Processing-free type lithographic printing plate material

A processing-free lithographic printing plate, which comprises a support having deposited thereon a composition containing germanium and sulfur and at least one of a metal or metal compound in a physically mixed state.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a processing-free type lithographic 
printing plate material and, more particularly, to a processing-free type 
lithographic printing plate material which can be mounted, after exposure, 
on a printing press without any processing to conduct printing. In this 
specification, both the material for preparing a lithographic printing 
plate and the lithographic printing press plate prepared from the material 
are called "lithographic printing plate," for simplicity and as is common 
in the art. 
2. Description of the Prior Art 
Heretofore, as lithographic printing plates, those which are called 
deep-etch plates and PS (presensitized) plates have enjoyed the most 
popularlity. Deep-etch plates are obtained by coating a negative type 
light-sensitive resin on a grained Al or Zn plate and printing thereon a 
positive original. After development-processing, the plate is etched or a 
tincture applied thereto without etching, and then, after applying thereto 
a lacquer, removing the light-sensitive resin layer hardened by exposure. 
On the other hand, PS plates have a constitution in which a 
light-sensitive resin is coated mainly on an aluminum plate. Press plates 
can be prepared therefrom by printing thereon a positive or negative 
original and, after development processing, applying a developing ink or a 
protective lacquer to the hardened light-sensitive resin layer 
constituting image areas. As is described above, PS plates have the 
advantage in that several processing steps can be omitted in obtaining 
press plates as compared with deep-etch plates. However, a developing step 
and the like are still required. 
Processing-free type lithographic printing plates have been suggested which 
enable the processing steps of lithographic printing plates after exposure 
to be omitted and printing to be conducted by directly mounting the 
exposed plates on a printing press without any chemical processings. In 
this specification, the term "processing-free" is used in the 
above-described sense. U.S. Pat. No. 3,650,743 describes this type of 
lithographic plates in detail. According to the disclosure, the process 
for preparing a lithographic printing plate involves using an 
electromagnetic radiation-respondent member having a three-layered 
structure (each layer being intimately adhered to each other) comprising a 
metallic first layer, a second layer of a material capable of reacting, 
upon being exposed, with the first layer to form a mutual reaction 
product, and a third layer of a material which does not react with the 
second layer. The process comprises exposing the second layer to an image 
using electromagnetic radiation through the first or third layer to 
thereby selectively form the mutual reaction product, thus imparting to 
the areas where the reaction product is formed a 
hydrophilicity-to-oleophilicity relationship different from that at the 
remaining unreacted areas. 
In this process, the light-sensitive layer of the light-sensitive material 
to be used has a two-layered structure comprising a first layer and a 
second layer, as disclosed above, and extremely toxic materials such as 
arsenic trisulfide, arsenic pentasulfide, etc., are used as a 
light-sensitive element. Therefore, this lithographic printing plate can 
not be said to be desirable due to the toxicity of the materials used and 
the multi-layered structure. 
SUMMARY OF THE INVENTION 
As a result of extensive investigations on processing-free type 
lithographic printing plates, a processing-free type lithographic printing 
plate which is different from the above-described conventional 
lithographic printing plates, which solves various problems encountered 
with conventional lithographic printing plates, and which possesses 
excellent properties as compared with processing-free type lithographic 
plate using an arsenic-containing compound has been developed. 
That is, the present invention provides a processing-free type lithographic 
printing plate (material) which comprises a base plate having deposited 
thereon a composition containing germanium and sulfur and at least one of 
a metal or a metal compound in a physically mixed state. 
DETAILED DESCRIPTION OF THE INVENTION 
In comparison with the lithographic printing plate described in U.S. Pat. 
No. 3,650,743, the processing-free type lithographic printing plate of the 
present invention is greatly different therefrom in the following various 
aspects. That is, although both this invention and the disclosure of U.S. 
Pat. No. 3,650,743 relate to processing-free type lithographic printing 
plates, that of the United States Patent uses a three-layered, 
radiation-respondent member as described above, whereas, in that of the 
present invention, the respective components of the light-sensitive layer 
are deposited onto a base plate in a physically mixed state and not in a 
multi-layered state. Also, as to the components of the light-sensitive 
layer, that of the United States Patent uses a metal and arsenic 
trisulfide or arsenic pentasulfide, while the present invention uses a 
metal and a composition containing germanium and sulfur. Furthermore, with 
the United States Patent plate, the light sensitivity desired to prepare a 
radiation-respondent member is obtained by bringing a metal into contact 
with arsenic trisulfide or arsenic pentasulfide, while, in the present 
invention, the germanium- and sulfur-containing composition itself is 
light-sensitive and a metal is used to improve printability additionally. 
Thus, each component exhibits an absolutely different function in both 
plates. 
These differences will become clearer from the detailed description of the 
present invention to be given hereinafter. In particular, it is to be 
emphasized that, as compared with arsenic trisulfide or arsenic 
pentasulfide used in the United States Patent, the composition containing 
germanium and sulfur of this invention is much superior in the prevention 
of toxic pollution and exhibits quite excellent physical and chemical 
properties. In particular, it is greatly significant in the completion of 
the present invention that the composition containing germanium and sulfur 
has a greater hydrophilicity. 
The present invention is described in detail below. 
