U.S. patent application number 09/934838 was filed with the patent office on 2002-10-10 for positive photosensitive composition positive photosensitive lithographic printing plate and method for making positive photosensitive lithographic printing plate.
This patent application is currently assigned to Mitsubishi Chemical Corporation. Invention is credited to Murata, Akihisa, Nagasaka, Hideki.
Application Number | 20020146635 09/934838 |
Document ID | / |
Family ID | 27278408 |
Filed Date | 2002-10-10 |
United States Patent
Application |
20020146635 |
Kind Code |
A1 |
Nagasaka, Hideki ; et
al. |
October 10, 2002 |
Positive photosensitive composition positive photosensitive
lithographic printing plate and method for making positive
photosensitive lithographic printing plate
Abstract
A positive photosensitive composition showing a difference in
solubility in an alkali developer as between an exposed portion and
a non-exposed portion, which comprises, as components inducing the
difference in solubility, (a) a photo-thermal conversion material,
and (b) a high molecular compound, of which the solubility in an
alkali developer is changeable mainly by a change other than a
chemical change.
Inventors: |
Nagasaka, Hideki; (Yokohama,
JP) ; Murata, Akihisa; (Yokohama, JP) |
Correspondence
Address: |
OBLON SPIVAK MCCLELLAND MAIER & NEUSTADT PC
FOURTH FLOOR
1755 JEFFERSON DAVIS HIGHWAY
ARLINGTON
VA
22202
US
|
Assignee: |
Mitsubishi Chemical
Corporation
Chiyoda-ku
JP
|
Family ID: |
27278408 |
Appl. No.: |
09/934838 |
Filed: |
August 23, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09934838 |
Aug 23, 2001 |
|
|
|
08906258 |
Aug 5, 1997 |
|
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Current U.S.
Class: |
430/190 ;
430/165; 430/191; 430/192; 430/193; 430/302 |
Current CPC
Class: |
B41C 2210/24 20130101;
B41N 1/083 20130101; Y10S 430/127 20130101; Y10S 430/145 20130101;
B41M 5/465 20130101; B41C 2210/262 20130101; B41C 2210/02 20130101;
B41C 1/1008 20130101; B41C 2210/06 20130101; Y10S 430/106 20130101;
B41C 2210/22 20130101 |
Class at
Publication: |
430/190 ;
430/191; 430/192; 430/193; 430/165; 430/302 |
International
Class: |
G03F 007/023; G03F
007/30 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 6, 1996 |
JP |
8-207013 |
Nov 14, 1996 |
JP |
8-302722 |
Nov 22, 1997 |
JP |
9-009264 |
Claims
What is claimed is:
1. A positive photosensitive composition showing a difference in
solubility in an alkali developer as between an exposed portion and
a non-exposed portion, which comprises, as components inducing the
difference in solubility, (a) a photo-thermal conversion material,
and (b) a high molecular compound, of which the solubility in an
alkali developer is changeable mainly by a change other than a
chemical change.
2. The positive photosensitive composition according to claim 1,
wherein the photo-thermal conversion material (a) is a
light-absorbing dye having an absorption band covering a part or
whole of a wavelength region of from 650 to 1300 nm.
3. The positive photosensitive composition according to claim 1,
wherein the photo-thermal conversion material (a) is at least one
compound selected from a cyanine dye, a polymethine dye, a
squarilium dye, a croconium dye, a pyrylium dye and a thiopyrylium
dye.
4. The positive photosensitive composition according to claim 1,
wherein the high molecular compound (b) is a novolak resin and/or a
polyvinyl phenol resin.
5. The positive photosensitive composition according to claim 1,
wherein the high molecular compound (b) is a novolak resin.
6. The positive photosensitive composition according to claim 1,
which does not contain, in the positive photosensitive composition,
a compound susceptible to a photochemical sensitizing effect by the
photo-thermal conversion material.
7. The positive photosensitive composition according to claim 1,
which contains, as a further component of the positive
photosensitive composition, a solubility-suppressing agent (c)
capable of lowering the dissolution rate, in the alkali developer,
of a blend comprising an infrared absorbing dye of component (a)
and a high molecular compound of component (b).
8. The positive photosensitive composition according to claim 7,
wherein the solubility-suppressing agent (c) is a compound not
susceptible to a photochemical sensitizing effect by the
photo-thermal conversion material.
9. The positive photosensitive composition according to claim 7,
wherein the solubility-suppressing agent (c) is a compound capable
of lowering the dissolution rate, in the alkali developer, of the
blend comprising an infrared absorbing dye of component (a) and a
high molecular compound of component (b) to a level of at most
50%.
10. The positive photosensitive composition according to claim 7,
wherein the solubility-suppressing agent (c) is at least one member
selected from sulfonic acid esters, phosphoric acid esters,
aromatic carboxylic acid esters, carboxylic anhydrides, aromatic
ketones, aromatic aldehydes, aromatic amines and aromatic
ethers.
11. The positive photosensitive composition according to claim 7,
wherein the solubility-suppressing agent (c) is a compound having
substantially no photosensitivity to ultraviolet light.
12. The positive photosensitive composition according to claim 7,
wherein the solubility-suppressing agent (c) is an o-quinone
diazide compound.
13. The positive photosensitive composition according to claim 7,
wherein the solubility-suppressing agent (c) is an o-quinone
diazide compound of a novolak resin.
14. The positive photosensitive composition according to claim 1,
which contains substantially no photo-acid-generator, as a
component of the positive photosensitive composition.
15. A positive photosensitive composition comprising a
photo-thermal conversion material and an alkali-soluble resin and
having a characteristic represented by B<A where A is the
solubility, in an alkali developer, at an exposed portion of the
composition, and B is the alkali solubility after heating of the
exposed portion.
16. A positive photosensitive lithographic printing plate having a
positive photosensitive composition according to claim 1, formed on
a support.
17. The positive photosensitive lithographic printing plate having
a positive photosensitive composition according to claim 15, formed
on a support.
18. A method for making a positive photosensitive lithographic
printing plate, which comprises a step of scanning and exposing a
positive photosensitive lithographic printing plate according to
claim 16 by means of a light ray belonging to a wavelength region
of from 650 to 1300 nm and having a light intensity sufficient to
let the high molecular compound form an image.
19. A method for making a positive photosensitive lithographic
printing plate, which comprises a step of scanning and exposing a
positive photosensitive lithographic printing plate according to
claim 16 by means of a light ray belonging to a wavelength region
of from 650 to 1300 nm and having a light intensity of at least
2.times.10.sup.6 mJ/s.multidot.cm.sup.2.
20. The method for making a positive photosensitive lithographic
printing plate according to claim 18, wherein the light source for
the light ray is a semiconductor laser or a YAG laser.
21. A method for making a positive photosensitive lithographic
printing plate, which comprises a step of scanning and exposing a
positive photosensitive lithographic printing plate according to
claim 17 by means of a light ray belonging to a wavelength region
of from 650 to 1300 nm and having a light intensity sufficient to
let the high molecular compound form an image.
22. A method for making a positive photosensitive lithographic
printing plate, which comprises a step of scanning and exposing a
positive photosensitive lithographic printing plate according to
claim 17 by means of a light ray belonging to a wavelength region
of from 650 to 1300 nm and having a light intensity of at least
2.times.10.sup.6 mJ/s.multidot.cm.sup.2.
23. The method for making a positive photosensitive lithographic
printing plate according to claim 21, wherein the light source for
the light ray is a semiconductor laser or a YAG laser.
Description
[0001] The present invention relates to a novel positive
photosensitive composition sensitive to a light ray in a wavelength
region of from 650 to 1300 nm. More particularly, it relates to a
positive photosensitive composition suitable for direct plate
making by means of a semiconductor laser or a YAG laser, a positive
photosensitive lithographic printing plate employing the
composition and a method for making a positive photosensitive
lithographic printing plate.
[0002] Along with the progress in the image treating technology by
computers, an attention has been drawn to a photosensitive or heat
sensitive direct plate making system wherein a resist image is
formed directly from digital image information by a laser beam or a
thermal head without using a silver salt masking film. Especially,
it has been strongly desired to realize a high resolution laser
photosensitive direct plate making system employing a high power
semiconductor laser or YAG laser, from the viewpoint of downsizing,
the environmental light during the plate making operation and plate
making costs.
[0003] On the other hand, as image-forming methods wherein laser
photosensitivity or heat sensitivity is utilized, there have
heretofore been known a method of forming a color image by means of
a sublimable transfer dye and a method of preparing a lithographic
printing plate. Known as the latter is, for example, a method of
preparing a lithographic printing plate by means of the curing
reaction of a diazo compound (e.g. JP-A-52-151024, JP-B-2-51732,
JP-A-50-15603, JP-B-3-34051, JP-B-61-21831, JP-B-60-12939 and U.S.
Pat. No. 3,664,737), or a method of preparing a lithographic
printing plate by means of the decomposition reaction of
nitrocellulose (e.g. JP-A-50-102403 and JP-A-50-102401).
