1. Field of the invention.
[0001] The present invention relates to a heat mode recording material and to a method for
making images therewith. More in particular the present invention relates to an improvement
of the quality, i.e. a low minimum density, of an image obtained with a heat mode
recording material so that these images can be used as masks in a printing plate making
process.
2. Detailed description of the invention.
[0002] In the process for preparing lithographic printing plates contact originals are prepared
containing text and graphics. These originals are then used for imaging a printing
plate. Such contact originals can be made by manually preparing a paste-up or they
can be prepared by the aid of a computer. In the latter case the computer may control
an output device, generally a laser, for imaging a recording material.
[0003] A particular desirable recording material for imaging a printing plate contains the
image on a transparent support allowing the printing plate to be exposed through the
support of the recording material. In order to obtain a printing plate having good
printing properties it is of particular importance that the minimum density, i.e.
the density at the non-image areas, of the image on the recording material is extremely
low. Generally it will be required that the minimum density of the image used as a
mask for exposing the printing plate is below 0.05.
[0004] A commonly used recording material is a silver halide photographic material that
offers such advantages as high sensitivity, high density and good resolving power.
However a silver halide photographic material requires special liquids for processing
and as a consequence a lot of chemical waste is produced. Further silver halide photographic
materials are susceptible to ambient light thus requiring handling in the dark.
[0005] Due to the above disadvantages of silver halide photographic material, especially
the ecological disadvantage, the need for more convenient and ecologically more acceptable
recording materials exists.
[0006] Especially interesting recording materials are heat mode recording materials because
they are generally not susceptible to ambient light and can thus be handled in day
light. Heat mode recording materials are disclosed in e.g. US-P-4.123.309, US-P-4.123.578,
US-P-4.157.412, US-P-4.547.456 and PCT application WO 88/04237. The latter application
discloses a web having an image forming surface and a porous layer of an image forming
substance. The element further comprises a heat sensitive substance. Upon imaging
with a laser the image forming surface is liquefied at the exposed parts thereby penetrating
the porous layer and improving its adherence to the web while at the non-exposed parts
liquefying of the image forming surface does not take place and as a consequence the
adherence of the porous layer to the web remains poor. The porous layer can then be
removed in the non-exposed areas using a stripping tape or by simply rubbing. Due
to the subtle balance of adhesion forces between the porous layer and the image forming
surface and the cohesive forces within the porous layer the removal of the porous
layer with a stripping tape has to be performed under very stringent conditions and
even then lateral cracks of the porous layer in the exposed parts may occur resulting
in a decreased image density. The resulting image may be scratch sensitive and a protective
layer should be laminated thereto which is inconvenient.
[0007] GB-A-2.029.267 discloses a heat mode recording material comprising on a support a
metallic recording layer and a protective surface layer. Upon imaging with a laser
the density of the metallic recording layer is reduced at the exposed areas due to
melting of the metallic layer in these areas. Such a recording material is however
unsuitable for imaging a printing plate because of the poor contrast and high fogging
level of the image that is obtained
[0008] In non-prepublished EP-A 573092 a heat mode recording material has been described
containing on a support a heat mode recording layer of e.g. carbon black dispersed
in a polymeric binder and on top thereof a surface layer. After imaging with a powerful
laser, the recording material is rubbed to remove the recording layer and surface
layer in the exposed areas. Although images of good quality are obtained, the minimum
density of the images is still insufficient to use them as masks in the making of
printing plates.
[0009] WO 92/06410 discloses a heat mode recording material that comprises a support substrate
(i), at least one intermediate "dynamic release layer" (ii) essentially coextensive
therewith and an imaging radiation-ablative carrier topcoat (iii) also essentially
coextensive therewith, said imaging radiation-ablative carrier topcoat (iii) including
an imaging amount of a contrast imaging material contained therein, and said at least
one dynamic release layer (ii) absorbing such imaging radiation at a rate sufficient
to effect the imagewise ablation mass transfer of at least said carrier topcoat (iii).
