Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
10~93~3
The present invent10n relates to a method for
developing a photosensitive resin plate. More part~cularly,
it relates to a method for develop$ng a photosensitve resin
plate after exposure by the utilization of a suction force.
In developing a photosensitive resin plate after
exposure to form an image, there has hitherto been employed a
rinsing out method, a.g. spraying a developer on the plate or
dippin~ the plate ln a developer while applying ultrasonic waves
thereto so as to dissolve or disperse the resin composition at
the non-exposed and non-hardened portion of the photosensitive
layer on the plate into the developer. The developers used for
this purpose are organic solvents, aqueous alkali solutions,
water, etc. The rinsing out method, however, produces disadvantage-
ausly a large amount of waste liq~or. In case of a photosensitive
resln plate having a photosens$tive layer containing an unsaturated
polyester, for example, 20 to 40 liters of an aqeuous alkali
solution is consumed for developing 10 plates, each having a
size of 420 x 594 cm, For this reason, the rinsing out method
is always faced with the problem of disposal of waste liquor
and requires a special installation for this purpose.
Recently, as a substitute for the rinsing out method,
there has been proposed an a~r jet method wherein development
is effected by blowing off the resin composition at the non-
exposed and non-hardened portion of the photosensitve layer.
Since no developer is used therein, it does not involve any
difficult problem occurring from waste liquor or its disposal.
Howéver, it has a different problem such as noise and odor.
It is the ob~ect of the present invent~on to provide
a method for developing photosensitve resin plates which overcomes
the above problems,
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The method or development o~ this lnvention comprises
applying suctlon to the surface of the photosensitive layer of a
photosensitive re9in plate after expo~ure to form an image BO .
that the resin composition at the non-exposet and non-hardened
portion of the photosensitive layer is removed therefrom.
It i5 applicable to any photosensitive resin plate
of which the photosensitive layer is in a liquid or viscous
state, for instance, made of a conventional resin composition
comprising an unsaturated polyester or an unsaturated polyurethane
with a polymerizable monomer thereto, a photosensitizer and a
neat polymerization inhibitor.
The lower is the viscosity of the resin ccmposition,
the faster the development rate can be. Even with one having
a high viscosity up to about 30,000 cp, the elimination of the
resin composition at the non-exposed and non-hardened portion may
be accomplished to attain the development, although it is however
frequently preferred to lower the viscosity of the resin composition
by application of heat thereto. To obtain a perfect letterpress,
exposure may be again made after completion of the development
by removal of the resin composition at the non-exposed and non-
hardened portlon with suction.
When a more perfect development i9 required, any
post-treatment such as spraying of a developer or wiping with
a blottlng paper may be applied after removal of the resin
composition at the non-exposed and non-hardened portion with
suction. When using a developer for the post-treatment, its
amount may be sufficient to eliminate the resin composition
remaining after development with suction. Thus, the developer
may be used in a very small amount for a much longer period,,in
comparison with that to be used ln the rinsing out method.
The application of suction to the surface of the photo-
sensltive layer may be effected by facing the said surface to a
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~uction port through wh~ch 9uctlon 1~ applled while moving
elther one of them relative to the other.
A larger suction rate and a higher degree of
reduction are favored for attaining the prompt elimination
of the resin compo~ition at the non-exposed and non-hardened
portion. Among them, a larger suction rate may be rather
preferred to a higher degree of reduction.
In order to attain a rapid development, a suction
rate of not less than about 0.1 m / min per 1 cm of the
suction port is normally desira~le, although the condition is
more or less varied with the size of the photosensitive resin
plate to be treated, the thickness of the relief, the area of
the æuction port, the viscosity of the resin composition and
the liXe. The suction rate, as u~ed herein, is intended to mean
the value obtained by dividing the exhaust rate of the used
- suction pump by the area of the suction port. The shape of the
suctlon port may bè any conventional one such as a slit, net or
grid. The size of the suction port may be appropriately selected
depending on the size of the photosensitive resin plate, the
thickness of the relief, the viscosity of the resin composition
and the liXe.
