about 20 hours after the end of
the hot rolling step and before the end of the cold rolling step,
crystal grains are refined, and the appearance after the roughening
treatment process becomes uniform. In the case of the annealing
step in the continuous annealing furnace, when the temperature is
less than 400.degree. C., the effect may not be sufficient. On the
other hand, in the case of the annealing step at more than
550.degree. C. or over more than 60 seconds, the effect is
saturated, which is not preferable economically. In the case of the
annealing step in the batch furnace, when the temperature is less
than 300.degree. C., the single Si can be easily separated, and the
effect of crystal grain refining may not be sufficient. Also, when
the annealing time is less than 1 hour, the effect of crystal grain
refining may not be sufficient. In the case of the annealing step
at more than 500.degree. C. or over more than 20 hours, the crystal
grains become coarse and the appearance after the roughening
treatment process may become non-uniform.
Cold Rolling Step:
[0071] Conditions for the cold rolling step are not particularly
limited, and it is only necessary to follow a normal procedure. The
final cold rolling ratio may be determined in accordance with the
required strength or the thickness of the product sheet, and it is
only necessary that the cold rolling step is carried out with
rolling reduction of about 60 to about 98%. Straightening with a
leveler may be performed after the final cold rolling step.
Surface Treatment Step:
[0072] In order to manufacture a lithographic printing plate
support from the aluminum alloy sheet for a lithographic printing
plate obtained as above, a surface treatment step for roughening,
anodization and the like is carried out. This surface treatment
method is not particularly limited, and utilizes any one of or two
or more in combination of a mechanical method, a chemical method,
and an electrochemical method which are performed according to a
normal procedure. An etching amount by the surface treatment is
preferably about 1 to about 10 .mu.m from the surface of the
aluminum alloy sheet. With the etching amount less than about 1
.mu.m, the roughening may be insufficient, and the plate wear
resistance may be poor. On the other hand, if the etching amount
exceeds about 10 .mu.m, the etching amount is too large, which is
not preferable economically.
[0073] A photosensitive layer is applied to the aluminum alloy
sheet for a lithographic printing plate obtained by the above
steps, and the resulting plate is dried so that the lithographic
printing plate support is obtained.
EXAMPLES
[0074] The present invention will be described below in more detail
based on examples of the invention and comparative examples.
Conditions other than those described in the claims are exemplified
in order to explain effects of the present invention in the
conditions of a normal procedure, and these conditions do not limit
a technical scope of the present invention.
Invention Examples 1 to 22 and Comparative Examples 23 to 33
[0075] In production of an aluminum alloy with the compositions A
to Z and a to g shown in Table 1, the aluminum metal was melted at
745.degree. C. Then, the molten metal was mechanically stirred at
745.degree. C. over 30 minutes, using a stirring machine provided
with three blades. Moreover, the molten metal was held at
735.degree. C. over 40 minutes. Then, the in-line degassing
treatment process was carried out by blowing argon gas into the
molten metal, using the in-line degassing treatment device (SNIF).
Moreover, the aluminum carbide and oxides were removed by filtering
the molten metal by using a ceramic tube filter as an in-line
filter. Thereafter, a crystal grain refining agent was added so as
to have a concentration as described in each of compositions A to Z
and a to g. The stirring time from the addition of the crystal
grain refining agent was 0 minutes.
[0076] The temperature of the molten metal from the in-line
degassing treatment process to the addition of the crystal grain
refining agent was 700.degree. C.
