Photosensitive compositions

A photosensitive composition containing an o-naphthoquinonediazido compound of Formula I ##STR1## wherein X is an oxy or amino group, Y is a cyano or nitro group, and n is an integer of 2 to 5, and an organic dye capable of changing its color when the photosensitive composition is exposed.

This invention relates to photosensitive compositions suitable for use in 
the preparation of lithographic printing plates, letterpress printing 
plates, IC circuits or photomasks and more particularly to photosensitive 
compositions which are so designed that visible images can be obtained 
immediately after exposure by virture of using combinations or certain 
o-naphthoquinonediazide compounds and certain organic dyes in said 
compositions. 
It is well known to use, as photosensitive compositions which form 
photoresists, compounds of ester or amide of 
o-naphthoquinonediazidosulfonic acid. Because of extremely excellent 
efficiencies, these compounds are being widely used on an industrial scale 
for the preparation of lithographic printing plates, especially the 
so-called presensitized plates (hereinafter called "PS plates") comprising 
a support and a layer of photosensitive composition having been previously 
formed thereon, or they are being extensively used in the industries as 
photoresists for letterpress printing plates, IC circuits, photomasks or 
printed circuits. Photosensitive compositions having contained therein 
these compounds, however, have such drawbacks as mentioned hereinafter. 
That is, these compounds which show a yellow color per se, come to fade and 
become a colorless or pale yellow photolysis component on exposure. 
Accordingly, in the exposure operation under a yellow safty lamp, the 
operator can not distinguish exposure areas from unexposed areas after the 
exposure. On this account, mishandling such as multiple exposure occurs in 
the course of such an exposing operation so-called "multiple operation", 
where an original is placed on a part of plate and exposed, and then is 
replaced on another part of the plate successively, or an operation where 
an unwanted image is removed by exposure. 
Some attempts have heretofore been made so as to form visible images 
immediately after exposure of photosensitive compositions in order to 
obviate these drawbacks mentioned above. 
Such attempts so as to obtain a visible image include, for example, the use 
of reducible salts of varied types in admixture with diazo compounds as 
disclosed in U.S. Pat. Nos. 2,066,913 and 2,618,555; the use of 
photosensitive diazo substances in combination with acidbase indicators as 
disclosed in Japanese Patent Publication No. 2203/1965; the use of 
combinations of diazo resins and merocyanine dyes as disclosed in Japanese 
Patent Publication No. 3041/1974; the use of homogeneously pulverized 
organic coloring matters capable of changing color at pH 2.5-6.6 as 
disclosed in Japanese Patent Publication No. 21093/1965; the use of esters 
of amides of o-naphthoquinonediazidosulfonic acid, 
o-naphthoquinonediazido-4-sulfonic acid halogenide and a salt-forming 
organic compound as a dye as disclosed in Japanese Laid-Open-to-Public 
Publication No. 36209/1975; and photosoluble compositions comprising 
o-naphthoquinonediazide compounds, novolak resins and cyclic acid 
anhydrides, o-naphthoquinonediazido-4-sulfonic acid halogenide and an 
organic dye capable of changing its color tone on interaction with a 
photolysis product of the o-naphthoquinonediazido-4-sulfonic acid 
halogenide. 
In the attempt thus improved, however, visible images obtained by means of 
exposure are not found to be sufficient in their contrast in the course of 
actual operation under a yellow safety lamp, and no improvement is brought 
about to such an extent that the aforesaid exposing operation can be 
carried out without trouble. Even in the case where sufficient contrast 
has been obtained, an adverse influence is exerted on sensitivity or 
developability, or when the compositions have been stored for a long 
period of time images with sufficient contrast can not be obtained, and 
thus the compositions have not been improved yet to demonstrate 
satisfactory efficiencies. 
An object of the present invention is to provide photosensitive 
compositions, from which such drawbacks of the prior art have been 
eliminated so that visible images sufficient in contrast can be obtained 
immediately after exposure, the properties of which suffering from no 
change even after a long storage and exerting no adverse influence on 
efficiencies of photosensitive compositions inherently required for, such 
as sensitivity, developability, etc. 