First, the base plate to be used in the present invention is a base plate 
having a hydrophilic surface and a suitable rigidity, and includes all of 
those plates which have been used as base plates for conventional 
lithographic printing plates or which have the possibility to be used as a 
base plate. For example, a metal plate, a synthetic resin sheet whose 
surface has been rendered hydrophilic, a laminate of a metal plate or 
metal foil and a synthetic resin sheet or paper and the like can be used 
as a base plate. 
An Al plate and a Zn plate are usually used as a metal plate. However, the 
so-called multi-layer plates which include a bimetal plate comprising an 
aluminum plate having a copper or chromium layer or comprising a copper 
plate having a chromium layer, a trimetal plate comprising a steel plate 
having a copper layer and a chromium layer, an aluminum clad plate 
comprising an aluminum alloy plate having a pure aluminum layer, a 
laminate of a plastic sheet or paper and an aluminum foil and the like, 
can also be used. In the case of using these metal plates, graining is 
preferably employed so as to improve water-retaining properties and the 
intimate adhesion between the metal plate and the composition containing 
germanium and sulfur. Chemical or electrical treatment of the grained 
surface, if necessary, has also been conducted with conventional PS 
plates, and the like. In particular, with Al plates, such a treatment has 
generally been conducted to form an alumite layer on the grained surface 
through anodic oxidation as disclosed in U.S. Pat. Nos. 2,115,339, 
2,119,031, 3,280,734, and 3,511,661. Further, it is possible to further 
improve the adaptability as a lithographic printing plate by processing 
the surface with a suitable acid or alkali. Sulfuric acid, phosphoric 
acid, oxalic acid, and the like can be used as the electrolytic solution 
for conducting the anodic oxidation of the Al plate. Treatments such as 
graining an Al plate and laying a porous chromium plating on the surface 
thereof can also be conducted. The thus-prepared base plates can also be 
utilized. 
Examples of synthetic resin sheets whose surface has been rendered 
hydrophilic are a cellulose triacetate sheet whose surface has been 
saponified to render the surface hydrophilic, and a synthetic resin sheet 
such as a sheet of polyethylene terephthalate, polyvinyl chloride, 
polycarbonate, polystyrene or polypropylene having a hydrophilic layer 
coated on the surface thereof. 
In utilizing a metallic surface, it is not necessary to use a completely 
metallic base plate, and it is possible to partly replace the mechanical 
strength of the plate with suitable synthetic resins or paper. It is 
possible to utilize a composite sheet prepared by laminating a metallic 
layer and a synthetic resin sheet or paper. 
A composition containing germanium and sulfur, which is one of the most 
characteristic aspects of the present invention, is obtained using as the 
starting materials, germanium, sulfur and, if desired, other elements or 
compounds in a predetermined atomic ratio, sealing them in a quartz vessel 
under a reduced pressure of about 10.sup.-2 to 10.sup.-7 Torr, 
heat-melting at the temperature of about 500.degree. to about 
1,300.degree. C., and stirring for a long period of time to make the melt 
uniform, then quenching the melt by immersion into water or taking out the 
melt into air at the cooling rate of about 0.1 to about 100.degree. 
C./sec. Needless to say, not only simple substances of germanium and 
sulfur but also germanium sulfide which is a compound of both of the 
elemental substances can be used. 
Therefore, the Ge-S composition of the present invention can be devided 
into the main three classes of Ge-S, Ge-S-X and Ge-S-X-Y and the ratio of 
Ge and S components in the composition is within 1 .ltoreq. S/Ge &lt; 16, 
preferably 1 .ltoreq. S/Ge &lt; 9. The components of X and Y is effective in 
controlling the reactivity against the metal layer, the chemical and 
thermal stability and the physical strength and the hydrophilic and 
oleophilic properties of a physically mixed layer of the composition. The 
specific examples of the components X and Y include metallic elements such 
as Al, Mg, Ti, V, Mn, Co, Ni, Mo, W, Sn, Zn, Pb, Ag, Pd, In, K, As or the 
like, semi-metallic elements such as Sb, Si, Bi, Se, Te or the like and 
non-metallic elements such as O, P, I or the like. These components are 
selected as non- or less toxic components in view of the production of 
printing plates without causing any pollutions. 
Specific examples of compositions containing germanium and sulfur usable in 
the present invention are illustrated below. 