[0004] In recent years, a technique in which a chemical
amplification type photoresist is combined with a long wavelength
light ray absorbing dye, has been proposed. For example,
JP-A-6-43633 discloses a photosensitive material wherein a certain
specific squarilium dye is combined with a photo-acid-generator and
a binder.
[0005] Further, as a technique of this type, a technique for
preparing a lithographic printing plate by exposing a
photosensitive layer containing an infrared ray absorbing dye
latent Bronsted acid, a resol resin and a novolak resin, in an
image pattern by e.g. a semiconductor laser has been proposed
(JP-A-7-20629). Further, the same technique wherein a s-triazine
compound is used instead of the above latent Bronsted acid, has
also been proposed (JP-A-7-271029).
[0006] However, these conventional techniques were not necessarily
adequate in their performance from a practical viewpoint. As a more
serious problem, in the case of such a chemical amplification type
photosensitive plate, it was usually essential to have a heat
treatment step after exposure, and due to variation of heat
treatment conditions or the like, the stability in the quality of
the image thereby obtainable was not necessarily adequate, and a
technique containing no such a step has been desired. In the
above-mentioned JP-A-7-20629 and JP-A-7-271029, a method for
obtaining a positive image without requiring the above-mentioned
post heat treatment, is proposed, but no specific Examples are
given, and no specific method or no fact of obtaining such a
positive image is disclosed. Further, in such a technique, the
photosensitive material is sensitive also to ultraviolet light, and
it is necessary to carry out the operation under yellow light
containing no ultraviolet light, such being problematic from the
viewpoint of the operation efficiency.
[0007] Further, in U.S. Pat. No. 5,491,046, a plate-making method
particularly an exposure method, using such a composition is
disclosed, but no Example is given for a positive image.
[0008] Further, JP-A-60-175046 discloses a radiation sensitive
composition comprising an alkali-soluble phenol resin and a
radiation sensitive onium salt, which is photo-dissolvable. It is
disclosed that in the composition, photo-decomposable decomposition
of the onium salt induces the resin to regain the solubility, to
satisfy the basic requirement for a photo-dissolvable system, and
that the onium salt can be sensitized by an electromagnetic
spectrum of a wide range ranging from ultraviolet light to visible
light or even to infrared light.
[0009] Such an image is formed essentially by a difference in the
solubility in a developer as between an exposed portion and a
non-exposed portion. For such a difference to be caused, it is
common that one of the components in the composition undergoes a
chemical change, and to induce such a chemical change, an additive
such as a photo-acid-generator, a radical initiator, a crosslinking
agent or a sensitizer, is frequently required, whereby there has
been a problem that a system will be complicated.
[0010] The present invention has been made in view of the
above-described various problems.
[0011] Namely, it is an object of the present invention to provide
a positive photosensitive composition and a positive photosensitive
lithographic printing plate, which are simple in their
construction, which are suitable for direct recording by e.g. a
semiconductor laser or a YAG laser and which have high sensitivity
and excellent storage stability.
[0012] Another object of the present invention is to provide a
novel positive photosensitive material and a positive
photosensitive lithographic printing plate, which are highly
sensitive to an infrared ray and which require no post exposure
heat treatment.
[0013] A further object of the present invention is to provide a
photosensitive material and a positive photosensitive lithographic
printing plate, which do not require an operation under yellow
light and whereby the operation can be carried out under usual
white light containing ultraviolet light.
[0014] A still further object of the present invention is to
provide a positive photosensitive lithographic printing plate which
is excellent in a burning property as a lithographic printing
plate.
[0015] Still another object of the present invention is to provide
a plate-making method, whereby a positive photosensitive
lithographic printing plate can be exposed at high sensitivity.
[0016] Such objects of the present invention can be accomplished by
the following constructions of the present invention:
[0017] A positive photosensitive composition showing a difference
in solubility in an alkali developer as between an exposed portion
and a non-exposed portion, which comprises, as components inducing
the difference in solubility,
[0018] (a) a photo-thermal conversion material, and
[0019] (b) a high molecular compound, of which the solubility in an
alkali developer is changeable mainly by a change other than a
chemical change.
[0020] A positive photosensitive composition comprising a
photo-thermal conversion material and an alkali-soluble resin and
having a characteristic represented by B<A where A is the
solubility, in an alkali developer, at an exposed portion of the
composition, and B is the alkali solubility after heating of the
exposed portion.
[0021] A positive photosensitive lithographic printing plate having
such a positive photosensitive composition formed on a support.
[0022] A method for making a positive photosensitive lithographic
printing plate, which comprises a step of scanning and exposing
such a positive photosensitive lithographic printing plate by means
of a light ray belonging to a wavelength region of from 650 to 1100
nm and having a light intensity sufficient to let the high
molecular compound form an image.
[0023] Now, the present invention will be described in detail with
reference to the preferred embodiments.
[0024] Heretofore, as a positive photosensitive composition, a
system has been known which comprises an alkali-soluble resin and
an o-quinone diazide group-containing compound as a
photosensitivity-imparting component. It is believed that with this
system, upon irradiation of ultraviolet light which can be absorbed
by the o-quinone diazide group-containing compound, the diazo
moiety will decompose to finally form carboxylic acid, whereby the
alkali-solubility of the resin increases, so that only the exposed
portion will dissolve in an alkali developer to form an image.
Further, in the composition disclosed in the above-mentioned
JP-A-60-175046, the photo-decomposable decomposition of the onium
salt contributes to the solubility of the resin. Namely, in these
systems, a component in a photosensitive composition undergoes a
chemical change.
[0025] Surprisingly, the present invention provides a
photosensitive composition capable of forming a positive image with
a very simple system of a photo-thermal conversion material and an
alkali soluble resin where no chemical change is expected.
[0026] The reason as to why the photosensitive composition of the
present invention provides such an excellent effect is not clearly
understood. However, it is considered that the light energy
absorbed by the photo-thermal conversion material is converted to
heat, and the alkali-soluble resin at the portion subjected to the
heat undergoes a change other than a chemical change, such as a
change in conformation, whereby the alkali solubility at that
portion increases, so that an image can be formed by an alkali
developer.
[0027] Such an effect is attributable mainly to a change other than
a chemical change. This is assumed, for example, from a reversible
phenomenon such that when a photosensitive composition of the
present invention once irradiated, is heated around 50.degree. C.
for 24 hours, the alkali solubility of the exposed portion once
increased immediately after the exposure, often returns to a state
close to the state prior to the exposure. Thus, the present
invention provides a positive photosensitive composition comprising
a photo-thermal conversion material and an alkali-soluble resin,
which has a characteristic represented by B<A, where A is the
solubility, in the alkali developer, at an exposed portion of the
composition, and B is the alkali solubility after heating of the
exposed portion. Further, the relation between the glass transition
temperature (or the softening temperature) of the photosensitive
composition itself and the likelihood of the reversible phenomenon,
was examined, whereby it was found that the lower the temperature,
the more likely the phenomenon. This also supports the
above-described mechanism.
[0028] Accordingly, it should be understood that the essential
constituting components of the positive photosensitive composition
of the present invention are a photo-thermal conversion material of
component (a) and a high molecular compound of component (b) only,
and a material which increases the alkali solubility of an
alkali-soluble resin by an action of active radiation, such as the
above-mentioned o-quinone diazide group-containing compound, or a
material such as a combination of a compound (a
photo-acid-generator) which forms an acid by active radiation, with
a compound, of which the solubility in a developer increases by an
action of the acid, is not substantially required. Further, the
positive photosensitive composition of the present invention is
used exclusively for forming a positive image, and a material which
becomes insoluble in a developer by an action of active radiation,
such as a diazo resin, a crosslinking agent and a combination of an
ethylenic monomer with a polymerization initiator, which are used
as components of a negative photosensitive composition, and a
sensitizer for activating them, are also not substantially
required. Thus, the composition of the present invention is clearly
distinguished also from a photosensitive composition which is
useful as both positive and negative photosensitive compositions.
Further, the composition of the present invention not contain a
compound susceptible to a photochemical sensitizing effect by the
photo-thermal conversion material and is clearly distinguished from
the composition disclosed in JP-A-60-175046.
[0029] The positive photosensitive composition of the present
invention may contain a solubility-suppressing agent (dissolution
inhibitor) which is capable of lowering the alkali solubility of
the photosensitive layer prior to exposure, as described
hereinafter.
[0030] Now, the photo-thermal conversion material (hereinafter
referred to as a light-absorbing dye) as the first component used
for the positive photosensitive composition of the present
invention, will be described. This material is not particularly
limited so long as it is a compound capable of converting absorbed
light to heat. However, it is preferably a light-absorbing dye (a)
having an absorption band covering a part or whole of a wavelength
region of from 650 to 1300 nm. The light-absorbing dye to be used
in the present invention is a compound which effectively absorbs
light in a wavelength region of from 650 to 1300 nm, while it does
not substantially absorb, or absorbs but is not substantially
sensitive to, light in an ultraviolet region, and which will not
modify the photosensitive composition by a weak ultraviolet ray
which may be contained in white light. Specific examples of such a
light-absorbing dye will be presented in Table 1.