After extensive researches, the present inventors propose a photosensitive 
composition containing an o-naphthoquinonediazide compound represented by 
the following general formula (which will be called the 
o-naphthoquinonediazide compound of the present invention). 
General formula: 
##STR2## 
wherein X represents an oxy (--O--) or amino (.dbd.NH.sub.2) group; Y 
represents an electron attractive substituent; and n is an integer of 1 to 
5. 
The aforesaid o-naphthoquinonediazide compounds of the present invention 
are characterized by having in the molecular structure at least one 
electron attractive substituent represented by Y in the aforesaid general 
formula, and the presence of the substituent greatly contributes to the 
efficiency of visible image obtained after exposure, to which the object 
of the present invention is directed. That is, in case where any compound 
having no substituent as referred to above or having substituents which 
are electron donative groups, no visible image is obtained or even when 
visible images are obtained more or less, they are of no practical value, 
whereas when the o-naphthoquinonediazide compounds having electron 
attractive substituents are used, visible images can be obtained, giving a 
satisfactory contrast sufficient to carry out the aforesaid operation 
without any difficulty. A preferable example of the electron attractive 
substituent is a fluorine, chlorine or bromine atom, a nitro, cyano, 
vinyl, carbamoyl, --COOR.sub.1, --COR.sub.2 or --SO.sub.3 R.sub.3 in which 
R.sub.1, R.sub.2 and R.sub.3 individually represent a lower alkyl group 
(e.g. methyl, ethyl, propyl, butyl, t-butyl), aryl group (e.g. phenyl, 
naphthyl) or aralkyl group (e.g. benzyl), preferably the lower alkyl group 
has 1 to 4 carbon atoms and the aryl and aralkyl groups individually have 
6 to 10 carbon atoms. 
These electron attractive substituents may be located at any of the o-, m- 
and p-positions with respect to, but the effect obtainable by the use of 
the compound having the substituents at the o- or p-position is generally 
greater than that obtainable by the case of the m-position, and the number 
of the substituents amounting to 1 to 3 may be preferable, but the effect 
obtainable by the use of the disubstitution or trisubstitution compound is 
greater than that of the monosubstitution compund. A more preferable 
example of an electron attractive substituent is a nitro or cyano group. 
The naphthoquinone nuclei of the o-naphthoquinonediazide compounds may have 
a substituent. 
Typical examples of the o-naphthoquinonediazide compounds of the present 
invention may be exemplified below, though there are included in the scope 
of the present compound such as having varying combinations according to 
the kind, number and substitution position of the electron attractive 
groups and to the linking group X as selected. 
##STR3## 
The o-naphthoquinonediazide compound of the present invention can be 
prepared according to a procedure similar to the under-mentioned common 
process for the synthesis of the prior art o-naphthoquinonediazide 
compounds, per se, known. 
That is, the present o-naphthoquinonediazide compounds are readily prepared 
by dissolving naphthoquinone-(1,2)-diazido-(2)-4-sulfonyl chloride and 
phenols or anilines having the aforesaid electron attractive substituents 
in dioxane or tetrahydrofuran, followed by dropwise addition thereto of an 
aqueous solution of alkali such as sodium carbonate or potassium 
carbonate. 
The o-naphthoquinonediazide compounds thus prepared and used in the present 
invention withstand a long term storage and do not show such inconvenient 
properties for photosensitive substances, as hydroscopicity, liability to 
decomposition if they are stored in the dark place. 
The o-naphthoquinonediazide compound of the present invention is used to 
prepare a photosensitive composition in combination with an organic dye 
capable of changing its color when the photosensitive composition is 
exposed. Changing color includes a fading out of color or a changing color 
tone etc. The organic dye is thought to change its color on an interaction 
(for example, a weak chemical reaction) with a photolysis product of the 
said o-naphthoquinonediazide compound caused by an exposure. 