TABLE-US-00001 TABLE 1 Aluminum Alloy Components (mass %) Alloy Fe
Si Cu Ti B C Mg A 0.11 0.07 0.012 0.022 0.0004 0.0001 0.001 Within
B 0.22 0.09 0.008 0.011 0.0005 0.0002 0.422 the C 0.38 0.08 0.033
0.018 0.0008 0.0000 0.032 Inven- D 0.58 0.11 0.021 0.015 0.0011
0.0001 0.121 tion E 0.34 0.01 0.022 0.021 0.0009 0.0000 0.492 F
0.38 0.03 0.031 0.026 0.0007 0.0000 0.088 G 0.25 0.19 0.007 0.024
0.0005 0.0001 0.004 H 0.28 0.24 0.015 0.022 0.0004 0.0002 0.011 I
0.25 0.12 0.0001 0.019 0.0006 0.0000 0.025 J 0.34 0.09 0.006 0.023
0.0009 0.0001 0.041 K 0.27 0.07 0.038 0.011 0.0008 0.0000 0.055 L
0.33 0.09 0.049 0.008 0.0007 0.0001 0.005 M 0.31 0.06 0.031 0.006
0.0004 0.0000 0.006 N 0.37 0.08 0.032 0.028 0.0003 0.0000 0.095 O
0.35 0.07 0.025 0.047 0.0006 0.0001 0.071 P 0.24 0.12 0.007 0.028
0.0001 0.0001 0.315 Q 0.26 0.11 0.009 0.026 0.0003 0.0000 0.225 R
0.35 0.06 0.016 0.022 0.0011 0.0001 0.089 S 0.39 0.05 0.014 0.018
0.0018 0.0001 0.002 T 0.26 0.11 0.009 0.026 0.0001 0.0003 0.015 U
0.35 0.06 0.016 0.022 0.0002 0.001 0.045 V 0.39 0.05 0.014 0.018
0.0001 0.0019 0.151 W 0.08 0.14 0.022 0.015 0.0012 0.0001 0.002
With- X 0.62 0.12 0.025 0.013 0.0008 0.0000 0.012 out Y 0.39 0.004
0.015 0.019 0.0006 0.0001 0.036 the Z 0.31 0.27 0.022 0.021 0.0005
0.0002 0.005 Inven- a 0.29 0.14 0.0000 0.026 0.0007 0.0000 0.122
tion b 0.28 0.15 0.052 0.022 0.0009 0.0001 0.225 c 0.33 0.07 0.031
0.004 0.0003 0.0000 0.062 d 0.25 0.09 0.034 0.052 0.0005 0.0001
0.033 e 0.29 0.12 0.014 0.024 0.0000 0.0000 0.009 f 0.38 0.11 0.009
0.018 0.0021 0.0001 0.111 g 0.35 0.06 0.008 0.014 0.0001 0.0022
0.055
[0077] The molten metal having been subjected to the melting and
treatment steps as above was cast in accordance with the normal
procedure of the DC casting method so as to fabricate an ingot of
the aluminum alloy. This ingot was subjected to the homogenization
treatment step under the condition of 560.degree. C. and 6 hours.
After that, the ingot was cooled to a room temperature once, and
was then heated to 430.degree. C. for the hot rolling step.
Subsequently, the hot rolling step with the start temperature of
425.degree. C. and the end temperature of 320.degree. C. was
carried out. Moreover, the cold rolling step with the rolling
reduction of 85% was carried out so as to obtain the aluminum alloy
sheet for a lithographic printing plate with the thickness of 0.30
mm.
(Measurement and Evaluation of Aluminum Carbide Concentration)
[0078] The aluminum carbide concentration was measured in
compliance with an alkali hydroxide Cracked gas chromatography
method described in LIS A09-1-1971 (LIS: Light Metal Industrial
Standard) as follows: An amount of 0.2 g of the aluminum alloy
sheet fabricated as above was put into a reaction tank, and air in
the inside of the tank is fully replaced with He. After the
replacement of air with, a NaOH aqueous solution (20 volumetric %,
approximately 20 ml) was dripped using a dripping funnel.
Immediately after the dripping, the stirring step was performed by
rotating a stirrer, while the reaction tank was heated, so that the
aluminum alloy sample containing the aluminum carbide and the NaOH
aqueous solution were fully reacted with each other. At this time,
CH.sub.4 generated by the reaction between the aluminum carbide and
moisture is trapped by an active coal column immersed in liquid
N.sub.2. After the aluminum alloy sample and the NaOH aqueous
solution have fully reacted, the trapped CH.sub.4 was evaporated by
immersing the active coal column in water bath. The quantity of the
evaporated CH.sub.4 was determined by a gas chromatography (HP6890
by Hewlett Packard). A CH.sub.4 amount was determined using a
calibration curve using a standard gas obtained by diluting
CH.sub.4 with N.sub.2 and preparing in advance. Subsequently, this
CH.sub.4 amount was converted to the aluminum carbide
concentration. Here, as the aluminum carbide, Al4C.sub.3,
Al.sub.2C.sub.6, Al.sub.4O.sub.4C and the like can be cited, but as
the aluminum carbide converted as the aluminum carbide
concentration was represented by Al.sub.4C.sub.3.
[0079] The aluminum carbide concentration acquired as above was
evaluated, and the concentration not more than 8 ppm is acceptable,
while the concentration exceeding 8 ppm is rejected. The results
are shown in Table 2. The aluminum carbide concentration in the
used aluminum metal was measured in advance, and it was 18 ppm.
TABLE-US-00002 TABLE 2 Area Occupancy of the Aggregation Fault
Tolerance Substances with of the Aluminum Respect to the
Aggregation Photosensitive Carbide Circle Having a Substance Pit
Uniformity Layer after Concentration Radius of 5 .mu.m Density
after the Ink Stain Long-term Alloy (ppm) (%) (Nos./50 cm.sup.2)
Roughening Resistance Storage Invention Example 1 A 3.4 <10 --
.largecircle. .circleincircle. .circleincircle. Invention Example 2
B 2.8 <10 -- .circleincircle. .circleincircle. .circleincircle.
