U.S. patent application number 10/957625 was filed with the patent office on 2005-03-03 for method for forming image and apparatus for forming image.
This patent application is currently assigned to LASTRA S.p.A.. Invention is credited to Okamoto, Hideaki.
Application Number | 20050048404 10/957625 |
Document ID | / |
Family ID | 18934401 |
Filed Date | 2005-03-03 |
United States Patent
Application |
20050048404 |
Kind Code |
A1 |
Okamoto, Hideaki |
March 3, 2005 |
Method for forming image and apparatus for forming image
Abstract
A method for forming an image, which comprises subjecting a
photosensitive layer of a photosensitive lithographic printing
plate having a photosensitive layer comprising a photopolymerizable
composition formed on a support surface to scanning exposure with a
laser light having a wavelength in a range of from 650 to 1,300 nm,
developing an image, and then further subjecting the photosensitive
lithographic printing plate having the developed image to whole
image exposure with a light exposure energy of from 1 to 70 times
larger than the light exposure energy at the time of the laser
light scanning exposure.
Inventors: |
Okamoto, Hideaki; (Kanagawa,
JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
LASTRA S.p.A.
Manerbio (Brescia)
IT
|
Family ID: |
18934401 |
Appl. No.: |
10/957625 |
Filed: |
October 5, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10957625 |
Oct 5, 2004 |
|
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10098598 |
Mar 18, 2002 |
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Current U.S.
Class: |
430/302 |
Current CPC
Class: |
B41C 2210/22 20130101;
B41C 2210/24 20130101; B41C 2210/06 20130101; B41C 1/1075 20130101;
Y10S 430/145 20130101; G03F 7/40 20130101; Y10S 430/146 20130101;
B41C 2210/04 20130101; B41C 1/1008 20130101 |
Class at
Publication: |
430/302 |
International
Class: |
G03F 007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 19, 2001 |
JP |
2001-077682 |
Claims
1-14. (canceled)
15. An apparatus for forming an image, which comprises continuously
connecting the following steps (1) to (3): (1) a scanning exposure
step of subjecting a photosensitive layer of a photosensitive
lithographic printing plate having a photosensitive layer
comprising a photopolymerizable composition formed on a support
surface to scanning exposure with a laser light having a wavelength
in a range of from 650 to 1,300 nm, (2) a developing step of
developing an image on the photosensitive lithographic printing
plate after the scanning exposure, and (3) a whole image exposure
step of subjecting the photosensitive lithographic printing plate
after the development to whole image exposure with a light exposure
energy of from 1 to 70 times larger than the light exposure energy
at the time of the laser light scanning exposure used at the step
(1).
16. The apparatus for forming an image according to claim 15,
wherein the light exposure energy at the whole image exposure step
(3) is at most 50 times larger than the light exposure energy at
the scanning exposure step (1).
17. The apparatus for forming an image according to claim 16,
wherein the light exposure energy at the whole image exposure step
(3) is from 1 to 30 times larger than the light exposure energy at
the scanning exposure step (1).
18. The apparatus for forming an image according to claim 17,
wherein the light exposure energy at the whole image exposure step
(3) is from 1.2 to 25 times larger than the light exposure energy
at the scanning exposure step (1).
19. The apparatus for forming an image according to claim 15,
wherein a light intensity on the image-forming surface at the whole
image exposure step (3) is at least 10 mW/cm.sup.2.
20. The apparatus for forming an image according to claim 19,
wherein the light intensity on the image-forming surface at the
whole image exposure step (3) is from 15 to 700 mW/cm.sup.2.
21. The apparatus for forming an image according to claim 15,
wherein a temperature of the image-forming surface at the whole
image exposure step (3) is from 20 to 300.degree. C.
22. The apparatus for forming an image according to claim 15,
wherein a light source at the whole image exposure step (3) is a
mercury lamp.
23. The apparatus for forming an image according to claim 15,
wherein the light exposure energy at the whole image exposure step
(3) is from 10 mJ/cm.sup.2 to 10 J/cm.sup.2.
24. An image produced by the process comprising: subjecting a
photosensitive layer of a photosensitive lithographic printing
plate to scanning exposure with a laser light having a wavelength
in a range of from 650 to 1,300 nm, the photosensitive layer
comprising a photopolymerizable composition formed on a support
surface; developing an image on the photosensitive lithographic
printing plate after the scanning exposure; and subjecting the
photosensitive lithographic printing plate after the developing to
whole image exposure with a light exposure energy of from 1 to 70
times larger than a light exposure energy at the scanning
exposure.
25. An image according to claim 24, wherein the light exposure
energy at the whole image exposure is at most 50 times larger than
the light exposure energy at the scanning exposure.
26. An image according to claim 25, wherein the light exposure
energy at the whole image exposure is from 1 to 30 times larger
than the light exposure energy at the scanning exposure.
27. An image according to claim 26, wherein the light exposure
energy at the whole image exposure is from 1.2 to 25 times larger
than the light exposure energy at the scanning exposure.
28. An image according to claim 24, wherein a light intensity on
the image-forming surface at the whole image exposure is at least
10 mW/cm.sup.2.
29. An image according to claim 24, wherein the light intensity on
the image-forming surface at the whole image exposure is from 15 to
700 mW/cm.sup.2.
30. An image according to claim 24, wherein a temperature of the
image-forming surface at the whole image exposure is from 20 to
300.degree. C.
31. An image according to claim 24, wherein a light source at the
whole image exposure is a mercury lamp.
32. An image according to claim 24, wherein the light exposure
energy at the whole image exposure is from 10 mJ/cm.sup.2 to 10
J/cm.sup.2.
33. An apparatus for forming an image, comprising: a photosensitive
lithographic printing plate having a support surface on which a
photosensitive layer comprising a photopolymerizable composition is
formed; a scanning exposure device configured to expose the
photosensitive layer with a laser light having a wavelength in a
range of from 650 to 1,300 nm; a developer configured to develop an
image on the photosensitive lithographic printing plate; and a
whole image exposure device configured to subject the
photosensitive lithographic printing plate with a light exposure
energy of from 1 to 70 times larger than a light exposure energy of
the scanning exposure device.
34. The apparatus for forming an image according to claim 33,
wherein the whole image exposure device comprises a mercury lamp.
Description
[0001] The present invention relates to a method for forming an
image, which comprises exposing a photosensitive lithographic
printing plate having a photosensitive layer comprising a
photopolymerizable composition formed on a support surface to a
laser light having a wavelength in a range of from 650 to 1,300
nm.
[0002] Heretofore, there has been commonly used a method for
forming an image of a photosensitive lithographic printing
plate-having a photosensitive layer comprising a photopolymerizable
composition, which comprises light-exposing the photosensitive
layer of the photosensitive lithographic printing plate having the
photosensitive layer comprising a photopolymerizable composition
containing an ethylenic unsaturated compound formed on a support
surface to polymerize and cure the ethylenic unsaturated compound
in the photopolymerizable composition on the light-exposed part,
and then dissolving and removing the unexposed part to form an
image. However, as the light-exposing method, scanning exposure
with a laser light such as an argon ion laser, an FD-YAG laser, a
semiconductor laser, a YAG laser or the like, which provides a
highly efficient productivity, has been noted, and among them, a
semiconductor laser having an infrared wavelength range of from 650
to 1,300 nm has been favorably noted.
[0003] However, when the photopolymerizable composition is
subjected to scanning exposure with the infrared laser light, the
photopolymerizable composition having a high sensitivity is
sensitized with a minute light leaked from a laser head to provide
uneven images (causing "banding phenomenon"), and as this result,
there is provided a problem that reproducibility of the image thus
formed is poor. The banding phenomenon can be controlled and
avoided if the infrared laser light output is made small, but it is
difficult to form an image having such a sufficient strength as to
provide a satisfactory printing resistance.
[0004] On the other hand, in the process of employing scanning
exposure with an argon ion laser light having a wavelength of 488
nm or an FD-YAG laser light having a wavelength of 532 nm, it has
been studied to improve an image strength by treatment after the
scanning exposure. For example, a process comprising laser scanning
exposure and whole image post-exposure after developing treatment
or the like has been proposed (see U.S. Pat. No. 6,010,824,
JP-A-11-265069 and JP-A-2001-42546). However, in order to improve
an image strength by carrying out the whole image post-exposure
after the developing treatment, it has been necessary to use a
light exposure energy of about at least 100 times larger than a
light exposure energy required at the time of scanning exposure
with a laser light, as described in JP-A-2000-66416.
