Field of the invention
[0001] The present invention relates to thermographic recording materials with improved
shelf-life, improved stability to incident light and improved archivability.
Background of the invention.
[0002] In direct thermal imaging the visible image pattern is formed by imagewise heating
of a recording material containing matter that by chemical or physical process changes
colour or optical density. Such direct thermal imaging materials can be rendered photothermographic
by incorporating a photosensitive agent which after exposure to UV, visible or IR
light is capable of catalyzing or participating in a thermographic process bringing
about changes in colour or optical density. Examples of photothermographic materials
are the so called "Dry Silver" photographic materials of the 3M Company, which are
reviewed by D. A. Morgan in "Handbook of Imaging Science", edited by A. R. Diamond,
page 43, published by Marcel Dekker in 1991.
[0003] EP-A 692 391 discloses a heat-sensitive recording material being suited for use in
direct thermal imaging and comprising in the order given: (i) a transparent polymeric
support, (ii) a heat-sensitive imaging layer, and (iii) a protective layer characterized
in that the protective layer is an opaque layer containing uniformly distributed in
an organic hydrophilic polymeric binder at least one opacifying pigment in the form
of particulate material some of which protrudes from the surface of said binder and
has anti-stick properties with regard to a thermal print head, wherein the opacity
of layer (iii) corresponds with an absorption and/or scattering of at least 80% of
the light of the visible wavelength range (400 to 700 nm). The invention examples
of EP-A 692 391 disclose a protective layer consisting of 11% by weight of gelatin
and 89% by weight of opacifying anatase-type titanium dioxide particles.
[0004] WO95/12495 discloses a method of recording an image by image-wise heating a recording
material, the recording material comprising on the same side of a support, called
the heat-sensitive side, (1) one or more layers comprising an imaging composition
essentially consisting of (i) a substantially light-insensitive organic silver salt
being in thermal working relationship with (ii) a reducing agent, and (2) at the same
side covering the imaging composition a protective layer, characterized in that the
image-wise heating proceeds with a thermal head contacting the heat-sensitive side
and through the protective layer mainly comprising a cured polymer or cured polymer
composition.
[0005] Ever tighter solvent emission regulations and measures to avoid solvent explosions,
make the avoidance of solvent emission during the coating of thermosensitive elements
with a protective layer desirable. However, coating with protective layers based on
polyvinyl alcohol and tetra-alkyl orthosilcates, such as described in WO95/12495,
or polyvinyl alcohol and polysilicic acid as described in US 4,741,992, results in
the emission of alcohols. There is therefore a need for water-based protective coatings
for thermosensitive and photo-addressable thermally developable elements based on
substantially light-insensitive organic silver salts and reducing agents with good
adhesion and transport properties in a thermographic printer using a thermal head,
but without deterioration in thermographic imaging characteristics such as maximum
and minimum print densities.
Objects of the invention.
[0006] It is therefore an object of the present invention to provide a water-based protective
layer for thermographic recording materials with good transport and imaging properties.
[0007] Further objects and advantages of the invention will become apparent from the description
hereinafter.
Summary of the invention
[0008] The above objects of the present invention are realized by providing a thermographic
recording material, thermally developable under substantially water-free conditions,
comprising a support and a thermosensitive element, the thermosensitive element being
provided with a protective layer and the thermosensitive element containing a substantially
light-insensitive silver salt of an organic carboxylic acid, a reducing agent therefor
in thermal working relationship therewith and a binder, characterized in that the
protective layer contains at least one proteinaceous binder and non-opacifying inorganic
particles with a weight averaged diameter of less than 1µm in a concentration of between
5 and 70% by weight with respect to the weight of the protective layer.
[0009] Preferred embodiments of the present invention are disclosed in the detailed description
of the invention.
Detailed description of the invention.
[0010] In a preferred embodiment the substantially light-insensitive thermographic recording
materials of the present invention are black and white thermographic recording materials.
Definitions
[0011] By substantially light-insensitive is meant not intentionally light sensitive.
