1. Field of the invention.
[0001] The present invention relates to an improved heat mode recording element containing
a thin metal recording layer.
2. Background of the invention.
[0002] Recording materials have been disclosed on which records are made thermally by the
use of intense radiation like laser beams having a high energy density. In such thermal
recording or heat mode recording materials information is recorded by creating differences
in reflection and/or in transmission optical density on the recording layer. The recording
layer has high optical density and absorbs radiation beams which impinge thereon.
The conversion of radiation into heat brings about a local temperature rise, causing
a thermal change such as evaporation or ablation to take place in the recording layer.
As a result, the irradiated parts of the recording layer are totally or partially
removed, and a difference in optical density is formed between the irradiated parts
and the unirradiated parts (cf. US Pat. Nos. 4,216,501, 4,233,626, 4,188,214 and 4,291,119
and British Pat. No. 2,026,346)
[0003] The recording layer of such heat mode recording materials is usually made of metals,
dyes, or polymers. Recording materials like this are described in 'Electron, Ion and
Laser Beam Technology", by M. L. Levene et al.; The Proceedings of the Eleventh Symposium
(1969); "Electronics" (Mar. 18, 1968) , P. 50; "The Bell System Technical Journal",
by D. Maydan, Vol. 50 (1971), P. 1761; and "Science", by C. O. Carlson, Vol. 154 (1966),
P. 1550.
[0004] Recording on such thermal recording materials is usually accomplished by converting
the information to be recorded into electrical time series signals and scanning the
recording material with a laser beam which is modulated in accordance with the signals.
This method is advantageous in that recording images can be obtained on real time
(i.e. instantaneously). Recording materials of this type are called "direct read after
write" (DRAW) materials. DRAW recording materials can be used as a medium for recording
an imagewise modulated laser beam to produce a human readable or machine readable
record. Human readable records are e.g. micro-images that can be read on enlargement
and projection. An example of a machine readable DRAW recording material is the optical
disc. To date for the production of optical discs tellurium and its alloys have been
used most widely to form highly reflective thin metal films wherein heating with laser
beam locally reduces reflectivity by pit formation (ref. e.g. the periodical 'Physik
in unserer Zeit', 15. Jahrg. 1984/Nr. 5, 129-130 the article "Optische Datenspeicher"
by Jochen Fricke). Tellurium is toxic and has poor archival properties because of
its sensitivity to oxygen and humidity. Other metals suited for use in DRAW heat-mode
recording are given in US-P-4499178 and US-P-4388400. To avoid the toxicity problem
other relatively low melting metals such as bismuth have been introduced in the production
of a heat-mode recording layer. By exposing such a recording element very shortly
by pulses of a high-power laser the radiation is converted into heat on striking the
bismuth layer surface. As a result the writing spot ablates or melts a small amount
of the bismuth layer. On melting the layer contracts on the heated spot by surface
tension thus forming small cavitations or holes. As a result light can pass through
these cavitations and the density is lowered to a certain Dmin value depending on
the laser energy irradiated.
[0005] Heat mode recording materials usually do not require development and fixing processes
and do not require darkroom operations because of their insensitivity to room light.
Therefore they constitute a valuable alternative to conventional photosensitive materials
based on silver halide emulsions, e.g. for phototype-setting or image-setting applications.
As is generally known silver halide materials have the advantage of high potential
intrinsic sensitivity and excellent image quality. On the other hand they show the
drawback of requiring several wet processing steps employing chemical ingredients
which are suspect from an ecological point of view. For instance the commonly used
developing agent hydroquinone is allergenic and the biodegradation of disposed phenidone
is too slow. As a consequence it is undesirable that depleted solutions of this kind
would be discharged into the public sewerage; they have to be collected and destroyed
by combustion, a cumbersome and expensive process.
