Water based photosensitive composition with hydrolyzate of mammal collagen

A water based photosensitive composition comprises a hydrolyzate of a mammal collagen and a photosensitizer serving to cross-link the hydrolyzate when exposed to an active light. The hydrolyzate has a number-average molecular weight, Mn, of 2,000 to 30,000 and an intrinsic viscosity, [.eta.], of 0.060 to 0.155 dl/g in a 0.15 mole citric acid buffer solution maintained at 40.degree.C. Also, the hydrolyzate is capable of maintaining the formability of the collagen fold. A photoresist pattern formed by using the composition exhibits a high resolution, a good dyeing property and a strong corrosion resistance.

BACKGROUND OF THE INVENTION 
This invention relates to a water based photosensitive composition 
containing a water-soluble polymer and photosensitizer. 
In the conventional making of a name plate or precision part, a resist 
pattern is formed on a support member by a photosensitive composition 
which, when exposed to an active light, indicates different degrees of 
solubility in a solvent between the portion exposed to the active light 
and the portion not exposed to the active light. Depending on the object 
intended, the photosensitive composition is demanded to have such property 
as can provide a strong anticorrosive photo resist or a satisfactorily 
colored photo resist. In either case, a water based photosensitive 
composition is preferred which excels in promoting labor hygienics and 
reducing cost. 
Macro molecular substance (polymer) hitherto used in the production of the 
above-mentioned water based photosensitive composition include natural 
macro molecular substance such as gelatin, casein, fish glue, and egg 
albumin and synthetic water-soluble macro molecular substance such as 
polyvinyl alcohol, polyvinyl pyrrolidone, and polyacryl amide. The 
photosensitivity and image-resolving property of a photosensitive 
composition particularly prepared from a mixture of a macro molecular 
substance and photosensitizer largely depend as a rule on the average 
molecular weight of a macro molecular substance contained in the 
photosensitive composition. To ensure a desired photosensitive property, 
therefore, it is necessary to accurately control the average molecular 
weight of a macro molecular substance used. The molecular weight of a 
refined natural macro molecular substance depends to a large extent on the 
molecular weight of the raw material and on the refining process. Since 
the raw material consists of molecules widely differing from each other in 
molecular weight, it is difficult to prepare a refined natural macro 
molecular substance of a desired average molecular weight. Thus, a 
photosensitive composition containing a natural macro molecular substance 
tends to fail to exhibit a satisfactory photosensitivity and 
image-resolving power. With respect to gelatin in particular which has a 
low solubility in water and is extremely difficult to handle at ordinary 
temperature, it is necessary to heat gelatin for its dissolution, 
application and development. Casein has to be dispersed in water by being 
dissolved in an alkali solution. 
Casein is a globular protein which belongs to a conjugated protein (or 
phosphoprotein). On the other hand, gelatin is a fibrous protein belonging 
to a simple protein (or scleroprotein). Both gelatin and casein have a 
large average molecular weight. This means that gelatin and casein have a 
high setting point, that is, a low solubility in water, and, when applied 
as a photosensitive solution, have a high photosensitivity and a high dark 
reaction rate. Egg albumin is a globular protein belonging to the simple 
protein, has an average molecular weight which is not appreciably large, a 
high solubility in water and can be easily handled at ordinary 
temperature. However, the egg albumin contains a large amount of cystin 
due to its specific molecular structure and tends to give rise to thermal 
vulcanization and coagulation, and consequently is found unstable when 
used as a photosensitive composition. Synthetic water-soluble macro 
molecular substance can be produced with a prescribed average molecular 
weight and controlled, for example, in photosensitivity and 
image-resolving property with greater ease than natural macro molecular 