The organic dyes include triphenylmethane dyes, for example, basic 
triphenylmethane dyes such as Victoria Pure Blue BOH (produced by Hodogaya 
Kagaku K.K.), Patent Pure Blue (produced by Sumitomo Mikuni Kagaku K.K.), 
Sudan Blue II (produced by BASF), Crystal Violet, Marachite Green, 
Fuchsine, etc., and acidic triphenylmethane dyes such as Gresol Red, 
Thymol Blue, etc., and in addition thereto further include oil soluble 
dyes such as Oil Blue #603 and Oil Red 5B (both produced by Orient Kagaku 
Kogyo K.K.), etc. Of the organic dyes mentioned above, basic 
triphenylmethane dyes are particularly preferable. Some of these dyes are 
well known in the prior arts above-mentioned. 
The above-mentioned dyes may be used either singly or, if necessary, in the 
form of mixture thereof. 
The present invention relates to photosensitive compositions comprising at 
least one of the o-naphthoquinonediazide compounds of the present 
invention and the above-mentioned organic dye or dyes. The present 
photosensitive compositions, however, may be incorporated with other 
substances of various kinds for the purpose of improving film forming 
property, mechanical strength and photographic efficiency. First, the 
present photosensitive compositions can contain, as photosensitive 
substance, the prior art o-naphthoquinonediazide compounds, per se, known. 
Preferably known o-naphthoquinonediazide compounds for the above purpose 
are esters of naphthoquinone-(1,2)-diazido-(2)-sulfonic acid chloride with 
phenol or cresolformaldehyde resins. Other useful o-naphthoquinonediazide 
compounds, per se, known include those as disclosed, for example, in the 
Japanese Patent Publication Nos. 5083/1975, 5084/1975, 483/1976, 
24641/1975, 34934/1977, 34932/1977 and 36008/1977. 
The photosensitive compositions can further be incorporated with 
non-photosensitive resins with the view of improving film forming 
property, mechanical strength, resistance to chemicals, etc. 
The non-photosensitive resins effectively usable for this purpose, either 
singly or in combination, may include, for example, alkali soluble resins, 
for example, phenol or formaldehyde novolak resins, m-cresol formaldehyde 
novolak resins, m-xylenol formaldehyde novolak resins, shellac, rosin, 
polyacrylic acid, polymethacrylic acid, methacrylic acid methyl 
methacrylate copolymers, methacrylic acid styrene copolymers, 
poly-p-hydroxystyrene, copolymers containing p-hydroxymethacrylanilide 
derivatives as disclosed in the Japanese Patent Publication No. 34931/1977 
and copolymers containing p-hydroxymethacrylate derivatives as disclosed 
in the Japanese Patent Publication No. 41052/1977. 
Besides the above-mentioned additives, the present photosensitive 
compositions may be incorporated with various additives according to 
various purposes. For instance, the compositions may contain, for the 
purpose of improving their coating properties, such additives, for 
example, as cellulose alkyl esters, ethylene oxide type surface active 
agents and fluorine-containing type surface active agents (e.g. FC-430 and 
FC-431 produced by Minesota Mining and Manufacturing Co., Ltd.) and 
further, for the purpose of improving physical properties of the resulting 
coatings of the composition, such plasticizers, for example, as dibutyl 
phthalate, butyl glycolate, tricresyl phosphate, dioctyl adipate, etc. 
In the present photosensitive composition which contain such components as 
mentioned above, no particular limitation is placed on mixing ratio of 
these components. However, there are used the present 
o-naphthoquinonediazide compound of the aforesaid general formula in an 
amount, by weight, based on the total amount of the composition, of 
0.1-70%, preferably 1-40%, the organic dye capable of changing its color 
tone on interaction with a photolysis product of said 
o-naphthoquinonediazide compound in an amount, based on the total amount 
of the composition, of 0.1-20%, preferably 0.5-5%, and the additives in an 
amount, based on the total amount of the composition, of 0.01-20%, 
preferably 0.05-10%, though the amount of said additives may vary, in 
general, depending on the kind of the additives used. 