[0006] However, recording elements based on a thin metal layer show the drawback that the
thin metal film may reflect more than 50 % of the laser radiation, wasting the energy
of the laser radiation. Accordingly, such material may require a substantial amount
of energy for recording. Therefore, a high output laser light source is required if
records are to be made by high-speed scanning. Methods to reduce reflectance are proposed
in the Japanese Unexamined Patent Publications Nos. 40479/71 and 74632/76. However
the proposed solutions have other drawbacks. Moreover, due to the high specular reflectance
interference patterns arise with periods depending on the thickness of the protective
cover usually present to protect the scratch-sensitive metal layer. As a consequence
of these interference phenomena the finished image has an uneven and splodgy appearance.
[0007] It is an object of the present invention to provide an improved heat mode recording
element based on a thin metal layer which shows reduced or no interference patterns
on laser recording.
[0008] It is a further object of the present invention to provide a method for the formation
of a heat mode image which has no uneven or splodgy appearance.
3. Summary of the invention.
[0009] The objects of the present invention are realized by providing a heat mode recording
element comprising, in order :
(a) a support,
(b) a layer containing a roughening agent,
(c) a metal recording layer,
(d) a protective element.
[0010] In a preferred embodiment the metal layer is a vacuum-deposited thin bismuth layer
having a thickness preferably comprised between 0.1 and 0.6 µm. The average particle
size of the roughening agent preferably ranges between 0.3 and 2.0 µm, most preferably
around 1.0 µm. A preferred roughening agent is composed of polymethylmethacrylate
beads.
[0011] The layer containing the roughening agent can be the subbing layer of the support
or can be an extra layer between the subbing layer and the metal layer.
[0012] The protective element preferably comprises a cover sheet and an adhesive layer.
4. Detailed description of the invention.
[0013] The different elements constituting the heat mode recording material of the present
invention will now be explained in more detail.
[0014] Although the support of the heat mode element can in principle be an opaque paper
base preference is given to a transparent organic resin support. Useful transparent
organic resin supports include e.g. cellulose nitrate film, cellulose acetate film,
polyvinylacetal film, polystyrene film, polyethylene terephthalate film, polycarbonate
film, polyvinylchloride film or poly-Alpha-olefin films such as polyethylene or polypropylene
film. The thickness of such organic resin film is preferably comprised between 0.07
and 0.35 mm. In a most preferred embodiment of the present invention the support is
a polyethylene terephthalate layer provided with a subbing layer.
[0015] The layer containing the roughening agent can be the subbing layer itself applied
to the support or can be an extra layer between the subbing layer and the metal layer.
[0016] In principle layer (b) can contain no binder at all but preferably it contains a
binder. Tis layer (b) can be coated in principle from an organic solvent or from an
aqueous medium depending on the chemical nature of the binder. Organic solvent-soluble
binders include e.g. polymers derived from α,β-ethylenically unsaturated compounds
such as e.g. polymethyl methacrylate polyvinyl chloride, a vinylidene chloride-vinyl
chloride copolymer polyvinyl acetate, a vinyl acetate-vinyl chloride copolymer, a
vinylidene chloride-acrylonitrile copolymer, a styrene-acrylonitrile copolymer chlorinated
polyethylene, chlorinated polypropylene, a polyester, a polyamide, polyvinylbutyral
etc. Several organic solvents can be used for dissolving and coating these polymers.
On the other hand water-soluble binders coatable from an aqueous medium can be used,
e.g. gelatin, polyvinyl alcohol, polyvinyl pyrrolidone, carboxymethyl cellulose, methyl
cellulose, ethyl cellulose, gum arabic, casein, different kinds of water-soluble latices,
etc.