3. Summary of the invention.
[0010] It is an object of the present invention to provide a heat mode recording material
that can yield images of high density and contrast so that they can be used as masks
for imaging a printing plate.
[0011] It is a further object of the present invention to provide a method for making images
of high density and contrast by means of a heat mode recording material.
[0012] Further objects of the present invention will become clear from the description hereinafter.
[0013] According to the present invention there is provided a heat mode recording material
comprising on a transparent support a recording layer containing a light to heat converting
substance, an image forming substance and a binder characterised in that there is
present a heat decomposable intermediate layer between said transparent support and
said recording layer and said heat decomposable intermediate layer being hardened
and contiguous to said recording layer.
[0014] According to the present invention there is provided a method for making an image
comprising image-wise exposing a heat mode recording material as defined above to
light and rubbing the heat mode recording material to remove the recording layer in
the exposed areas.
4. Detailed description of the invention
[0015] Due to the presence of the heat decomposable hardened intermediate layer an image
can be obtained that is practically free from fog i.e. of which the non-image density
is practically zero. Consequently the obtained images are suitable for use as masks
in the imaging of printing plates. With the term "heat decomposable" in connection
with the present invention is meant that the intermediate layer at least partially
decomposes and/or that the adhesion of the recording layer to the intermediate layer
is reduced at the exposed areas.
[0016] As a heat decomposable hardened intermediate layer in accordance with the present
invention there can be used any polymeric layer that is readily decomposable at the
temperature generated in the heat mode recording material. Depending on the type of
the light source used and the exposure time the temperature generated in the heat
mode recording material may reach 300°C to 800°C. It will furthermore be clear that
the decomposition of the intermediate layer may not yield colored reaction products
remaining on the heat mode recording material after rubbing.
[0017] It has been found that a particular suitable polymer for use in the heat decomposable
intermediate layer is an auto-oxidising polymer such as nitro-cellulose. It is furthermore
essential to harden the intermediate layer. Thus, according to the most preferred
embodiment of the present invention there is used a layer containing a hardened nitro-cellulose.
Hardening of nitro-cellulose may be accomplished by means of an aromatic or aliphatic
polyisocyanate, the latter being preferred.
[0018] The recording layer according to the present invention comprises a light to heat
converting substance and an image forming substance. In an especially preferred embodiment
the image forming substance and light to heat converting substance are the same substance.
The light to heat converting substance in connection with the present invention is
a compound that is capable of absorbing a substantial amount of the exposure radiation
and subsequently releasing the associate energy mainly in the form of heat. Preferably
the thickness of the heat mode recording layer is not more than 2.5µm and most preferably
not more than 1.5µm. When the thickness of the recording layer becomes too large not
all of the recording layer can be removed in the exposed areas so that a high fogging
level results.
[0019] Suitable light to heat converting substances are e.g. carbon black, metals or metal
alloys preferably having a low melting point and low conductivity e.g. Bi, Ge, Sn,
Te etc., infrared or near infrared dyes as disclosed in e.g. US-4833124, EP-321923,
US-4772583, US-4942141, US-4948776, US-4948777, US-4948778, US-4950639, US-4950640,
US-4912083, US-4952552, US-5024990, US-5023229 etc. or infrared absorbing pigments
such as e.g. HEUCODOR™ metal oxide pigments available from Heubach Langelsheim.
[0020] Suitable image forming substances to be used in accordance with the invention are
substances that can yield sufficient density in the desired range of the spectrum,
e.g. in the visual or in the UV part of the spectrum. Examples of image forming substances
are e.g. dyes or dye pigments. In an especially preferred embodiment the image forming
substance and light to heat converting substance are the same substance. Compounds
that can be used as image forming substance and light to heat converting substance
are e.g. carbon black or metals.