Ge-S System 
GeS, GeS.sub.15, Ge.sub.35 S.sub.65, GeS.sub.2, GeS.sub.4, Ge.sub.15 
S.sub.85 
Ge-S-X System 
Ge.sub.35 S.sub.60 Al.sub.5 (amorphous substance), Ge.sub.35 S.sub.60 
P.sub.5 (crystalline substance), Ge.sub.35 S.sub.60 Sb.sub.5 (amorphous 
substance), Ge.sub.35 S.sub.60 Si.sub.5 (amorphous), Ge.sub.35 S.sub.60 
Mg.sub.5 (amorphous substance + crystalline), Ge.sub.35 S.sub.60 Ti.sub.5 
(amorphous substance + GeS.sub.2 + TiS.sub.2), Ge.sub.35 S.sub.60 V.sub.5 
(amorphous substance + GeS.sub.2 + V.sub.2 S.sub.3), Ge.sub.35 S.sub.60 
Mn.sub.5 (amorphous substance + Mn.sub.2 GeS.sub.4), Ge.sub.35 S.sub.60 
Co.sub.5 (amorphous substance + GeS.sub.2), Ge.sub.35 S.sub.60 Ni.sub.5 
(amorphous substance + GeS.sub.2), Ge.sub.35 S.sub.60 Ta.sub.5 (amorphous 
substance + TaS.sub.2), Ge.sub.35 S.sub.60 Mo.sub.5 (amorphous substance + 
MoS.sub.2), Ge.sub.35 S.sub.60 W.sub.5 (amorphous substance + WS.sub.2 + 
crystalline), Ge.sub.35 S.sub.60 Sn.sub.5 (amorphous substance + 
.beta.-SnS.sub.2 or .alpha.-Sn.sub.1 + xS.sub.2), Ge.sub.35 S.sub.60 
Zn.sub.5 (amorphous substance + ZnS), Ge.sub.35 S.sub.60 Pb.sub.5 
(amorphous substance + GeS.sub.2), Ge.sub.25 S.sub.70 Bi.sub.5 (amorphous 
substance), Ge.sub.20 S.sub.70 Bi.sub.10 (amorphous substance), Ge.sub.10 
S.sub.70 Bi.sub.20 (amorphous substance), Ge.sub.20 S.sub.80 Bi.sub.10 
(amorphous substance), Ge.sub.40 S.sub.60 Bi.sub.1 (amorphous substance), 
Ge.sub.5 S.sub.80 Bi.sub.15 (amorphous substance), Ge.sub.35 S.sub.60 
Bi.sub. 10 (amorphous substance + Bi), Ge.sub.35 S.sub.60 Bi.sub.15 
(amorphous substance + Bi), Ge.sub.40 S.sub.60 Bi.sub.5 (amorphous 
substance + Bi), Ge.sub.40 S.sub.60 Bi.sub.10 (amorphous substance + Bi), 
Ge.sub.35 S.sub.60 Bi.sub.2 (amorphous substance + Bi), Ge.sub.38.46 
S.sub.61.54 Bi.sub.5 (amorphous substance + Bi), Ge.sub.37.74 S.sub.62.26 
Bi.sub.5 (amorphous substance + Bi), Ge.sub.31.3 S.sub.68.7 Bi.sub.5 
(amorphous substance + GeS.sub.2), Ge.sub.20 S.sub.60 Bi.sub.20 (amorphous 
substance + GeS.sub.2), Ge.sub.10 S.sub.60 Bi.sub.30 (amorphous substance 
+ Bi.sub.2 S.sub.3), Ge.sub.40 S.sub.60 Bi.sub.15 (amorphous substance + 
Bi + GeS.sub.2), Ge.sub.10 S.sub.50 Bi.sub.40 (amorphous substance + Bi + 
Bi.sub.2 S.sub.3), Ge.sub.35 S.sub.60 Bi.sub.5 (amorphous substance + Bi + 
GeS.sub.2 + GeS), Ge.sub.35 S.sub.65 Bi.sub.5 (amorphous substance + Bi + 
GeS.sub.2 + GeS), Ge.sub. 33.3 S.sub.66.7 Bi.sub.15 (amorphous substance + 
Bi + GeS.sub.2 + GeS), Ge.sub.20 S.sub.50 Bi.sub.30 (amorphous substance + 
Bi + GeS.sub.2 + Bi.sub.2 S.sub.3), Ge.sub.45 S.sub.50 Bi.sub.5 (GeS + 
Bi), Ge.sub.20 S.sub.80 O.sub.0.2, Ge.sub.20 S.sub.80 O.sub.20, Ge.sub.42 
S.sub.58 Ag.sub.0.1, Ge.sub.42 S.sub.58 Ag.sub.2, Ge.sub.36 S.sub.55 
I.sub.9, Ge.sub.35 S.sub.60 Al.sub.15, Ge.sub.20 S.sub.75 Al.sub.5, 
Ge.sub.30 S.sub.60 P.sub.10, Ge.sub.30 S.sub.60 Sb.sub.10, Ge.sub.25 
S.sub.50 Sb.sub.25 
Ge-S-X-Y System 
Ge.sub.25 Si.sub.10 S.sub.60 Bi.sub.5 (amorphous substance + Bi), Ge.sub.30 
Si.sub.5 S.sub.60 Bi.sub.5 (amorphous substance + Bi + GeS.sub.2), 
Ge.sub.20 Si.sub.15 S.sub.60 Bi.sub.5 (amorphous substance + Bi + 
SiS.sub.2), Ge.sub.15 Si.sub.20 S.sub.60 Bi.sub.5 (amorphous substance + 
Bi + SiS.sub.2), Ge.sub.10 Si.sub.25 S.sub.60 Bi.sub.5 (amorphous 
substance + Bi + SiS.sub.2 + Bi.sub.2 S.sub.3 + GeS.sub.2), Ge.sub.33 
S.sub.57 Bi.sub.5 Ag.sub.5 (amorphous substance + Bi), Ge.sub.30 S.sub.60 
Bi.sub.5 Ag.sub.5 (amorphous substance + Bi + GeS.sub.2 + GeS), Ge.sub.34 
S.sub.59 Bi.sub.5 Ag.sub.2 (amorphous substance + Bi + GeS.sub.2 + GeS), 
Ge.sub.33 S.sub.57 Bi.sub.5 O.sub.5 (amorphous substance + Bi), Ge.sub.20 
S.sub.80 P.sub.10 O.sub.2, Ge.sub.20 S.sub.80 P.sub.10 O.sub.20, Ge.sub.20 
S.sub.60 Sb.sub.5 P.sub. 5, Ge.sub.15 S.sub.70 Sb.sub.7.5 P.sub.7.5, 
Ge.sub.10 S.sub.80 P.sub.10 Pb.sub.0.5, Ge.sub.10 S.sub.80 P.sub.10 
Pd.sub.5, Ge.sub.10 S.sub.80 P.sub.10 Bi.sub.10, Ge.sub.35 S.sub.60 
P.sub.5 Bi.sub.5, Ge.sub.35 S.sub.60 Bi.sub.5 I.sub.5 
In the above-described examples, the subscript numerals represent the 
composition ratios in terms of the atomic ratios of the starting 
materials. Some of them are not normalized, and hence the sum of the 
subscript numerals sometimes exceeds 100. Compositions containing oxygen 
are prepared by melting as the oxides. The parenthetical descriptions 
qualitatively represent the results obtained by X-ray analysis of the 
compositions. All of them are not amorphous solids called chalcogenide 
glasses, but some compositions contain crystalline substances. The 
lithographic printing plate of the present invention can also be obtained 
using such compositions. 