[0012] By substantially solvent-free aqueous medium is meant that solvent, if present, is
present in amounts below 10% by volume of the aqueous medium.
[0013] By non-opacifying inorganic particles is meant inorganic particles which do not absorb
and/or scatter at least 80% of the light of the visible wavelength range (400 to 700
nm) thereby rendering the layer in which they are present opaque i.e. preventing transmission
of visible light by reflection or dispersion.
[0014] By the term essentially colourless is meant colourless to the naked eye.
[0015] By the term "heat solvent" is meant a non-hydrolyzable organic material which is
in a solid state in the recording layer at temperatures below 50°C, but upon heating
becomes a plasticizer for the recording layer and/or a liquid solvent for at least
one of the redox-reactants.
[0016] Heating in a substantially water-free condition as used herein, means heating at
a temperature of 80 to 250°C. The term "substantially water-free condition" means
that the reaction system is approximately in equilibrium with water in the air, and
water for inducing or promoting the reaction is not particularly or positively supplied
from the exterior to the element. Such a condition is described in T. H. James, "The
Theory of the Photographic Process", Fourth Edition, Macmillan 1977, page 374.
Mon-opacifying inorganic particles
[0017] The particle size of the non-opacifying inorganic particles having a weight averaged
particle size of less than 1µm used in the thermographic recording materials according
to the present invention may be determined by such techniques as electron microscopy
for particle sizes in the range 1 to 10,000 nm, photo-correlation spectroscopy, static
light scattering for particle sizes in the range 300 to 1,500 nm, quasi-elastic light
scattering (QELS) for the hydrodynamic diameters in the range 10 to 3,000 nm, light
scattering particle size analyzers based on Mie scattering or Fraunhofer diffraction
e.g. the COULTER™ LS230 from COULTER CORP. which combines Fraunhofer diffraction with
polarization intensity differential scattering (PIDS), ultracentrifuge measurements
for particle sizes in the range 10 to 20,000 nm in a gravity field of 20 to 200,000g.
sedimentation analysis and specific surface area measurements using the BET method
according to ISO NORM 9277.1995(E) and DIN NORM 66 131 of October 1973.
[0018] Suitable non-opacifying inorganic particles include colloidal silica, china clay
and kaolin.
Protective layer
[0019] According to the thermographic recording material of the present invention, a thermosensitive
element is provided with a protective layer, the protective layer containing at least
one proteinaceous binder and non-opacifying inorganic particles with a weight averaged
diameter of less than 1µm, with non-opacifying inorganic particles with a weight averaged
diameter 0.4µm or less being preferred and those with a weight averaged diameter of
0.2µm or less being particularly preferred. The concentration of the non-opacifying
inorganic particles in the protective layer with respect to the weight of the protective
layer is between 5 and 70% by weight, with 15 to 63% by weight being preferred and
20 to 50% by weight being particularly preferred.
[0020] In general the protective layer protects the thermosensitive element from atmospheric
humidity and from surface damage by scratching etc. and prevents direct contact of
printheads or heat sources with the recording layers. Protective layers for thermosensitive
elements which come into contact with and have to be transported past a heat source
under pressure, have to exhibit resistance to local deformation and good slipping
characteristics during transport past the heat source during heating as well as excellent
adhesion to the thermosensitive element which they protect.
[0021] The non-opacifying inorganic particles are preferably essentially colourless. The
protective layer preferably contains a non-cationic surfactant, and may contain a
dissolved lubricating material and/or particulate material, e.g. talc particles, optionally
protruding from the surface. Examples of suitable lubricating materials are a surface
active agent, a liquid lubricant, a solid lubricant or mixtures thereof, which may
be used with or without a polymeric binder.
Proteinaceous binders
[0022] Suitable proteinaceous binders include gelatin, modified gelatins such as phthaloyl
gelatin, zein etc., with gelatin being preferred. It is preferred that the halide
ion concentration in the proteinaceous binders present in the protective layer together
do not exceed 300ppm, with not exceeding 150ppm being particularly preferred and not
exceeding 100ppm being especially preferred. The alkali metal ion concentration in
the proteinaceous binder(s) used in the protective layer of the thermographic and
photothermographic recording materials of the present invention together preferably
do not exceed 500ppm, with not exceeding 100ppm being particularly preferred and not
exceeding 50ppm being especially preferred.