1TABLE 1 S-1 1 S-2 2 S-3 3 S-4 4 S-5 5 S-6 6 S-7 7 S-8 8 S-9 9 S-10
10 S-11 11 S-12 12 S-13 13 S-14 14 S-15 15 S-16 16 S-17 17 S-18 18
S-19 19 S-20 20 S-21 21 S-22 22 S-23 23 S-24 24 S-25 25 S-26 26
S-27 27 S-28 28 S-29 29 S-30 30 S-31 31 S-32 32 S-33 33 S-34 34
S-35 35 S-36 36 S-37 37 S-38 38 S-39 39 S-40 40 S-41 41 S-42 42
S-43 43 S-44 44 S-45 45 S-46 46 S-47 47 S-48 48 S-49 49 S-50 50
S-51 51 S-52 52 S-53 53
[0031] These dyes can be prepared by conventional methods.
[0032] Among these, a cyanine dye, a polymethine dye, a squarilium
dye, a croconium dye, a pyrylium dye and a thiopyrylium dye are
preferred. Further, a cyanine dye, a polymethine dye, a pyrylium
dye and a thiopyrylium dye are more preferred.
[0033] Among these, particularly preferred is a cyanine dye of the
following formula (I) or a polymethine dye of the formula (II) in a
wavelength region of from 650 to 900 nm, and a pyrylium dye or a
thiopyrylium dye of the following formula (III) in a wavelength
region of from 800 to 1300 nm: 54
[0034] wherein each of R.sup.1 and R.sup.2 is a C.sub.1-8 alkyl
group which may have a substituent, whereiri the substituent is a
phenyl group, a phenoxy group, an alkoxy group, a sulfonic acid
group, or a carboxyl group; Q.sup.1 is a heptamethine group which
may have a substituent, wherein the substituent is a C.sub.1-8
alkyl group, a halogen atom or an amino group, or the heptamethine
group may contain a cyclohexene ring or a cyclopentene ring having
a substituent, formed by mutual bonding of substituents on two
methine carbon atoms of the heptamethine group, wherein the
substituent is a C.sub.1-6 alkyl group or a halogen atom; each of
m.sup.1 and m.sup.2 is 0 or 1; each of Z.sup.1 and Z.sup.2 is a
group of atoms required for forming a nitrogen-containing
heterocyclic ring; and X.sup.- is a counter anion. 55
[0035] wherein each of R.sup.3 to R.sup.6 is a C.sub.1-8 alkyl
group; each of Z.sup.4 and Z.sup.5 is an aryl group which may have
a substituent, wherein the aryl group is a phenyl group, a naphthyl
group, a furyl group or a thienyl group, and the substituent is a
C.sub.1-4 alkyl group, a C.sub.1-8 dialkylamino group, a C.sub.1-8
alkoxy group and a halogen atom; Q.sup.2 is a trimethine group or a
pentamethine group; and X.sup.- is a counter anion. 56
[0036] wherein each of Y.sup.1 and Y.sup.2 is an oxygen atom or a
sulfur atom, each of R.sup.7, R.sup.8, R.sup.15 and R.sup.16 is a
phenyl group or a naphthyl group which may have a substituent,
wherein the substituent is a C.sub.1-8 alkyl group or a C.sub.1-8
alkoxy group; each of l.sup.1 and l.sup.2 which are independent of
each other, is 0 or 1; each of R.sup.9 to R.sup.14 is a hydrogen
atom or a C.sub.1-8 alkyl group, or R.sup.9 and R.sup.10, R.sup.11
and R.sup.12, or R.sup.13 and R.sup.14, are bonded to each other to
form a linking group of the formula: 57
[0037] wherein each of R.sup.17 to R.sup.19 is a hydrogen atom or a
C.sub.1-6 alkyl group, and n is 0 or 1; Z.sup.3 is a halogen atom
or a hydrogen atom; and X.sup.- is a counter anion.
[0038] The counter anion X.sup.- in each of the above formulas (I),
(II) and (III) may, for example, be an inorganic acid anion such as
Cl.sup.-, Br.sup.-, I.sup.-, ClO.sub.4.sup.-, BF.sub.4.sup.- or
PF.sub.6.sup.-, or an organic acid anion such as a benzenesulfonic
acid, p-toluenesulfonic acid, naphthalene-1-sulfonic acid or acetic
acid.
[0039] The proportion of such a light-absorbing dye in the positive
photosensitive composition of the present invention is preferably
from 0.1 to 30 wt %, more preferably from 1 to 20 wt %.
[0040] Now, the high molecular compound (hereinafter referred to as
a polymer or a resin) (b), of which the solubility in an alkali
developer is changeable mainly by a change other than a chemical
change, as the second component used for the positive
photosensitive composition of the present invention, will be
described. As such a polymer, alkali-soluble resins such as a
novolak resin, a resol resin, a polyvinyl phenol resin and a
copolymer of an acrylic acid derivative, may, for example, be
mentioned. Among them, a novolak resin or a polyvinyl phenol resin
is preferred.
[0041] The novolak resin may be one prepared by polycondensing at
least one member selected from aromatic hydrocarbons such as
phenol, m-cresol, o-cresol, p-cresol, 2,5-xylenol, 3,5-xylenol,
resorcinol, pyrogallol, bisphenol, bisphenol-A, trisphenol,
o-ethyphenol, m-ethylphenyl, p-ethylphenol, propylphenol,
n-butylphenol, t-butylphenol, 1-naphthol and 2-naphthol, with at
least one aldehyde or ketone selected from aldehydes such as
formaldehyde, acetoaldehyde, propionaldehyde, benzaldehyde and
furfural and ketones such as acetone, methyl ethyl ketone and
methyl isobutyl ketone, in the presence of an acid catalyst.
[0042] Instead of the formaldehyde and acetaldehyde,
paraformaldehyde and paraldehyde may, respectively, be used. The
weight average molecular weight calculated as polystyrene, measured
by gel permeation chromatography (hereinafter referred to simply as
GPC), of the novolak resin (the weight average molecular weight by
the GPC measurement will hereinafter be referred to as Mw) is
preferably from 1,000 to 15,000, more preferably from 1,500 to
10,000.
[0043] The aromatic hydrocarbon of a novolak resin may, for
example, be preferably a novolak resin obtained by polycondensing
at least one phenol selected from phenol, o-cresol, m-cresol,
p-cresol, 2,5-xylenol, 3,5-xylenol and resorcinol, with at least
one member selected from aldehydes such as formaldehyde,
acetaldehyde and propionaldehyde.
[0044] Among them, preferred is a novolak resin which is a
polycondensation product of an aldehyde with a phenol comprising
m-cresol/p-cresol/2,5-xylenol/3,5-xylenol/resorcinol in a mixing
molar ratio of 40 to 100/0 to 50/0 to 20/0 to 20/0 to 20, or with a
phenol comprising phenol/m-cresol/p-cresol in a mixing molar ratio
of 1 to 100/0 to 70/0 to 60. Among aldehydes, formaldehyde is
particularly preferred. Further, as described hereinafter, the
photosensitive composition of the present invention may further
contain a solubility-suppressing agent. In such a case, preferred
is a novolak resin which is a polycondensation product of an
aldehyde with a phenol comprising m-cresol/p-cresol/2,5-xyl-
enol/3,5-xylenol/resorcinol in a mixing molar ratio of 70 to 100/0
to 30/0 to 20/0 to 20, or with a phenol comprising
phenol/m-cresol/p-cresol in a mixing molar ratio of 10 to 100/0 to
60/0 to 40.
[0045] The polyvinyl phenol resin may be a polymer of one or more
hydroxystyrenes such as o-hydroxystyrene, m-hydroxystyrene,
p-hydroxystyrene, 2-(o-hydroxyphenyl)propylene,
2-(m-hydroxyphenyl)propyl- ene and 2-(p-hydroxyphenyl)propylene.
Such a hydroxystyrene may have a substituent such as a halogen such
as chlorine, bromine, iodine or fluorine, or a C.sub.1-4 alkyl
group, on its aromatic ring. Accordingly, the polyvinyl phenol may
be a polyvinyl phenol having a halogen or a C.sub.1-4 alkyl
substituent on its aromatic ring.
[0046] The polyvinyl phenol resin is usually prepared by
polymerizing one or more hydroxystyrenes which may have
substituents in the presence of a radical polymerization initiator
or a cationic polymerization initiator. Such a polyvinyl phenol
resin may be the one subjected to partial hydrogenation. Or, it may
be a resin having a part of OH groups of a polyvinyl phenol
protected by e.g. t-butoxycarbonyl groups, pyranyl group, or
furanyl groups. Mw of the polyvinyl phenol resin is preferably from
1,000 to 10,0000, more preferably from 1,500 to 50,000.