The photosensitive compositions of the present invention are applied to a 
variety of uses after coating on a suitable support such as aluminum 
plate, zinc plate, copper plate, plastic film, paper, and laminated 
plates, for example, bimetals, trimetals, copper foils for printed 
circuit, plastic sheets, chromium oxide-evaporated glass sheets, etc. In a 
coating liquid used for coating the present photosensitive composition on 
the support, a concentration of total solids of the composition is 
desirably 1-50% by weight based on an organic solvent in the coating 
liquid. The organic solvents suitably used, either singly or in the form 
of mixture thereof, in the coating liquid are methyl cellosolve, ethyl 
cellosolve, dioxane, acetone, .gamma.-butyrolactone, tetrachloroethane, 
tetrahydrofuran, dimethylsulfoxide, dimethylformamide, methyl cellosolve 
acetate and ethyl cellosolve acetate. 
When using the photosensitive materials thus obtained, any process 
conventionally used for materials of this kind is applicable. For 
instance, a transparent original bearing thereon a line image, dot image 
or the like is brought into close contact with a photosensitive surface of 
the material, followed by exposure and development with an aqueous alkali 
solution, thereby obtaining a positive type relief image relative to the 
original. Preferably usable sources of light for exposure include a 
mercury lamp, metal halide lamp, xenon lamp, carbon arc lamp, etc. The 
aqueous alkali solution for use in development includes an aqueous 
solution of sodium hydroxide, potassium hydroxide, sodium carbonate, 
potassium carbonate, sodium silicate, sodium metasilicate, disodium 
hydrogen phosphate, trisodium hydrogen phosphate, etc. A concentration of 
the aqueous alkali solution used in that case is generally 0.1-10% by 
weight, though the concentration may vary according to the kind of the 
photosensitive composition and of the alkali used. In order to accelerate 
development and inhibit uneven development, the aqueous alkali solution 
used may be incorporated with a small amount of a surface active agent, an 
organic solvent miscible with water and the like additives suitable for 
these purposes.

The present invention is more fully illustrated below with reference to 
examples, but it should be construed that embodiments of the invention are 
not limited only to those examples. 
EXAMPLE 1 
On an aluminum sheet of 0.24 mm in thickness grained by brush polishing 
technique, was coated by means of a rotary coating machine a 
photosensitive liquid of the following composition and then dried at 
110.degree. C. for 3 minutes to obtain a printing plate for lithography. 
Composition of photosensitive liquid: 
______________________________________ 
Naphthoquinone-(1,2)-diazido-(2)-4- 
1.4 g 
sulfonic acid-2,4-dinitrophenyl 
ester (exemplified compound 10) 
m-Cresol formaldehyde novolak resin 
7.6 g 
(MP-707 produced by Gunei Kagaku K.K.) 
Condensate of naphthoquinone-(1,2)- 
5.0 g 
diazido-(2)-5-sulfonic acid chloride 
with m-cresol formaldehyde novolak 
resin (condensation rate: 25 mol %) 
Victoria Pure Blue BOH produced by 
0.1 g 
Hodogaya Kagaku K.K.) C.I. No. 42595 
Tricresyl phosphate 0.14 g 
Ethyl cellosolve 100 g 
______________________________________ 
After drying, the photosensitive layer thus formed on the aluminum sheet 
had a weight of 2.78 g/m.sup.2. 
On the thus obtained photosensitive printing plate for lithograpy were 
brought into close contact with the photosensitive layer a positive copy 
of halftone photograph and a step tablet for sensitivity measurement and 
then exposed for 70 seconds at a distance of 1 meter from a 2 KW metal 
halide lamp. Immediately after the exposure, the dye in the exposed 
portion of photosensitive layer faded and a clear distinction in color 
tone between the exposed and unexposed portions was observed. The visible 
image thus obtained was such that even register marks of the copy could be 
visualized. 
Subsequently, the exposed printing plate was subjected to vat development 
with a 4% aqueous sodium metasilicate solution at 25.degree. C. for 45 
seconds, whereupon the portion faded by exposure was removed after having 
been dissolved, and a blue positive relief image excellent in affinity for 
printing ink. When an offset press fitted with the thus obtained printing 
plate was set in motion, copies of printed matter bearing a favorable 
image thereon were obtained. 