substance. However, a resist film utilizing a synthetic water-soluble 
resin is low in adhesiveness to a substrate and in elasticity. Thus, if 
the resist film is used as a photo resist, side etching is promoted. Also, 
the resist film mentioned fails to exhibit a sufficient resistance to 
corrosion, rendering it necessary to cure the resist film with anhydrous 
chromic acid. Further the said photo resist has an undesirably low 
dyeability to a hydrophilic dyestuff. This drawback can be easily inferred 
from the following fact. Where a water soluble macro molecular substance, 
synthetic or natural, is dyed, then its dyeing density largely depends on 
the bonding strength of the ionic bonds between a functional group 
contained in said macro molecular substance and a dyestuff applied. It is 
known that the extent of said bonding is defined by a number of functional 
groups contained in said water-soluble macro molecular substance. Usable 
hydrophilic dyes include direct, acid and basic dyes. An amino group in 
the macro molecular substance functions as an adsorption site for direct 
and acid dyes which contains a sulfonic groups in the molecule. A 
carboxylic group functions as an adsorption site for basic dyes which 
contains an amino groups in the molecule. Where comparison is made between 
a number of amino groups contained in a natural water-soluble macro 
molecular substance and that contained in a synthetic water-soluble macro 
molecular substance, the natural water-soluble macro molecular substance 
contains about 1.0 m eq of amino groups per g of macro molecular 
substance, while the synthetic water-soluble macro molecular substance 
contains about 0.1 m eq of amino groups per g of macro molecular 
substance. As seen from these numerical data, the synthetic water-soluble 
macro molecular substance can be expected to provide the amount of ionic 
bonding only accounting for about one-tenth of that observed in the 
natural water-soluble macro molecular substance. 
SUMMARY OF THE INVENTION 
It is the object of this invention to provide a novel water based 
photosensitive composition free of the drawbacks accompanying the 
conventional water based photosensitive materials. 
To attain the above-mentioned object, this invention provides a water based 
photosensitive composition, which comprises: 
a hydrolyzate of a mammal collagen; and 
a photosensitizer serving to cross-link said hydrolyzate when exposed to an 
active light, said hyrolyzate having a number-average molecular weight, 
Mn, of 2,000 to 30,000 and a intrinsic viscosity, [.eta.], of 0.060 to 
0.155 dl/g as measured in 0.15 mole of citric acid buffer solution at 
40.degree. C., and being capable of maintaining the helix-formability of 
the collagen fold. 
The "helix-formability of the collagen fold" used herein denotes that, even 
if the polypeptide chain forming collagen molecule has been severed by 
hydrolysis, each of the resultant shorter polypeptide chains is capable of 
forming a triple-helical structure characteristic of the collagen 
molecule. 
The intrinsic viscosity, [.eta.], of the hydrolyzate as measured in 0.15 
mole of citric acid buffer solution at 40.degree. C. is simply referred to 
as "the intrinsic viscosity of the hydrolyzate". 
The above-mentioned natural water based photosensitive composition 
embodying this invention is deposited in a thin layer on a substrate. 
After tightly contacted to a photo mask, said water based photosensitive 
composition layer is exposed to an active light, when developed at the 
next stage, said photosensitive composition layer can form a resist 
pattern assuring high resolving degree and high contrast on the substrate. 
The water based photosensitive composition of the invention has further 
advantages that the photosensitivity of said photosensitive composition 
can be controlled by the number-average molecular weight of the peptide 
resin; the photo resist thus obtained has good dyeability and high 
corrosion resistance; said photo resist allows for easy development by 
water and excels in the handling property; and the subject photosensitive 
composition is minimized in dark reaction, thereby assuring high storage 
stability.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The mammal collagen used in this invention includes those which are 
obtained from the bones, or hides (skins) of cattles, pigs and sheep. 