[0047] More preferably, the polyvinyl phenol resin is a polyvinyl
phenol which may have a C.sub.1-4 alkyl substituent on its aromatic
ring, particularly preferably an unsubstituted polyvinyl
phenol.
[0048] If Mw of the above novolak resin or polyvinyl phenol resin
is smaller than the above range, no adequate coating film tends to
be obtained, and if it exceeds the above range, the solubility of
the non-exposed portion in an alkali developer tends to be small,
whereby a pattern tends to be hardly obtainable.
[0049] Among the above described resins, a novolak resin is
particularly preferred.
[0050] The proportion of such a resin in the positive
photosensitive composition comprising the above-described
components (a) and (b) to be used in the present invention, is
preferably from 70 to 99.9 wt %, more preferably from 80 to 99 wt
%.
[0051] The photosensitive composition of the present invention may
further contain, as its component, a solubility-suppressing agent
(dissolution inhibitor) (c) capable of lowering the dissolution
rate, in the alkali developer, of a blend comprising a
light-absorbing dye (a) and the above-mentioned alkali-soluble
resin (b) (such a solubility-suppressing agent (c) will hereinafter
be referred to simply as a solubility-suppressing agent).
[0052] When such a solubility-suppressing agent is incorporated in
the photosensitive composition of the present invention, the
photosensitive composition may sometimes exhibits an excellent
positive photosensitive property. The action of the
solubility-suppressing agent in the composition is not necessarily
clear. However, it is believed at least that the photosensitive
material made of this composition not only exhibits a
solubility-suppressing characteristic at a non-exposed portion
against the developer by the addition of the solubility-suppressing
agent, while showing no such an effect at an exposed portion, but
also often exhibits a dissolution-accelerating effect i.e. an
effect of increasing the contrast between the exposed portion and
the non-exposed portion, whereby an excellent positive image can be
formed. However, the composition of the present invention is one,
of which the solubility in an alkali developer is changed by a
change other than a chemical change. Accordingly, the
solubility-suppressing agent should also be a compound which
undergoes no chemical change by exposure. In other words, it is a
compound not susceptible to a photochemical sensitizing effect by
the photo-thermal conversion material.
[0053] The photosensitive composition of the present invention
contains an alkali-soluble resin (b) and a light-absorbing dye (a)
as essential components. Accordingly, the solubility-suppressing
agent (c) is one showing an effect of suppressing the dissolution
of a blend of components (a) and (b), as mentioned above. However,
it is believed that such an agent serves substantially to suppress
dissolution of the alkali-soluble resin (b).
[0054] The solubility-suppressing agent must be at least a compound
which is capable of suppressing, by its addition, the dissolving
rate, in the alkali developer, of the blend comprising the above
components (a) and (b) to a level of at most 80%, and it is
preferably a compound capable of suppressing the dissolution rate
to a level of at most 50%, more preferably at most 30%.
[0055] As a simple method for measuring the solubility-suppressing
effect, for example, a blend of predetermined amounts of the above
components (a) and (b) is firstly coated on a support, and the
coated support is immersed in the alkali developer, whereby the
interrelation between the immersion time and the reduction in the
film thickness is obtained. Then, a predetermined amount of a
sample of the solubility-suppressing agent is incorporated to the
above blend, then the blend is coated in the same film thickness as
above, and the relation between the immersion time and the
reduction in the film thickness is obtained in the same manner.
From these measured values, a ratio of the dissolution rates of the
two can be obtained. Thus, the effect of lowering the dissolution
rate of the sample of the solubility-suppressing agent used can be
measured as such a relative rate. Specific examples wherein various
suppressing agents are incorporated in an amount corresponding to
20 wt % of the novolak resin, are described in Examples given
hereinafter.
[0056] It has been found that a wide range of compounds can be used
as effective solubility-suppressing agents for the present
invention. However, such a solubility-suppressing agent is required
to remain in the photosensitive layer under a stabilized condition,
and it is accordingly preferably solid at room temperature under
atmospheric pressure or a liquid having a boiling point of at least
180.degree. C. under atmospheric pressure. effective compounds may,
for example, be sulfonic acid esters, phosphoric acid esters,
aromatic carboxylic acid esters, aromatic disulfones, carboxylic
anhydrides, aromatic ketones, aromatic aldehydes, aromatic amines
and aromatic ethers. These compounds may be used alone or in
combination as a mixture of two or more of them.
[0057] More specifically, they may, for example, be sulfonic acid
esters such as ethyl benzenesulfonate, n-hexyl benzenesulfonate,
phenyl benzenesulfonate, benzyl benzenesulfonate, phenylethyl
benzenesulfonate, ethyl p-toluenesulfonate, t-butyl
p-toluenesulfonate, n-octyl p-toluenesulfonate, 2-ethylhexyl
p-toluenesulfonate, phenyl p-toluenesulfonate, phenylethyl
p-toluenesulfonate, ethyl 1-naphthalenesulfonate, phenyl
2-naphthalenesulfonate, benzyl 1-naphthalenesulfonate, phenylethyl
1-naphthalenesulfonate, and bisphenyl A dimethyl sulfonate;
phosphoric acid esters such as trimethyl phosphate, triethyl
phosphate, tri(2-ethylhexyl) phosphate, triphenyl phosphate,
tritolyl phosphate, tricresyl phosphate, and tri-(1-naphthyl)
phosphate; aromatic carboxylic acid esters such as methyl benzoate,
n-heptyl benzoate, phenyl benzoate, 1-naphthyl benzoate, n-octyl
1-pyridine carboxylate, and tris(n-butoxycarbonyl)-s-triazine;
carboxylic anhydrides such as mono-, di- or tri-chloroacetic
anhydride, phenyl succinic anhydride, maleic anhydride, phthalic
anhydride, and benzoic anhydride; aromatic ketones such as
benzophenone, acetophenone, benzil and
4,4'-dimethylaminobenzophenone; aldehydes such as
p-dimethylaminobenzalde- hyde, p-methoxybenzaldehyde,
p-chlorobenzaldehyde, and 1-naphthoaldehyde; aromatic amines such
as triphenylamine, diphenylamine, tritolylamine, and
diphenylnaphthylamine; and aromatic ethers such as ethylene glycol
diphenyl ether, 2-methoxynaphthalene, diphenyl ether, and
4,4'-diethoxybisphenol A. These compounds may be substituted by a
substituent of the type not to impair the effects of the present
invention, such as an alkyl group, an alkoxy group, a halogen atom
or a phenyl group. Further, such a compound may have a structure in
which it is combined into a polymer or a resin. For example, it
may, for example, be a sulfonic acid ester supported by an ester
bond on a hydroxyl group of a novolak resin or a polyvinyl phenol.
Such a structure may sometimes brings about an excellent
suppressing effect.
[0058] Such a solubility-suppressing agent may contain, in its
structure, a compound of the type having photosensitivity to
ultraviolet light, such as an o-quinone diazide group-containing
compound such as an o-quinone diazide sulfonic acid ester, or an
aromatic disulfone such as diphenyldisulfone, whereby an excellent
image can be obtained. However, in such a case, it is usually
required to carry out the operation under yellow light.
Accordingly, a more preferred specific embodiment of the present
invention is an embodiment wherein a solubility-suppressing agent
having substantially no photosensitivity to ultraviolet light. As
shown in Examples of this specification, it is a photosensitive
material durable for an operation for a long period of time in an
environment of white light, and such a photosensitive material will
bring about a substantial merit from the practical viewpoint. Such
a solubility-suppressing agent (c) which is used as the case
requires, may be incorporated preferably in an amount of at most 50
wt %, more preferably at most 40 wt %, based on the total weight of
the components (a) and (b).
[0059] In a case where an o-quinone diazide group-containing
compound is used as the solubility-suppressing agent, if the
photosensitive composition is irradiated with ultraviolet ray, a
positive image can be obtained in the same manner as the
conventional composition. However, the photosensitive composition
of the present invention is advantageously characterized in forming
an image by a light within a wavelength region of from 650 to 1300
nm, and it is believed that within this wavelength region, no
substantial reaction for photo decomposition of the o-quinone
diazide group-containing compound will take place. This is evident
also from the disclosure in JP-A-60-175046 reading "in contrast to
quinone diazide and diazonium salt which can not be sensitized or
can only slightly be sensitized, an onium salt can readily be
sensitized by a wide range of compounds over the entire visible and
infrared regions of an electromagnetic spectrum". However, it is
known that a 1,2-diazoketone such as an o-quinone diazide
group-containing compound, undergoes a decomposition reaction also
by heat. Accordingly, it is likely that when a light within a
wavelength region of from 650 to 1300 nm is irradiated, it may be
decomposed by the heat converted by a light-absorbing dye, and as a
result, an increase in the alkali solubility of the exposed portion
may be brought about.
[0060] It should be understood that in the present invention, the
difference in the solubility in the developer as between an exposed
portion and a non-exposed portion is essentially accomplished by a
combination of the light-absorbing dye and the high molecular
compound, Of which the solubility in an alkali developer varies
depending upon the light absorption of the dye.