Invention Example 3 C 2.2 <10 -- .circleincircle.
.circleincircle. .circleincircle. Invention Example 4 D 3.6 10 1
.largecircle. .circleincircle. .largecircle. Invention Example 5 E
0.2 <10 -- .largecircle. .circleincircle. .circleincircle.
Invention Example 6 F 2.7 <10 -- .circleincircle.
.circleincircle. .circleincircle. Invention Example 7 G 2.2 <10
-- .circleincircle. .circleincircle. .circleincircle. Invention
Example 8 H 1.1 <10 -- .largecircle. .largecircle.
.circleincircle. Invention Example 9 I 3.4 <10 -- .largecircle.
.circleincircle. .circleincircle. Invention Example 10 J 3.8 22 1
.circleincircle. .circleincircle. .largecircle. Invention Example
11 K 1.8 <10 -- .circleincircle. .circleincircle.
.circleincircle. Invention Example 12 L 0.8 <10 -- .largecircle.
.circleincircle. .circleincircle. Invention Example 13 M 1.2 <10
-- .circleincircle. .circleincircle. .circleincircle. Invention
Example 14 N 0.0 <10 -- .circleincircle. .circleincircle.
.circleincircle. Invention Example 15 O 0.5 <10 -- .largecircle.
.largecircle. .circleincircle. Invention Example 16 P 2.4 <10 --
.largecircle. .circleincircle. .circleincircle. Invention Example
17 Q 2.2 <10 -- .circleincircle. .circleincircle.
.circleincircle. Invention Example 18 R 3.7 23 1 .circleincircle.
.circleincircle. .largecircle. Invention Example 19 S 5.8 15, 46 2
.circleincircle. .largecircle. .largecircle. Invention Example 20 T
2.2 <10 -- .largecircle. .circleincircle. .circleincircle.
Invention Example 21 U 5.0 100 1 .circleincircle. .circleincircle.
.largecircle. Invention Example 22 V 6.0 20, 50 2 .circleincircle.
.largecircle. .largecircle. Comparative Example 23 W 4.4 35 1 X
.circleincircle. .largecircle. Comparative Example 24 X 3.4 <10
-- X .circleincircle. .circleincircle. Comparative Example 25 Y 3.1
<10 -- X .circleincircle. .circleincircle. Comparative Example
26 Z 3.3 <10 -- X X .circleincircle. Comparative Example 27 a
3.4 <10 -- X .circleincircle. .circleincircle. Comparative
Example 28 b 3.8 15 1 X .circleincircle. .largecircle. Comparative
Example 29 c 2.2 <10 -- X .circleincircle. .circleincircle.
Comparative Example 30 d 3.4 <10 -- .circleincircle. X
.circleincircle. Comparative Example 31 e 3.4 <10 -- X
.circleincircle. .circleincircle. Comparative f 8.5 25, 37, 15, 40
4 .circleincircle. X X Example 32*.sup.1) Comparative g 9.1 65, 23,
39, 18, 15 5 .circleincircle. X X Example 33*.sup.1) *.sup.1)A
defect occured on the surface.
[0080] The obtained aluminum alloy sheet was immersed in a 10 mass
% aqueous sodium hydroxide solution at 70.degree. C. for 30 seconds
and etched, and was washed with flowing water. Then, the washed
sheet was neutralized with a 20 mass % nitric acid aqueous
solution, and was further washed with water. This aluminum alloy
sheet was subjected to the electrolytic roughening treatment in 1
mass % nitric acid aqueous solution with an electric quantity at an
anode of 300 coulomb/dm.sup.2, using a sinusoidal alternating
waveform current under the condition of VA=12.7 V. The surface
roughness was measured, which was 0.45 .mu.m (expressed in terms of
Ra). Subsequently, this aluminum alloy sheet was immersed in a 30
mass % sulfuric acid aqueous solution at 55.degree. C., and is
subjected to a desmutting process for 2 minutes. Thereafter, in a
20 mass % sulfuric acid aqueous solution at 33.degree. C., a
cathode was arranged on the grained surface, and the aluminum alloy
sheet was anodized at a current density of 5A/dm2 for 50 seconds.
The anodized film amount was 2.6 g/m2. The aluminum alloy sheet
subjected to the above surface treatment step was made to be a
support 1.