Furthermore, the present example was compared in respect of efficiency of 
the visible image obtained immediately after exposure, that of the visible 
image obtained after exposure but after a certain lapse of time, and 
stability of sensitivity of the photosensitive printing plate as prepared 
and stored under certain conditions, with comparative examples involving 
systems different from that of the present example to obtain the results 
as shown in Tables 1 and 2, said comparative examples involving 1 the 
same system as in the present example but without addition thereto of the 
o-naphthoquinonediazide compound of the present invention (Comparative 
Example 1), 2 the same system as in the present example but using an 
o-naphthoquinonediazide compound having an electron donative group in 
place of the present o-naphthoquinonediazide compound (Comparative Example 
2) and 3 the same system as in the present example but using 
naphthoquinone-(1,2)-diazido-(2)-4-sulfonic acid chloride instead of the 
present o-naphthoquinonediazide compound. 
The comparison of efficiencies of the visual images obtained after exposure 
was made by measurement (using a yellow filter) of reflection densities of 
the exposed and unexposed portions and by visual observation of the images 
under a yellow lamp, and the comparison of sensitivities of the 
photosensitive plates was made by measurement of the exposure time 
required for making completely clear the third step of a step tablet No. 2 
manufactured by Eastman Kodak Co. under the same exposure conditions as in 
the present example. 
COMATIVE EXAMPLE 1 
Example 1 was repeated except that the exemplified compound 10 was not 
added to the photosensitive liquid. 
COMATIVE EXAMPLE 2 
Example 1 was repeated except that 
naphthoquinone-(1,2)-diazido-(2)-4-sulfonic acid-2,4-dimethylphenyl ester 
of the following formula was in place of, and in the same amount as that 
of, the exemplified compound 10 in the photosensitive liquid. 
##STR4## 
COMATIVE EXAMPLE 3 
Example 1 was repeated except that 
naphthoquinone-(1,2)-diazido-(2)-4-sulfonic acid chloride (disclosed in 
Japanese Laid-Open-to-Public Publn. No. 36209/1975) was used in place of, 
and in the same amount as that of, the exemplified compound 10 in the 
photosensitive liquid. 
TABLE 1 
__________________________________________________________________________ 
Comparison in efficiency between visible images 
obtained after exposure as well as in storage 
stability between photosensitive compositions 
on storage 
Stored in dry thermostat 
Stored in hydrothermostat 
On the spot 55.degree. C., 2%, for 6 days 
40.degree. C., 80%, for 6 days 
Difference Difference Difference 
Density observed 
Density observed 
Density observed 
Composition 
Exposed 
Unexposed 
by visual 
Exposed 
Unexposed 
by visual 
Exposed 
Unexposed 
by visual 
prescribed 
portion 
portion 
observation 
portion 
portion 
observation 
portion 
portion 
observation 
__________________________________________________________________________ 
Example 1 
0.50 0.75 .circle. 
0.55 0.74 .circle. 
0.58 0.74 .circle. 
Comparative 
0.74 0.75 X 0.71 0.73 X 0.73 0.74 X 
Example 1 
Comparative 
0.75 0.77 X 0.74 0.75 X 0.74 0.74 X 
Example 2 
Comparative 
0.47 0.74 .circle. 
0.57 0.65 .DELTA. 
0.67 0.69 X 
Example 3 
__________________________________________________________________________ 
(Remarks) 
The result of visual observation of a difference in density between the 
exposed and unexposed portions of the image formed after exposure was 
represented by the sign .circle. wherein a clear difference was observed, 
the sign .DELTA. wherein a difference observed was somewhat not clear, an 
the sign X wherein a difference was not clear. 
TABLE 2 
______________________________________ 
Comparison in sensitivity between 
photosensitive compositions on storage 
Stored Stored in 
in dry thermostat 
hydrothermostat 
Composition 55.degree. C., 2%, 
40.degree. C., 80%, 
prescribed 
On the spot 
for 6 days for 6 days 
______________________________________ 
Example 1 
70 sec. 76 sec. 76 sec. 