[0017] In a preferred embodiment the roughening agent is incorporated in the subbing layer
applied to the polyester support, in other words this subbing layer constitutes layer
(b). This subbing layer can be applied before or after stretching of the polyester
film support. The polyester film support is preferably biaxially stretched at an elevated
temperature of e.g. 70-120°C, reducing its thickness by about 1/2 to 1/9 or more and
increasing its area 2 to 9 times. The stretching may be accomplished in two stages,
transversal and longitudinal in either order or simultaneously. The subbing layer
is preferably applied by aqueous coating between the longitudinal and transversal
stretch, in a thickness of 0.1 to 5 µm. In case of a bismuth recording layer the subbing
layer preferably contains, as described in European Patent Application EP 0 464 906,
a homopolymer or copolymer of a monomer comprising covalently bound chlorine. Examples
of said homopolymers or copolymers suitable for use in the subbing layer are e.g.
polyvinyl chloride, polyvinylidene chloride, a copolymer of vinylidene chloride, an
acrylic ester and itaconic acid, a copolymer of vinyl chloride and vinylidene chloride,
a copolymer of vinyl chloride and vinyl acetate, a copolymer of butylacrylate vinyl
acetate and vinyl chloride or vinylidene chloride, a copolymer of vinyl chloride,
vinylidene chloride and itaconic acid, a copolymer of vinyl chloride, vinyl acetate
and vinyl alcohol etc.. Polymers that are water dispersable are preferred since they
allow aqueous coating of the subbing layer which is ecologically advantageous.
[0018] Said homopolymer or copolymer may be prepared by various polymerization methods of
the constituting monomers. For example, the polymerization may be conducted in aqueous
dispersion containing a catalyst and activator, e.g., sodium persulphate and meta
sodium bisulphite, and an emulsifying and/or dispersing agent. Alternatively, the
homopolymers or copolymers used with the present invention may be prepared by polymerization
of the monomeric components in the bulk without added diluent, or the monomers may
be reacted in appropriate organic solvent reaction media.
[0019] The roughening agent incorporated in layer (b) - for many actual substances this
term will be equivalent to the more familiar terms "matting agent" or "spacing agent",
but the term is chosen for its functional aspect - must fulfil several requirements
for the successful practice of the present invention. Chemical nature, concentration
and particle distribution of the roughening agent must be chosen in such a way that
a certain degree of uneveness can be introduced in the metal recording layer. It is
shown that this uneveness can reduce the occurence of interference patterns because
the reflectance gets more diffuse. It will be clear that the roughening agent must
be closely packed in the layer. It will also be easily understood that the thickness
of layer (b), the average particle size and the coverage of the roughening agent must
be tuned to each other in such a way that a sufficient number of the roughening particles
must protrude above the interface layer (b) / metal layer in order to induce local
deformation spots into this metal layer. When the average particle size is too low
the roughening agent will not be able to introduce uneveness in the metal layer. When
the average particle size is too great too high a coverage will be required which
would make layer (b) too thick. So it is clear that an optimal particle size should
be chosen for the roughening agent and that this optimum will depend on the mechanical
strenght of the metal layer and therefore on its thickness. For the preferred embodiment
of a bismuth layer with a thickness of about 0.3 µm the average particle size of the
roughening agent preferably ranges from 0.3 to 2.0 µm, and is most preferably about
1.0 µm. In this case the coverage of the roughening agent preferably ranges from 0.05
to 1.0 g/m², and is most preferably about 0.6 g/m².
[0020] It will also be clear that the optimal amount/m² of the binder will be dependent
on the average particle size of the roughening agent.
[0021] The degree of roughness of layer (b) is best characterized by the so-called R
a value. This so-called average roughness value is defined as the arithmic average
value of the absolute amounts of all the measured distances of the roughness profile
from the middle line within the measured interval. Layer (b) preferably has a R
a value of at least 0.2 µm.
[0022] The roughening agent can be chosen from a wide variety of chemical classes and commercial
products provided the particles chosen show an excellent mechanical and thermal stability.