[0061] An o-quinone diazide group-containing compound has
absorption in an ultraviolet to visible region. Accordingly, if
such an o-quinone diazide group-containing compound is used as the
solubility-suppressing agent, it is usually required to carry out
the operation under yellow light. However, such a compound may
often bring about a desirable burning property. Such an o-quinone
diazide group-containing compound may, for example, be preferably
an ester compound of o-quinone diazide sulfonic acid with various
aromatic polyhydroxy compounds or with a polycondensed resin of a
phenol and an aldehyde or ketone.
[0062] The phenol may, for example, be a monohydric phenol such as
phenol, o-cresol, m-cresol, p-cresol, 3,5-xylenol, carbacrol or
thimol, a dihydric phenol such as catechol, resorcinol or
hydroquinone, or a trihydric phenol such as pyrogallol or
fluoroglucine. The aldehyde may, for, example, be formaldehyde,
benzaldehyde, acetaldehyde, croton aldehyde or furfural. Among
them, preferred are formaldehyde and benzaldehyde. The ketone may,
for example, be acetone or methyl ethyl ketone.
[0063] Specific examples of the polycondensed resin include a
phenol/formaldehyde resin, a m-cresol/formaldehyde resin, a m- and
p-mixed cresol/formaldehyde resin, a resorcinol/benzaldehyde resin,
and a pyrogallol/acetone resin. The molecular weight (Mw) of such a
polycondensed resin is preferably from 1,000 to 10,000, more
preferably from 1,500 to 5,000.
[0064] The condensation ratio of o-quinone diazide sulfonic acid to
the OH group of a phenol group of the above o-quinone diazide
compound (the reaction ratio per one OH group) is preferably from 5
to 80%, more preferably from 10 to 45%.
[0065] Among the o-quinone diazide compounds, particularly
preferred is an o-quinone diazide compound obtained by reacting
1,2-naphthoquinone diazide sulfonyl chloride with a pyrogallol
acetone resin.
[0066] The photosensitive composition of the present invention is
prepared usually by dissolving the above described various
components in a suitable solvent. The solvent is not particularly
limited so long as it is a solvent which presents an excellent
coating film property and provides sufficient solubility for the
components used. It may, for example, be a cellosolve solvent such
as methylcellosolve, ethylcellosolve, methylcellosolve acetate or
ethylcellosolve acetate, a propylene glycol 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 or dipropylene glycol
dimethyl ether, an ester solvent such as butyl acetate, amyl
acetate, ethyl butyrate, butyl butylate, diethyl oxalate, ethyl
pyruvate, methyl-2-hydroxy butyrate, ethyl acetate, methyl lactate,
ethyl lactate or methyl 3-methoxypropionate, an alcohol solvent
such as heptanol, hexanol, diacetone alcohol or furfuryl alcohol, a
ketone solvent such as cyclohexanone or methyl amyl ketone, a
highly polar solvent such as dimethyl formamide, dimethyl acetamide
or n-methyl pyrrolidone, or a solvent mixture thereof, or the one
having an aromatic hydrocarbon added thereto. The proportion of the
solvent is usually within a range of from 1 to 20 times in a weight
ratio to the total amount of the photosensitive material.
[0067] The photosensitive composition of the present invention may
contain various additives, such as a dye, a pigment, a coating
property-improving agent, a development-improving agent, an
adhesion-improving agent, a sensitivity-improving agent, an
oleophilic agent, etc. within a range not to impair the performance
of the composition.
[0068] As a method for coating the photosensitive composition on
the surface of a support, to be used in the present invention, a
conventional method such as rotational coating, wire bar coating,
dip coating, air knife coating, roll coating, blade coating or
curtain coating may, for example, be employed. The coated amount
varies depending upon the particular use, but is usually preferably
from 0.1 to 10.0 g/m.sup.2 (as the solid content). The temperature
for drying is, for example, from 20 to 150.degree. C., preferably
from 30 to 120.degree. C. The support on which a photosensitive
layer made of the photosensitive composition of the present
invention will be formed, may, for example, be a metal plate of
e.g. aluminum, zinc, steel or copper, a metal plate having
chromium, zinc, copper, nickel, aluminum, iron or the like plated
or vapor-deposited thereon, a paper sheet, a plastic film, a glass
sheet, a resin-coated paper sheet, a paper sheet having a metal
foil such as an aluminum foil bonded thereto, or a plastic film
having hydrophilic treatment applied thereto. Among them, preferred
is an aluminum plate. As the support for a photosensitive
lithographic printing plate of the present invention, it is
particularly preferred to employ an aluminum plate having grain
treatment applied by brush polishing or electrolytic etching in a
hydrochloric acid or nitric acid solution, having anodizing
treatment applied in a sulfuric acid solvent and, if necessary,
having surface treatment such as pore sealing treatment
applied.
[0069] The light source for image exposure of the photosensitive
lithographic printing plate of the present invention is preferably
a light source for generating a near infrared laser beam of from
650 to 1,300 nm. For example, a YAG laser, a semiconductor laser or
LED may be mentioned. Particularly preferred is a semiconductor
laser or a YAG laser which is small in size and has a long useful
life. With such a laser light source, scanning exposure is usually
carried out, and then development is carried out with a developer
to obtain a lithographic printing plate having a developed
image.
[0070] The laser light source is used to scan the surface of a
photosensitive material in the form of a high intensity light ray
(beam) focused by a lens, and the sensitivity characteristic
(mJ/cm.sup.2) of the positive lithographic printing plate of the
present invention responding thereto may sometimes depend on the
light intensity (mJ/s.multidot.cm.sup.2) of the laser beam received
at the surface of the photosensitive material. Here, the light
intensity (mJ/s.multidot.cm.sup.2) of the laser beam can be
determined by measuring the energy per unit time (mJ/s) of the
laser beam on the printing plate by a light power meter, measuring
also the beam diameter (the irradiation area: cm.sup.2) on the
surface of the photosensitive material, and dividing the energy per
unit time by the irradiation area. The irradiation area of the
laser beam is usually defined by the area of the portion exceeding
1/e.sup.2 intensity of the laser peak intensity, but it may simply
be measured by sensitizing the photosensitive material showing
reciprocity law.
[0071] The light intensity of the light source to be used in the
present invention is preferably at least 2.0.times.10.sup.6
mJ/s.multidot.cm.sup.2, more preferably at least 1.0.times.10.sup.7
mJ/s.multidot.cm.sup.2. If the light intensity is within the above
range, the sensitivity characteristic of the positive lithographic
printing plate of the present invention can be improved, and the
scanning exposure time can be shortened, such being practically
very advantageous.
[0072] As the developer to be used for developing the
photosensitive lithographic printing plate of the present
invention, an alkali developer composed mainly of an aqueous alkali
solution is preferred.
[0073] As the alkali developer, an aqueous solution of an alkali
metal salt such as sodium hydroxide, potassium hydroxide, sodium
carbonate, potassium carbonate, sodium metasilicate, potassium
metasilicate, sodium secondary phosphate or sodium tertiary
phosphate, may, for example, be mentioned. The concentration of the
alkali metal salt is preferably from 0.1 to 20 wt %. Further, an
anionic surfactant, an amphoteric surfactant or an organic solvent
such as an alcohol, may be added to the developer, as the case
requires.
[0074] Now, the present invention will be described-in further
detail with reference to Examples. However, it should be understood
that the present invention is by no means restricted to such
specific Examples.
[0075] The esterification ratio in Examples was obtained from the
charged ratio.
[0076] Preparation of a Lithographic Printing Plate
[0077] Preparation of an Aluminum Plate (I)
[0078] An aluminum plate (material: 1050, hardness: H16) having a
thickness of 0.24 mm was subjected to degreasing treatment at
60.degree. C. for one minute in a 5 wt % sodium hydroxide aqueous
solution and then to electrolytic etching treatment in an aqueous
hydrochloric acid solution having a concentration of 0.5 mol/l at a
temperature of 25.degree. C. at a current density of 60 A/dm.sup.2
for a treating time of 30 seconds. Then, it was subjected to desmut
treatment in a 5 wt % sodium hydroxide aqueous solution at 600C for
10 seconds and then to anodizing treatment in a 20 wt % sulfuric
acid solution at a temperature of 20.degree. C. at a current
density of 3 A/dm.sup.2 for a treating time of one minute. Further,
it was subjected to a hydrothermal pore sealing treatment with hot
water of 80.degree. C. for 20 seconds to obtain an aluminum plate
(I) as a support for a lithographic printing plate.
EXAMPLES 1 TO 10
[0079] A photosensitive liquid comprising the following components,
was coated by a wire bar on an aluminum plate (I) prepared by the
above described method and dried at 85.degree. C. for 2 minutes,
followed by stabilizing in an oven of 55.degree. C. to obtain a
photosensitive lithographic printing plate having a photosensitive
layer with a film thickness of 24 mg/dm.sup.2.