[0005] In view of the above-mentioned prior arts of forming an
image by exposing a photopolymerizable photosensitive lithographic
printing plate to an infrared laser light, an object of the present
invention is to provide a method for forming an image by exposing a
photopolymerizable photosensitive lithographic printing plate to an
infrared laser light, which can produce such a sufficient image
strength as to provide a satisfactory printing resistance and also
can provide an excellent image-reproducibility.
[0006] As mentioned above, when carrying out scanning exposure with
an infrared laser light, it was necessary to reduce a laser light
output in order to prevent "banding phenomenon". When carrying out
such scanning exposure with the infrared laser light, a light
exposure energy required at the time of carrying out whole image
exposure after development is required to be such a high level as
at least 100 times larger than a light exposure energy required at
the time of the scanning exposure, as described in the conventional
prior arts.
[0007] However, the present inventors have intensively studied and
discovered that the above object can be achieved by carrying out
scanning exposure with an infrared laser light and further carrying
out whole image exposure with a light exposure energy of at most 70
times larger than a light exposure energy required at the time of
the scanning exposure with the infrared laser light, and the
present invention has been accomplished on the basis of this
discovery.
[0008] Thus, the first feature of the present invention resides in
a method for forming an image, which comprises subjecting a
photosensitive layer of a photosensitive lithographic printing
plate having a photosensitive layer comprising a photopolymerizable
composition formed on a support substrate to a laser light having a
wavelength in a range of from 650 to 1,300 nm, developing an image
and then further subjecting the developed printing plate to whole
image exposure with a light exposure energy of at most 70 times
larger than the light exposure energy required at the time of the
scanning exposure with the laser light.
[0009] Also, the second feature of the present invention resides in
an apparatus for forming an image, which comprises forming an image
with the following continuously connected steps:
[0010] (1) a scanning exposure step of subjecting a photosensitive
layer of a photosensitive lithographic printing plate having a
photosensitive layer comprising a photopolymerizable composition
formed on a support surface to scanning exposure with a laser light
having a wavelength in a range of from 650 to 1,300 nm,
[0011] (2) a developing step of developing an image of the printing
plate after the scanning exposure, and
[0012] (3) a whole image exposure step of subjecting the printing
plate after the development to whole image exposure with a light
exposure energy of at most 70 times larger than the light exposure
energy at the time of the scanning exposure with the laser light
used at the step (1).
[0013] A photopolymerizable composition as a photosensitive layer
of a photosensitive lithographic printing plate of the present
invention preferably contains the following components (A) to
(D):
[0014] (A) an ethylenic unsaturated compound,
[0015] (B) a sensitizing dye absorbing a light having a wavelength
in a range of from 650 to 1,300 nm,
[0016] (C) a photopolymerization initiator, and
[0017] (D) a high molecular binder.
[0018] In the present invention, an ethylenic unsaturated compound
as the component (A) constituting a preferable photopolymerizable
composition is addition-polymerized by the action of a
photopolymerization initiation system containing a
photopolymerization initiator as the following described component
(C) when the photopolymerizable composition is subjected to
irradiation with an active light ray, and the ethylenic unsaturated
compound is a compound having at least one radical-polymerizable
ethylenic unsaturated bond in a molecule, which may be crosslinked
and cured as the case requires.
[0019] The ethylenic unsaturated compound may be a compound having
one ethylenic unsaturated bond in a molecule such as unsaturated
carboxylic acids including (meth)acrylic acid (the term
"(meth)acryl" means "acryl or methacryl", hereinafter the same),
crotonic acid, isocrotonic acid, maleic acid, itaconic acid,
citraconic acid or the like, and their alkyl esters, and
(meth)acrylonitrile, (meth)acrylamide, styrene, and the like. When
considering polymerizability and crosslinkability, and in
connection therewith, considering to enlarge a difference in
solubility in a developer between an exposed part and an unexposed
part, it is preferable to use a compound having at least two
ethylenic unsaturated bonds in a molecule, and it is particularly
preferable to use an acrylate compound, the unsaturated bond of
which is derived from a (meth)acryloyloxy group.
[0020] Typical examples of the compound having at least two
ethylenic unsaturated bonds in a molecule include esters of an
unsaturated carboxylic acid and a polyhydroxy compound,
urethane(meth)acrylates of a hydroxy(meth)acrylate compound and a
polyisocyanate compound, epoxy(meth)acrylates of a (meth)acrylic
acid or a hydroxy(meth)acrylate compound and a polyepoxy compound,
(meth)acryloyloxy group-containing phosphates, and the like.
[0021] Examples of the esters include reaction products of the
above-mentioned unsaturated carboxylic acids with aliphatic
polyhydroxy compounds such as ethylene glycol, diethylene glycol,
triethylene glycol, tetraethylene glycol, propylene glycol,
tripropylene glycol, trimethylene glycol, tetramethylene glycol,
neopentyl glycol, hexamethylene glycol, nonamethylene glycol,
trimethylolethane, tetramethylolethane, trimethylolpropane,
glycerol, pentaerythritol, dipentaerythritol, sorbitol, and their
ethylene oxide adducts, propylene oxide adducts, diethanolamine,
triethanolamine or the like, and their particular examples include
ethylene glycol di(meth)acrylate, diethylene glycol
di(meth)acrylate, triethylene glycol di(meth)acrylate,
tetraethylene glycol di(meth)acrylate, propylene glycol
di(meth)acrylate, tripropylene glycol di(meth)acrylate,
tetramethylene glycol di(meth)acrylate, neopentyl glycol
di(meth)acrylate, hexamethylene glycol di(meth)acrylate,
nonamethylene glycol di(meth)acrylate, trimethylolethane
tri(meth)acrylate, tetramethylolethane tri(meth)acrylate,
trimethylolpropane di(meth)acrylate, trimethylolpropane
tri(meth)acrylate, trimethylolpropane ethylene oxide adduct
tri(meth)acrylate, glycerol di(meth)acrylate, glycerol
tri(meth)acrylate, glycerol propylene oxide adduct
tri(meth)acrylate, pentaerythritol di(meth)acrylate,
pentaerythritol tri(meth)acrylate, pentaerythritol
tetra(meth)acrylate, dipentaerythritol di(meth)acrylate,
dipentaerythritol tri(meth)acrylate, dipentaerythritol
tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate,
dipentaerythritol hexa(meth)acrylate, sorbitol tri(meth)acrylate,
sorbitol tetra(meth)acrylate, sorbitol penta(meth)acrylate,
sorbitol hexa(meth)acrylate or the like, and their corresponding
crotonate, isocrotonate, maleate, itaconate, citraconate, and the
like.
[0022] Further examples of the esters include reaction products of
the above-mentioned unsaturated carboxylic acids with aromatic
polyhydroxy compounds such as hydroquinone, resorcin, pyrogallol,
bisphenol F, bisphenol A or the like, particular example of which
include hydroquinone di(meth)acrylate, resorcin di(meth)acrylate,
pyrogallol tri(meth)acrylate or the like, reaction products of the
above-mentioned unsaturated carboxylic acids with heterocyclic
polyhydroxy compounds such as tris(2-hydroxyethyl)isocyanurate or
the like, particular examples of which include
tris(2-hydroxyethyl)isocyanurate di(meth)acrylate or
tri(meth)acrylate, reaction products of unsaturated carboxylic
acids with polyhydric carboxylic acids and polyhydroxy compounds,
particular examples of which include a condensate of (meth)acrylic
acid and phthalic acid, a condensate of (meth)acrylic acid, maleic
acid and diethylene glycol, a condensate of (meth)acrylic acid,
terephthalic acid and pentaerythritol, a condensate of
(meth)acrylic acid, adipic acid, butanediol and glycerin, and the
like.