Preferred roughening agents include following :
- the spherical polymeric beads disclosed in US 4,861,818 ;
- the alkali-soluble beads of US 4,906,560 and EP 0 584 407 ;
- the insoluble polymeric beads disclosed in EP 0 466 982 ;
- polymethylmethacrylate beads ;
- copolymers of methacrylic acid with methyl- or ethylmethacrylate ;
- TOSPEARL siloxane particles (e.g. types T105, T108, T103, T120) marketed by Toshiba
Co ;
- SEAHOSTAR polysiloxane - silica particles (e.g. type KE-P50) marketed by Nippon Shokubai
Co ;
- ROPAQUE particles, being polymeric hollow spherical core/sheat beads, marketed by
Rohm and Haas Co, and described e.g. is US-P's 4,427,836, 4,468,498 and 4,469,825
;
- ABD PULVER, marketed by BASF AG ;
- CHEMIPEARL, spherical poymeric particles, marketed by Misui Petrochemical Industries,
Ltd.
[0023] In principle, a thin intermediate layer can be applied between layer (b) and the
metal recording layer for reasons of protection against physical damage. In this case
the thin intermediate layer is coated together with layer (b) by slide hopper coating.
It can contain the same kinds of binder as layer (b) at a coverage of lower than 1
g/m² in order not to loose the roughening effect. However in a preferred embodiment
there is no such an intermediate layer and the metal recording layer is positioned
immediately on top of layer (b) in order to get the full effect of the uneveness introduced
by the roughening agent.
[0024] Possible metals for the recording layers in this invention include Mg, Sc, Y, Ti,
Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Co, Ni, Ru, Rh, Pd, Ir, Pt, Cu, Ag, Au,
Zn, Cd, Al, Ga, In, Si, Ge, Sn, As, Sb, Bi, Se, Te. These metals can be used alone
or as a mixture or alloy of at least two metals therof. Due to their low melting point
Mg, Zn, In, Sn, Bi and Te are preferred. The most preferred metal for the practice
of this invention is Bi.
[0025] The metal recording layer may be applied on top of the layer containing the roughening
agent by vapor deposition, sputtering, ion plating, chemical vapor deposition, electrolytic
plating, or electroless plating. In the preferred case of Bi the recording layer is
preferably provided by vapor deposition in vacuo. A method and an apparatus for such
a deposition are disclosed in EP 0 384 041.
[0026] The thickness of this Bi layer is preferably comprised between 0.1 and 0.6 µm. When
this thickness is too low the recorded images do not have sufficient density. When
on the other hand the thickness is too high the sensitivity tends to decrease and
the minimal density, i.e. the density after laser recording on the exposed areas tends
to be higher.
[0027] Since the metal layer is very sensitive to mechanical damage a protective element
must be provided on top of the metal layer. In a preferred embodiment this protective
element comprises a transparent organic resin, acting as cover sheet, and an adhesive
layer. A method for applying such a protective element by lamination in the same vacuum
environment as wherein the deposition of the metal layer took place is disclosed in
EP 0 384 041, cited above. The cover sheet can be chosen from the group of polymeric
resins usable for the support of the heat mode element. In a preferred embodiment
the cover sheet is also polyethylene terephthalate but preferably substantially thinner
than the polyethylene terephthalate of the support.
[0028] For the adherence of the hard protective outermost resin layer to the heat mode recording
layer preferably a layer of a pressure-sensitive adhesive resin can be used. Examples
of such resins are described in US-P 4,033,770 for use in the production of adhesive
transfers (decalcomanias) by the silver complex diffusion transfer process. in the
Canadian Patent 728,607 and in the United States Patent 3,131,106.
[0029] Pressure-sensitive adhesives are usually composed of (a) thermoplastic polymer(s)
having some elasticity and tackiness at room temperature (about 20°C), which is controlled
optionally with a plasticizer and/or tackifying resin. A thermoplastic polymer is
completely plastic if there is no recovery on removal of stress and completely elastic
if recovery is instantaneous and complete.
[0030] Particularly suitable pressure-sensitive adhesives are selected from the group of
polyterpene resins, low density polyethylene, a copoly(ethylene/vinyl acetate), a
poly(C₁-C₁₆)alkyl acrylate, a mixture of poly(C₁-C₁₆)alkyl acrylate with polyvinyl
acetate, and copoly(vinylacetate-acrylate) being tacky at 20°C.