(Measurement of Area Occupancy Ratio of Aggregation Substances)
[0081] The area occupancy ratio of the aggregation substances of
the T--B-based compound and the aluminum carbide, the T--C-based
compound and the aluminum carbide, and the T--B-based compound, the
T--C-based compound and the aluminum carbide distributed within 50
cm.sup.2 on the surface of the aluminum alloy sheet subjected to
the above surface treatment step were measured using an electronic
probe microanalyzer. Measurement spots were determined by
arbitrarily selecting 20 pieces of the aggregation substances. A
circle having a radius of 5 .mu.m was provided around the selected
the aggregation substances as the center, and the area occupancy
ratio of the aggregation substances with respect to the circle was
measured. The area occupancy ration was obtained by dividing a
value of an area occupied by the each aggregation substances by an
area of the circle. An area occupancy ratio of less than 10% was
rated as acceptable. The result is shown in Table 2.
(Measurement of Number of Present Aggregation Substances)
[0082] In the above measurement, when there are the aggregation
substances with the area occupancy ratio of not less than 10%, the
number thereof was counted. The number of the aggregation
substances present within a range of 50 cm.sup.2 being 1 or 2 was
rated as acceptable, while the number exceeding 2 was rated as
rejected. The result was shown in Table 2. The measurements of the
area occupancy ratio and the number of the aggregation substances
on the surface of the aluminum alloy sheet are preferably made on
the support 1 which is subjected to the above surface treatment
step, but since fine scars or projections and recesses caused by
the roughening treatment are present, the discrimination may be
difficult. In that case, the measurement may be made on the surface
which is subjected to a smoothing treatment. The smoothing
treatment method includes mechanical polishing, electrolytic
polishing and the like. Also, the polishing depth should be 1 to 10
.mu.m, and it is important that it should be equal to the depth to
be etched by the above surface treatment step. Also, since the
aluminum carbide is oxidized by the reaction with moisture and
oxygen in the atmosphere, the measurement needs to be made quickly
after the surface treatment step.
Evaluation of Pit Uniformity after Roughening
[0083] A piece having a certain size (30.times.30 cm) was cut out
of the aluminum alloy sheet subjected to the above surface
treatment step as a test piece, and the pit uniformity was
evaluated. Evaluation was made by visually observing the appearance
of the test piece over the entire width, and the piece with the
favorable pit uniformity over the entire width was rated as very
good (.circleincircle.), the piece which was partially poor but
practically has no problem as good (.largecircle.), and the pieces
which was poor over the entire width was rated as poor (X). The
pieces with .circleincircle. and .largecircle. were rated as
acceptable, while those with X were rated as rejected. The result
is shown in Table 2.
[0084] This support 1 was coated with a base coating liquid having
the following composition so that a dried application amount
becomes 2 mg/m.sup.2 using a bar coater and was dried at 80.degree.
C. for 20 seconds, to thereby obtain a support 2.
(Composition of Base Coating Liquid)
[0085] Polymer (P1) (chemical structure is shown below) . . . 0.3
mass parts
[0086] Purified Water . . . 60.0 mass parts
[0087] Methanol . . . 939.7 mass parts
##STR00001##
[0088] This support 2 was coated with a photosensitive substance
having the following composition using a bar coater, and then it
was dried at 90.degree. C. for 1 minute, to thereby form a
photosensitive layer. The mass of the dried photosensitive layer
was 1.35 g/m.sup.2.
(Composition of Photosensitive Substance)
[0089] Polymerizable compound (1)) <chemical structure is shown
below> (PLEX6661-O, by Degussa Japan Co., Ltd.) . . . 1.69 mass
parts
[0090] Binder Polymer (1)) <chemical structure is shown
below> . . . 1.87 mass parts
[0091] Sensitizing Dye (1)) <chemical structure is shown
below> . . . 0.13 mass parts
[0092] Polymerization Initiator (1)) <chemical structure is
shown below> . . . 0.46 mass parts
[0093] Chain Transfer Agent (1)) <chemical structure is shown
below> . . . 0.44 mass parts
[0094] Dispersed Substance of .epsilon.-Phthalocyanine Pigment . .
. 1.70 mass parts
[0095] (pigment: 15 mass parts, dispersing agent (allyl
methacrylate/methacrylic acid copolymer (mass average molar weight:
60 thousands, copolymerization molecular ratio: 83/17)): 10 mass
parts, cyclohexanone: 15 mass parts)
[0096] Thermal Polymerization Inhibitor (N-nitrosophenyl
hydroxylamine aluminum salt) . . . 0.012 mass parts
[0097] Dispersed Substance of Yellow Pigment . . . 0.5 mass parts
(yellow pigment Novoperm Yellow H2G (by Clariant): 15 mass parts,
dispersing agent (allyl methacrylate/methacrylic acid copolymer
(mass average molar weight: 60 thousands, copolymerization
molecular ratio: 83/17)): 10 mass parts, cyclohexanone: 15 mass
parts)
[0098] Fluorine Surfactant (1) (mass average molecular weight: 10
thousands)) <chemical structure is shown below> . . . 0.03
mass parts
[0099] Methyl Ethyl Ketone . . . 27.0 mass parts
[0100] Propylene Glycol Monomethyl ether . . . 26.7 mass parts
##STR00002## ##STR00003##
[0101] This photosensitive layer was coated with a protective layer
application aqueous solution having the following composition using
a bar coater so that a dried application mass becomes 2.5
g/m.sup.2, and was dried at 120.degree. C. for 1 minute, to thereby
obtain a photosensitive lithographic printing plate original
plate.