[0023] Also, examples of the urethane (meth)acrylates include
reaction products of hydroxy(meth)acrylate compounds such as
hydroxymethyl(meth)acrylate, hydroxyethyl(meth)acrylate, glycerol
di(meth)acrylate, pentaerythritol tri(meth)acrylate,
tetramethylolethane tri(meth)acrylate, or the like, with
polyisocyanate compounds such as aliphatic polyisocyanates
including hexamethylene diisocyanate, 2,4,4-trimethylhexamethylene
diisocyanate, lysine methyl ester diisocyanate, lysine methyl ester
triisocyanate, dimer acid diisocyanate, 1,6,11-undecatriisocyanate,
1,3,6-hexamethylene triisocyanate, 1,8-diisocyanate-4-isocyanate
methyloctane or the like, cycloaliphatic polyisocyanates including
cyclohexane diisocyanate, dimethylcyclohexane diisocyanate,
4,4'-methylenebis(cyclohexyl isocyanate), isophorone diisocyanate,
bicycloheptane triisocyanate or the like, aromatic polyisocyanates
including p-phenylene diisocyanate, 2,4-tolylene diisocyanate,
2,6-tolylene diisocyanate, xylylene diisocyanate,
tetramethylxylylene diisocyanate, 4,4'-diphenylmethane
diisocyanate, tolidine diisocyanate, 1,5-naphthalene diisocyanate,
tris(isocyanatephenylmethane), tris(isocyanatephenyl)thiophosphate
or the like, or heterocyclic polyisocyanates including isocyanurate
or the like.
[0024] Also, examples of the epoxy(meth)acrylates include reaction
products of (meth)acrylic acid or the above-mentioned
hydroxy(meth)acrylate compounds with polyepoxy compounds such as
aliphatic polyepoxy compounds including (poly)ethylene glycol
polyglycidyl ether, (poly)propylene glycol polyglycidyl ether,
(poly)tetramethylene glycol polyglycidyl ether,
(poly)pentamethylene glycol polyglycidyl ether, (poly)neopentyl
glycol polyglycidyl ether, (poly)hexamethylene glycol polyglycidyl
ether, (poly)trimethylolpropane polyglycidyl ether, (poly)glycerol
polyglycidyl ether, (poly)sorbitol polyglycidyl ether or the like,
aromatic polyepoxy compounds including a phenol novolac polyepoxy
compound, a bromated phenol novolac polyepoxy compound, a (o-, m-,
p-)cresol novolac polyepoxy compound, a bisphenol A polyepoxy
compound, a bisphenol F polyepoxy compound or the like, or
heterocyclic polyepoxy compounds including sorbitan polyglycidyl
ether, triglycidyl isocyanurate, triglycidyl
tris(2-hydroxyethyl)isocyanurate or the like.
[0025] Also, examples of the (meth)acryloyloxy group-containing
phosphates including preferably compounds represented by the
following formulae (Ia) or (Ib). 1
[0026] (In the formulae (Ia) and (Ib), R.sup.21 is a hydrogen atom
or a methyl group, n is an integer of from 1 to 25, and m is 1, 2
or 3.)
[0027] In the above formulae, n is preferably from 1 to 10,
particularly from 1 to 4, and examples of their compounds include
(meth)acryloyloxyethyl phosphate,
bis[(meth)acryloyloxyethyl]phosphate, (meth)acryloyloxyethylene
glycol phosphate, or the like, and they may be used respectively
alone or in a mixture.
[0028] Also, in addition to the above compounds, examples of other
ethylenic unsaturated compounds include (meth)acrylamides such as
ethylenebis(meth)acrylamide or the like, allyl esters such as
diallyl phthalate or the like, and vinyl group-containing compounds
such as divinyl phthalate or the like. These ethylenic unsaturated
compounds may be used respectively alone or in a mixture of two or
more.
[0029] In the present invention, in view of exposure sensitivity,
printing resistance and developing properties, it is preferable to
use the above-mentioned (meth)acryloyloxy group-containing
phosphates as an ethylenic unsaturated compound of the component
(A), and the content of the phosphates in the total ethylenic
unsaturated compounds of the component (A) is preferably from 1 to
60 wt %, more preferably from 5 to 50 wt %.
[0030] Also, a sensitizing dye of the component (B) constituting a
preferable photopolymerizable composition in the present invention
can efficiently absorb a light in the infrared zone, particularly
in a wavelength range of from 650 to 1,300 nm, transferring its
photo-excitation energy to a photopolymerization initiator of the
component (C), decomposing the photopolymerization initiator, and
promoting a sensitizing function of generating an active radical
inducing polymerization of an ethylenic unsaturated compound of the
component (A).
[0031] In the present invention, the sensitizing dye has a
structure having a hetero atom such as a nitrogen atom, an oxygen
atom or a sulfur atom bonded with a polymethine (--CH.dbd.).sub.n
chain, and is a typically widely defined cyanine type dye having a
basic structure wherein the hetero atoms form heterocyclic rings
which are bonded by way of a polymethine chain. Examples of the
sensitizing dye include quinoline type (so-called cyanine type),
indole type (so-called indocyanine type), benzothiazole type
(so-called thiocyanine type), pyririum type, thiopyririum type,
squaririum type, croconium type or azulenium type dyes, and
so-called polymethine type dyes having a basic structure having
non-cyclic hetero atoms bonded by way of a polymethine chain. Among
them, cyanine type dyes such as quinoline type, indole type,
benzothiazole type, pyririum type or thiopyririum type dyes, and
polymethine type dyes are preferable.
[0032] In the present invention, among the above-mentioned cyanine
type dyes, dyes expressed by the following formula (IIa), (IIb) or
(IIc) are particularly preferable as a quinoline type dye. 2
[0033] (In the above formulae (IIa), (IIb) and (IIc), R.sup.1 and
R.sup.2 are respectively independently an alkyl group which may
have a substituent, an alkenyl group which may have a substituent,
an alkynyl group which may have a substituent or a phenyl group
which may have a substituent, L.sup.1 is a tri-, penta-, hepta-,
nona- or undeca-methine group which may have a substituent, and two
substituents on the penta-, hepta-, nona- or undeca-methine group
may be connected to each other to form a C.sub.5-7 cycloalkene
ring, and a condensed benzene ring may have a substituent, and in
such a case, adjacent two substituents may be connected to each
other to form a condensed benzene ring. X.sub.a.sup.- is a counter
anion.)
[0034] With respect to R.sup.1 and R.sup.2 in the formulae (IIa),
(IIb) and (IIc), a carbon number of an alkyl group is generally
from 1 to 15, preferably from 1 to 10, and a carbon number of an
alkenyl group or an alkynyl group is generally from 2 to 15,
preferably from 2 to 10, and examples of substituents of these
groups and a phenyl group include a C.sub.1-15, preferably
C.sub.1-10 alkoxy group, a phenoxy group, a hydroxy group or a
phenyl group, and examples of substituents of L.sup.1 and a
condensed benzene ring include an alkyl group having the same
carbon number as mentioned above, and the like.
[0035] Also, preferable examples of indole type and benzothiazole
type dyes include dyes expressed by the following formula (III).
3
[0036] (In the above formula (III), Y.sup.1 and Y.sup.2 are
respectively independently a dialkylmethylene group or a sulfur
atom; R.sup.3 and R.sup.4 are respectively independently an alkyl
group which may have a substituent, an alkenyl group which may have
a substituent, an alkynyl group which may have a substituent or a
phenyl group which may have a substituent; L.sup.2 is a tri-,
penta-, hepta-, nona- or undeca-methine group, and two substituents
on the penta-, hepta-, nona- or undeca-methine group may be
connected to each other to form a C.sub.5-7 cycloalkene ring; and a
condensed benzene ring may have a substituent, and in such a case,
adjacent two substituents may be connected to each other to form a
condensed benzene ring. X.sub.a.sup.- is a counter anion.)
[0037] With respect to R.sup.3 and R.sup.4 in the formula (III), a
carbon number of an alkyl group is generally from 1 to 15,
preferably from 1 to 10, and a carbon number of an alkenyl group or
an alkynyl group is generally from 2 to 15, preferably from 2 to
10, and examples of substituents of these groups and a phenyl group
include a C.sub.1-15, preferably C.sub.1-10 alkoxy group, a phenoxy
group, a hydroxy group or a phenyl group, and examples of
substituents of L.sup.2 and a condensed benzene ring include an
alkyl group having the same carbon number as mentioned above, and
the like.