[0031] In the production of a pressure-adhesive layer an intrinsically non-tacky polymer
may be tackified by the adding of a tackifying substance, e.g. plasticizer or other
tackifying resin.
[0032] Examples of suitable tackifying resins are the terpene tackifying resins described
in the periodical "Adhesives Age", Vol. 31, No. 12, November 1988, p. 28-29.
[0033] According to another embodiment the protective element is laminated or adhered to
the heat-mode recording layer by means of a heat-sensitive also called heat-activatable
adhesive layer or thermoadhesive layer, examples of which are described also in US-P
4,033,770. In such embodiment the laminating material consisting of adhesive layer
and abrasion resistant protective layer and/or the recording web material to be protected
by lamination are heated in their contacting area to a temperature beyond the softening
point of the adhesive. Heat may be supplied by electrical energy to at least one of
the rollers between which the laminate is formed or it may be supplied by means of
infra-red radiation. The laminating may proceed likewise by heat generated by high-frequency
micro-waves as described e.g. in published EP-A 0 278 818 directed to a method for
applying a plastic covering layer to documents.
[0034] A survey of pressure and/or heat-sensitive adhesives is given by J. Shields in "Adhesives
Handbook", 3rd. ed. (1984) , Butterworths - London, Boston, and by Ernest W. Flick
in "Handbook of Adhesive Raw Materials" (1982), Noyens Publications, Park Ridge, New
Jersey - USA.
[0035] The adhesive layer may be heat-curable or ultra-violet radiation curable. For heat-curable
organic resins and curing agents therefore reference is made e.g. to the above mentioned
"Handbook of Adhesive Raw Materials", and for UV curable resin layers reference is
made e.g. to "UV Curing: Science and Technology" - Technology Marketing Corporation.
642 Westover Road - Stanford - Connecticut - USA - 06902 (1979). However, in heat
mode recording with a meltable metal layer preference is given to an easily deformable
adhesive layer so that it does not form a hindrance for the formation of small metal
globules in the areas of the recording layer struck by high intensity radiation energy
laser energy. The easy deformability of the adhesive interlayer is in favour of recording
sensitivity.
[0036] For several applications of a heat mode DRAW material such as the one of the present
invention the dimensional stability is of utmost importance. Fields of application
where the requirements for dimensional stability are very stringent are e.g. those
where the heat moded image serves as an intermediate for the exposure of a lithographic
printing plate, or as a master mask for the production of microelectronic integrated
circuits or printed circuit boards (PCB) . To improve the dimensional stablility one
or more barrier layers can be applied onto the heat mode recording element retarding
the uptake of water vapour as disclosed in European Patent Application Appl. No. 93201366,
filed 12 May, 1993. In a preferred embodiment this barrier layer is a vapour-deposited
glass layer substantially composed of SiO
x, x ranging from 1.2.to 1.8. Such a barrier layer can be applied to one of or to both
outermost sides of the complete finished heat mode element of the present invention,
or to one of or to both sides of the support of the recording element before the element
is further produced.
[0037] For the formation of a heat mode image using the element of the present invention
any laser can be used which provides enough energy needed for the production of sufficient
heat for this particular process of image formation. In a preferred embodiment a powerful
infra-red laser is used. Most preferably a Nd-YLF laser is used emitting at 1053 nm.
[0038] The present invention will be illustrated now by the following example without however
being limited thereto.