[0023] The halide ion concentration in organic materials can be determined by standard analytical
techniques e.g. ion chromatography. The following method using ion chromatography
has been found to give reliable and reproducible values for halide ion concentration
in proteinaceous binders: 1 ml of 0.1N silver nitrate is added to an accurately weighed
sample weighing about 5 g in weight in a 100 ml beaker and then 5 ml of 70% nitric
acid is added. The mixture is then boiled for about 15 minutes, whereupon the organic
material is decomposed, the chloride ions are released into solution and then are
bound by the silver ions forming a silver halide precipitate. After cooling the suspension
is filtered in a Millipore™ and the residue thoroughly washed with deionized water.
The filter is then transferred to a test-tube with a stopper and 10 ml of 0.008% ammonium
sulfide are added. The mixture is then shaken for 20 minutes to convert the silver
halide precipitate to a silver sulfide precipitate and release the halide ions into
solution. The solution is then injected, after dilution should this be necessary,
into a DIONEX™ QIC ANALYSER with an AG3 guard column and an AS3 separator column and
the halide ion concentration determined. Chloride ion concentrations down to 10µg
Cl
-/ml sample can be detected using this technique.
[0024] Alkali metal ions in organic materials can be determined by digesting an accurately
weighed Ca. 500 mg sample with nitric acid and hydrogen peroxide in a closed destruction
system. Then diluting to 25 ml with deionized water and injecting into an inductively
coupled plasma to determine the alkali ion concentration.
[0025] Table 1 shows that the chloride ion concentration present in gelatin as determined
by ion chromatography using a DIONEX QIC ANALYSER ion chromatograph varies according
to gelatin type from 5300 to 17ppm and the sodium ion concentration varies between
less than 100ppm to 2600ppm:
Table 1
GELATIN type |
general description |
chloride ion concentration [ppm] |
sodium ion concentration [ppm] |
GEL01 |
low viscosity |
5300 |
- |
GEL02 |
hydrolyzed gelatin |
2900 |
1700 |
GEL03 |
calcium-free, low viscosity |
1270 |
- |
GEL04 |
calcium-free, medium viscosity |
17 |
<100 |
GEL05 |
calcium-free, low viscosity |
<40 |
2600 |
GEL06* |
calcium-free, low viscosity |
<40 |
<100 |
GEL07 |
calcium-containing, medium viscosity |
≤ 250# |
- |
GEL08 |
calcium-free, high viscosity |
≤ 200# |
- |
GEL09 |
calcium-free, medium viscosity |
≤ 150# |
- |
GEL10 |
calcium-containing, low viscosity |
150-300# |
- |
* type 17881, a calcium-free gelatin with low potassium ion, sodium ion and chloride-ion
concentrations from AGFA-GEVAERT GELATINEFABRIEK |
# manufacturer's specification |
[0026] Gelatin can be present in two forms dependent upon amongst other things upon the
conditions under which it is dried. Above a temperature of 40°C a gelatin solution
behaves as a normal polyelectrolyte. Upon gelation triple helices are formed. With
increasing gelation temperature, the thermostabilization of the gel structures increases
slightly because of increasing mobility of the gelatin segments with lead to an ever
more perfect triple helix structure as can be seen by the increase in melting point.
Upon drying the already formed aggregates of helices orientate in a planar manner,
due to adhesion to the support layer. This results in the strong vertical swelling,
several hundred % and smaller lateral swelling of layers separated from a support.
If the layer temperature is higher, fewer gel structures form and the lateral swelling
is greater [see Photographic Gelatin, R. J. Croome and F. G. Clegg, Focal Press, London
(1965)]. If the layer temperature is 10 to 15°C during the drying process, the so-called
gel-form of gelatin is produced with a pronounced triple helix structure as characterized
by X-ray diffraction spectra [see Nature 168, 837 (1951)], whereas drying at temperatures
of 20 to 30°C produces so-called sol-gelatin in which the triple helix structure is
substantially absent.