Lithographic printing plates prepared by vacuum-evaporating the composition 
containing germanium and sulfur, for example, on a grained Al plate 
provides, when exposed and provided with damping water, a negative or 
positive image, to which a protective ink is applied. For example, 
GeS.sub.1.5, GeS.sub.2, GeS.sub.4, GeS.sub.5.67, Ge.sub.35 S.sub.60 
Bi.sub.5, Ge.sub.42 S.sub.58 Ag.sub.2, etc., provide positive type images, 
whereas Ge.sub.15 S.sub.70 S.sub.67.5 P.sub.7.5, Ge.sub.30 S.sub.60 
Sb.sub.5 P.sub.5, etc., provide negative type images. However, since the 
compositions containing Ge and S become more hydrophilic upon being 
irradiated with light, many of them provide positive type images. Also, 
the composition becomes more oleophilic as the amount of sulfur in the 
composition increases. 
Images obtained using a single layer of the composition containing 
germanium and sulfur are a slightly indistinct and, when printing is 
conducted using them, the durability thereof is so low that they are not 
so practical. As a result of various experiments and investigations to 
remove this defect, it has been found that a processing-free type 
lithographic printing plate having an extremely excellent resolving power 
and a practical durability can be obtained using at least one metal and/or 
one metal compound in a physically mixed state in the composition. This 
will be described in detail below. 
(1) Use of a Metal in a Physically Mixed State in the Composition 
Metal was vacuum-evaporated onto a grained Al plate in an average amount of 
0.085 to 4.0 .mu.g/cm.sup.2, followed by vacuum-evaporating thereon 
Ge.sub.35 S.sub.60 Bi.sub.5 in an average amount of 2.0 to 2.5 
.mu.g/cm.sup.2. When the characteristics of the resulting samples were 
examined, they all showed positive type light-sensitive characteristics. 
That is, an oily ink adhered to the unexposed areas to form image areas, 
whereas the exposed areas became hydrophilic and formed non-image areas 
where ink did not adhere. The degrees of hydrophilicity and oleophilicity 
vary considerably depending upon the kind of metal employed. Examples of 
metals capable of increasing the oleophilicity as compared with the case 
of depositing Ge.sub.35 S.sub.60 Bi.sub.5 alone are copper, silver, gold, 
aluminium, gallium, indium, tin, vanadium, selenium, chromium, iron, 
magnesium, germanium, bismuth, manganese, cobalt, nickel, thallium, 
antimony, lead, tellurium, or palladium. Of these, Cu, Ag, Al, In, Sn and 
Cr increase the oleophilicity to a great extent, Au, Ga, Ge, V and Fe 
increase the oleophilicity considerably and Se increases the oleophilicity 
slightly. On the other hand, examples of metals capable of increasing the 
hydrophilicity as compared with the case of using Ge.sub.35 S.sub.60 
Bi.sub.5 alone are Mg, Bi, Mn, Co and Ni. Of these, Mn, Co and Ni 
increases the hydrophilicity to a great extent and Mg and Bi increase the 
hydrophilicity slightly. Also, examples of metals which produce almost no 
difference in hydrophilicity and oleophilicity as compared with the case 
of using Ge.sub.35 S.sub.60 Bi.sub.5 alone are Cd, Tl, Sb, Te and Pd. 
Furthermore, good results were obtained with Cu, Al, Au and Sn when the 
composition containing germanium and sulfur was vacuum-evaporated onto a 
grained Al plate and these metals were vacuum-evaporated thereon, followed 
by conducting printing. 
Good results were obtained with samples prepared by vacuum-evaporating 
Ge.sub.35 S.sub.60 Bi.sub.5 onto a grained Al plate in an amount of 2.4 
.mu.g/cm.sup.2 and then vacuum-evaporating Cu in a deposited amount of 1.0 
.mu.g/cm.sup.2. 
Good results were obtained with samples prepared by vacuum-evaporating 
Ge.sub.35 S.sub.60 P.sub.5 onto a grained Al plate in a deposited amount 
of 2.4 .mu.g/cm.sup.2 and vacuum-evaporating aluminum in an amount of 0.14 
.mu.g/cm.sup.2 or vacuum-evaporating Sn in a deposited amount of 0.18 
.mu.g/cm.sup.2. 