[0021] According to the most preferred embodiment of the present invention the recording
layer is a layer containing carbon black and a polymeric binder preferably having
a good thermal degradation. Examples of binders that can be used are e.g. gelatin,
cellulose, cellulose esters e.g. cellulose acetate, nitrocellulose, polyvinyl alcohol,
polyvinyl pyrrolidone, a copolymer of vinylidene chloride and acrylonitrile, poly(meth)acrylates,
polyvinyl chloride, silicone resin etc.. The recording layer may further contain other
ingredients such as e.g. wetting agents, matting agents, anti-oxidizing agents etc..
[0022] The recording layer is preferably covered with a surface layer. Upon image-wise exposure
to radiation a corresponding image-wise heat pattern will be formed in the recording
layer due to the conversion of the radiation into heat by the light to heat converting
substance. This heat pattern will cause image-wise decomposition of the recording
layer and optionally of the surface layer that may be on top thereof. At the sufficiently
exposed parts of the recording material the recording layer will be sufficiently decomposed
so that the recording layer and optional surface layer can be easily removed at these
parts by simply rubbing the recording material. The optional surface layer may also
be decomposed due to the heat generated at the exposed parts, however this is not
a requirement because the decomposition of the recording layer at the exposed parts
can be sufficient to also remove the surface layer by rubbing.
[0023] The optional surface layer on top of the recording layer offers the advantage that
no or little decrease of the density in the non-exposed parts occurs during rubbing
which may otherwise occur as a consequence of possible damaging of the recording layer
during rubbing.
[0024] The optional surface layer in accordance with the present invention preferably also
contains a polymer that shows good thermal degradation. Examples of polymers that
can be used in the surface layer are e.g. gelatin, cellulose, cellulose eaters e.g.
cellulose acetate, nitrocellulose, polyvinyl alcohol, polyvinyl pyrrolidone, a copolymer
of vinylidene chloride and acrylonitrile, poly(meth)acrylates, polyvinyl chloride,
a copolymer of styrene and butadiene, silicone resins etc... Preferably used silicone
resins are hardened silicone resins.
[0025] Preferably the silicone resin contains one or more components one of which is generally
a linear silicone polymer terminated with a chemically reactive group at both ends
and a multifunctional component as a hardening agent. The silicone resin can be hardened
by condensation curing, addition curing or radiation curing.
[0026] Condensation curing can be performed by using a hydroxy terminated polysiloxane that
can be cured with a multifunctional silane. Suitable silanes are e.g. acetoxy silanes,
alkoxy silanes and silanes containing oxime functional groups. Generally the condensation
curing is carried out in the presence of one or more catalyst such as e.g. tin salts
or titanates. Alternatively hydroxy terminated polysiloxanes can be cured with a polyhydrosiloxane
polymer in the presence of a catalyst e.g. dibutyltindiacetate.
[0027] Addition curing is based on the addition of Si-H to a double bond in the presence
of a platinum catalyst. Silicone coatings that can be cured according to the addition
curing thus comprise a vinyl group containing polymer, a platinum catalyst e.g. chloroplatinic
acid complexes and a polyhydrosiloxane e.g. polymethylhydrosiloxane. Suitable vinyl
group containing polymers are e.g. vinyldimethyl terminated polydimethylsiloxanes
and dimethylsiloxane/vinylmethyl siloxane copolymers.
[0028] Radiation cure coatings that can be used in accordance with the present invention
are e.g. U.V. curable coatings containing polysiloxane polymers containing epoxy groups
or electron beam curable coatings containing polysiloxane polymers containing (meth)acrylate
groups. The latter coatings preferably also contain multifunctional (meth)acrylate
monomers.
[0029] The surface layer may contain additional substances such as plasticizers, pigments,
matting agents, anti-statica etc.. Part of the light to heat converting substance
may also be incorporated in the surface layer.
[0030] The thickness of the surface layer is preferably between 0.1µm and 3µm and more preferably
between 0.1µm and 1µm.