The hyrolysis product of the collagen whose molecular chain consists of a 
peptide bond is generally referred to as "peptide resin". With the method 
of this invention, the average molecular weight of the peptide resin can 
be freely controlled by optionally selecting the conditions for the 
hydrolysis of collagen. Various samples of peptide resin were produced 
from cattle bones or pig skins, the physical properties of said samples 
being shown in Table 1 below. The following relationship is deduced from 
FIG. 1 showing relationship between the number-average molecular weight, 
Mn, of the peptide resin and the specific viscosity, [.eta.], of the 
hydrolyzate of the collagen 
EQU [.eta.]=4.90.times.10.sup.-3 Mn.sup.0.333 
TABLE 1 
__________________________________________________________________________ 
Control Control 
Control 
Sample A 1 2 3 4 5 6 B C 
__________________________________________________________________________ 
Raw material 
Cattle 
Cattle 
Cattle 
Cattle 
Cattle 
Cattle 
Pig Cattle 
Cattle 
bone bone 
bone 
bone 
bone 
bone 
skin 
bone bone 
(gelatin) 
1. Number-average 
1,010 
2,020 
4,750 
7,830 
14,080 
26,500 
8,520 
35,200 
about 
molecular weight --Mn 100,000 
2. Intrinsic vis- 
0.050 
0.060 
0.078 
0.090 
0.123 
0.146 
0.102 
0.160 
0.75 
cosity [.eta.] (dl/g) 
3. Setting point 
less less 
less 
less 
9.8 16.2 
less 
20.2 26.5 
(.degree.C.) 
than 5 
than 5 
than 5 
than 5 than 5 
4. Relative light 
600 300 150 100 37 12 100 3 1 
sensitivity 
__________________________________________________________________________ 
The items of the experiments listed in Table 1 above were determined in the 
following manner. 
1. Item of experiment: number-average molecular weight Mn 
Determined by Van Slyke method 
2. Item of experiment: Intrinsic viscosity, [.eta.], 
Solutions (40.degree. C.) of various peptide resin samples were prepared 
with 0.15 mole citric acid buffer solution of pH 3.7 (a mixture of sodium 
citrate and citric acid). The intrinsic viscosity of the peptide resin 
solutions was determined from the following equation: 
##EQU1## 
where: .eta.=viscosity of peptide resin solution 
.eta..sub.0 =viscosity of citric acid buffer solution 
C=concentration (g/dl) of peptide resin solution 
3. Item of experiment: Setting point 
Determination was made of the setting point of the 10% by weight solution 
of the respective peptide resin samples. 
4. Item of experiment: Relative light sensitivity 
The relative light sensitivity of the peptide resin samples was expressed 
by an index of a light quantum indicating the photo cross-linking 
characteristic of a photosensitive solution prepared from a mixture of 
ammonium bichromate and peptide resin in the weight ratio of 1:1. The 
photosensitivity of said peptide resin samples expressed by a smaller 
index was taken to be higher. 
The mammal collagen was hydrolyzed by letting an acid, an alkali and an 
enzyme act on said collagen by properly controlling the temperature, 
reaction time and pressure used in the hydrolysis. In this case, severe 
hydrolysis conditions provide a peptide resin having a smaller average 
molecular weight, while gentle hydrolysis conditions produce a peptide 
resin having a larger average molecular weight. For reference, description 
is now given of the case where the mammal collagen was hydrolyzed by 
hydrochloric acid. Where the hydrolysis was carried out under the 
conditions set forth in Table 2 below, the rate of hydrolysis was 
controlled by an added amount of hydrochloric acid. 
Table 2 
Temperature (.degree.C.): 80 to 120 
Collagen concentration (wt%): 10 to 40 
Time (hr): 1 to 4 
Pressure (kg/cm.sup.2): atmospheric to 2 
FIG. 2 indicates the rate of hydrolysis carried out under the conditions: 
Temperature (.degree.C): 80 
Collagen concentration (wt%): 20 
Time (hr): 3 
A photosensitizer carrying out a photochemical cross-linking reaction with 
a peptide resin upon exposure to an active light includes bichromates such 
as ammonium bichromate, sodium bichromate, and potassium bichromate; and 
diazonium salts such as p-diazophenyl amine, 
1-diazo-4-dimethylaminobenzene.multidot.hydrofluoborate, 
1-diazo-3-methyl-4-dimethylaniline.multidot.sulfate, 
1-diazo-3-monoethylnaphtylamine and/or paraformaldehyde condensates 
thereof. However, the photosensitizer is not be limited to the compounds 
listed above. Namely, any other water soluble photosensitizer well serves 
the purpose, provided it can form a coordinate bond with a group of the 
peptide resin which has a lone pair of electrons such as --COOH, 
--NH.sub.2, --OH, --CONH.sub.2 and .dbd.CO. 