[0080] Photosensitive Liquid
2 High molecular compound: Novolak resin as 0.9 g identified in
Table 2 Light-absorbing dye: Amount as identified Compound as
identified in in Table 2 Table 2 Colorant: Victoria Pure Brue BOH
0.008 g Solvent: Cyclohexanone 9 g
[0081] The above photosensitive lithographic printing plate was
mounted on a rotary drum, and scanning exposure was carried out by
a laser beam (40 mW) formed by focusing a semiconductor laser (830
nm, by Applied Techno K.K.) by a lens to a beam diameter of 25
.mu.m, under a yellow lamp. Then, development was carried out at
25.degree. C. for 30 seconds with a solution having an alkali
developer SDR-1 (for a positive printing plate, manufactured by
Konica K.K.) diluted the number of times as identified in Table 2.
From the maximum number of revolutions of the drum which gave a
positive image line with a width of 25 .mu.m, the sensitivity was
obtained in terms of the energy value. The results are shown in
Table 2.
3TABLE 2 Number of Light- diluted Novolak absorbing times of
Sensitivity Examples resin dye (wt %) SDR-l (mJ/cm.sup.2) Example 1
SK-188 S-53 12 times 110 (3%) Example 2 SK-135 S-53 6 times 80 (3%)
Example 3 SK-136 S-53 12 times 100 (3%) Example 4 SK-223 S-53 6
times 80 (3%) Example 5 SK-223 S-53 6 times 75 (3%) Example 6
SK-135 S-4 6 times 180 (3%) Example 7 SK-135 S-43 6 times 80 (3%)
Example 8 SK-135 S-11 6 times 120 (3%) Example 9 SK-135 S-22 6
times 140 (3%) Example 10 SK-135 S-23 6 times 140 (3%) In Table 2,
the abbreviations in the column for "Novolak resin" represent the
following novolak resins, respectively. The ratio in the bracket ()
represents a mol % ratio of phenol/m-cresol/p-cresol. SK-188:
SK-188, manufactured by Sumitomo Dures Company (50/30/20) SK-135:
SK-135, manufactured by Sumitomo Dures Company (10/70/30) SK-136:
SK-136, manufactured by Sumitomo Dures Company (0/90/10) SK-223:
SK-223, manufactured by Sumitomo Dures Company (5/57/38) In Table
2, the abbreviations in the column for "Light-absorbing dye"
represent the compounds as identified in Table 1, respectively.
EXAMPLES 11 TO 19 AND REFERENCE EXAMPLES 1 TO 3
[0082] Then, with respect to some of these photosensitive
lithographic printing plates, the influence of the light intensity
of the laser beam was examined by the following method.
[0083] Namely, while fixing the received energy of the
semiconductor laser (830 nm) at the surface of the photosensitive
material at a level of 40 mJ/s, the light intensity was changed by
adjusting the focusing degree by the lens, so that the sensitivity
corresponding to each light intensity was obtained. The sensitivity
was obtained from the number of revolutions of the drum which gave
an image (positive) reproducing the exposed beam diameter. Further,
the received energy of the laser was measured by using a light
power meter TQ8210 (manufactured by Advantest Company).
[0084] The results of the obtained sensitivity mJ/cm.sup.2 are
shown in Table 3.
4 TABLE 3 Photosensitive lipthographic printing plate Light
Lithographic Lithographic Lithographic inten- printing plate
printing plate printing plate sity of Example 2 of Example 4 of
Example 5 12.7 .times. Exam- 100 Exam- 100 Exam- 90 10.sup.6 mJ/
ple 11 mJ/s .multidot. cm.sup.2 ple 14 mJ/s .multidot. cm.sup.2 ple
17 mJ/s .multidot. cm.sup.2 s .multidot. cm.sup.2 8.13 .times.
Exam- 300 Exam- 240 Exam- 160 10.sup.6 ple 12 ple 15 ple 18 5.66
.times. Exam- 3,600 Exam- 2,700 Exam- 1,800 10.sup.6 ple 13 ple 16
ple 19 1.04 .times. Refe- >7,200 Refe- >7,200 Refe- >7,200
10.sup.6 rence rence rence Exam- Exam- Exam- ple 1 ple 2 ple 3 In
Table 3, ">7200" means that no image was formed (no dissolution
of the image portion was observed) with 7200 mJ/cm.sup.2.
EXAMPLES 20 TO 42 AND REFERENCE EXAMPLES 4 TO 8
[0085] A photosensitive liquid comprising the following components,
was coated by a wire bar on an aluminum plate (I) prepared by the
above-described method and dried at 85.degree. C. for 2 minutes,
followed by stabilizing in an oven of 55.degree. C., to obtain a
photosensitive lithographic printing plate having a photosensitive
layer with a film thickness of 20 mg/dm.sup.2.
[0086] Photosensitive Liquid
5 Light-absorbing dye: Compound as 0.015 g identified in Table 4
High molecular compound: Novolak resin: 0.5 g the above mentioned
SK-188 Solubility-suppressing agent: Compound as 0.1 g identified
in Table 4 Solvent: Cyclohexanone 5.3 g
[0087] Then, evaluation was made with respect to the following
items. The results are shown in Table 4.
[0088] Sensitivity
[0089] With respect to the above photosensitive lithographic
printing plates, the sensitivity was determined in terms of the
energy value in the same manner as in Example 1. However, the
alkali developer SDR-1 was used by diluting it to a standard level
(6 times).
[0090] Dissolution-suppressing Effect
[0091] The above photosensitive lithographic printing plates were
immersed in an alkali developer, whereupon the time (seconds) until
the respective photosensitive layers were completely dissolved, was
measured. The dissolution-suppressing effect was obtained by the
following formula. 1 Dissolution - suppressing effect = Dissolution
time of the photosensitive layer in Reference Example 4 Dissolution
time of the photosensitive layer in each Example
[0092] The lower the value of the dissolution-suppressing effect,
the longer the time required for dissolution i.e. the higher the
dissolution-suppressing effect.
6 TABLE 4 Light- Dissolution- absorbing Sensitivity suppressing dye
Solubility-suppressing agent (mJ/cm.sup.2) effect Example 20 S-1
Phenylethyl p-toluenesulfonate 110 0.25 Example 21 S-1 Ethyl
p-toluenesulfonate 110 0.4 Example 22 S-1 Phenyl p-toluenesulfonate
110 0.3 Example 23 S-1 1,2,3-pyrogarolditosilat- e 80 0.2 Example
24 S-1 Tris(2-ethylhexyl) phosphate 110 0.15 Example 25 S-1
Triphenyl phosphate 110 0.1 Example 26 S-1 Dimethyl phthalate 110
0.4 Example 27 S-1 Diphenyl disulfone 80 0.15 Example 28 S-1
Benzophenone 80 0.1 Example 29 S-1 p-Dimethylamino benzaldehyde 80
0.2 Example 30 S-1 Triphenylamine 80 0.1 Example 31 S-1 Ethylene
glycol phenyl ether 80 0.15 Example 32 S-1 2-Methoxynaphthalene 80
0.35 Example 33 S-1 Monochloroacetic anhydride 110 0.05 Example 34
S-1 Phenylmaleic anhydride 80 0.3 Example 35 S-1 p-Toluene sulfonic
acid ester 110 0.25 of pyrogallol-acetone resin *1 110 0.2 Example
36 S-1 5-Naphthoquinone diazide sulfonic acid ester of
pyrogallol-acetone resin *1 Example 37 S-4 Phenylethyl
p-toluenesulfonate 220 0.3 Example 38 S-43 Phenylethyl
p-toluenesulfonate 80 0.25 Example 39 S-8 Phenylethyl
p-toluenesulfonate 80 0.2 Example 40 S-13 Phenylethyl
p-toluenesulfonate 110 0.25 Example 41 S-21 Phenylethyl
p-toluenesulfonate 140 0.25 Example 42 S-25 Phenylethyl
p-toluenesulfonate 160 0.2 Reference S-1 Nil No image 1 Example 4
formed Reference S-1 Trimethylol ethane No image 0.9 Example 5
formed Reference S-1 1,4-Cyclohexadione No image 1 Example 6 formed
Reference S-1 1,4-Cyclohexadiol No image >1 Example 7 formed
Reference S-1 Benzoic acid No image >1 Example 8 formed *1
Average molecular weight of the pyrogallol-acetone resin; 2500,
esterification ratio: 20% In Table 4, the abbreviations in the
column for "Light-absorbing dye" represents the compounds as
identified in Table 1, respectively. Further, "no image formed" in
the column for "Sensitivity" means that the photosensitive layer
was completely dissolved.
EXAMPLE 43
[0093] A photosensitive lithographic printing plate was prepared to
have a photosensitive layer having the same compositional ratio as
in Example 20, and using a semiconductor laser under the same
conditions as in Example 20, a printing pattern was baked with an
exposure of 150 mJ/cm.sup.2 to obtain a printing plate. Using this
printing plate, printing of 40000 sheets was carried out, whereby
good printed images were obtained.