[0031] When the recording material comprises a recording layer and surface layer the total
thickness thereof is preferably kept as low as possible. By keeping the layer thickness
at a low level the imaged parts of the recording material can be more easily removed
and further the sharpness and resolution of the image can be improved in this way.
Preferably the total thickness will not exceed 7µm and most preferably will not exceed
5µm.
[0032] The heat mode recording material used in accordance with the invention may contain
additional layers such as e.g. one or more layers between the support and the heat
decomposable intermediate layer for improving the adhesion thereof to the support.
[0033] According to a special embodiment of the present invention there may be provided
a further image forming layer on top of the recording layer in order to increase the
density of the image. A particularly suitable layer for this purpose is a vapour deposited
metal layer such e.g. a layer of bismuth, silver, aluminium etc...
[0034] According to a pratical embodiment of the present invention a peelable polymeric
film may be provided on top of the recording layer or on top of the surface layer
when present. Such polymeric film avoids contamination of the exposure device by parts
of the recording material that may otherwise be ablated during exposure. The polymeric
film is removed after an image has been formed on the recording material. The polymeric
film further avoids the occurence of electric discharges when taking a recording material
out of a pile. To further reduce such discharge the peelable polymeric film may be
given an antistatic treatment.
[0035] Suitable polymeric films for use in accordance with the present invention are e.g.
polyester, polycarbonate or polystyrene film, cellulose derivatives, polyolefines,
polyvinylchloride, etc. Preferably the peelable polymeric film is metallized or it
may be a polymeric film being pigmented with a conductive pigment such as e.g. carbon
black, a metal or metal oxide etc.. Preferably the peelable polymeric film has a thickness
between 3µm and 100µm and more preferably between 10µm and 50µm. A thin peelable polymeric
film offers the advantage that it can be laminated to the recording material without
the aid of an adhesive and that it can be easily removed afterwards. However, the
peelable polymeric film in connection with the present invention may also be laminated
to the recording material using an adhesive provided the adhesive does not cause adverse
effects on the imaging properties of the recording material or damage when peeled
off.
[0036] Suitable transparent supports for the heat mode recording material used in connection
with present invention are e.g. a polyester film support, polycarbonate film, polystyrene
film etc.. The thickness of the support is preferably between 0.1mm and 0.35mm.
[0037] According to the method of the present invention the heat mode recording material
is image-wise exposed to light, preferably through the support of the recording material
and subsequently rubbed to remove the recording layer and optional surface layer at
the exposed parts. The exposure is preferably accomplished using a laser. Preferably
used lasers are e.g. semiconductor lasers, YAG lasers e.g. Nd-YAG lasers, Argon lasers
etc.. The laser may have a power output between 40 and 7500mW and preferably operates
in the infrared part of the spectrum.
[0038] Rubbing in connection with the present invention is preferably carried in two steps.
In a first step the recording material may be rubbed e.g. by means of a brush under
essentially dry conditions, without the aid of a liquid, to remove the exposed areas.
In a second step a liquid that does not swell the recording layer may be used to take
away any residual dust that may still be present. A particular suitable liquid for
this purpose in case the recording layer and/or the surface layer is hydrophobic is
water optionally containing a detergent.
[0039] According to the present invention the image obtained according to the above described
method can be used as an original for imaging a lithographic printing plate.
[0040] Thus a lithographic printing plate precursor containing an oleophobic or oleophilic
base is imaged using as an original an image obtainable by the above described method
so that an image-wise pattern of respectively oleophilic or oleophobic parts is formed
on the oleophobic or oleophilic background. Exposure may take place through the support
of the imaged recording material being in contact with the lithographic printing plate
precursor.