Among the amino acids constituting a collagen molecule, the content of 
imino acid groups, i.e., proline and hydroxy proline, is deeply related 
with the temperature at which a collagen molecule is denatured. An 
increase in the content of a pyrolidine ring of the imino acids in 
collagen molecule leads to the increase in thermal stability of the 
collagen molecule helix, and consequently to a rise in the 
collagen-denaturation temperature. Therefore, an animal whose collagen has 
a higher denaturation temperature is known to be more adapted to live in a 
warmer environment. This means that the collagen of the animals living in 
a warm enviroment contains a larger amount of imino acids, thereby 
elevating the thermal stability of the collagen molecule helix and 
assuring a greater collagen-fold forming ability. Conversely, with fishes 
living in a cold environment, for example, a cold current, such as cods 
and halibuts, the imino acid content in the collagen of these fishes 
decreases, leading to a decline in the thermal stability of the collagen 
molecular helix and consequently in the collagen-fold forming ability. It 
can be easily inferred that an animal living in a zone intermediate 
between the warm and cold zones can preserve an intermediate physiological 
characteristic. 
Where the peptide bond is broken by the hydrolysis of the collagen of the 
above-mentioned animals to decrease the average molecular weight of the 
peptide resin, then a decline results in the thermal stability of the 
collagen molecular helix, and consequently a fall in the setting point of 
the hydrolyzate of the mammal collagen and a rise in the water solubility 
thereof. As seen from FIG. 3 below showing a comparison between the 
optical rotation of the samples of the peptide resins (whose description 
is given in Table 3 below) obtained by the hydrolysis of the mammal 
collagen, the peptide resin still preserves a high collagen-fold forming 
ability as indicated by curve f, though the main chain of said peptide 
resin has been served by hydrolysis even to the extent indicated in Table 
3. As compared with a fish glue obtained from the collagen of the skin of 
a cod living in a cold current (indicated by curve h and having a number 
average molecular weight, Mn, of 42,000 and intrinsic viscosity, [.eta.], 
of 0.253), the peptide resin obtained by the hydrolysis of the mammal 
collagen exhibits to have a higher collagen-fold forming ability. 
TABLE 3 
__________________________________________________________________________ 
Number-average 
Intrinsic viscosity 
Samples number 
Origin of 
molecular weight 
[.eta.] of the peptide 
Curve 
in Table 1 
collagen 
(--Mn) resin (dl/g) 
__________________________________________________________________________ 
a Control C 
Cattle bone 
About 
100,000 
0.75 
(gelatin) 
b 5 Cattle bone 
26,500 
0.146 
c 4 Cattle bone 
14,080 
0.123 
d 3 Cattle bone 
7,830 
0.090 
e 2 Cattle bone 
4,750 
0.078 
f 1 Cattle bone 
2,020 
0.060 
g Control A 
Cattle bone 
1,010 
0.050 
h -- Cod skin 42,000 
0.253 
__________________________________________________________________________ 
As used herein, the term "optical rotation characteristic" of the peptide 
resin is defined to mean the amount of the helical collagen fold structure 
of the peptide resin formed when a solution of a peptide resin whose 
concentration is adjusted to about 1% by weight with a citric acid buffer 
liquid solution of pH 6.8 (prepared from a mixture of sodium citrate and 
citric acid) is suddenly cooled from an atmosphere of b 40.degree. C. to 
that of 2.degree. C. The optical rotation characteristic of the peptide 
resin is determined by the Rudolph-type polarimeter. The readings on said 
polarimeter obtained after 10, 20, 30, 60, 120 and 180 minutes after the 
start were used in determining the specific optical rotation 
characteristic [.alpha.].sub.D of the peptide resin from the following 
equation. 