EXAMPLE 44
[0094] The same photosensitive material as in Example 20, was
subjected to entire-surface exposure for 2 hours at a distance of 2
m from a light source comprising two white fluorescent lamps of 40
W (FLR 40 SW, manufactured by Mitsubishi Denki Kabushiki Kaisha),
and then image exposure was carried out in the same manner as in
Example 20. As a result, a good positive image similar to the one
obtained in Example 20, was obtained, and no particular abnormality
was observed.
EXAMPLE 45
[0095] The same photosensitive material as in Example 33 was
evaluated under the same conditions as in Example 44, whereby a
similar good positive image was obtained.
EXAMPLE 46
[0096] The same photosensitive material as in Example 25 was
evaluated under the same conditions as in Example 44, whereby a
similar good positive image was obtained.
COMPARATIVE EXAMPLE 1
[0097] Using the same light-absorbing dye as used in Example 20 and
using a photosensitive liquid having the following composition,
coating and drying were carried out in the same manner to obtain a
chemical amplification type negative photosensitive material.
7 High molecular compound: Same as used in 0.5 g Example 20
Light-absorbing dye: Same as used in 0.015 g Example 20
Crosslinking agent Cymel 300 (manufactured by 0.1 g Mitsui Cyanamid
Company) Tris(trichloromethyl)-s-triazine 0.015 g
[0098] The obtained photosensitive material was subjected to
entire-surface exposure under the same conditions as in Example 44,
then subjected to image exposure in the same manner, heated at
100.degree. C. for 3 minutes and then developed with the same
developer. As a result, heavy fogging was observed over the entire
surface, and no negative image was obtained.
COMPARATIVE EXAMPLE 2
[0099] Using a commercially available positive PS plate KM-3
(manufactured by Konica Company), entire surface exposure was
carried out under the same conditions as in Example 44, and
development was carried out with the same developer. As a result,
the image was dissolved over the entire surface, and no positive
image was obtained.
EXAMPLES 47 TO 60 AND REFERENCE EXAMPLES 9 TO 14
[0100] A photosensitive liquid comprising the following components,
was coated by a wire bar on an aluminum plate (I) prepared by the
above-described method and dried at 85.degree. C. for 2 minutes,
followed by stabilizing in an oven of 55.degree. C. to obtain a
photosensitive lithographic printing plate as identified in Table 5
(A to F) having a photosensitive layer with a thickness of 24
mg/dm.sup.2.
[0101] Photosensitive Liquid
8 Light-absorbing dye: S-53 (compound as 0.0135 g identified in
Table 1) High molecular compound: above mentioned 0.5 g SK-188
Solubility-suppressing agent: compound 0.15 g as identified in
Table 5 Colorant: Victoria Pure Blue BOH 0.004 g Solvent:
cyclohexanone 5.5 g
[0102]
9TABLE 5 Photosensitive lithographic printing plate
Solubility-suppressing agent A p-Toluene sulfonic acid ester of
pyrogallol/acetone resin *1 B 5-Naphthoquinone diazide sulfonic
acid ester of pyrogallol/acetone resin *1 C Triphenylamine D
Ethylene glycol diphenyl ether E Triphenyl phosphate F
Monochloroacetic anhydride *1 Weight average molecular weight of
pyrogallol/acetone resin: 2,500, esterification ratio: 20%
[0103] Then, with respect to these photosensitive lithographic
printing plates, the influence of light intensity was examined by
the same method as in Example 11 using the same semiconductor
laser.
[0104] As shown in Table 6, the light intensity was changed at four
levels, whereby the sensitivities corresponding to the respective
levels were obtained. The results are shown in Table 6.
10TABLE 6 Light Photosensitive lithographic printing plate
intensity A B C D E F 12.7 .times. 10.sup.6 Exam- 100 Exam- 120
Exam- 80 Exam- 100 Exam- 100 Exam- 120 mJ/s .multidot. cm.sup.2 ple
47 mJ/s .multidot. cm.sup.2 ple 50 mJ/s .multidot. cm.sup.2 ple 53
mJ/s .multidot. cm.sup.2 ple 55 mJ/s .multidot. cm.sup.2 ple 57
mJ/s .multidot. cm.sup.2 ple 59 mJ/s .multidot. cm.sup.2 8.13
.times. 10.sup.6 Exam- 690 Exam- 400 -- -- -- -- ple 48 ple 51 5.66
.times. 10.sup.6 Exam- 3,600 Exam- 1,600 Exam- 1,300 Exam- 3,000
Exam- 3,000 Exam- 3,600 ple 49 ple 52 ple 54 ple 56 ple 58 ple 60
1.04 .times. 10.sup.6 Refe- >7,200 Refe- >7,200 Refe-
>7,200 Refe- >7,200 Refe- >7,200 Refe- >7,200 rence
rence rence rence rence rence Exam- Exam- Exam- Exam- Exam- Exam-
ple 9 ple 10 ple 11 ple 12 ple 13 ple 14 In Table 6, ">7200"
means that no image was formed (no dissolution of the image portion
was observed) with 7200 mJ/cm.sup.2.
EXAMPLES 61 TO 67
[0105] A photosensitive liquid comprising the following components,
was coated by a wire bar on an aluminum plate (I) prepared by the
above-described method and dried at 85.degree. C. for two minutes,
followed by stabilizing in an oven at 55.degree. C. to obtain a
photosensitive lithographic printing plate having a photosensitive
layer with a film thickness of 24 mg/dm.sup.2.
[0106] Photosensitive Liquid
11 High molecular compound: novolak resin SK-135 0.9 g
Light-absorbing dye: compound as identified 0.027 g in Table 7
Colorant: Victoria Pure Blue BOH 0.008 g Solvent:
cyclohexanone/chloroform (=3V/1V) 12 g
[0107] Then, the above photosensitive lithographic printing plate
was mounted on a rotary drum, and scanning exposure was carried out
by a laser beam (480 mW) formed by focusing a YAG laser (1064 nm,
by Applied Techno K.K.) by a lens to a beam diameter of 30 .mu.m,
under a yellow lamp. Then, an alkali developer SDR-1 (for a
positive printing plate, manufactured by Konica K.K.) was diluted 6
times, and development was carried out at 25.degree. C. for 30
seconds. From the maximum number of revolutions of the drum which
gave a positive image line with a width of 30 .mu.m, the
sensitivity was obtained in terms of the energy value. The results
are shown in Table 7.
12 TABLE 7 Light-absorbing Sensitivity dye (mJ/cm.sup.2) Example 61
S-40 230 Example 62 S-25 170 Example 63 S-31 190 Example 64 S-22
170 Example 65 S-23 210 Example 66 S-28 190 Example 67 S-35 190
EXAMPLES 68 TO 73 AND REFERENCE EXAMPLES 15 AND 16
[0108] Then, with respect to some of these photosensitive
lithographic printing plates, the influence of light intensity of a
YAG laser beam was examined by the following method.
[0109] Namely, the sensitivity was obtained in the same manner as
in Example 11 except that the semiconductor laser (830 nm, 40 mW)
in Example 11 was changed to the above YAG laser (1064 nm, 480 mW),
i.e. the light intensity was changed by adjusting the focusing
degree by a lens and the sensitivity corresponding to each beam
diameter was obtained in the same manner as in Example 11.
[0110] The results of the obtained sensitivity are shown in Table
8.
13 TABLE 8 Photosensitive lithographic printing plate Lithographic
Lithographic Light printing plate of printing plate of intensity
Example 61 Example 64 53 .times. 10.sup.6 Example 230 Example 170
mJ/s.cm.sup.2 68 mJ/s.cm.sup.2 71 mJ/s.cm.sup.2 9.8 .times.
10.sup.6 Example 2,140 Example 1,430 69 72 4.8 .times. 10.sup.6
Example 6.000 Example 4,500 70 73 1.75 .times. 10.sup.6 Refer-
>8,000 Refer- >8,000 ence ence Example Example 15 16 In Table
8, ">8000" means that no positive image was formed (no
dissolution of the image portion was observed) with 8000
mJ/cm.sup.2.
REFERENCE EXAMPLES
[0111] As shown in the following Reference Examples, the positive
image-forming mechanism of the present invention is distinctly
different from the conventional positive image-forming mechanism
accompanying a photochemical change. Namely, in the photosensitive
layer of the present invention, the phenomenon of increased
solubility formed at a portion exposed to a laser readily
diminishes or disappears by heat treatment. This will specifically
be exemplified below.