A preferred embodiment is illustrated in the drawings in
which:
Figure 1 is a perspective view of a suction drum and
Figure 2 is a sectional view of the drum and photosensitive
plate.
In the drawings, the suction drum (1) is provided with
a suctlon port in the form of a slit, and a duct (3), which is
connected to a source of suction. The photosensitive resin plate
(4) after exposure is moved over the suction port (2) in the
direction of the arrow i~n such manner that the photosensitive
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109~9313
layer ls closely faced to the suction port. In the photosensitve
layer, there are the expoeed and hardened portions (5) and the
non-exposed and non-hardened port~ons (6). When each of the non-
exposed and non-hardened portions reaches on the suction port,
the resin compos~tion is removed from the photosensitve resin
plate and sucked into the suction drum and retained at the bottom.
Although the suction drum ls fixed and the photosensitive
resin plate ls moved in the embodiment shown in Figures 1 and 2,
the suction drum may be moved with the photosensitive resin plate
being fixed.
By covering the circumference of the suction port with
a soft, resilient material such as rubber or polyurethane and
bringing the surface of the photosensitive layer into close
acce~s to the suction port over the same, the development can be
carried out very efficiently without causing any damage to the
lmage portion of the photosensitive resin plate. The rate of
movement of the plate or the suction port may be more rapid when
the vlscosity of the resin composition i5 lower. For this reason,
heating of the plate with any heating means provided near the
suction port so as to lower the viscosity of the resin composition
is favourable for attainment of the rapid and complete development.
On the size of the photosensitive resin plate, there
ls no specific limitation. Also, it is applicable to any plate
having a relief thickness of from about several microns to several
milllmeters.
As understood from the above descriptions, it is an
advantageous feature of the invention that large volumes of waste
liquor are not produced during development, since the resin
compositlon at the non-exposed and non-hardened portion is simply
removed by a suctlon force. By the use of an appropriate suction
3~ apparatus, the removed resin composition can be collected and
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1049313
retained therein. Such resin composition may be easily dl8po9ed
of, for instance7 by burning beczuse the amount i3 relatively
~mall or s~b~ected to repeated use beca~se 7ao contamination is
present therein.
Another advantageous feature of the invention is that,
~lnce the resin composition at the non-exposed and non-hardened
portion is sucked one-sidely through the suction port, any
adherence of the removed resin composition on any part of the
plate does not occ~r so that the development can be accomplished
efficiently within a short period of time. In the rinsing out
method, the adherence of the sludge of the resin composition
dispersed in the developer occurs frequently, and a troublesome
operation for eliminating this may become necessary.
A further advantageous feature of the invention is
that, since no chemical is used, a high degree of safety is
assured from the viewpoint not only of human health but also
of flre.
The method of the present invention is utilizable
not only for the preparation of a printing plate but also for
various other mouldings using photosensitive resins.
A preferred embodiment of the invention is illustrated
by the following Example.
EXAMPLE
On an iron plate of 128 x 182 cm in size, a photo-
sensitive resin composition containing an unsaturated polyester
(9,000 cp) is coated to make a photosensitive layer having a
thickrless of 0. 8 mm. On the photosensitive layer of the thus
prepared photosensitive resin plate, a negative film sandwiched by
a cover film and a glass plate was placed thereon in such a manner
that the glass plate is present at the top to make a close contact.
Exposure is effected by, irradiation with an ultravio71et fluorescent
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lamp for 3 mlnutes. The exposed surface i~ closely faced to a
~uctlon port in slit form ~4 mm wide, 15 cm long) provided on
a ~uction drum of 8 cm in diameter, which is connected to a
suction pump with an exh~ust rate of 3.6 m3 J min and moved
over the suction port in about 30 seconds, whereby the res$n
composition at the non-exposed and non-hardened portion is
eliminated at a rate of 91 X by wei~ht. Then, the thus de~eloped
surface is again subjected to exposure by irradiation with an
ultraviolet fluorescent lamp for 3 minutes to obtain a complete
letterpress.
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