##EQU2## 
where: C=concentration (% by weight) of peptide resin solution 
l=20 cm (optical path) 
X=rotation angle (degree) 
D line used wave length .lambda.=589 nm 
As the collagen-fold forming ability of the peptide resin progressively 
rises the absolute value of the optical rotation degree increases. 
The photochemical cross-linking property of a photosensitive agent depends 
on the average molecular weight of a macro molecular substance contained 
in said photosensitizer. Namely, as is well known, the photosensitivity of 
the photosensitizer rises, as its average molecular weight increases. 
However, a natural protein, particularly a macro molecular substance such 
as collagen which has a peculiar structure, namely, a collagen-fold 
forming ability indicates a complicated behavior due to its specific 
structural factors. In other words, where discussion is made of the 
photosensitive property of a photosensitizer containing a macro molecular 
substance obtained from the collagen, then it is necessary to pay 
attention to not only the average molecular weight of said macro molecular 
substance but also its collagen fold-forming function. The number of 
molecules of the macro molecular substance per unit volume becomes smaller 
as the macro molecular substance has a larger average molecules weight 
where a macro molecular substance is made into an insoluble mixture by 
reaction with a photosensitizer. Consequently, a smaller number of 
cross-links is required to make the macro molecular substance into an 
insoluble mixture, as the macro molecular substance has a larger average 
molecular weight, thereby elevating the photosensitivity of the macro 
molecular substance containing the photosensitizer. On the other hand, the 
resolving power of said macro molecular substance containing the 
photosensitizer tends to fall, because said macro molecular substance is 
likely to swell at the time of development due to the presence of a 
smaller number of cross-links per unit volume. Conversely, where the macro 
molecular substance has a smaller average molecular weight, then the 
phenomenon contrary to that described above is observed. Contrary to the 
above-mentioned theoretical inference, a peptide resin having a high 
collagen-fold forming ability forms not only molecular cross-links with 
the photosensitizer but also apparent cross-links resulting from the 
specific structure of the helix of collagen fold which enables a peptide 
resin having a smaller averages molecular weight to produce a suitable 
photosensitivity. Further, because of increase in the crosslinkage 
density, the peptide, resin permits forming a relief image excellent in a 
resolving power and the distinctiveness of image lines. In addition, the 
surface of the relief image is rendered tough. This means that said 
peptide resin having a smaller average molecular weight itself can be made 
into a tough corrosion-resistant photo resist layer. Referring to 
hydrophilic dyes such as direct dyes, acidic dyes and basic dyes, the 
functional group of a macro molecular substance should be formed of an 
amino group or carboxylic group. The peptide resin embodying this 
invention is produced by the hydrodysis of a peptide bond of a mammal 
collagen. As the hydrolysis proceeds, the amino group and carboxylic group 
at the end of a molecular chain processively increase in number, enabling 
the peptide resin to be easily dyed. This means that the peptide resin 
embodying the present invention surpasses the general natural protein in 
respect of dyeability. Experiments were further made with the dark 
reaction of photosensitive solutions prepared by adding ammonium 
bichromate to the samples of peptide resin (samples Nos. 1 to 5 given in 
Table 1) in the weight ratio of 1:4 to 1:10. The sample mixtures were 
heated at 50.degree. C. and allowed to stand in an atmosphere having a 
relative humidity of 65% for 24 hours. Determination was made of the dark 
reaction of the above-mentioned samples of the photosensitive solutions of 
the peptide resin. Said photosensitive solutions did not indicate any rise 
in the photosensitivity resulting from the dark reaction, proving that the 
peptide resin photosensitive solution embodying this invention is more 
useful as a photosensitive composition. The theoretic ground on which this 
favorable result of the photosensitive solution of the invention is based 
has not yet been fully understood. In this connection, however, it is 
assumed that as previously mentioned, the peptide resin assures the secure 
formation of a collagen fold; the hydrolysis of the peptide bond of the 
collagen shortens the molecular chain of the collagen, giving rise to a 
decline in the thermal stability of the collagen-fold forming ability; the 
thermal cross-linking activation of the peptide resin is promoted, while 
the thermal stability of the collagen fold of the peptide resin has been 
permally deteriorated; consequently the peptide resin decreases in 
apparent cross-linking and indicates a smaller dark reaction, thus 
assuring a higher storage stability. As inferred from Table 1 mentioned 
above, a peptide resin hydrolyzed to a number-average molecular weight, 
Mn, of 30,000 and a lower intrinsic viscosity, [.eta.], than 0.155 dl/g 
has a lower setting point than ordinary temperature. This means said 
hydrolyzed peptide resin is very soluble in water and can be easily 
handled. 
