Lithographic printing plate precursor

Details Lithographic printing plate precursor Lithographic printing plate precursor

2003-02-24

2004-09-21

Gilliam, Barbara (Department: 1752)

Radiation imagery chemistry: process, composition, or product th

Microcapsule, process, composition, or product

C430S270100, C430S271100

Reexamination Certificate

active

06794104

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a lithographic printing plate precursor having a hydrophilic layer and an image-forming layer on a support, which can be on-press developed after scan exposure based on digital signals and ensures a long press life and less printing stain.
BACKGROUND OF THE INVENTION
The lithographic printing plate in general consists of a hydrophobic (ink-receptive) image area of repelling a fountain solution and accepting ink in the printing process and a hydrophilic image area of accepting the fountain solution. Such a lithographic printing plate has been heretofore manufactured by mask-exposing a PS plate comprising a hydrophilic support having provided thereon an ink-receptive photosensitive resin layer, through a lith film and then dissolving and thereby removing the photosensitive resin layer in the non-image area with a developer.
In recent years, a digitization technique of electronically processing, storing and outputting image information using a computer has been widespread, as a result, a computer-to-plate (CTP) technique of directly forming an image on a lithographic printing plate precursor without using a lith film by scanning high directivity light such as laser light based on digitized image information has been developed.
On the other hand, in the conventional production of a printing plate using a PS plate, a step of dissolving and removing the non-image area after exposure is indispensable and moreover, an after-treatment step of washing the developed printing plate with water or treating it with a rinsing solution containing a surfactant or with a desensitizing solution containing gum arabi, starch derivative or the like is usually necessary. These additive wet treatments are cumbersome and particularly in consideration of global environment recently arising as a great concern, improvement thereof is another matter to be solved in conventional techniques.
Under these circumstances, a simple and dry treatment or no treatment is more strongly demanded from both the environmental aspect and the aspect of more streamlining the process accompanying the digitization. In other words, a printing plate precursor for CTP system, which can be used as it is for printing without passing a wet treatment after the recording of an image, is being demanded.
As one of the methods for dispensing with the treatment step, a method called on-press development is known, where an exposed printing plate precursor is fixed on a cylinder of a press and a fountain solution and/or an ink are supplied while rotating the cylinder, thereby removing the non-image area in the image-forming layer of the printing plate precursor. Namely, this is a system of fixing a printing plate precursor as it is on a press after exposure and completing the treatment during the normal printing preparatory process.
With respect to such a lithographic printing plate precursor for CTP suitable for on-press development, for example, Japanese Patent 2,938,397 describes a lithographic printing plate where a photosensitive layer comprising a hydrophilic binder polymer having dispersed therein thermoplastic hydrophobic polymer fine particles is provided on a hydrophilic substrate. In this patent publication, it is stated that the on-press development can be performed by exposing the lithographic printing plate with an infrared laser to cause combination of the thermoplastic hydrophobic polymer fine particles due to heat and thereby form an image, then fixing the plate on a plate cylinder of a press, and supplying a fountain solution and/or an ink.
Also, JP-A-2001-162961 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) describes a heat-sensitive lithographic printing plate precursor comprising a support having thereon a hydrophilic layer for forming an image, the hydrophilic layer comprising a hydrophilic binder polymer and a microcapsule enclosing hydrophobic components, and states that this printing plate precursor can be on-press developed.
JP-A-2001-205952 describes a lithographic printing plate precursor where a hydrophilic layer comprising a heat reactive compound is provided on a support and a heat-sensitive layer comprising a compound as the other party for the reaction of the heat reactive compound is further provided on the hydrophilic layer. In this lithographic printing plate precursor, the hydrophilic layer and the heat-sensitive layer undergo a chemical reaction when heated and are bound and therefore, the press life is improved.
However, lithographic printing plate precursors by conventional techniques are still insufficient in the printing performance such as staining resistance or press life.
SUMMARY OF THE INVENTION
An object of the present invention is to solve these problems, that is, to provide a lithographic printing plate precursor having good on-press developability, more improved in the staining resistance at printing, and ensuring sufficiently high strength of fine dot or line and a long press life.
(1) A lithographic printing plate precursor comprising a water-resistant support, a hydrophilic layer and an image-forming layer, in this order, said hydrophilic layer comprising a fine particulate hydrophobicizing precursor and a hydrophilic binder polymer, and said image forming layer comprising a light-heat converting substance and a microcapsule encapsulating a hydrophobic substance, wherein the hydrophilic binder polymer is a composite material of a hydrophilic organic polymer and a polymer having a group including: at least one atom selected from a metal atom and semimetal atom; and an oxygen atom connecting with the at least one atom selected from a metal atom and semimetal atom.
(2) The lithographic printing plate precursor as described in the item (1), wherein the hydrophilic organic polymer is (A) a hydrophilic organic polymer having a group capable of forming a hydrogen bond with the polymer having a group including: at least one atom selected from a metal atom and semimetal atom; and an oxygen atom connecting with the at least one atom selected from a metal atom and semimetal atom.
(3) The lithographic printing plate precursor as described in the item (1), wherein the hydrophilic organic polymer is (B) a hydrophilic organic polymer having a silane coupling group at the terminal, represented by the following formula (I):
wherein R
01
, R
02
, R
03
and R
04
each independently represents a hydrogen atom or a hydrocarbon group having from 1 to 8 carbon atoms, m represents 0, 1 or 2, n represents an integer of 1 to 8, L represents a single bond or an organic linking group, W represents —NHCOR
05
, —CONH
2
, —CON(R
05
)
2
, —COR
05
, —OH, —CO
2
M or —SO
3
M, and R
05
represents an alkyl group having from 1 to 8 carbon atoms, M represents a hydrogen atom, an alkali metal, an alkaline earth metal or an onium.
(4) The lithographic printing plate precursor as described in the item (1), which further comprises a surface graft hydrophilic layer on the hydrophilic layer, the surface graft hydrophilic layer comprising a polymer compound having a hydrophilic functional group, wherein the polymer compound is chemically bonded to the surface of the hydrophilic layer.
(5) The lithographic printing plate precursor as described in the item (4), wherein the polymer compound having a hydrophilic functional group is a linear polymer compound chemically bonded at the terminal of the polymer compound chain to the hydrophilic layer directly or through another binding polymer compound chemically bonded to the hydrophilic layer.
(6) The lithographic printing plate precursor as described in the item (1), wherein the polymer having a group including: at least one atom selected from a metal atom and semimetal atom; and an oxygen atom connecting with the at least one atom selected from a metal atom and semimetal atom is a polymer obtained by the hydrolytic polycondensation of at least one compound represented by the following formula (II):
(R
0
)
k
M
0
(Y)
z-k
wherein R
0
represents a hydrogen atom, a hydrocarbon group or a

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