(Composition of Protective Layer Application Aqueous Solution)
[0102] PVA105 (polyvinyl alcohol, saponification degree 98 molar %,
by Kuraray Co., Ltd.) . . . 1.80 mass parts
[0103] PVP-K30 (polyvinyl pyrrolidone, by BASF) . . . 0.40 mass
parts
[0104] Emalex 710 (by Nihon Emulsion Co., Ltd.) . . . 0.03 mass
parts
[0105] Luviskol VA64W (by BASF) . . . 0.04 mass parts
[0106] The Above Polymer (P1) . . . 0.05 mass parts
[0107] Purified Water . . . 36.5 mass parts
[0108] The obtained photosensitive printing plate was adjusted with
Vx9600CTP by Fuji
[0109] Film Corporation (light-source wavelength: 405 nm) so that
an exposure amount on a sensitizing material is 0.05 mJ/cm.sup.2
and drawing was made in an image state. Thereafter, a preheating
was performed within 30 seconds, and a development was made by the
developing solution at 25.degree. C. using PS processor Inter
Plater 850HD by G&J in which an alkali developing solution
having the following composition was incorporated.
(Composition of Alkali Developing Solution)
[0110] Potassium Hydroxide . . . 0.15 g
[0111] Polyoxyethylene Naphthyl ether (n=13) . . . 5.0 g
[0112] Chelest 400 (chelating agent) . . . 0.1 g
[0113] Water . . . 94.75 g
(Ink Stain Resistance)
[0114] The developed lithographic printing plate was washed with
water and dried, and a printing test using 100 thousand copies was
carried out using an offset rotary press. Thereafter, a degree of
dot-like stains in a non-image area was visually evaluated.
Evaluation was made such that a favorable copy without dot-like
stains over the entire non-image area was rated as very good
(.circleincircle.), a copy with some dot-like stains but without a
practical problem was rated as good (.largecircle.), and a copy
with dot-like stains causing a practical problem was rated as poor
(X). The .circleincircle. and .largecircle. marks were rated as
acceptable, while the X mark was rated as rejected. The result is
shown in Table 2.
(Fault Tolerance of Photosensitive Layer after Long-Term
Storage)
[0115] Moreover, the lithographic printing plate on which the
photosensitive layer was formed as above was stored for three
months under the atmosphere at a room temperature and the humidity
within a range of 20 to 90%, and occurrence of a defect in the
photosensitive layer was evaluated. Evaluation was made such that a
plate without defects in the photosensitive layer was rated as very
good (.circleincircle.), a plate with some defects but without a
practical problem was rated as good (.largecircle.), and a plate
with defects causing a practical problem was rated as poor (X). The
.circleincircle. and .largecircle. marks were rated as acceptable,
while the X mark was rated as rejected. The result is shown in
Table 2.
[0116] In Invention Examples 1 to 22, the aluminum carbide
concentration was not more than 8 ppm, the area occupancy ratio of
the aggregation substances was less than 10%. Although, the area
occupancy ratio is not less than 10%, the density of the
aggregation substances was not more than 2 per 50 cm.sup.2. Both
the cases were acceptable. Moreover, the pit uniformity after the
roughening, the ink stain resistance, and the fault tolerance of
the photosensitive layer after long-term storage were all
acceptable.
[0117] In Comparative Example 23, since the Fe content of the
aluminum alloy W was too small, the pits generated by the
roughening treatment were non-uniform.
[0118] In Comparative Example 24, since the Fe content of the
aluminum alloy X was too large, the pits generated by the
roughening treatment were non-uniform.
[0119] In Comparative Example 25, since the Si content of the
aluminum alloy Y was too small, the pits generated by the
roughening treatment were non-uniform.
[0120] In Comparative Example 26, since the Si content of the
aluminum alloy Y was too large, the pits generated by the
roughening treatment were non-uniform, and also the single Si was
separated, to thereby causing ink stains.
[0121] In Comparative Example 27, since the Cu content of the
aluminum alloy a was too small, the pits generated by the
roughening treatment were non-uniform.
[0122] In Comparative Example 28, since the Cu content of the
aluminum alloy b was too large, the pits generated by the
roughening treatment were non-uniform.