[0038] Also, preferable examples of pyririum type and thiopyririum
type dyes include dyes expressed by the following formula (IVa),
(IVb) or (IVc). 4
[0039] (In the above formulae (IVa), (IVb) and (IVc), Z.sup.1 and
Z.sup.2 are respectively independently an oxygen atom or a sulfur
atom; R.sup.5, R.sup.6, R.sup.7 and R.sup.8 are respectively
independently a hydrogen atom or an alkyl group, or R.sup.5 and
R.sup.7, and R.sup.6 and R.sup.8 respectively may be connected to
each other to form a C.sub.5 or C.sub.6 cycloalkene ring; L.sup.3
is a mono-, tri-, penta-, or hepta-methine group which may have a
substituent, and two substituents on the tri-, penta- or
hepta-methine group may be connected to each other to form a
C.sub.5-7 cycloalkene ring; and a pyririum ring and a thiopyririum
ring may have a substituent, and in such a case, adjacent two
substituents may be connected to each other to form a condensed
benzene ring. X.sub.a.sup.- is a counter anion.) In the above
formulae (IVa), (IVb) and (IVc), an alkyl group of R.sup.5,
R.sup.6, R.sup.7 and R.sup.8 has usually a carbon number of from 1
to 15, preferably from 1 to 10; examples of a substituent of
L.sup.3 include an alkyl group having the same carbon number as
above, and the like; and examples of substituents of a pyririum
ring and a thio pyririum ring include an aryl group such as a
phenyl group or the like.
[0040] Also, preferable examples of a polymethine type dye include
dyes expressed by the following formula (V). 5
[0041] (In the above formula (V), R.sup.9, R.sup.10, R.sup.11 and
R.sup.12 are respectively independently an alkyl group, and
R.sup.13 and R.sup.14 are respectively independently an aryl group
which may have a substituent, a furyl group or a thienyl group;
L.sup.4 is a mono-, tri-, penta- or hepta-methine group which may
have a substituent, and two substituents on the tri-, penta- or
hepta-methine group may be connected to each other to form a
C.sub.5-7 cycloalkene ring; and a quinone ring and a benzene ring
may have a substituent. X.sub.a.sup.- is a counter anion.)
[0042] In the above formula (V), an alkyl group of R.sup.9,
R.sup.10, R.sup.11 and R.sup.12 has usually a carbon number of from
1 to 15, preferably from 1 to 10; an aryl group of R.sup.13 and
R.sup.14 has usually a carbon number of from 6 to 20, preferably
from 6 to 15, and preferable examples of R.sup.13 and R.sup.14
include a phenyl group, a 1-naphtyl group, a 2-naphtyl group, a
2-furyl group, a 3-furyl group, a 2-thienyl group and a 3-thienyl
group, and examples of their substituents include an alkyl group
having the same carbon number as above, an alkoxy group having the
same carbon number as above, a dialkylamino group, a hydroxy group
or a halogen atom; and examples of substituents of L.sup.4, a
quinone ring and a benzene ring include an alkyl group having the
same carbon number as above, and the like.
[0043] Also, examples of a counter anion X.sub.a.sup.- in the above
formulae (IIa to IIc), (III), (IVa to IVc) and (V), include
inorganic acid anions such as Cl.sup.-, Br.sup.-, I.sup.-,
ClO.sub.4.sup.-, PF.sub.6.sup.-, SbF.sub.6.sup.-, AsF.sub.6.sup.-,
and inorganic boric acids such as BF.sub.4.sup.-, BCl.sub.4.sup.-
or the like, and organic acid anions such as benzene sulfonic acid,
toluene sulfonic acid, naphthalene sulfonic acid, acetic acid and
organic boric acids having an organic group such as methyl, ethyl,
propyl, butyl, phenyl, methoxyphenyl, naphthyl, fluorophenyl,
difluorophenyl, pentafluorophenyl, thienyl, pyrrolyl or the
like.
[0044] Also, in the above formulae (IIa to IIc), (III), (IVa to
IVc) and (V), a polymethine chain of L.sup.1, L.sup.2, L.sup.3 and
L.sup.4 may preferably have a barbituric acid anion group or a
thiobarbituric acid anion group expressed by the following formula
(VI), as a substituent to form an internal salt, or a polymethine
chain of L.sup.1, L.sup.2, L.sup.3 and L.sup.4 may preferably form
a squaric acid anion group or a thiosquaric acid anion group
expressed by the following formula (VII), or a croconic acid anion
group or a thiocroconic acid anion group expressed by the following
formula (VIII), to form an internal salt. (In this case, an
external anion is not necessary.) 6
[0045] (In the above formulae (VI), (VII) and (VIII), Z.sup.3,
Z.sup.4, Z.sup.5, Z.sup.6, Z.sup.7 and Z.sup.8, are respectively
independently an oxygen atom or a sulfur atom, and R.sup.15 and
R.sup.16 are respectively independently a hydrogen atom, an alkyl
group which may have a substituent, an alkenyl group which may have
a substituent, an alkoxy group which may have a substituent or a
phenyl group which may have a substituent.)
[0046] With regard to R.sup.15 and R.sup.16 of the above formula
(VI), an alkyl group or an alkoxy group has usually a carbon number
of from 1 to 15, preferably from 1 to 5, and an alkenyl group has
usually a carbon number of from 2 to 15, preferably from 2 to 5,
and among them, an alkyl group is preferable, particular examples
of which include a methyl group, an ethyl group, a propyl group or
a butyl group.
[0047] Also, with regard to the polymethine chain of L.sup.1,
L.sup.2, L.sup.3 and L.sup.4 in the formulae (IIa to IIc), (III),
(IVa to IVc) and (V), a hepta-methine chain is preferable to a
wavelength range of from 700 to 850 nm, and a nona-methine chain is
preferable to a wavelength range of from 850 to 950 nm, and an
undeca-methine chain is preferable to a wavelength range of from
950 to 1,300 nm.
[0048] Among quinoline type dyes expressed by the above formulae
(IIa to IIc), an indole type or benzothiazole type dye expressed by
the above formula (III), cyanine type dyes such as pyririum type or
thiopyririum type dye expressed by the above formulae (IVa to IVc),
and a polymethine type dye expressed by the above formula (V), an
indole type or benzothiazole type dye expressed by the above
formula (III) are particularly preferable in the present
invention.
[0049] Also, a photopolymerization initiator of the component (C)
constituting a preferable photopolymerizable composition in the
present invention is a radical-generating agent generating an
active radical in the presence of a sensitizing dye of the
component (B) when irradiated with light. Examples of the
photopolymerization initiator include halogenated hydrocarbon
derivatives, organic borates (as disclosed in JP-A-62-143044,
JP-A-62-150242, JP-A-9-188685, JP-A-9-188686, JP-A-9-188710, U.S.
Pat. No. 2,764,769, and "Rad Tech '98. Proceeding Apr. 19-22, 1998,
Chicago" by Kunz, Martin), titanocene compounds (as disclosed in
JP-A-59-152396 and JP-A-61-151197), hexaarylbiimidazol compounds
(as disclosed in JP-B-6-29285), and diaryl iodonium salts, organic
peroxides, and the like. In the present invention, halogenated
hydrocarbon derivatives and organic borates are particularly
preferable.