Thermosensitive element
[0027] According to the present invention, the thermosensitive element contains a substantially
light-insensitive silver salt of an organic carboxylic acid, a reducing agent therefor
in thermal working relationship therewith and a binder. By thermal working relationship
with one another is meant that during the thermal development process the reducing
agent must be present in such a way that it is able to diffuse to the particles of
substantially light-insensitive silver salt of an organic carboxylic acid so that
reduction thereof can take place. The thickness of the thermosensitive element is
preferably in the range of 1 to 50 µm.
[0028] In a particularly preferred embodiment of the present invention the thermosensitive
element further contains a photosensitive silver halide, making the thermographic
recording material photothermographic.
Silver salts of an organic carboxylic acid
[0029] Preferred substantially light-insensitive silver salts of an organic carboxylic acid
used in the present invention are silver salts of aliphatic carboxylic acids known
as fatty acids, wherein the aliphatic carbon chain has preferably at least 12 C-atoms,
e.g. silver laurate, silver palmitate, silver stearate, silver hydroxystearate, silver
oleate and silver behenate, which silver salts are also called "silver soaps". Other
silver salts of an organic carboxylic acid as described in GB-P 1,439,478, e.g. silver
benzoate, may likewise be used to produce a thermally developable silver image. Combinations
of different silver salt of an organic carboxylic acids may also be used in the present
invention.
Auxiliary film-forming binders of the thermosensitive element
[0030] Suitable water-dispersible binders for use as auxiliary binders in the thermographic
and photothermographic recording materials of the present invention may be any water-insoluble
polymer. It should be noted that there is no clear cut transition between a polymer
dispersion and a polymer solution in the case of very small polymer particles resulting
in the smallest particles of the polymer being dissolved and those slightly larger
being in dispersion. Preferred water-dispersible binders for use according to the
present invention are water-dispersible film-forming polymers with covalently bonded
ionic groups selected from the group consisting of sulfonate, sulfinate, carboxylate,
phosphate, quaternary ammonium, tertiary sulfonium and quaternary phosphonium groups.
Further preferred water-dispersible binders for use according the present invention
are water-dispersible film-forming polymers with covalently bonded moieties with one
or more acid groups.
[0031] The above mentioned binders or mixtures thereof may be used in conjunction with waxes
or "heat solvents" also called "thermal solvents" or "thermosolvents" improving the
reaction speed of the redox-reaction at elevated temperature.
Organic reducing agents
[0032] Suitable organic reducing agents for the reduction of silver salt of an organic carboxylic
acid particles are organic compounds containing at least one active hydrogen atom
linked to O, N or C, such as is the case with, aromatic di- and tri-hydroxy compounds;
aminophenols; METOL™; p-phenylene-diamines; alkoxynaphthols, e.g. 4-methoxy-1-naphthol
described in US-P 3,094,41; pyrazolidin-3-one type reducing agents, e.g. PHENIDONE™;
pyrazolin-5-ones; indan-1,3-dione derivatives; hydroxytetrone acids; hydroxytetronimides;
hydroxylamine derivatives such as for example described in US-P 4,082,901; hydrazine
derivatives; and reductones e.g. ascorbic acid; see also US-P 3,074,809, 3,080,254,
3,094,417 and 3,887,378.
[0033] Catechol-type reducing agents, i.e. reducing agents containing at least one benzene
nucleus with two hydroxy groups (-OH) in ortho-position, such as catechol, 3-(3,4-dihydroxyphenyl)
propionic acid, 1,2-dihydroxybenzoic acid, gallic acid and esters e.g. methyl gallate,
ethyl gallate, propyl gallate, tannic acid, and 3,4-dihydroxy-benzoic acid esters
are preferred, with those described in EP 692 733 and EP-A 903 625 being particularly
preferred. Other suitable reducing agents are sterically hindered phenols, bisphenols
and sulfonamidophenols.