The water based photosensitive composition embodying this invention is 
produced by adding 5 to 50% by weight or preferably 10 to 30% by weight of 
a photosensitizer to the peptide resin. The peptide resin photosensitive 
composition thus produced is deposited in a thin layer on a substrate of, 
for example, a glass plate or iron plate by means of whirler coating or 
dip coating. After tightly contacted to a photo mask, the thin deposited 
layer of said photosensitive composition is exposed to an active light 
emitted from, for example, a mercury lamp, ultrapressure mercury lamp, or 
metal halide lamp. A patterned image produced on the substrate after water 
development is used as a corrosion resistant layer or colored layer. 
This invention will be more fully understood from the examples which 
follow. 
EXAMPLE 1 
Hydrochloric acid was added to a cattle bone collagen solution (collagen 
concentration: 20% by weight) at the rate of 1.52.times.10.sup.-3 mole per 
1 g of the collagen. The mixture was hydrolyzed at 80.degree. C. and 
ordinary pressure for 3 hours, producing a peptide resin having a 
number-average molecular weight, Mn, of 4,750 and intrinsic viscosity, 
[.eta.], of 0.078 dl/g. A peptide resin photosensitive composition 
prepared by mixing 20% by weight of the peptide resin with 2% by weight of 
a sulfate of a condensate of p-diazo diphenylamine and paraformaldehyde 
was applied to the surface of a glass substrate with a thickness of 1 to 2 
microns. After dried, a photo mask was tightly contacted to the 
photosensitive composition layer. A light emitted from a 3 kw 
ultrapressure mercury lamp, disposed 60 cm apart from said photosensitive 
layer, was projected on said photosensitive layer for about 90 seconds, 
followed by spraying water onto the photosensitive layer for about 1 
minute for the developing purpose, thereby obtaining a relief pattern. 
Also, another sample, i.e., a glass substrate coated with the peptide 
resin photosensitive material, was allowed to stand for 24 hours under an 
atmosphere having a temperature of 50.degree. C. and a humidity of 65%, 
with no change recognized in photosensitivity after the test. 
The resultant relief pattern was dyed for 4 minutes with a 2% solution of 
Direct Deep Black EX (trade name of a direct dye, C.I. 30,235, produced by 
Nihon Kayaku K.K.), followed by water-washing and, then, drying the relief 
pattern so as to obtain a dry plate bearing a dyed pattern exhibiting a 
light-shielding property equal to that of a lith-type photosensitive 
material having a transmissive density "D" of 4.0 or more. Also, the dyed 
pattern exhibited a resolution of 2 to 3 .mu. which is fully comparable 
with that of a high resolution plate of silver salt. 