[0050] Examples of the halogenated hydrocarbon derivatives include
preferably a s-triazine compound having at least one mono-, di-, or
trihalogen-substituted methyl group bonded to a s-triazine ring,
particular examples of which include
2,4,6-tris(monochloromethyl)-s-triaz- ine,
2,4,6-tris(dichloromethyl)-s-triazine,
2,4,6-tris(trichloromethyl)-s-- triazine,
2-methyl-4,6-bis(trichloromethyl)-s-triazine,
2-n-propyl-4,6-bis(trichloromethyl)-s-triazine,
2-(.alpha.,.alpha.,.beta.-
-trichloroethyl)-4,6-bis(trichloromethyl)-s-triazine,
2-phenyl-4,6-bis(trichloromethyl)-s-triazine,
2-(p-methoxyphenyl)-4,6-bis- (trichloromethyl)-s-triazine,
2-(3,4-epoxyphenyl)-4,6-bis(trichloromethyl)- -s-triazine,
2-(p-chlorophenyl)-4,6-bis(trichloromethyl)-s-triazine,
2-[1-(p-methoxyphenyl)-2,4-butadienyl]-4,6-bis(trichloromethyl)-s-triazin-
e, 2-styryl-4,6-bis(trichloromethyl)-s-triazine,
2-(p-methoxystyryl)-4,6-b- is(trichloromethyl)-s-triazine,
2-(p-i-propyloxystyryl)-4,6-bis(trichlorom- ethyl)-s-triazine,
2-(p-tolyl)-4,6-bis(trichloromethyl)-s-triazine,
2-(p-methoxynaphthyl)-4,6-bis(trichloromethyl)-s-triazine,
2-(p-ethoxynaphthyl)-4,6-bis(trichloromethyl)-s-triazine,
2-(p-ethoxycarbonylnaphthyl)-4,6-bis(trichloromethyl)-s-triazine,
2-phenylthio-4,6-bis(trichloromethyl)-s-triazine,
2-benzylthio-4,6-bis(tr- ichloromethyl)-s-triazine,
2,4,6-tris(dibromomethyl)-s-triazine,
2,4,6-tris(tribromomethyl)-s-triazine,
2-methyl-4,6-bis(tribromomethyl)-s- -triazine,
2-methoxy-4,6-bis(tribromomethyl)-s-triazine, and the like. Among
them, bis(trihalomethyl)-s-triazine compounds such as
2-methyl-4,6-bis(trichloromethyl)-s-triazine,
2-phenyl-4,6-bis(trichlorom- ethyl)-s-triazine,
2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine- ,
2-(3,4-epoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine,
2-[1-(p-methoxyphenyl)-2,4-butadienyl]-4,6-bis(trichloromethyl)-s-triazin-
e, 2-(p-methoxystyryl)-4,6-bis(trichloromethyl)-s-triazine,
2-(p-i-propyloxystyryl)-4,6-bis(trichloromethyl)-s-triazine or the
like are preferable since they provide a photopolymerizable
composition excellent in stability with time.
[0051] Also, examples of other halogenated hydrocarbon derivatives
are illustrated in JP-A-53-133428, JP-A-62-58241, German Patent No.
3337024, and "Journal of Heterocyclic Chemistry" by M. P. Hutt, E.
F. Flslager, L. M. Werbel, Vol. 7, No. 3 (1970).
[0052] Also, preferable examples of the organic borates include a
compound expressed by the following formula (IX). 7
[0053] (In the above formula (IX), R.sup.17, R.sup.18, R.sup.19 and
R.sup.20 are respectively independently an alkyl group which may
have a substituent, an alkenyl group which may have a substituent,
an alkynyl group which may have a substituent, an aryl group which
may have a substituent or a heterocyclic group, and they may be
connected to each other to form a cyclic structure, and at least
one of them is an alkyl group which may have a substituent.
X.sub.b.sup.+ is a counter cation.)
[0054] With respect to R.sup.17, R.sup.18, R.sup.19 and R.sup.20 in
the above formula (IX), an alkyl group has usually a carbon number
of from 1 to 15, preferably from 1 to 5, and an alkenyl group or an
alkynyl group has usually a carbon number of from 2 to 15,
preferably from 2 to 5, and an aryl group has usually a carbon
number of from 6 to 20, preferably from 6 to 15, and a heterocyclic
group has usually a carbon number of from 4 to 20, preferably from
4 to 15, and examples of a substituent for these groups include a
halogen atom, an alkyl group, an alkoxy group, a trifluoromethyl
group, a trimethyl silyl group and the like.
[0055] Examples of an organic boron anion of an organic borate
expressed by the formula (IX) include n-butyl-methyl-diphenyl boron
anion, n-butyl-triphenyl boron anion,
n-butyl-tris(2,4,6-trimethylphenyl)boron anion,
n-butyl-tris(p-methoxyphenyl)boron anion, n-butyl-tris(p-fluorophe-
nyl)boron anion, n-butyl-tris(m-fluorophenyl)boron anion,
n-butyl-tris(3-fluoro-4-methylphenyl)boron anion,
n-butyl-tris(2,6-difluo- rophenyl)boron anion,
n-butyl-tris(2,4,6-trifluorophenyl)boron anion,
n-butyl-tris(2,3,4,5,6-pentafluorophenyl)boron anion,
n-butyl-tris(p-chlorophenyl)boron anion,
n-butyl-tris(trifluoromethyl)bor- on anion,
n-butyl-tris(2,6-difluoro-3-pyrrolylphenyl)-boron anion, and the
like.
[0056] Also, examples of a counter cation X.sub.b.sup.+ include an
onium compound such as iodonium cation, sulfonium cation,
phosphonium cation, ammonium cation or alkali metal cation, and
pyrririum cation, thiopyrririum cation, indolium cation, and the
like, and an organic ammonium cation such as tetraalkyl ammonium is
particularly preferable.
[0057] Also, in the present invention, as a method for making a
sensitizing dye of the above component (B) and an organic borate
photopolymerization initiator of the above component (C) present in
the photopolymerizable composition, there are an ordinary method
for blending a salt of a dye cation of the above sensitizing dye
and an optionally selected counter anion with a salt of an organic
boron anion of the above organic borate and an optionally selected
counter cation, and a method for blending a salt formed from a dye
cation of the above sensitizing dye and an organic boron anion of
the above organic borate, and the latter method is preferable.
[0058] Also, a high molecular binder of the component (D)
constituting a preferable photopolymerizable composition of the
present invention, has a function as a binder for an ethylenic
unsaturated compound of the component (A), a sensitizing dye of the
component (B) and a photopolymerization initiator of the component
(C), and examples of the high molecular binder include a homo- or
co-polymer of (meth)acrylic acid, (meth)acrylic acid ester,
(meth)acrylonitrile, (meth)acrylamide, maleic acid, styrene, vinyl
acetate, vinylidene chloride, maleimide or the like, and polyamide,
polyester, polyether, polyurethane, polyvinyl butyral, polyvinyl
pyrrolidone, polyethylene oxide, acetyl cellulose, and the like.
Among them, a carboxyl group-containing polymer is preferable in
view of alkali-developing properties, and concrete examples include
a copolymer containing (meth)acrylic acid and (meth)acrylic acid
alkyl (C.sub.1-10) ester, or further styrene, as copolymerizing
components, and preferably this carboxyl group-containing polymer
has an acid value of from 10 to 250 and a weight average molecular
weight of from 0.5 to 1,000,000.
[0059] Further, a preferable high molecular binder has an ethylenic
unsaturated bond in a side chain, and the ethylenic unsaturated
bond is preferably expressed by the following formula (Xa), (Xb) or
(Xc). 8
[0060] (In the above formulae (Xa), (Xb) and (Xc), R.sup.22 is a
hydrogen atom or a methyl group, R.sup.23, R.sup.24, R.sup.25,
R.sup.26 and R.sup.27 are respectively independently a hydrogen
atom, a halogen atom, an amino group, a dialkylamino group, a
carboxyl group, an alkoxycarbonyl group, a sulfo group, a nitro
group, a cyano group, an alkyl group which may have a substituent,
an alkoxy group which may have a substituent, an alkylamino group
which may have a substituent, an alkylsulfonyl group which may have
a substituent, an aryl group which may have a substituent, an
aryloxy group which may have a substituent, an arylamino group
which may have a substituent, or an arylsulfonyl group which may
have a substituent, and Z.sup.9 is an oxygen atom, a sulfur atom,
an imino group or an alkylimino group.
[0061] Examples of substituents for an alkyl group, an alkoxy
group, an alkylamino group, an alkylsulfonyl group, an aryl group,
an aryloxy group, an arylamino group and an arylsulfonyl group in
R.sup.23 to R.sup.27 include an alkyl group, an alkoxy group, an
alkylthio group, an amino group, a dialkylamino group, a nitro
group, a cyano group, a phenyl group, a halogen atom, and the
like.
[0062] A high molecular binder having an ethylenic unsaturated bond
in a side chain expressed by the above formula (Xa) is obtained by
reacting a carboxyl group-containing polymer with an aliphatic
epoxy group-containing unsaturated compound such as allylglycidyl
ether, glycidyl (meth)acrylate, .alpha.-ethylglycidyl (meth)
acrylate, glycidyl crotonate, glycidyl isocrotonate,
crotonylglycidyl ether, itaconic acid monoalkyl monoglycidyl ester,
fumaric acid monoalkyl monoglycidyl ester, maleic acid monoalkyl
monoglycidyl ester or the like, or a cycloaliphatic epoxy
group-containing unsaturated compound such as
3,4-epoxycyclohexylmethyl(meth)acrylate, at a temperature of about
80 to 120.degree. C. for about 1 to 50 hours, so as to react from 5
to 90 mol %, preferably from 30 to 70 mol %, of the carboxyl group
of the carboxyl group-containing polymer.