[0041] According to a practical embodiment of the present invention for obtaining a lithographic
printing plate, a plate precursor containing an aluminium support carrying on a hydrophilic
(oleophobic) surface a photosensitive coating of e.g. a photopolymerizable composition
or a diazo resin etc. is exposed to actinic radiation in contact with an imaged heat
mode recording material of the present invention and is subsequently developed so
that an image-wise pattern of oleophilic parts remains on the oleophobic background.
Such type of printing plate precursors are described in e.g. EP-A-450199, EP-A-476187,
US-P-3971660, EP-A-167751, EP-A-48909, DE-A-3036174, DE-A-3717757, DE-A-3228429, US-P-4268667.
[0042] According to another embodiment of the invention for obtaining a lithographic printing
plate a silver salt diffusion transfer plate precursor containing a silver halide
photosensitive layer and an image receiving layer is camera or contact exposed using
an imaged heat mode recording material of the present invention and is subsequently
developed according to the silver salt diffusion transfer process. Such type of printing
plate precursors are described in e.g. EP-A-410500, EP-A-474922, US-P-4297429.
[0043] The present invention will now be illustrated by the following examples without however
limiting the invention thereto. All parts are by weight unless otherwise specified.
The optical densities listed in the examples were measured with a McBeth TR924 visible
light densitometer. The polyester base was used as the reference when measuring optical
densities.
EXAMPLE 1
[0044] To a polyethylene terephthalate support was coated a dispersion for the recording
layer according to following composition:
168.0 g |
n-butanone |
6.0 g |
nitrocellulose E510™ (1) |
23.7 g |
carbon black Special Schwarz 250 (2) |
1.9 g |
Solsperse™24000 (3) |
0.47 g |
Solsperse™ 5000 (4) |
(1) E510 (tradename) is a medium molecular nitrocellulose, supplier Wolff Walsode
Co. |
(2) Special Schwarz™250 (tradename) is a carbon black from Degussa |
(3) Solsperse™24000 (tradename) is a wetting agent from ICI |
(4) Solsperse™ 5000 (tradename) is a wetting agent from ICI |
[0045] The recording layer was applied at a dry coating weight of about 1.5 g/m2, corresponding
to an optical density of about 3.0.
[0046] To this recording layer was then coated following coating composition for a surface
layer:
651 g |
EXXSOL™ DSP 80/110 (5) |
20.5 g |
PS 255 (6) |
43.4 g |
PS 447.6 (7) |
1.8 g |
SYL-OFF™7367 (8) |
0.3 g |
PC 072 (9) |
(5) Exxsol™DSP 80/110 (tradename) is a nahptha i.e. mixture of paraffins and in which
the content of aromatics has been reduced, supplier Exxon Chemicals. |
(6) PS 255 (tradename) is a poly (dimethylsiloxane/methylvinylsiloxane) copolymer,
gum, from Huls. |
(7) PS 447.6 (tradename) is a vinyldimethyl terminated polydimethylsiloxane with a
viscosity of 65,000 ctsk., molecular weight about 119,000 from Huls |
(8) Syl-Off™7367 (tradename) is the cross-linker used and is a solution of 71% of
methyl hydrogen polysiloxane in ethynylcyclohexene, from Dow Corning |
(9) PC 072 (tradename) is a divinyltetramethyl disiloxane complex of platinum in xylene,
supplier Huls. |
[0047] The surface layer coating composition was coated on the recording layer to a dry
coating weight of 2.0 g/m2 to obtain an oleophobic top layer. Subsequent the surface
layer was cured for 300 s (5 min.) at 130°C.
[0048] The thus prepared heat mode recording material was image-wise exposed through the
support with a Nd-YLF laser (1053nm) at a linear writing speed of 32.8 m/s, with a
spot diameter of (1/e2) and a power output at the surface of the recording material
of 1600 mW. After imaging, the recording layer together with the surface layer were
image-wise removed by rubbing with a dry cotton pad. The obtained image portions were
post-cleaned with a cotton pad wetted with a 1% aqueous dilution of a commercial detergent.