Control 1 
An experiment was conducted as in Example 1, except that polyvinyl alcohol 
was used in place of the peptide resin. The transmissive density "D" of 
the resultant dyed pattern was less than 1.0. Also, fog was found in the 
non-image portion, and pin holes were recognized in the dyed pattern, 
leading to an unsatisfactory dyed pattern. In order to achieve a 
transmissive density "D" equal to that in Example 1, it was necessary to 
make the photosensitive layer formed on the glass substrate thicker than 
10 .mu. and to form an anti-halation layer. In this case, the produced dry 
plate exhibited a resolution of only about 30 .mu.. 
EXAMPLE 2 
Hydrochloric acid was added to a cattle bone collagen solution (collagen 
concentration: 20% by weight) in an amount of 1.14.times.10.sup.-3 mole/g 
of collagen, followed by hydrolyzing the collagen for 3 hours at a 
temperature of 80.degree. C. and under atmospheric pressure so as to 
obtain a peptide resin having a number-average molecular weight, Mn, of 
14,080 and an intrinsic viscosity, [.eta.], of 0,123 dl/g. An iron plate 
for a shadow mask defatted by trichloroethylene and alkali was coated by 
using a whirler in a thickness of 1 to 2 .mu. with a peptide resin 
photosensitive composition containing 20% by weight of the peptide resin 
and 4% by weight of ammonium bichromate. After the coating was dried, a 
photo mask was tightly contacted to the coating and the film was exposed 
to light for about 30 seconds, using a light source similar to that used 
in Example 1. Then, a developing treatment was performed for about 1 
minute by water spray so as to obtain a resist pattern of high resolution; 
an image line 10 .mu. wide was fully resolved. The resultant resist 
pattern was subjected to a burning treatment for 5 minutes at 250.degree. 
C., followed by etching the resist pattern for 10 minutes with a 45 Be 
ferric chloride solution maintained at 50.degree. C. The holes made by the 
etching was found rectilinear as desired, and pin holes caused by 
deterioration of the resist portion were not found at all. For comparison, 
a similar experiment was conducted by using a casein-based photosensitive 
solution. Where the photosensitive coating was as thick as above, the 
resultant resist pattern was low in corrosion resistance. Specifically, 
the resist portion was corroded by the etchant so as to give rise to 
innumerable pin holes, failing to perform the role of a resist. 
EXAMPLE 3 
Hydrochloric acid was added to pig skin collagen solution (collagen 
concentration: 20% by weight) in an amount of 1.20.times.10.sup.-3 mole/g 
of collagen, followed by hydrolyzing the collagen for 3 hours at a 
temperature of 80.degree. C. and under atmospheric pressure so as to 
obtain a peptide resin having a number-average molecular weight Mn of 
8,520 and an intrinsic viscosity of 0.102 dl/g. An iron plate for shadow 
mask defatted in advance was coated by using a whirler in a thickness of 2 
to 5 .mu. with a photosensitive material containing 20% by weight of the 
peptide resin mentioned above and 4% by weight of ammonium bichromate. 
After the coating was dried, a negative film was tightly attached to the 
coating and the film was exposed to light for about 1 minute, using a 
light source similar to that used in Example 1. Then, a developing 
treatment was performed for about 1 minute by water spray so as to obtain 
a resist pattern of high resolution; an image line about 10 .mu. wide was 
fully resolved. Further, the resist pattern was etched as in Example 2. 
The resultant etching holes were found rectilinear as desired. 
Control 2 
Hydrochloric acid was added to cattle bone collagen solution (collagen 
concentration: 20% by weight) in an amount of 0.52.times.10.sup.-3 mole/g 
collagen, followed by hydrolyzing the collagen for 3 hours at a 
temperature of 80.degree. C. and under atmospheric pressure so as to 
obtain a peptide resin having a number-average molecular weight, Mn, of 
35,200 and an intrinsic viscosity, [.eta.], of 0.160 dl/g. The produced 
peptide resin was found to exhibit a setting point of 20.2.degree. C. A 
photosensitive solution containing the peptide resin was accompanied by 
such a large viscosity fluctuation with temperature that it was difficult 
to form a uniform coating layer at room temperature.