EXAMPLE
- preparation of heat mode recording elements
[0039] The following substrates for the deposition of a bismuth layer were prepared :
- reference 1 (R-1) : this substrate consisted of a polyethylene terphthalate support
sheet subbed with a layer containing 0.16 g/m² of a copolymer consisting of 88 mole
% of vinylidene chloride, 10 mole % of methylacrylate and 2 mole % of itaconic acid,
serving as a binder, and also containing 0.04 g/m² of SiO₂ with an average particle
size of 0.1 µm. A backing layer was also present containing, as antistatic element
5.2 mg/m² of an epoxysilane hydrolyzed in polysulphonic acid, and 5 mg/m² of SiO₂
with an average particle size of 0.1 µm. This reference 1 element was taken from current
manufacturing by Agfa-Gevaert N.V. ;
- reference 2 (R-2) : an aqueous coating solution was prepared containing the same copolymer
consisting of 88 mole % of vinylidene chloride, 10 mole % of methylacrylate and 2
mole % of itaconic acid, serving as a binder, and two conventional commercial wetting
agents. This solution was coated on top of a subbed polyethylene terephthalate substrate
corresponding to reference 1. After drying this extra layer contained 0.45 g/m² of
the copolymer ;
- invention 1 (I-1) : this substrate was similar to reference 2 with the exception that
the extra layer contained only 0.16 g/m² of the copolymeric binder and 0.09 g/m² of
roughening agent ROPAQUE OP62 LO, having an average particle size of 0.5 µm, purchased
from Rohm and Haas Co.
- invention 2 (I-2) : this substrate was similar to reference 2 with the exception that
the extra layer further contained a roughening agent consisting of polymethylmethacrylate
beads, having an average particle size diameter of 1.0 µm, at a coverage of 0.59 g/m².
[0040] To these four substrates a bismuth layer of 0.3 µm thickness was applied by vacuum-deposition
(vacuum of 10⁻² Pa) in a Leybold apparatus, after a weak corona discharge of 0.05
Ampère. To the bismuth layer was laminated in vacuo a protective element consisting
of a 8 µm thick adhesive layer containing copoly(butylacrylate-vinylacetate), and
of a cover sheet being a 12 µm thick polyethylene terephthalate foil.
- image formation and evaluation of image quality
[0041] The four recording elements were exposed by means of a high-power internal drum laser
recorder with following characteristics :
- laser type : Nd-YLF laser ;
- wavelenght : 1053 nm ;
- spot diameter (1/e²) : 18 µm ;
- pitch : 10.58 µm ;
- velocity of the rotating scanning mirror : 1663 rpm ;
- drum radius : 188.6 mm ;
The elements were exposed through the protective laminate side. Full areas and
separate scan lines (1 on / 10 off) were exposed at different laser powers ranging
between 480 mW and 1330 mW. The obtained image quality was evaluated as follows.
(a) Dmax and Dmin
[0042] The densities of exposed and unexposed full areas were measured with a MACKBETH TD904
densitometer equipped with a UV-filter and a measuring spot of 3 mm. The results (mean
values of different measurements, expressed in thousands) are summarized in table
1.
TABLE 1
element |
Dmax |
Dmin |
|
|
480 mW |
700 mW |
900 mW |
1110 mW |
1260 mW |
1330 mW |
R-1 |
362 |
290 |
133 |
53 |
37 |
30 |
29 |
R-2 |
390 |
345 |
98 |
46 |
35 |
31 |
32 |
I-1 |
380 |
332 |
142 |
49 |
34 |
32 |
31 |
I-2 |
289 |
233 |
108 |
49 |
34 |
32 |
31 |
[0043] From table 1 it is clear that at least a laser power output, measured on the recording
element plane, of 1110 mW is necessary to get a maximal density differentiation between
exposed and unexposed areas. At this and above this power the presence or absence
of a roughening agent has little influence on Dmin.
(b) macroscopic evaluation of homogeneity
[0044] The macroscopic homogeneity was defined as the minimal laser power at which the full
areas and lines showed no interference patterns or interference fringes any more.
These values are summarized in table 2 :
TABLE 2
element |
homogeneity |
|
full areas |
lines |
R-1 |
> 1330 |
> 1330 |
R-2 |
> 1330 |
> 1330 |
I-1 |
1200-1260 |
> 1330 |
I-2 |
1110-1200 |
1110-1200 |
[0045] The interference phenomena disappeared at a lower laser power when the recording
elements contained a roughening agent. The best result was obtained with roughening
agent polymethylmethacrylate having an average grain size of 1.0 µm.