[0049] The image portions showed a residual optical density of 0.05.
EXAMPLE 2
[0050] To a polyethylene terephthalate support was coated a base coat layer according following
composition:
100 g |
n-butanone |
10.0 g |
nitrocellulose E510™ (1) |
6.7 g |
Desmodur™N75 (10) |
0.3 g |
Siccatol™ZN12 (11) |
(10) Desmodur™N75 (tradename) is an aliphatic polyisocyanate crosslinking agent solution
(75% solids) recommend for application in clear non yellowing coatings, supplier Bayer. |
(11) Siccatol™ZN12 (tradename) is a 12% Zn-octanoate solution (catalyst) supplied
by Akzo. |
[0051] The base coat was applied to a dry coating weight about 1.0 g/m2 and cured for 10
min. at 120°C.
[0052] To this base coat was then coated the coating composition from example 1 for the
recording layer to obtain a coating showing an optical density of 3.7.
To the recording layer was then coated the composition for the surface layer described
in example 1 to a dry coating weight of about 2.0 g/m2. Subsequent the surface layer
was cured for 300 s (5 min.) at 130°C.
[0053] The thus prepared heat mode recording material was image-wise exposed through the
backside with a Nd-YLF laser (1053nm) at a linear writing speed of 32.8 m/s, with
a spot diameter of (1/e2) and a power output at the surface of the recording material
of 1600 mW. After imaging, the recording layer together with the surface layer were
image-wise removed by rubbing with a dry cotton pad. The obtained image portions were
post-cleaned with a cotton pad wetted with a 1% dilution of a commercial detergent.
[0054] The image portions showed a very low residual optical density of 0.02. (measured
with a McBeth™TR924 - visible light densitometer) towards the uncoated polyester base
taken as reference.
EXAMPLE 3
[0055] To a polyethylene terephthalate support was coated a base coat layer according to
example 2.
[0056] To the base coat was coated a dispersion for the recording layer according following
composition:
168.00 g |
n-butanone |
6.0 g |
nitrocellulose E510™ |
23.7 g |
carbon black Special Schwarz™250 |
1.9 g |
Solsperse™24000 |
0.47 g |
Solsperse™5000 |
0.2 g |
10 % solution of Tegoglide 410 (12) |
(12) Tegoglide™410 (tradename) is an alkylene siloxane blockcopolymer coating additive
from Goldsmith. In the application from example 4 it increases the slip properties
of the recording layer together with an enhancement of the scratch resistance. |
[0057] The thus prepared heat mode recording material was image-wise exposed through the
backside with a Nd-YLF laser (1053nm) at a linear writing speed of 32.8 m/s, with
a spot diameter of (1/e2) and a power output at plate level of 1600 mW. After imaging
the recording layer was image wise removed by rubbing with a dry cotton pad. The obtained
image portions were post-cleaned with a cotton pad wetted with a 1% aqueous dilution
of a commercial detergent.
[0058] The image portions showed a very low residual optical density of 0.02.
EXAMPLE 4
[0059] To a polyethylene terephthalate support was coated a base coat layer according to
example 2.
[0060] To the base coat was coated a dispersion for the recording layer according the composition
of example 1 to a dry coating weight according to an optical density of about 2.
[0061] To the recording layer was vacuum deposited a bismuth layer such that the resulting
optical density of the carbon black based recording layer together with the metallic
layer was 4.5.
[0062] To the recording layer was then coated the composition for the surface layer described
in example 1 to a dry coating weight of about 2.0 g/m2. Subsequent the surface layer
was cured for 300 s (5 min.) at 130°C.
[0063] The thus prepared heat mode recording material was image-wise exposed through the
backside with a Nd-YLF laser (1053 nm) at a linear writing speed of 32.8 m/s, with
a spot diameter of (1/e2) and a power output at the surface of the heat mode recording
material of 1600 mW. After imaging, the recording layer together with the metallic
layer and the surface layer were image-wise removed by rubbing with a dry cotton pad.