From these results, it is demonstrated that similar results can be obtained 
either by first vacuum-evaporating a metal or by vacuum-evaporating a 
metal after vacuum-evaporating the composition containing germanium and 
sulfur. This is an extremely interesting fact and is one aspect of the 
present invention, which is one proof of the fact that the metal and the 
composition are present in a physically mixed state. 
With some metals, the degree of hydrophilicity or oleophilicity varies also 
depending upon the amount deposited by vacuum evaporation. For example, 
with Ag, the hydrophilicity is increased when the deposited amount is 2 
.mu.g/cm.sup.2 as compared with the case when the Ag is vacuum-evaporated 
in a deposited amount of 0.5 .mu.g/cm.sup.2. Also, with Cd and Sb, an 
increase in the deposition amount leads to an increase in the 
oleophilicity. That is, it is clear from the above-described results that, 
when one metal is present in a physically mixed state in the composition 
containing germanium and sulfur, the hydrophilic or oleophilic surface 
characteristic varies depending upon the kind and the vacuum-evaporated 
amount of the metal. From these results, it is possible to optionally 
adjust the surface characteristics by vacuum-evaporating two or more 
metals in a suitable amount to allow both metals to be present in a 
physically mixed state. Thus, the scope of the compositions containing 
germanium and sulfur usable as a lithographic printing plate can be 
expanded, which is extremely effective. 
(2) Use of a Metal Compound in a Physically Mixed State in the Composition 
Metal compounds which can be used are metal halides such as PbI.sub.2, 
CuCl, CuI, TeCl.sub.4, HgI and AgI, metal sulfides such as Ag.sub.2 S, 
PbS, SnS, BiS, FeS, Fe.sub.2 S.sub.3, CdS and ZnS, and metal oxides such 
as V.sub.2 O.sub.5, MoO.sub.3, Ge.sub.2 O.sub.3, Bi.sub.2 O.sub.3, 
TiO.sub.2, PbO and TeO.sub.2. 
In the same manner as with metals, the metal compound was vacuum-evaporated 
on a grained Al plate in an average deposited amount of 0.15 to 0.45 
.mu.g/cm.sup.2 and Ge.sub.35 S.sub.60 Bi.sub.5 was vacuum-evaporated in an 
average deposited amount of 1.8 .mu.g/cm.sup.2 to examine the 
characteristics. Almost all of the thus-obtained light-sensitive surfaces 
comprising Ge.sub.35 S.sub.60 Bi.sub.5 and metal compounds exhibited 
positive type light-sensitive characteristics. As with the case of using 
metals, the degree of hydrophilicity or oleophilicity varies considerably 
depending upon the kind of the metal compound. Metal compounds capable of 
increasing the oleophilicity as compared with the case of using Ge.sub.35 
S.sub.60 Bi.sub.5 alone are CuI, AgI, FeS and TeO.sub.2 and metal 
compounds capable of increasing the oleophilicity or causing almost no 
change as compared with the case of using Ge.sub.35 S.sub.60 Bi.sub.5 
alone are CuCl, TeCl.sub.4, Ag.sub.2 S, PbS, CdS, ZnS, V.sub.2 O.sub.5, 
Ge.sub.2 O.sub.3, BiO.sub.3, PbO, etc. Also, metal compounds capable of 
increasing the hydrophilicity as compared with the case of using Ge.sub.35 
S.sub.60 Bi.sub.5 alone are PbI.sub.2, BiS, MoO.sub.3, TiO.sub.2, etc. 
Although it is not certain in vacuum-evaporating these metal compounds 
whether the vacuum-evaporated product has the same composition as the 
starting material or not, a vacuum evaporation monitor definitely shows 
that some substance is vacuum-evaporated, and the property which the 
vacuum-evaporated surface has is sufficiently reproducible when vacuum 
evaporation is conducted under the same conditions. 
Additionally, it has also been experimentally determined that, when SnS and 
Fe.sub.2 S.sub.3 are vacuum-evaporated, the light-sensitive characteristic 
changes from a positive type to a negative type as the exposure time is 
prolonged. The reason for this phenomenon is not completely clear. 
As is clear from the above-described results, when one metal compound is 
present in a physically mixed state in the composition containing 
germanium and sulfur, the hydrophilic or oleophilic surface characteristic 
can be changed by selecting the kind of metal compound employed. 
Therefore, it is possible to optionally adjust the surface characteristics 
by vacuum-evaporating two or more metal compounds in a suitable amount so 
that they are present in a physically mixed state. Thus, the scope of the 
compositions containing germanium and sulfur usable as a lithographic 
printing plate can be expanded in the same manner as with metals, which is 
also extremely effective. Needless to say, it is also possible to 
optionally adjust the surface characteristics by vacuum-evaporating a 
single metal compound in a suitable amount. Thus, the present invention is 
quite effective in the control of the surface characteristics which it 
provides. 
As has already been described, an extremely excellent resolving power and a 
sufficiently practical durability can be obtained and the surface 
characteristics can be adjusted as desired using the composition 
containing germanium and sulfur in a physically mixed state with at least 
one metal and/or one metal compound, which are extremely important in the 
practice of the present invention. 