[0063] Also, a high molecular binder having an ethylenic
unsaturated bond in a side chain expressed by the above formula
(Xb) is obtained by copolymerizing a compound having at least two
kinds of unsaturated groups such as allyl(meth)acrylate,
3-allyloxy-2-hydroxypropyl(meth)acrylate, cinnamyl(meth)acrylate,
crotonyl(meth)acrylate, methallyl(meth)acrylate,
N,N-diallyl(meth)acrylamide or the like, with an unsaturated
carboxylic acid such as (meth)acrylic acid or an unsaturated
carboxylic acid ester, so as to include the former unsaturated
group-containing compound in an amount of from 10 to 90 mol %
preferably from 30 to 80 mol %, in the total copolymer.
[0064] Also, a high molecular binder having an ethylenic
unsaturated bond in a side chain expressed by the above formula
(Xc) is obtained by copolymerizing a compound having at least two
kinds of unsaturated groups such as vinyl(meth)acrylate,
1-chlorovinyl(meth)acrylate, 2-phenylvinyl(meth)acrylate,
1-propenyl(meth)acrylate, vinyl crotonate, vinyl(meth)acrylamide or
the like with an unsaturated carboxylic acid such as (meth)acrylic
acid or an unsaturated carboxylic acid ester, so as to include the
former unsaturated group-containing compound in an amount of from
10 to 90 mol %, preferably from 30 to 80 mol %, in the total
copolymer.
[0065] With regard to respective contents of the ethylenic
unsaturated compound of the component (A), the sensitizing dye of
the component (B), the photopolymerization initiator of the
component (C) and the high molecular binder of the component (D) in
a preferable photopolymerizable composition of the present
invention, the preferable photopolymerizable composition contains
the sensitizing dye of the component (B) in an amount of preferably
from 0.01 to 20 parts by weight, more preferably from 0.05 to 10
parts by weight, the photopolymerization initiator of the component
(C) in an amount of preferably from 0.1 to 80 parts by weight, more
preferably from 0.5 to 60 parts by weight, and the high molecular
binder of the component (D) in an amount of preferably from 10 to
400 parts by weight, more preferably from 20 to 200 parts by
weight, to 100 parts by weight of the ethylenic unsaturated
compound of the component (A).
[0066] Further, the photopolymerizable composition of the present
invention may contain various additives such as a heat
polymerization-preventing agent such as hydroquinone,
t-methoxyphenol, 2,6-di-t-butyl-p-cresol or the like in an amount
of at most 2 parts by weight to 100 parts by weight of the
ethylenic unsaturated compound of the component (A), a coloring
agent such as an organic or inorganic dye or pigment in an amount
of at most 20 parts by weight to 100 parts by weight of the
ethylenic unsaturated compound of the component (A), a plasticizer
such as dioctyl phthalate, didodecyl phthalate, tricresyl phosphate
or the like in an amount of at most 40 parts by weight to 100 parts
by weight of the ethylenic unsaturated compound of the component
(A), a sensitivity-improving agent such as tertiary amine or thiol,
a coating property-improving agent such as a surfactant including a
fluorine type surfactant, or a development-accelerator, in an
amount of at most 10 parts by weight to 100 parts by weight of the
ethylenic unsaturated compound of the component (A), or a dye
precursor in an amount of 30 parts by weight to 100 parts by weight
of the ethylenic unsaturated compound of the component (A).
[0067] A photosensitive lithographic printing plate used in an
image-forming process of the present invention is produced by
preparing a coating solution of the above-mentioned
photopolymerizable composition by appropriately dissolving or
dispersing the above-mentioned respective components in an
appropriate solvent, coating the coating solution on the surface of
a support, heating and drying to form a photosensitive layer
comprising the above photopolymerizable composition on the surface
of the support.
[0068] Examples of the support for the photosensitive lithographic
printing plate of the present invention include well known supports
used in a photosensitive lithographic printing plate, such as a
metal plate, a synthetic resin film or the like, but a preferable
example is an aluminum plate or an aluminum alloy plate of an
aluminum alloy with silicon, copper, manganese, magnesium,
chromium, zinc, lead, bismuth or nickel, and the plate preferable
has a thickness of usually from 0.05 to 1 mm. Also, the aluminum or
aluminum alloy plate is used usually after having the surface
subjected to a surface-roughening treatment and then anodizing
treatment.
[0069] Examples of the surface-roughening treatment (sandblasting
treatment) include mechanical treating methods such as a brush
polishing method, a ball polishing method, a blast polishing
method,, a hydro-honing polishing method, or a buff polishing
method, or an electrolytic etching method, chemical etching method
or other commonly used methods, but among them, a brush polishing
method, a ball polishing method, a hydro-honing polishing method,
electrolytic etching method, or a chemical etching method is
preferable, and particularly, it is preferable to employ an
electrolytic etching method carrying out electrolysis by
alternating current or direct current in a hydrochloric acid or
nitric acid electrolyte having an acid density of about 0.5 to 5 wt
% at an electric current density of about 20 to 200 A/dm.sup.2
under an electric voltage of about 10 to 40 V at a temperature of
about 20 to 50.degree. C. Also, after the surface-roughening
treatment, a desmut treatment with an acid or alkali aqueous
solution may be carried out, if necessary.
[0070] The anodizing treatment is usually conducted by carrying out
electrolysis using an aluminum plate as an anode and using sulfuric
acid alone or an aqueous solution containing mainly sulfuric acid
together with oxalic acid, phosphoric acid, chromic acid or malonic
acid at an acid concentration of from 5 to 50 wt %, preferably from
15 to 30 wt %, at an electric current density of from 1 to 60
A/dm.sup.2 under an electric voltage of from 1 to 150 V at a
temperature of from 5 to 50.degree. C., preferably from 15 to
35.degree. C., for about 5 to 60 seconds.
[0071] Also, if necessary, a treatment with an alkali silicate such
as sodium silicate or hot water, or a dipping treatment in an
aqueous solution of a water-soluble high molecular compound such as
a resin having a cationic quaternary ammonium base or polyvinyl
sulfonic acid, may be carried out.
[0072] A solvent used for a coating solution of the
photopolymerizable composition to be coated on the support surface
is not specially limited but should have a satisfactory solubility
to the components to be used and provide satisfactory coating
properties, examples of which include a cellosolve type solvent
such as methyl cellosolve, ethyl cellosolve, methyl cellosolve
acetate, ethyl cellosolve acetate or the like, a propylene glycol
type solvent such as propylene glycol monomethyl ether, propylene
glycol monoethyl ether, propylene glycol monobutyl ether, propylene
glycol monomethyl ether acetate, propylene glycol monoethyl ether
acetate, propylene glycol monobutyl ether acetate, dipropylene
glycol dimethyl ether or the like, an ester type solvent such as
butyl acetate, amyl acetate, ethyl butyrate, butyl butyrate,
diethyl oxalate, ethyl pyruvate, ethyl-2-hydroxybutyrate,
ethylacetoacetate, methyl lactate, ethyl lactate, methyl
3-methoxypropyonate or the like, an alcohol type solvent such as
heptanol, hexanol, diacetone alcohol, furfuryl alcohol or the like,
a ketone type solvent such as cyclohexanone, methyl amyl ketone or
the like, a high polar solvent such as dimethylformamide,
dimethylacetoamide, N-methylpyrrolidone or the like, or their
mixture solvent, or further mixtures of aromatic hydrocarbons added
thereto. An amount of a solvent used is usually from 1 to 20 times
larger amount by weight to the total amount of a photopolymerizable
composition.
[0073] Examples of the coating method include conventionally well
known methods such as dip coating, spinner coating, spray coating,
roll coating, coating with a coating rod or the like. A coated
amount varies depending on its use but is such an amount as to
provide a dry film thickness in a range of preferably from 0.1 to
10 g/m.sup.2, more preferably from 0.5 to 5 g/m.sup.2.
[0074] The photosensitive lithographic printing plate of the
present invention preferably has an oxygen-shielding layer for
preventing a polymerization-inhibiting function by oxygen to the
photopolymerizable composition formed on the photosensitive layer
of the photopolymerizable composition formed on the support surface
as described above. However, an oxygen-shielding layer is not an
essential element but an optional element in the present
invention.