[0123] In Comparative Example 29, since the Ti content of the
aluminum alloy c was too small, the pits generated by the
roughening treatment were non-uniform.
[0124] In Comparative Example 30, since the Ti content of the
aluminum alloy d was too large, the coarse Al--Ti-based compound
was formed, and ink stains occurred.
[0125] In Comparative Example 31, since the total contents of B and
C of the aluminum alloy e was too small, the pits generated by the
roughening treatment were non-uniform.
[0126] In Comparative Example 32, since the content of B of the
aluminum alloy f was too large, the total contents of B and C were
too large, too. As a result, the aluminum carbide concentration was
too high, the aggregation density of the T--B-based compound was
also too large, and ink stains and a local defect in the
photosensitive layer after long-term storage occurred. Moreover, a
defect occurred on the surface by an aggregation of the T--B-based
compound.
[0127] In Comparative Example 33, since the content of C of the
aluminum alloy g was too large, the total contents of B and C were
too large, too. As a result, the aluminum carbide concentration was
too high, the aggregation density of the Ti--C compound was also
too large, and ink stains and a local defect in the photosensitive
layer after long-term storage occurred. Moreover, a defect occurred
on the surface by an aggregation of the T--C-based compound.
Invention Examples 34 to 49 and Comparative Examples 50 to 60
[0128] In production of an aluminum alloy containing 0.35% Fe,
0.09% Si, 0.025% Cu, 0.010% Ti, and 0.0005% B, the aluminum metal
was subjected to the melting step and the treatment step described
in Table 3. Here, the molten metal temperature in the stirring
process after the melting process was the same as the temperature
in the melting process. Also, after the crystal grain refining
agent was added, the molten metal temperature in the stirring
process was the same as the molten metal temperature in the
filtration treatment process using the in-line filter. The molten
metal subjected to the melting process and the treatment processes
as above was cast in compliance with the normal procedure of the DC
casting method, to thereby fabricate an ingot of the aluminum
alloy.
TABLE-US-00003 TABLE 3 Treatment Stage Melting In-line Degassing
Filtration Treatment Stirring Time Stage Treatment Process after
Adding Molten Retaining Process Process Using an In-line Filter
Crystal Grain Metal Stirring Molten Metal Molten Metal Applied/
Molten Metal Refining Temperature Process Temperature Time Applied/
Temperature Not Temperature Material Condition (.degree. C.) Time
(m) (.degree. C.) (m) Not Apllied (.degree. C.) Apllied (.degree.
C.) Time (m) 1 680 25 695 30 Applied 703 Applied 700 0 Within 2 745
40 740 25 Applied 735 Applied 718 1 Invention 3 780 30 742 27
Applied 729 Applied 715 2 4 732 8 732 35 Applied 732 Applied 720 1
5 742 12 745 42 Applied 738 Applied 718 1 6 740 45 738 44 Applied
733 Applied 722 2 7 722 55 722 38 Applied 729 Applied 709 3 8 743
20 680 28 Applied 700 Applied 698 2 9 731 25 742 34 Applied 705
Applied 699 1 10 720 38 780 49 Applied 722 Applied 718 0 11 718 24
718 12 Applied 718 Applied 711 0 12 711 22 711 23 Applied 711
Applied 699 3 13 740 40 740 54 Applied 738 Applied 718 1 14 729 25
722 38 Applied 745 Applied 735 0 15 746 35 745 25 Applied 780
Applied 780 0 16 739 25 739 49 Applied 680 Applied 680 9 17 790 35
735 25 Applied 729 Applied 715 2 Without 18 675 -- -- -- -- -- --
-- -- Invention 19 742 1 729 31 Applied 710 Applied 704 1 20 739 72
740 32 Applied 700 Applied 692 0 21 729 29 785 28 Applied 705
Applied 700 2 22 743 24 721 5 Applied 706 Applied 699 3 23 733 35
705 40 Applied 678 -- -- -- 24 745 40 733 25 Applied 792 Applied
776 0 25 719 25 719 22 Not Applied 712 Applied 701 0 26 729 28 735
35 Applied 722 Not 722 2 Applied 27 744 20 733 38 Applied 713
Applied 704 15
[0129] The obtained ingot was subjected to the homogenization
treatment step under the condition of 540.degree. C. and 3 hours.
Thereafter, the ingot was cooled to a room temperature once, and
was then heated to 420.degree. C. for the hot rolling step.
Subsequently, the ingot was subjected to the hot rolling step with
the start temperature of 415.degree. C. and the end temperature of
330.degree. C. Moreover, the hot rolled aluminum alloy plate was
subjected to the cold rolling step with rolling reduction of 80% to
thereby obtain an aluminum alloy sheet for a lithographic printing
plate with the thickness of 0.3 mm.