As has already been also described, in order to obtain the processing-free 
type lithographic printing plate of the present invention, (1) a 
composition containing germanium and sulfur and (2) at least one of a 
metal and a metal compound are deposited onto the above-described base 
plate in a physically mixed state. The term "physically mixed state" as 
used herein does not mean the state where both ingredients form complete 
films or layers on a base plate in a superposed disposition but rather 
means the microscopic condition in which there are areas where the surface 
of the base plate is uncovered, areas of the composition containing 
germanium and sulfur, areas of a metal or a metal compound, and areas 
where the composition containing germanium and sulfur and a metal or metal 
compound are superimposedly deposited, on the surface of the base plate. 
Therefore, the necessary condition for forming such a surface condition is 
to form on the base plate discontinuous areas of the composition 
containing germanium and sulfur and of a metal or a metal compound without 
forming completely continuous layers of the composition and a metal or a 
metal compound. When irregular unevenness exists on the base plate as with 
a grained Al plate, the surface condition appears to be more complicated. 
However, the reproducibility of the printing properties of surfaces 
obtained by forming a light-sensitive film under definite conditions has 
been confirmed. It is supposed that, within the scope of resolving power 
required in printing, a statisticly stable microscopic surface can be 
obtained. 
Suitable processes for forming the physically mixed state include a process 
of using a certain kind of mask superimposed on a base plate. For example, 
a stainless steel mesh screen is superposed on a grained Al plate and a 
composition containing germanium and sulfur is vacuum-evaporated thereon 
not in a film state but in a discontinuous state. Then, a mesh screen is 
superposed thereon and a metal or a metal compound is vacuum-evaporated 
thereon. In this case, upon vacuum-evaporating a metal or a metal 
compound, a mesh screen is superposed in such a manner that not all of the 
metal or metal compound to be vacuum-evaporated is deposited on the 
above-described already vacuum-evaporated composition and that all of the 
metal or metal compound is not vacuum-evaporated only onto the surface of 
the base plate not covered by the above-described composition. In this 
case, the printing property of the surface changes, in some cases, 
depending upon the area of portions where the composition containing 
germanium and sulfur and the metal or metal compound are superposed over 
each other. Therefore, mesh screens having a different screen pitch of the 
screen mesh or a different size of the openings can be used for 
vacuum-evaporating the composition containing germanium and sulfur and 
vacuum-evaporating the metal or metal compound. Also, masks having regular 
openings such as a mesh screen need not necessarily be used, and masks 
having irregular openings such as a grained screen can also be used. 
However, in the case of depositing the composition containing germanium 
and sulfur and the metal or the metal compound in this manner, it is 
impossible to increase the resolving power higher than the screen pitch of 
the openings of the mask. Therefore, masks having quite small openings and 
pitches must be used. Thus, unavoidably some equipment limits do exist 
with respect to the resolving power attainable. However, these limits are 
due to the equipment presently available and not due to the invention per 
se. 
It has become clear that, in the thus-prepared lithographic printing 
plates, there are, for example, areas of the grained surface of an Al 
plate, areas of the composition containing germanium and sulfur, areas of 
a metal or a metal compound and areas where a metal or a metal compound 
and the composition containing germanium and sulfur are superposed over 
each other, in a physically mixed state in certain area ratios based on 
the total surface area, and that the surface characteristics with respect 
to hydrophilicity and oleophilicity are different depending upon the 
ratios, from the case of each ingredient independently forming a single 
separate layer. In addition, with a grained surface, water-retaining 
properties or surface area is considerably increased as compared with a 
smooth surface, resulting in a complicated phenomenon. It is surmised 
that, by irradiating such a surface with light, the surface 
characteristics with respect to hydrophilicity and oleophilicity change at 
the irradiated areas and are different from that of the non-irradiated 
areas to form the images of the lithographic printing plate. 
As is described above, in using masks, there are unavoidable equipment 
limits on resolving power. In order to increase the resolving power, each 
ingredient must be deposited in an isle-like pattern having a more minute 
pitch using some means of achieving such. As a result of experiments and 
investigations on this point, it has been discovered that a certain amount 
of the vacuum-evaporated substances corresponds to the formation of an 
isle-like pattern having an extremely minute pitch and that, when the 
composition containing germanium and sulfur and a metal or a metal 
compound are vacuum-evaporated in such amounts, a surface having extremely 
good printing properties can be obtained. The process of the formation of 
the vacuum-evaporated substances is so complicated that it is not yet 
completely understood. However, in recent years, vacuum-evaporated films 
have been extensively studied by means of an electron microscope. The 
process of the growth of vacuum-evaporated substances can be divided, in 
some cases, into (1) the step of the formation of nuclei and the 
development of the nuclei to particles, (2) the step of aggregation of the 
particles, and (3) the step of repetition of the aggregation to form a 
continuous film. For example, studies on the thickness of a 
vacuum-evaporated film of Au and the particle density thereof through 
observation of an electron microscopy have been reported, in which the 
description is that the particle density increases until the 
vacuum-evaporated amount becomes 0.6 .mu.g/cm.sup.2 and then the particle 