[0075] The component for constituting the oxygen-shielding layer is
a polymer soluble in water or a mixture solvent of water with a
water-miscible organic solvent such as an alcohol including
methanol, ethanol, propanol, isononyl alcohol or the like or
tetrahydrofuran or the like, and examples of the polymer include
polyvinyl alcohol and its partially acetal-formed product, its
cation-modified product with a quaternary ammonium salt or the
like, a derivative of an anion-modified product with sodium
sulfonate or the like, polyvinyl pyrrolidone, polyethylene oxide,
methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose,
hydroxypropyl cellulose, gelatin, gum arabic,
methylvinylether-maleic anhydride copolymer, polyacrylic acid
ester-partially saponified product, and other copolymers of
copolymerizable components such as a hydroxyl group-containing
compound including hydroxyethyl(meth)acrylamide or the like, a
carboxyl group-containing compound including an unsaturated
carboxylic acid and its derivative including itaconic acid,
(meth)acrylic acid, vinyl pyrrolidone or the like.
[0076] Among them, a polyvinyl alcohol and its derivatives are
preferable in view of oxygen-shielding properties, and a product
having a saponification value of from 70 to 99 mol %, preferably
from 85 to 95 mol %, and a weight average molecular weight of from
2.0 to 500,000, preferably from 0.4 to 100,000, is preferable.
[0077] Further, in view of adhesion properties to a photosensitive
layer, it is preferable to contain a vinyl pyrrolidone type polymer
such as polyvinyl pyrrolidone, vinyl pyrrolidone-vinyl acetate
copolymer or the like, an acrylic polymer emulsion, a diisocyanate
compound, p-toluene sulfonic acid, hydroxy acetic acid or the like,
in an amount of from 0.1 to 60 parts by weight, preferably from 1
to 50 parts by weight, to 100 parts by weight of the polyvinyl
alcohol and its derivatives.
[0078] Still further, in view of preservation properties, it is
preferable to contain an organic acid such as succinic acid, an
organic acid salt such as ethylene diaminetetraacetic acid or the
like, and also a nonionic surfactant such as polyoxyethylene alkyl
phenyl ether or the like, an anionic surfactant such as sodium
dodecylbenzenesulfonate or the like, a cationic surfactant such as
alkyltrimethyl ammonium chloride, or the like, a defoaming agent, a
dye, a plasticizer, a pH regulator or the like, in an amount of at
most 10 parts by weight to 100 parts by weight of the polyvinyl
alcohol and its derivatives.
[0079] The oxygen-shielding layer is coated in the same manner as
in the coating method of the photosensitive layer by using water or
a solution of a mixture solvent of water with a water-miscible
organic solvent, and its coated amount is so as to provide a dry
film thickness in a range of preferably from 1 to 10 g/m.sup.2,
more preferably from 1.5 to 7 g/m.sup.2.
[0080] A method for forming an image in the present invention is
carried out by subjecting the photosensitive layer of the
photosensitive lithographic printing plate to scanning exposure
with a laser light having a wavelength range of from 650 to 1,300
nm, developing the image, and then subjecting the whole surface to
post-exposure.
[0081] A light source of the laser exposure is not specially
limited, examples of which include a semiconductor laser of 830 nm,
a YAG laser of 1,064 nm or the like.
[0082] Also, examples of a developer used in the development
include an alkali developer comprising an aqueous solution
containing from 0.1 to 10 wt % of an inorganic alkali salt such as
sodium silicate, potassium silicate, lithium silicate, ammonium
silicate, sodium metasilicate, potassium metasilicate, sodium
hydroxide, potassium hydroxide, lithium hydroxide, sodium
carbonate, sodium hydrogencarbonate, potassium carbonate, dibasic
sodium phosphate, tribasic sodium phosphate, dibasic ammonium
phosphate, tribasic ammonium phosphate, sodium borate, potassium
borate, ammonium borate or the like, or an organic amine compound
such as monomethylamine, dimethylamine, trimethylamine,
monoethylamine, diethylamine, triethylamine, monoisopropylamine,
diisopropylamine, monobutylamine, monoethanolamine, diethanolamine,
triethanolamine, monoisopropanolamine, diisopropanolamine or the
like.
[0083] Further, in order to improve an image quality or to reduce a
development time, the developer may further contain a nonionic
surfactant such as polyoxyethylene alkyl ethers, polyoxyethylene
alkylaryl ethers, polyoxyethylene alkyl esters, sorbitan alkyl
esters, monoglyceride alkyl esters or the like, an anionic
surfactant such as alkylbenzene sulfonates, alkylnaphthalene
sulfonates, alkyl sulfates, alkyl sulfonates, sulfosuccinic acid
ester salts or the like, an amphoteric surfactant such as
alkylbetaines, amino acids or the like, and a water-soluble organic
solvent such as isopropyl alcohol, benzyl alcohol, ethyl
cellosolve, butyl cellosolve, phenyl cellosolve, propylene glycol,
diacetone alcohol or the like. The developer preferably has a pH of
from 9 to 14.
[0084] The development is carried out by well known developing
methods including dipping development, spray development, brush
development, ultrasonic development or the like, usually at a
temperature of from 10 to 60.degree. C., preferably from 15 to
45.degree. C. for from 5 seconds to 10 minutes. At this time, the
oxygen-shielding layer may be previously removed by water or the
like, or mainly removed at the time of development.
[0085] After the developing treatment, it is essential for the
image-forming method of the present invention to carry out the
whole image exposure with an exposure energy of at most 70 times,
preferably at most 30 times, more preferably at most 25 times,
particularly preferably at most 20 times, most preferably at most
15 times larger than that of the scanning exposure with the laser
light. On the other hand, the lower limit of the whole image
exposure energy is at least 1 time, preferably at least 1.2 times,
more preferably at least 1.5 times, most preferably at least 2
times larger than that of the scanning exposure. If the whole image
exposure is not carried out, or if the whole image exposure is
carried out at an exposure energy of 70 times larger than that of
the scanning exposure with the laser light, an image strength
having a satisfactory printing resistance can not be obtained.
[0086] An exposure energy of the whole image exposure is not
specially limited, provided that the above relation between the
whole image exposure energy and the exposure energy of the scanning
exposure is satisfied, but in view of rationalization of the
image-forming step, it is preferable to carry out the whole image
exposure with an exposure energy in a range of from 10 mJ/cm.sup.2
to 10 J/cm.sup.2, preferably from 20 mJ/cm.sup.2 to 9 J/cm.sup.2,
more preferably from 50 mJ/cm.sup.2 to 8 J/cm.sup.2.
[0087] A light source of the whole image exposure is not specially
limited, examples of which include a carbon arc, a high pressure
mercury lamp, an ultra-high pressure mercury lamp, a low pressure
mercury lamp, a deep UV lamp, a xenon lamp, a metal halide lamp, a
fluorescent lamp, a tungsten lamp, a halogen lamp, an excimer laser
lamp or the like, and a light having a wavelength of from 200 to
1,100 nm is used. Among them, a mercury lamp and a metal halide
lamp are preferable, and a mercury lamp is particularly
preferable.
[0088] The whole image exposure process may be carried out either
by stopping an image or by continuously moving an image, and in
view of an image strength, it is preferable to provide a light
intensity in a range of from 10 mW/cm.sup.2 to 1 W/cm.sup.2,
preferably from 15 mW/cm.sup.2 to 700 mW/cm.sup.2, more preferably
from 25 mW/cm.sup.2 to 500 mW/cm.sup.2, on the image-forming
surface. In order to make a light intensity in the above-mentioned
range on the image-forming surface as mentioned above, it can be
made by an exposure method of raising an output (W) of a light
source by enhancing an output of a light source used or by
enhancing an output per unit length in case of using a rod-like
light source, or by an exposure method of making a light source
closer to the image-forming surface.
[0089] Also, at the time of the whole image exposure, it is
preferable to raise a temperature of the image-forming surface to a
temperature of from 20 to 300.degree. C., preferably from 23 to
250.degree. C., more preferably from 40 to 200.degree. C., by
heating with a radiation heat from a light source of the whole
image exposure or by heating with a hot plate, a drier, a ceramic
heater or the like. As a heating means, it is convenient and
preferable to employ a radiation heat from a light source. This
operation is preferable for further improving a printing
resistance.