[0130] The obtained aluminum alloy sheet for a lithographic
printing plate was subjected to the same surface treatment step as
in the above-described Invention Example 1, and was made to be the
aluminum alloy sheet support 1. The area occupancy ratio of
aggregation substances of the T--B-based compound and the aluminum
carbide, the T--C-based compound and the aluminum carbide, and the
T--B-based compound, the T--C-based compound and the aluminum
carbide on the surface of the support 1 were measured and evaluated
similarly to the example 1. Moreover, when the area occupancy of
the aggregation substances is not less than 10%, the number of the
aggregation substances was measured and evaluated similarly to the
example 1. Moreover, the pit uniformity after the roughening was
also evaluated similarly to the example 1. The results are shown in
Table 4.
TABLE-US-00004 TABLE 4 Fault Area Occupancy of Tolerance of the
Aggregation the Photo- Aluminum Substances with Aggregation Pit
sensitive Carbide Respect to the Circle Substance Uniformity Layer
Concentration Having a Radius of Density after the Ink Stain after
Long- No. Condition (ppm) 5 .mu.m (%) (Nos./50 cm.sup.2) Roughening
Resistance term Storage Invention Example 34 1 0.8 <10 --
.circleincircle. .circleincircle. .circleincircle. Invention
Example 35 2 0.0 <10 -- .circleincircle. .circleincircle.
.circleincircle. Invention Example 36 3 5.7 27, 48 2
.circleincircle. .largecircle. .largecircle. Invention Example 37 4
5.5 42, 39 2 .circleincircle. .largecircle. .largecircle. Invention
Example 38 5 2.9 <10 -- .circleincircle. .circleincircle.
.circleincircle. Invention Example 39 6 3.9 32 1 .circleincircle.
.circleincircle. .largecircle. Invention Example 40 7 4.2 45 1
.circleincircle. .largecircle. .largecircle. Invention Example 41 8
3.5 10 1 .circleincircle. .circleincircle. .largecircle. Invention
Example 42 9 3.4 <10 -- .circleincircle. .circleincircle.
.circleincircle. Invention Example 43 10 5.9 60, 40 2
.circleincircle. .largecircle. .largecircle. Invention Example 44
11 5.3 55, 34 2 .circleincircle. .largecircle. .largecircle.
Invention Example 45 12 5.0 100 1 .circleincircle. .circleincircle.
.largecircle. Invention Example 46 13 1.5 <10 --
.circleincircle. .circleincircle. .circleincircle. Invention
Example 47 14 2.3 <10 -- .circleincircle. .circleincircle.
.circleincircle. Invention Example 48 15 5.8 15, 50 2
.circleincircle. .largecircle. .largecircle. Invention Example 49
16 6.2 23, 57 2 .circleincircle. .largecircle. .largecircle.
Comparative Example 50 17 8.9 18, 24, 32, 44 4 .circleincircle. X X
Comparative 18 -- -- -- -- -- -- Example 51*.sup.2) Comparative
Example 52 19 9.5 25, 29, 31, 44, 20 5 .circleincircle. X X
Comparative 20 1.9 <10 -- .circleincircle. X .circleincircle.
Example 53*.sup.3) Comparative Example 54 21 9.2 38, 45, 22, 33 4
.circleincircle. X X Comparative Example 55 22 8.7 15, 18, 29, 59 4
.circleincircle. X X Comparative 23 -- -- -- -- -- -- Example
56*.sup.2) Comparative Example 57 24 8.9 20, 44, 35, 30 4
.circleincircle. X X Comparative 25 8.5 22, 23, 49, 32 4
.circleincircle. X X Example 58*.sup.3) Comparative Example 59 26
8.2 34, 59, 25 3 .circleincircle. X X Comparative 27 8.1 41, 48, 31
3 .circleincircle. X X Example 60*.sup.3) *.sup.2)The aluminum
alloy plate counld not produced stably. *.sup.3)A defect occured on
the surface.
[0131] Similarly to the example 1, the support 1 was coated with
the base coating liquid, and was dried to thereby obtain the
support 2. Moreover, similarly to the example 1, the support 2 was
coated with the photosensitive composition, and was dried to
thereby form the photosensitive layer. Finally, similarly to the
example 1, the formed photosensitive layer was coated with the
protective layer application aqueous solution, and was dried to
thereby obtain the photosensitive lithographic printing plate
original plate.
[0132] Similarly to the example 1, drawing was made in an image
state on the obtained photosensitive lithographic printing plate,
this was developed, washed with water, and dried. A printing test
using 100 thousand copies was carried out using an offset rotary
press. Similarly to the example 1, the photosensitive lithographic
printing plate obtained as above was tested and evaluated for the
ink stain resistance and the fault tolerance of the photosensitive
layer after long-term storage. The result is shown in Table 4.