REFERENCE EXAMPLES 17 TO 23
[0112] Preparation of an Aluminum Plate (II)
[0113] An aluminum plate (material: 1050, hardness: H16) having a
thickness of 0.24 mm was subjected to degreasing treatment at
60.degree. C. for one minute in a 5 wt % sodium hydroxide aqueous
solution and then to electrolytic etching treatment in an aqueous
hydrochloric acid solution having a concentration of 0.5 mol/l at a
temperature of 28.degree. C. at a current density of 55 A/dm.sup.2
for a treating time of 40 seconds. Then, it was subjected to desmut
treatment in a 4 wt % sodium hydroxide aqueous solution at
60.degree. C. for 12 seconds and then to anodizing treatment in a
20 wt % sulfuric acid solution at a temperature of 20.degree. C. at
a current density of 3.5 A/dm.sup.2 for a treating time of one
minute. Further, it was subjected to a hydrothermal pore sealing
treatment with hot water of 80.degree. C. for 20 seconds to obtain
an aluminum plate as a support for a lithographic printing plate
(II).
[0114] A photosensitive liquid comprising the following components,
was coated by a wire bar on the aluminum plate (II) prepared by the
above described method and dried at 85.degree. C. for 2 hours.
[0115] Photosensitive Liquid
14 High molecular compound: one as identified in 3.6 g Table 5
Light-absorbing dye: S-53 0.12 g Solubility-suppressing agent: one
as 0.72 g identified in Table 9, when used Colorant: Victoria Pure
Blue BOH 0.032 g Cyclohexanone 37 g
[0116] With respect to a sample of the obtained photosensitive
printing plate, the change in the dissolution property of an
exposed portion was examined as follows.
[0117] Firstly, each sample was exposed by a semiconductor laser or
a high pressure mercury lamp and then developed. In the former
case, exposure was carried out with an exposure of 200 mJ/cm.sup.2
in the same manner as in Example 1 and in the latter case, exposure
was carried out via a step tablet with a quantity of light giving
one clear step. Then, each sample was developed in the same manner
as in Example 1.
[0118] The photosensitive layer-remaining ratio at the exposed
portion of the positive image thus obtained, was of course 0%.
Then, another photosensitive printing plate prepared in the same
manner was exposed under the same conditions and then prior to the
developing step, a heat treatment step of maintaining at 55.degree.
C. for 20 hours was inserted, whereby the dissolving property of
the exposed portion was reduced, and at the obtainable positive
image portion, the photosensitive layer was not adequately removed,
and a residual film was usually observed. In such a case, the
photosensitive layer-remaining ratio (X) at the exposed portion can
be obtained by measuring the dissolution rates of the exposed and
non-exposed portions, and such a value will be an index for the
degree of reversibility. The obtained results are shown in Table
9.
15 TABLE 9 Photo- Components of photosensitive layer sensitive High
Light- Solubility Exposure layer- molecular absorbing suppressing
light remaining compound dye agent source ratio (X) Reference PR-4
*1 S-53 NQD IR 66% Example 17 Reference PR-4 S-53 NQD UV <5%
Example 18 Reference SK-135 *2 S-53 -- IR 37% Example 19 Reference
PR-4 S-53 -- IR 62% Example 20 Reference PR-4 S-53 Triphenyl- IR
71% Example amine 21 Reference PR-4 S-53 Ethylene IR 76% Example
glycol 22 dephenyl ether Reference PR-4 S-53 p-Toluene IR 87%
Example sulfonic acid 23 ester of pyrogallol/ acetone resin (Mw
2500), esterification ratio: 20% In Table 9, among abbreviations in
the column for "Exposure light source", IR represents the same
semiconductor laser as used in Example 1, and UV represents a high
pressure mercury lamp. In Table 9, an abbreviation "NQD" in the
column for "Solubility-suppressing agent" represents
pentahydroxybenzophenone naphthoquinone diazide sulfonic acid
ester, esterification ratio: 85%. *1 and *2: manufactured by
Sumitomo Dures Company
[0119] From the results shown in Table 9, the following can be
assumed. Firstly, the photosensitive layers used in Reference
Examples 17 and 18 are the same, and they contained naphthoquinone
diazide and an infrared-absorbing dye, but in the case of Reference
Example 18 where UV exposure was carried out, a known photochemical
change resulted, and even via heat treatment, the dissolution
property by exposure was maintained. On the other hand, as shown in
Reference Example 17, in the case where infrared laser exposure was
carried out, the dissolution property was substantially reduced,
and the photosensitive layer at the exposed portion partially
remained. This indicates that in the latter, the change is
attributable to some thermal physical change mechanism other than a
photochemical change. Further, also in the cases wherein infrared
laser was applied to various photosensitive layers shown in
Reference Examples 19 to 23, a behavior similar to Reference
Example 17 was shown, and the mechanism is assumed to be the same
as in Reference Example 17.
EXAMPLES 74 TO 77 AND COMPARATIVE EXAMPLES 3 AND 4
[0120] A photosensitive liquid comprising the following components,
was coated by a wire bar on an aluminum plate (I) prepared by the
above-described method and dried at 85.degree. C. for 2 minutes,
followed by stabilizing in an oven of 55.degree. C. to obtain a
photosensitive lithographic printing plate having a photosensitive
layer with a film thickness of 20 mg/dm.sup.2.
[0121] Photosensitive Liquid
16 Light-absorbing dye: compound as 0.02 g identified in Table 10
Alkali-soluble resin: m-cresol/p-cresol/phenol 0.5 g novolak resin
(SK-188) Solubility-suppressing agent: compound Amount as as
identified in Table 10 identified in Table 10 Solvent:
cyclohexanone 5.5 g
[0122] Then, evaluation was carried out with respect to the
following items. The results are shown in Table 10.
[0123] Safe Light Property
[0124] The above photosensitive lithographic printing plate was
exposed for 5 hours at a position of 1.5 m from two white lamps of
40 W and then developed with a developer prepared by diluting a
positive developer SDR-1 manufactured by Konica K.K. to 6 times,
whereupon the reflection density was measured by a reflection
densitometer manufactured by Macbeth Company, and it was converted
to a film-remaining ratio.
17 TABLE 10 Solubility- suppressing Light- agent absorbing Amount
Safe light dye Type (g) property Example 74 S-53 Y-1 0.1 100%
Example 75 S-53 Y-2 0.1 100% Example 76 S-53 Y-3 0.1 100% Example
77 S-53 Nil -- 100% Comparative S-53 Y-4 0.025 67% Example 3
Comparative S-53 Y-5 0.025 86% Example 4 In Table 10, abbreviations
in the column for "Solubility-suppressing agent" represents the
following compounds: Y-1: naphthyl sulfonic acid ester of
pyrogallol/acetone resin (Mw = 2500), esterification ratio: 20%
Y-2: p-toluene sulfonic acid ester of pyrogallol/acetone resin (Mw
= 2500), esterification ratio: 20% Y-3: 2-phenylethyl p-tolunate
Y-4: diphenyliodonium p-toluenesulfonate Y-5: triphenyl sulfonium
trifluoromethane
EXAMPLES 78 AND COMPARATIVE EXAMPLES 5, 6 AND 7
[0125] A photosensitive liquid comprising the following components,
was coated by a wire bar on an aluminum plate (I) prepared by the
above-described method and dried at 85.degree. C. for 2 minutes,
followed by stabilizing in an oven of 55.degree. C. to obtain a
photosensitive lithographic printing plate having a photosensitive
layer with a film thickness of 20 mg/dm.sup.2.
[0126] Photosensitive Liquid
18 Light-absorbing dye: compound as 0.02 g identified in Table 11
Alkali-soluble resin: m-cresol/p-cresol/phenol 0.5 g novolak resin
(SK-188) Solubility-suppressing agent: compound Amount as as
identified in Table 11 identified in Table 11 Solvent:
cyclohexanone 5.5 g
[0127] Then, evaluation was carried out with respect to the
following items. The results are shown in Table 10.
[0128] Burning Property
[0129] The above photosensitive lithographic printing plate was
heated in an oven at 200.degree. C. for 6 minutes, and then
immersed in Matsui Cleaning Agent (cleaning oil for printing) for 5
minutes. The reflection density was measured by a reflection
densitometer manufactured by Macbeth Company, and the
film-remaining ratio was evaluated.
19 TABLE 11 Solubility- suppressing Light- agent Burning property
absorbing Amount Immersed for dye Type (g) 5 minutes Example 78
S-53 Y-6 0.1 100% Comparative S-53 Y-4 0.025 0% Example 5
Comparative S-53 Y-5 0.025 0% Example 6 Comparative S-53 Nil -- 0%
Example 7 Y-4: diphenyliodonium p-toluenesulfonate Y-5: triphenyl
sulfonium trifluoromethane sulfonate Y-6: naphthoquinone diazide
5-sulfonic acid ester of pyrogallol/acetone resin (esterification
ratio: 20%)
[0130] Among solubility-suppressing agents, the onium salt has a
photosensitivity by itself, and accordingly, the amount was
controlled so that the absorbance at the same wavelength would not
be excessive.
[0131] According to the present invention, it is possible to
provide a positive photosensitive composition which has an
excellent sensitivity characteristic particularly to a near
infrared laser beam, which requires no post heat treatment and
makes the operation under white light possible and which has a very
simple structure; and a positive photosensitive lithographic
printing plate and a method for making a positive photosensitive
lithographic printing plate, employing such a composition.
* * * * *