density decreases exponentially. This result can be interpreted as 
follows. That is, the formation of nuclei is predominant until the 
vacuum-evaporated amount becomes about 0.6 .mu.g/cm.sup.2, then 
aggregation becomes predominant. Also, the particle sizes are in a 
Gaussian distribution versus the vacuum-evaporated amount, with the 
particle size increasing as the vacuum-evaporated amount increases. Thus, 
the developing mechanism from formation of nuclei to the aggregation of 
particles can be understood. As one example of the particle size 
distribution, the maximum particle size in an Au thin film deposited in an 
amount of 1.0 .mu.g/cm.sup.2 is said to be 60 A to 80 A. Also, it is 
observed that, until the deposited amount becomes about 6 .mu.g/cm.sup.2, 
the particle size distribution is quite uniform, but the particle form 
becomes extremely irregular when the deposited amount becomes around 2.0 
.mu.g/cm.sup.2 and particles of a long-sized form increase in number, the 
longitudinal size of such particles becoming 2,000 to 3,000 A. When the 
electric resistance of a thin film of Ag, Cu, Al, etc., is measured, the 
resistance value sharply increase when the deposited amount becomes 32 to 
34 .mu.g/cm.sup.2. From this, it appears that many bridges are formed in 
the isle-like deposits at the stage where the deposited amount slightly 
exceeds the above-described amount. It is extremely difficult to generally 
describe the relationship between the deposited amount and the isle-like 
form. In particular, a completely different structure may result depending 
upon the kind, form and temperature of the underlying substance, gases 
adsorbed on the underlying substance, the degree of vacuum upon vacuum 
evaporation, and the vacuum-evaporating rate. However, it appears that, 
when the deposited amount is 8 .mu.g/cm.sup.2 or less, the vacuum 
evaporation is in the stage before aggregation of the particles and, until 
the deposited amount becomes 32 to 34 .mu.g/cm.sup.2, it is in the stage 
of aggregation and, when the deposited amount becomes 80 .mu./cm.sup.2 or 
higher, a continuous film is formed. However, this can be applied to a 
quite smooth surface and, with a surface having unevenness of not less 
than 1 .mu. such as a grained surface, the situation is considerably 
changed. However, as to the isle-like discontinuous film necessary in the 
present invention, it has become clear that a vacuum-evaporated film 
obtained by vacuum-evaporating in an amount even about 60 .mu.g/cm.sup.2 
or less provides sufficient effectiveness, the resolving power thereof 
being improved. 
In this specification, vacuum evaporation is mainly described as the 
process for depositing the above-described composition in a "physically 
mixed state." However, known processes for forming a thin film including a 
sputtering process, an ion-plating process, an electrodeposition process, 
an electrophoresis process, a gas phase precipitation process, a spraying 
process, and the like can be used as well as the vacuum-evaporating 
process. It is needless to say that the above-described embodiments of 
this invention can be obtained by employing any of these processes. 
The sputtering process and the ion-plating process are analogous to the 
vacuum-evaporating process, and are effective for producing the 
lithographic printing plate of the present invention. For example, in 
order to deposit a metal or a metal compound, a direct current sputtering 
process is suitable, whereas an alternating current sputtering process is 
suitable in order to deposit the composition containing germanium and 
sulfur. 
Additionally, a combination of the use of the above-described mask and a 
process such as vacuum evaporation can also provide good results. 
Next, the printing characteristics of the resulting light-sensitive plate 
of this invention are described in detail taking, as an example, the 
depositing of (1) a composition containing germanium and sulfur and (2) at 
least one of a metal and a metal compound in a physically mixed state 
using a vacuum-evaporating process. 
First, GeS.sub.1.5 and Ag were used as the composition containing germanium 
and sulfur and as the metal, respectively. GeS.sub.1.5 was deposited on a 
grained Al plate in an amount ranging from about 1 .mu.g/cm.sup.2 to about 
12 .mu.g/cm.sup.2 and then Ag was deposited thereon in an amount ranging 
from about 0.2 .mu.g/cm.sup.2 to about 5 .mu.g/cm.sup.2 using a 
vacuum-evaporating process. Examination of the printing properties of the 
thus-obtained lithographic printing plate materials revealed the following 
fact. That is, as to the amount of Ag deposited on the base Al plate after 
first depositing GeS.sub.1.5 thereon, absolutely no printing images or 
only extremely indistinct images were obtained when the amount of silver 
deposited exceeded about 2 .mu.g/cm.sup.2. Images with good quality were 
obtained when the amount of deposited silver was not more than about 2 
.mu.g/cm.sup.2. In this case, printing images can be formed even when the 
amount of deposited GeS.sub.1.5 was about 12 .mu.g/cm.sup.2. However, in 
order to form images with good quality, the amount of deposited 
GeS.sub.1.5 had to be not more than 6 .mu.g/cm.sup.2. Further, when 
GeS.sub.1.5 was deposited in a deposited amount of not more than about 1 
.mu.g/cm.sup.2, images were formed by depositing Ag in an amount of about 
1 .mu.g/cm.sup.2, but no images or images with an extremely poor quality 
were formed by depositing Ag in an amount of about 2 .mu.g/cm.sup.2. Also, 
when GeS.sub.1.5 was deposited in an amount of about 1.5 .mu.g/cm.sup.2, 
images were formed by depositing Ag in an amount of about 1 
.mu.g/cm.sup.2, but no images or images with extremely poor quality were 
formed by depositing Ag in an amount of about 2 .mu.g/cm.sup.2. Further, 
when GeS.sub.1.5 was deposited in an amount of about 2.5 .mu.g/cm.sup.2, 
somewhat good images were obtained by depositing Ag in an amount of about 
1 .mu.g/cm.sup.2, but the image quality was deteriorated when the amount 
of deposited Ag became about 2 .mu.g/cm.sup.2. In the case of depositing 
GeS.sub.1.5 in an amount of not more than about 3 .mu.g/cm.sup.2, images 
with good image quality were obtained by depositing Ag in an amount of not 
more than about 1 .mu.g/cm.sup.2. Additionally, in each of the 
above-described cases, all the images obtained were positive. 