[0133] In Invention Examples 34 to 49, the aluminum carbide
concentration was not more than 8 ppm, the area occupancy ratio of
the aggregation substances was less than 10%. Although, the area
occupancy ratio is not less than 10%, the density of the
aggregation substances was not more than 2 per 50 cm.sup.2. Both
the cases were acceptable. Moreover, the pit uniformity after the
roughening, the ink stain resistance, and the fault tolerance of
the photosensitive layer after long-term storage were all
acceptable.
[0134] In Comparative Example 50, due to the fact that the molten
metal temperature during the melting stage was too high, soot
caused by imperfect combustion of fuel, carbon-containing compounds
and the like were reacted with the molten metal, and the aluminum
carbide was generated, resulting in increase in its concentration.
Further, the aggregation substance density with the T--B-based
compound was too high. As a result, ink stains at printing and
defects in the photosensitive layer after long-term storage
occurred.
[0135] In Comparative Example 51, since the molten metal
temperature during the melting stage was too low, an aluminum metal
and a mother alloy were not fully melted, and the aluminum alloy
sheet could not be produced stably.
[0136] In Comparative Example 52, since the stirring time after the
melting stage was too short, the effect of the aluminum carbide
removal by stirring was not sufficient, the concentration became
high, and the aggregation substance density with the T--B-based
compound was too high. As a result, ink stains at printing and
defects in the photosensitive layer after long-term storage
occurred.
[0137] In Comparative Example 53, since the stirring time after the
melting stage was too long, inclusions was included. As a result,
ink stains occurred. Moreover, defects were caused on the
surface.
[0138] In Comparative Example 54, due to the fact that the molten
metal temperature in the retaining process was too high, soot
caused by imperfect combustion of fuel, carbon-containing compounds
and the like were reacted with the molten metal, the aluminum
carbide was generated, resulting in increase in its concentration.
Further, the aggregation substance density with the T--B-based
compound was too high. As a result, ink stains at printing and
defects in the photosensitive layer after long-term storage
occurred.
[0139] In Comparative Example 55, since the retaining time was too
short, a separation of the aluminum carbide was insufficient, the
concentration became high. Further, the aggregation substance
density with the T--B-based compound was too high. As a result, ink
stains at printing and defects in the photosensitive layer after
long-term storage occurred.
[0140] In Comparative Example 56, since the molten metal
temperature in the in-line degassing treatment process was too low,
the molten metal was coagulated, and the aluminum alloy sheet could
not be produced stably.
[0141] In Comparative Example 57, due to the fact that the molten
metal temperature in the in-line degassing treatment process was
too high, soot caused by imperfect combustion of fuel,
carbon-containing compounds and the like were reacted with the
molten metal, and the aluminum carbide was generated, resulting in
increase in its concentration. Further, the aggregation substance
density with the T--B-based compound was too high. As a result, ink
stains at printing and defects in the photosensitive layer after
long-term storage occurred.
[0142] In Comparative Example 58, due to the fact that the in-line
degassing treatment was not performed, the decrease effect of the
aluminum carbide was insufficient, and the concentration became
high. Further, the aggregation substance density with the
T--B-based compound was too high. As a result, ink stains at
printing and defects in the photosensitive layer after long-term
storage occurred. Also, hydrogen gas removal was not sufficient,
and a surface defect occurred.
[0143] In Comparative Example 59, due to the fact that the
filtration treatment using an in-line filter was not performed,
removal of the aluminum carbide, inclusions such as oxides and the
like was not sufficient, resulting in increase in the concentration
of aluminum carbide. Further, the aggregation substance density
with the T--B-based compound was too high. As a result, ink stains
caused by the aluminum carbide and defects in the photosensitive
layer after long-term storage occurred. Also, inclusions caused
surface defects and ink stains.
[0144] In Comparative Example 60, due to the fact that the stirring
time of the aluminum molten metal after the addition of the crystal
grain refining agent was too long, the concentration of the
aluminum carbide became high. Further, the aggregation substance
density with the T--B-based compound was too high. As a result, ink
stains and defects in the photosensitive layer after long-term
storage occurred. Also, an aggregation of the Ti--B compound
occurred, which caused a surface defect.
INDUSTRIAL APPLICABILITY
[0145] According to the present invention, an aluminum alloy sheet
for a lithographic printing plate which is excellent in the pit
uniformity after roughening, the ink stain resistance in a
non-image area during printing, and the fault tolerance of a
photosensitive layer in storage under the atmosphere can be
obtained. Also, according to the manufacturing method of an
aluminum alloy sheet for a lithographic printing plate according to
the present invention, the aluminum alloy sheet for the
lithographic printing plate can be obtained reliably and
stably.
* * * * *