Comparative 
59 sec. 64 sec. 64 sec. 
Example 1 
Comparative 
70 sec. 76 sec. 76 sec. 
Example 2 
Comparative 
91 sec. 108 sec. 128 sec. 
Example 3 
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The time in the table represents an exposure time required for clearing 
the third step of the step tablet under irradiation with light from a 2 K 
metal halide lamp at the distance of 1 meter. 
As is clear from Table 1, in Comparative Example 1 using no 
o-naphthoquinonediazide compound of the present invention as well as in 
Comparative Example 2 using instead the o-naphthoquinonediazide compound 
having electron donative substituents, no difference in density between 
the exposed and unexposed portions of the image as obtained is observed 
or, if there is any, it is very small, and the difference cannot be 
actually detected at all under a yellow lamp. In another visible image 
system (Comparative Example 3) using instead the 
naphthoquinone-(1,2)-diazido-(2)-4-sulfonic acid, on the one hand, a 
visible image is obtained at least from the photosensitive plate before 
storing, but no visible image with practical usefulness can be obtained 
after storing the plate under the circumstances of high temperature or 
humidity since marked deterioration in efficiency of the stored plate is 
brought about and, moreover, deterioration in sensitivity is also brought 
about as can be seen from Table 2. 
In contradistinction thereto, a visible image with sufficient density 
difference and contrast can be obtained in Example 1 using the 
photosensitive composition of the present invention in both cases before 
and after storage, and no practical deterioration in sensitivity is 
brought about. 
In Examples 3 to 4 as conducted, there were obtained sharply printed out 
images by exposing photosensitive materials obtained in the manner similar 
to that of Example 1 and the photosensitive materials were found to have 
favorable storage stability comparable to that of Example 1. Consequently, 
Examples 3 to 4 are given below by merely referring to photosensitive 
liquids respectively used therein. 
EXAMPLE 2 
Composition of photosensitive liquid: 
______________________________________ 
Naphthoquinone-(1,2)-diazido-(2)-4- 
5.9 g 
sulfonic acid-2,6-chloro-4-nitrophenyl 
ester (Exemplified compound 12) 
m-Cresol formaldehyde novolak resin 
9.0 g 
(MP-707 produced by Gunei Kagaku K.K.) 
Crystal Violet 0.2 g 
Ethylcellulose 0.15 g 
Methyl cellosolve 100 g 
______________________________________ 
EXAMPLE 3 
Composition of photosensitive liquid: 
______________________________________ 
Naphthoquinone-(1,2)-diazido-(2)-4- 
0.5 g 
sulfonic acid-p-cyanophenyl ester 
(Exemplified compound 5) 
m- and p-Cresol mixture formaldehyde 
11.8 g 
novolak resin (MP-703 produced by 
Gunei Kagaku K.K.) 
Condensate (condensation rate: 33 mol %) 
7.7 g 
of naphthoquinone-(1,2)-diazido-(2)-5- 
sulfonic acid chloride with phenol 
formaldehyde novolak resin 
Patent Pure Blue (produced by Mikuni 
0.28 g 
Kagaku K.K.) 
Dibutyl phthalate 0.2 g 
Ethyl cellosolve acetate 100 g 
______________________________________ 
EXAMPLE 4 
Composition of photosensitive liquid: 
______________________________________ 
Naphthoquinone-(1,2)-diazido-(2)-4- 
0.2 g 
sulfonic acid-p-nitroanilide 
(Exemplified compound 13) 
Condensate of naphthoquinone-(1,2)- 
9.8 g 
diazido-(2)-5-sulfonic acid chloride 
with polyhydroquinone monomethacrylate 
resin (condensation rate: 80 mol %, 
disclosed in Japanese Patent Publn. 
No. 34934/1977) 
Thymol Blue 0.1 g 
Cyclohexanone 50 g 
Methyl cellosolve 50 g 
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