The obtained image portions were post-cleaned with a cotton pad wetted with a 1% aqueous
dilution of a commercial detergent.
[0064] The image portions showed a very low residual optical density of 0.01.
1. A heat mode recording material comprising on a transparent support a recording layer
containing a light to heat converting substance, an image forming substance and a
binder characterised in that there is present a heat decomposable intermediate layer
between said transparent support and said recording layer, said heat decomposable
intermediate layer being hardened and contiguous to said recording layer.
2. A heat mode recording material according to claim 1 wherein said heat decomposable
intermediate layer contains nitro-cellulose.
3. A heat mode recording material according to claim 2 wherein said nitro-cellulose is
hardened by means of a polyisocyanate.
4. A heat mode recording material according to any of the above claims further comprising
a surface layer on top of said recording layer.
5. A heat mode recording material according to any of the above claims wherein said light
to-heat converting substance and said image forming substance are the same.
6. A heat mode recording material according to claim 5 wherein said light-to-heat converting
substance and image forming substance are carbon black.
7. A method for making an image comprising the steps of image-wise exposing a heat mode
recording material comprising on a transparent support a recording layer containing
a light to heat converting substance, an image forming substance and a binder and
wherein there is present a heat decomposable intermediate layer between said transparent
support and said recording layer, said heat decomposable intermediate layer being
hardened and contiguous to said recording layer to light and subsequently rubbing
said recording material to remove the recording layer in the exposed areas.
8. A method according to claim 7 wherein said rubbing consists of two consecutive steps
wherein during a first step the heat mode recording material is rubbed under essentially
dry conditions and in a second step is rubbed with a liquid that is not capable of
swelling the recording layer.
9. A method according to claim 7 or 8 wherein said heat mode recording material is exposed
through its support.
10. A method according to any of claims 7 to 9 wherein said intermediate layer is hardened.
1. Ein wärmeempfindliches Aufzeichnungsmaterial, das auf einem transparenten Träger eine
Aufzeichnungsschicht mit einer Licht in Wärme umwandelnden Substanz, einer bilderzeugenden
Substanz und einem Bindemittel enthält, dadurch gekennzeichnet, daß zwischen dem transparenten
Träger und der Aufzeichnungsschicht eine wärmezersetzbare, gehärtete, an die Aufzeichnungsschicht
grenzende Zwischenschicht angeordnet ist.
2. Wärmeempfindliches Aufzeichnungsmaterial nach Anspruch 1, dadurch gekennzeichnet,
daß die wärmezersetzbare Zwischenschicht Nitrocellulose enthält.
3. Wärmeempfindliches Aufzeichnungsmaterial nach Anspruch 2, dadurch gekennzeichnet,
daß die Nitrocellulose mit einem Polyisocyanat gehärtet ist.
4. Wärmeempfindliches Aufzeichnungsmaterial nach irgendeinem der vorstehenden Ansprüche,
das auf der Aufzeichnungsschicht weiterhin eine Oberflächenschicht enthält.
5. Wärmeempfindliches Aufzeichnungsmaterial nach irgendeinem der vorstehenden Ansprüche,
dadurch gekennzeichnet, daß die Licht in Wärme umwandelnde Substanz und die bilderzeugende
Substanz dieselbe Substanz sind.
6. Wärmeempfindliches Aufzeichnungsmaterial nach Anspruch 5, dadurch gekennzeichnet,
daß die Licht in Wärme umwandelnde Substanz und die bilderzeugende Substanz Gasruß
sind.