[0034] Combinations of reducing agents may also be used that on heating become reactive
partners in the reduction of the substantially light-insensitive silver salt or an
organic carboxylic acid. For example, combinations of sterically hindered phenols
with sulfonyl hydrazide reducing agents such as disclosed in US-P 5,464,738; trityl
hydrazides and formyl-phenyl-hydrazides such as disclosed in US-P 5,496,695; trityl
hydrazides and formyl-phenyl-hydrazides with diverse auxiliary reducing agents such
as disclosed in US-P 5,545,505, US-P 5.545.507 and US-P 5,558,983; acrylonitrile compounds
as disclosed in US-P 5,545,515 and US-P 5,635,339; and 2-substituted malonodialdehyde
compounds as disclosed in US-P 5,654,130
Toning agents
[0035] In order to obtain a neutral black image tone in the higher densities and neutral
grey in the lower densities, the thermographic and photothermographic recording materials
according to the present invention may contain one or more toning agents. The toning
agents should be in thermal working relationship with the substantially light-insensitive
silver salt of an organic carboxylic acid and reducing agents during thermal processing.
Any known toning agent from thermography or photothermography may be used. Suitable
toning agents are the phthalimides and phthalazinones within the scope of the general
formulae described in US-P 4,082,901 and the toning agents described in US-P 3,074,809,
US-P 3,446,648 and US-P 3,844,797. Particularly useful toning agents are the heterocyclic
toner compounds of the benzoxazine dione or naphthoxazine dione type described in
GB-P 1,439,478, US-P 3,951,660 and US-P 5,599,647.
Stabilizers and antifoggants
[0036] In order to obtain improved shelf-life and reduced fogging, stabilizers and antifoggants
may be incorporated into the thermographic recording materials of the present invention.
Polycarboxylic acids and anhydrides thereof
[0037] According to the recording material of the present invention the thermosensitive
element may comprise in addition at least one polycarboxylic acid and/or anhydride
thereof in a molar percentage of at least 15 with respect to all the silver salt of
an organic carboxylic acid(s) present and in thermal working relationship therewith.
The polycarboxylic acid may be aliphatic (saturated as well as unsaturated aliphatic
and also cycloaliphatic) or an aromatic polycarboxylic acid. These acids may be substituted
e.g. with alkyl, hydroxyl, nitro or halogen. They may be used in anhydride form or
partially esterified on the condition that at least two free carboxylic acids remain
or are available in the heat recording step.
Surfactants and dispersants
[0038] Surfactants are surface active agents which are soluble compounds which reduce the
interfacial tension between a liquid and a solid. The thermographic and photothermographic
recording materials of the present invention may contain anionic, non-ionic or amphoteric
surfactants e.g.:
- Surfactant Nr. S01
- =ammonium dodecylphenylsulfonate;
- Surfactant Nr. S02
- =ANTAROX™ CO630, a nonylphenyloxypenta(ethyleneoxy) non-ionic surfactant supplied
by GAF.
- Surfactant Nr. S03
- =GAFAC™ RM710, a complex organic phosphate ester from GAF;
- Surfactant Nr. S04
- =ULTRAVON™ W, an aryl sulfonate from CIBA-GEIGY
- Surfactant Nr. S05
- =ARKOPAL™ N060 (previously HOSTAPAL™ W), a nonylphenylpolyethylene-glycol from HOECHST
- Surfactant Nr. S06
- =SAPONINE QUILAYA, containing 10% of saponines, 15% of tannins, 11% of calcium oxalate
and 64% of starch from SCHMITTMANN;
- Surfactant Nr. S07
- = NIAPROOF ANIONIC™ 4, supplied as a 27% concentrate of a sodium 1-(2'-ethylbutyl)-4-ethylhexylsulphate
by NIACET;
- Surfactant Nr. S08
- = ammonium salt of perfluoro-octanoic acid.