(c) microscopic evaluation of homogeneity
[0046] The recorded full areas and lines were enlarged 100 fold by means of a Nikon microscope
and photographed so that individual scan lines became visible.
[0047] An arbitrary qualification ranging from 0 to 5 was assigned to the physical quality
of the recorded full areas at 1200 mW power and 1330 mW power. This qualification
range had following meaning :
1 : inhomogeneous, very intense interference spots ;
2 : inhomogeneous, rather intense interference spots ;
3 : rather homogeneous, still slight interference ;
4 : practically completely homogeneous ; sometimes very slight interference ;
5 : very homogeneous ; no interference.
[0048] The quality results are summarized in table 3 :
TABLE 3
element |
quality at 1200 mw |
quality at 1330 mW |
R-1 |
1 |
2 |
R-2 |
2 |
3 |
I-1 |
4 |
5 |
I-2 |
5 |
5 |
[0049] The table clearly illustrates the superior results obtained with the elements according
to the present invention.
[0050] The recorded lines showed local variations in width due to local variations of laser
power as a consequence of interference. Table 4 summarizes the minimal and maximal
values of the line width (in µm) obtained with laser powers varying between 1110 and
1330 mW.
TABLE 4
Power |
elements |
|
R-1 min-max |
R-2 min-max |
I-1 min-max |
I-2 min-max |
1010 |
0 - 8 |
0 - 8 |
7 - 10 |
7 - 9 |
1110 |
0 - 8 |
5 - 11 |
7 - 10 |
8 - 9 |
1200 |
3 - 10 |
7 - 11 |
7 - 11 |
9.5-10 |
1260 |
5 - 11 |
7 - 11 |
9 - 12 |
10 - 11 |
1300 |
7-11.5 |
10 - 12 |
11 - 13 |
11-11.5 |
1330 |
7 - 12 |
10 - 12 |
11 - 13 |
11 - 12 |
[0051] It is clear from the table that the difference between minimal and maximal line width
is smaller with the elements according to the invention.
1. Heat mode recording element comprising, in order :
(a) a support,
(b) a layer containing a roughening agent,
(c) a metal recording layer,
(d) a protective element.
2. Heat mode recording element according to claim 1 wherein said layer containing a roughening
agent has a Ra value of at least 0.2 µm.
3. Heat mode recording element according to claim 1 or 2 wherein said roughening agent
has an average particle size between 0.3 and 2.0 µm.
4. Heat mode recording element according to claim 3 wherein said roughening agent having
an average particle size between 0.3 and 2.0 µm is present in layer (b) at a coverage
between 0.05 and 1.0 g/m².
5. Heat mode recording element according to any of claims 1 to 4 wherein said roughening
agent is polymethylmethacrylate.
6. Heat mode recording element according to any of claims 1 to 5 wherein said metal recording
layer is a bismuth layer.
7. Heat mode recording element according to claim 6 wherein said bismuth layer has a
thickness between 0.05 and 0.6 µm.
8. Heat mode recording element according to any of claims 1 to 7 wherein said support
is provided with a subbing layer and said layer (b) containing a roughening agent
is said subbing layer.
9. Heat mode recording element according to any of claims 1 to 8 wherein said protective
element comprises a polymeric cover sheet or layer being a transparent polymeric resin,
and an adhesive layer.
10. Method for the formation of a heat mode image comprising exposing information-wise
by intense laser radiation a heat mode recording element according to any of claims
1 to 9.
11. Method according to claim 10 wherein said intense laser radiation is produced by an
infra-red laser.
12. Method according to claim 11 wherein said infra-red laser is a Nd-YLF laser emitting
at 1053 nm.
13. Use of the heat mode image obtained according to the method of any of claims 10, 11,
or 12 as a master for the production of printed circuit boards or microelectronic
integrated circuits.
14. Use of the heat mode image obtained according to the method of any of claims 10, 11,
or 12 as a master for the exposure of a printing plate.