7. Ein Bildaufzeichnungsverfahren, in dem ein wärmeempfindliches Aufzeichnungsmaterial,
das auf einem transparenten Träger eine Aufzeichnungsschicht mit einer Licht in Wärme
umwandelnden Substanz, einer bilderzeugenden Substanz und einem Bindemittel enthält
und in dem zwischen dem transparenten Träger und der Aufzeichnungsschicht eine wärmezersetzbare,
gehärtete, an die Aufzeichnungsschicht grenzende Zwischenschicht angeordnet ist, bildmäßig
belichtet und die Aufzeichnungsschicht an den belichteten Bereichen vom Aufzeichnungsmaterial
abgerieben wird.
8. Ein Verfahren nach Anspruch 7, dadurch gekennzeichnet, daß der Abreibvorgang aus zwei
aufeinanderfolgenden Stufen besteht, wobei in einer ersten Stufe unter wesentlich
trockenen Bedingungen und in einer zweiten Stufe mit einer die Aufzeichnungsschicht
nicht schwellenden Flüssigkeit über dem wärmeempfindlichen Aufzeichnungsmaterial gerieben
wird.
9. Ein Verfahren nach Anspruch 7 oder 8, dadurch gekennzeichnet, daß das wärmeempfindliche
Aufzeichnungsmaterial durch seinen Träger belichtet wird.
10. Ein Verfahren nach irgendeinem der Ansprüche 7 bis 9, dadurch gekennzeichnet, daß
die Zwischenschicht gehärtet ist.
1. Matériau d'enregistrement thermosensible comprenant, sur un support transparent, une
couche d'enregistrement contenant une substance transformant la lumière en chaleur,
une substance formatrice d'image et un liant, caractérisé en ce qu'une couche intermédiaire
décomposable à la chaleur est présente entre ledit support transparent et ladite couche
d'enregistrement, ladite couche intermédiaire décomposable à la chaleur étant durcie
et contigue à ladite couche d'enregistrement.
2. Matériau d'enregistrement thermosensible selon la revendication 1, dans lequel ladite
couche intermédiaire décomposable à la chaleur contient de la nitrocellulose.
3. Matériau d'enregistrement thermosensible selon la revendication 2, dans lequel ladite
nitrocellulose est durcie au moyen d'un polyisocyanate.
4. Matériau d'enregistrement thermosensible selon l'une quelconque des revendications
ci-dessus, comprenant en outre une couche superficielle pardessus ladite couche d'enregistrement.
5. Matériau d'enregistrement thermosensible selon l'une quelconque des revendications
ci-dessus, dans lequel ladite substance transformant la lumière en chaleur et ladite
substance formatrice d'image sont une même substance.
6. Matériau d'enregistrement thermosensible selon la revendication 5, dans lequel ladite
substance transformant la lumière en chaleur et ladite substance formatrice d'image
sont du noir de carbone.
7. Procédé de formation d'une image, comprenant les étapes consistant à exposer à la
lumière, en forme d'image, un matériau d'enregistrement thermosensible comprenant
sur un support transparent une couche d'enregistrement contenant une substance transformant
la lumière en chaleur, une substance formatrice d'image et un liant, et dans lequel
une couche intermédiaire décomposable à la chaleur est présente entre ledit support
transparent et ladite couche d'enregistrement, ladite couche intermédiaire décomposable
à la chaleur étant durcie et contigue à ladite couche d'enregistrement, et ensuite
à frotter ledit matériau d'enregistrement pour éliminer la couche d'enregistrement
dans les zones exposées.
8. Procédé selon la revendication 7, dans lequel ledit frottement est constitué par deux
étapes consécutives dans lesquelles, au cours d'une première étape, on frotte le matériau
d'enregistrement thermosensible dans des conditions essentiellement sèches et dans
une seconde étape, on frotte avec un liquide qui n'a pas la capacité de faire gonfler
la couche d' enregistrement.
9. Procédé selon la revendication 7 ou 8, dans lequel ledit matériau d'enregistrement
thermosensible est exposé à travers son support.
10. Procédé selon l'une quelconque des revendications 7 à 9, dans lequel ladite couche
intermédiaire est durcie.