[0090] Also, in the present invention, in order to carry out the
above-mentioned image-forming process, such an image-forming
apparatus continuously connecting the following steps as
illustrated in FIG. 1 can be used.
[0091] (1) a scanning exposure step of subjecting a photosensitive
layer comprising a photopolymerizable composition formed on a
support surface of a photosensitive lithographic printing plate to
scanning exposure with a laser light having a wavelength range of
from 650 to 1,300 nm,
[0092] (2) a developing step of developing an image of the
photosensitive lithographic printing plate after the scanning
exposure step, and
[0093] (3) a whole image exposure step of subjecting the
photosensitive lithographic printing plate after the developing
step to whole image exposure with an exposure energy of from 1 to
70 times larger than that of the scanning exposure with the laser
light used in the above step (1).
[0094] The image-forming apparatus of the present invention may
comprise connecting separate apparatuses of respective steps (1) to
(3) or may comprise connecting an apparatus of the step (3) with an
apparatus comprising conventionally known steps (1) and (2).
[0095] Preferable conditions of respective steps may be the
above-mentioned conditions in the image-forming process.
EXAMPLES
[0096] Hereinafter, the present invention is further illustrated
with reference to Examples, but should not be limited thereto.
Examples 1 to 2 and Comparative Examples 1 to 2
[0097] A photosensitive lithographic printing plate was produced by
preparing a coating solution obtained by dissolving the following
ethylenic unsaturated compound of component (A), sensitizing dye of
component (B), photopolymerization initiator of component (C), high
molecular binder of component (D) and other components in a mixture
solvent of propylene glycol monomethyl ether
acetate/methoxypropanol (weight ratio 1/9) so as to provide a
concentration of 8.5 wt %, coating the coating solution on the
following aluminum plate support surface by a bar coater so as to
provide a dry film thickness of 2 g/m.sup.2, drying to form a
photosensitive layer comprising the photopolymerizable composition,
and further coating a mixed aqueous solution of polyvinyl
alcohol/polyvinyl pyrrolidone (weight ratio 5/5) thereon by a bar
coater so as to provide a dry film thickness of 3 g/m.sup.2, and
drying to form an oxygen-shielding layer.
[0098] Support:
[0099] An aluminum plate support was obtained by degreasing an
aluminum plate (thickness 0.24 mm) with a 3 wt % sodium hydroxide
aqueous solution, electrolytically etching the degreased aluminum
plate in a nitric acid bath of 18 g/l at 25.degree. C., at an
electric current density of 90 A/dm.sup.2 for 11 seconds, further
subjecting the electrolytically etched aluminum plate to desmut
treatment in a 4.5 wt % sodium hydroxide aqueous solution at
30.degree. C. for 2 seconds, neutralizing the treated aluminum
plate with a 10 wt % nitric acid aqueous solution at 25.degree. C.
for 5 seconds, washing with water, subjecting the washed aluminum
plate to anodizing treatment in a 30 wt % sulfuric acid bath at
30.degree. C., at an electric current density of 10 A/dm.sup.2 for
16 seconds, washing with water, and drying.
[0100] (A) Ethylenic Unsaturated Compound:
[0101] The following compound (A-1): 22 parts by weight
[0102] The following compound (A-2): 22 parts by weight
[0103] The following compound (A-3): 11 parts by weight 9
[0104] (B) Sensitizing Dye:
[0105] The following compound (B-1): 1.2 parts by weight 10
[0106] (C) Photopolymerization Initiator:
[0107] 2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine: 5
parts by weight
[0108] (D) High Molecular Binder:
[0109] Reaction product (acid value 53, 50 mol % of carboxyl group
of methacrylic acid component reacted) obtained by reacting
3,4-epoxycyclohexylmethyl acrylate with methyl methacrylate (80 mol
%)/methacrylic acid (20 mol %) copolymer (weight average molecular
weight: 500,000): 45 parts by weight
[0110] Other Components:
[0111] Pigment (ethyl violet): 7.5 parts by weight
[0112] Surfactant ("Emulgen 104P", manufactured by Kao Corp.): 2
parts by weight
[0113] Surfactant ("S-381", manufactured by Asahi Glass Company,
Limited): 0.3 part by weight
[0114] Each of the photosensitive lithographic printing plates
obtained above was treated by subjecting to laser scanning exposure
with a 830 nm laser irradiating apparatus ("Trendsetter",
manufactured by Creo Company) under conditions as shown in the
following Table 1, removing an oxygen-shielding layer by washing
with water, and then developing by dipping the above treated
printing plate in a developer comprising an aqueous solution
containing 2 wt % of potassium silicate and 3.4 wt % of sodium
alkylnaphthalenesulfonate (concentration 35 wt %, "Pelex NBL",
manufactured by Kao Corp.) at 30.degree. C. for about 20 seconds,
and rubbing the printing plate with a sponge one time. The printing
plate thus developed was coated with a gum solution ("CTP Plus
Finisher", manufactured by Western.multidot.Lithotic Company) and
was dried.
[0115] The printing plate thus treated was subjected to whole image
exposure by using a high pressure mercury lamp exposure apparatus
equipped with a conveyor under such conditions as to provide an
exposure amount and a light intensity on the image-forming surface
shown in the following Table 1 by changing the position of a lamp
house with a cold mirror using a 125 W/cm high pressure mercury
lamp (manufactured by I Graphics Company) from 15 to 50 cm apart
from the printing plate surface and changing a conveyor speed. The
image-forming surface was heated by a radiation heat from the
mercury lamp to a temperature of from 40 to 70.degree. C. The
respective light exposure amounts and light intensities were
measured by "UVPZ-1", manufactured by I Graphics Company.
[0116] After the whole image exposure, a printing resistance of
each lithographic printing plate was evaluated by measuring a
remaining rate of 1% small dots of 175 lines at the time when
printing 80,000 sheets of papers, and the results are shown in the
following Table 1.
[0117] Evaluation symbol mark .largecircle.: small dots remained
without any defect.
[0118] Evaluation symbol mark .DELTA.: a part of small dots
disappeared but the majority remained.
[0119] Evaluation symbol mark .times.: substantially all of small
dots disappeared.
1 TABLE 1 Laser scanning exposure Whole image exposure Exposure
Exposure Light Wavelength amount (X) amount (Y) intensity Printing
(nm) (mJ/cm.sup.2) (mJ/cm.sup.2) Y/X (mW/cm.sup.2) resistance
Example 1 830 80 300 3.8 .ltoreq.110 .largecircle. Example 2 830 80
150 1.9 .ltoreq.110 .largecircle. Comparative 830 80 Without -- --
X Example 1 whole image exposure Comparative 830 80 8,000 100
.ltoreq.110 -- *1 Example 2 *1: A clear image could not be obtained
because of fusion of a gum solution.
Examples 3 to 4
[0120] Photosensitive printing plates were prepared and exposed to
light, and were subjected to a test for evaluating a printing
resistance, in the same manner as in Example 1, except that the
printing plates were subjected to whole image exposure by using a
low pressure mercury lamp exposure apparatus (Ster-L-Ray G48T6L
manufactured by Atlantic Ultraviolet Co., Ltd.) under such
conditions as to provide an exposure amount and a light intensity
on the image-forming surface shown in the following Table 2 by
changing a conveyor speed. The image-forming surface was heated by
a radiation heat from the mercury lamp to a temperature of
25.degree. C. The respective light exposure amounts and light
intensities were measured by "UVPZ-1", manufactured by I Graphics
Company.
[0121] The results are shown in the following Table 2.
2 TABLE 2 Laser scanning exposure Whole image exposure Exposure
Exposure Light Wavelength amount (X) amount (Y) intensity Printing
(nm) (mJ/cm.sup.2) (mJ/cm.sup.2) Y/X (mW/cm.sup.2) resistance
Example 3 830 80 300 3.8 20 .largecircle. Example 4 830 80 500 6.3
20 .largecircle.
[0122] According to the present invention, a sufficient image
strength having a satisfactory printing resistance can be provided
when an image is formed by subjecting a photopolymerizable
photosensitive lithographic printing plate to an infrared laser
light exposure, and an image-forming method excellent also in
reproducibility of an image can be provided.
[0123] The entire disclosure of Japanese Patent Application No.
2001-77682 filed on Mar. 19, 2001 including specification, claims,
drawings and summary are incorporated herein by reference in its
entirety.
* * * * *