Results with GeS.sub.2 and Ag obtained by conducting the same experiments 
are summarized as follows. That is, images with good image quality were 
obtained by depositing GeS.sub.2 in an amount of not more than about 3 
.mu.g/cm.sup.2. The suitable amount of Ag to be deposited decreased as the 
amount of deposited GeS.sub.2 decreased. As was the same as described 
above, when GeS.sub.2 was deposited in an amount of about 1.5 
.mu.g/cm.sup.2, good images were obtained by depositing Ag in an amount of 
about 1 .mu.g/cm.sup.2. All images obtained in these experiments were 
positive. 
Similar experiments were conducted with the combination of GeS.sub.4 and 
Ag. Extremely interesting results were obtained with respect to this 
combination. 
First, positive images were obtained when GeS.sub.4 was deposited in an 
amount of not more than about 1.8 .mu.g/cm.sup.2, whereas negative images 
were obtained when GeS.sub.4 was deposited in an amount of not less than 
about 2.4 .mu.g/cm.sup.2. This point is extremely interesting. In the 
region where positive images were formed, the amount of deposited Ag 
sufficient to obtain good images was slightly greater than in the 
foregoing two cases, for example, about 2 .mu.g/cm.sup.2. However, when 
the amount of deposited Ag exceeded about 3 .mu.g/cm.sup.2, no images were 
obtained. The range of the amount of deposited GeS.sub.4 where negative 
images were obtained is not less than about 2.4 .mu.g/cm.sup.2. When 
GeS.sub.4 was deposited in an amount of about 2.4 .mu.g/cm.sup.2, negative 
images were obtained although they were not so good and, when GeS.sub.4 
was deposited in an amount of not less than about 3 .mu.g/cm.sup.2, good 
images were obtained. As to the amount of Ag to be deposited in such a 
case, a fairly large amount serves to provide good images, with about 3 to 
4 .mu.g/cm.sup.2 being the best. When the amount of deposited Ag exceeded 
about 5 .mu.g/cm.sup.2, good images were not necessarily obtained. 
Another aspect of this system is that, in some cases, negative images are 
obtained by exposure for a short time whereas positive images result upon 
exposure for a long period of time. This is also quite interesting. 
With the system of a physically mixed layer of GeS.sub.5.67 and Ag, 
positive images were obtained by depositing GeS.sub.5.67 in an amount of 
not more than about 1.8 .mu.g/cm.sup.2 while negative images were obtained 
by depositing GeS.sub.5.67 in an amount greater than about 1.8 
.mu.g/cm.sup.2, as is the same as with the system of a physically mixed 
layer of GeS.sub.4 and Ag. In this system too, short time exposure 
provides negative images while long time exposure provides positive 
images. 
The system of Ge.sub.15 S.sub.70 Sb.sub.7.5 P.sub.7.5 and Ag is also 
interesting, which provides negative images in most cases. However, the 
relationship with the amount of deposited Ag is not so greatly different 
from the foregoing two systems. 
With the system of Ge.sub.35 S.sub.60 Bi.sub.5 and Ag, interesting results 
as follows were observed. That is, good positive images were obtained when 
Ge.sub.35 S.sub.60 Bi.sub.5 was deposited in an amount ranging from about 
1.8 to 6 .mu.g/cm.sup.2 and Ag was deposited in an amount of not more than 
about 1 .mu.g/cm.sup.2. When the Ag film was thicker than this, short time 
exposure provided positive images while long time exposure provided 
negative type images. 
As is seen in the above-described examples, it is apparent that a 
significant relationship exists between the property of the 
light-sensitive surface and the deposited amount of materials forming the 
surface, the light-sensitive surface being obtained with the composition 
of the invention containing germanium and sulfur and at least one of a 
metal and a metal compound in a physically mixed state. This will be 
summarized below with reference to the formation of negative or positive 
images. 
(1) The kind of the composition containing germanium and sulfur and the 
deposition ratio of the composition to the metal or metal compound 
determines whether the resulting images are negative or positive images. 
(2) When the deposited amount of the composition containing germanium and 
sulfur is not more than about 1.8 .mu.g/cm.sup.2, positive images often 
result regardless of the kind of composition containing germanium and 
sulfur. 
(3) In order to obtain good images, the deposited amount of the composition 
containing germanium and sulfur must fall within a certain range dependent 
by the kind of composition containing germanium and sulfur and, in 
addition, the metal or the metal compound must be deposited in a thickness 
less than the thickness of the composition containing germanium and sulfur 
and in a ratio less than a certain level. The limit of the ratio generally 
can not be described but, in many cases, the maximum ratio is about 1/3, 
with a smaller ratio providing better results. However, when the deposited 
amount of the composition containing germanium and sulfur exceeds about 3 
.mu.g/cm.sup.2, the maximum deposited amount of the metal or the metal 
compound becomes definite and is about 1 .mu.g/cm.sup.2 or less. 
The processing-free type lithographic printing plate of the present 
invention to be obtained as described above enables printing by merely 
exposing the plate and immediately mounting the plate on a printing press. 
The printing plate possesses sufficient durability to print as many as 
several ten thousand impressions. Thus, the present invention is clearly 
an extremely useful invention from an industrial viewpoint.