[0039] Suitable dispersants are natural polymeric substances, synthetic polymeric substances
and finely divided powders, for example finely divided non-metallic inorganic powders
such as silica.
Other ingredients
[0040] In addition to the ingredients the substantially light-insensitive thermographic
recording material may contain other additives such as free fatty acids, silicone
oil, ultraviolet light absorbing compounds, white light reflecting and/or ultraviolet
radiation reflecting pigments and/or optical brightening agents.
Support
[0041] The support for the substantially light-insensitive thermographic recording material
according to the present invention may be transparent, translucent or opaque and is
preferably a thin flexible carrier made e.g. from paper, polyethylene coated paper
or transparent resin film, e.g. made of a cellulose ester, e.g. cellulose triacetate,
polypropylene, polycarbonate or polyester, e.g. polyethylene terephthalate. The support
may be in sheet, ribbon or web form. The support may be subbed with a subbing layer.
It may also be made of an opacified resin composition.
Photosensitive silver halide
[0042] The photosensitive silver halide used in the present invention may be employed in
a range of 0.1 to 100 mol percent; preferably, from 0.2 to 80 mol percent; particularly
preferably from 0.3 to 50 mol percent; especially preferably from 0.5 to 35 mol %;
and especially from 1 to 12 mol % of substantially light-insensitive organic silver
salt.
[0043] The silver halide may be any photosensitive silver halide such as silver bromide,
silver iodide, silver chloride, silver bromoiodide, silver chlorobromoiodide, silver
chlorobromide etc. The silver halide may be in any form which is photosensitive including,
but not limited to, cubic, orthorhombic, tabular, tetrahedral, octagonal etc. and
may have epitaxial growth of crystals thereon.
[0044] The silver halide used in the present invention may be employed without modification.
However, it may be chemically sensitized with a chemical sensitizing agent such as
a compound containing sulphur, selenium, tellurium etc., or a compound containing
gold, platinum, palladium, iron, ruthenium, rhodium or iridium etc., a reducing agent
such as a tin halide etc., or a combination thereof. The details of these procedures
are described in T. H. James, "The Theory of the Photographic Process", Fourth Edition,
Macmillan Publishing Co. Inc., New York (1977), Chapter 5, pages 149 to 169.
Spectral sensitization
[0045] The photosensitive silver halide in the photo-addressable thermally developable element
of the photothermographic recording material, according to the present invention,
may be spectrally sensitized with a spectral sensitizer, optionally together with
a supersensitizer. Various known dyes are suitable spectral sensitizers including
cyanine, merocyanine, styryl, hemicyanine, oxonol, hemioxonol and xanthene dyes.
Antihalation dyes
[0046] The thermographic recording materials used in the present invention may also contain
antihalation or acutance dyes which absorb light which has passed through the photosensitive
thermally developable photographic material, thereby preventing its reflection. Such
dyes may be incorporated into the photosensitive thermally developable photographic
material or in any other layer of the photographic material of the present invention.
Antistatic layer
[0047] In a preferred embodiment the thermographic recording material of the present invention
an antistatic layer is applied to an outermost layer.
Coating
[0048] The coating of any layer of the substantially light-insensitive thermographic recording
materials of the present invention may proceed by any coating technique e.g. such
as described in Modern Coating and Drying Technology, edited by Edward D. Cohen and
Edgar B. Gutoff, (1992) VCH Publishers Inc., 220 East 23rd Street, Suite 909 New York,
NY 10010, USA.
Thermographic printing
[0049] Thermographic imaging is carried out by the image-wise application of heat either
in analogue fashion by direct exposure through an image of by reflection from an image,
or in digital fashion pixel by pixel either by using an infra-red heat source, for
example with a Nd-YAG laser or other infra-red laser, or by direct thermal imaging
with a thermal head. Heating takes place in a substantially water-free condition.
[0050] In thermal printing, image signals are converted into electric pulses and then through
a driver circuit selectively transferred to a thermal printhead. The thermal printhead
consists of microscopic heat resistor elements, which convert the electrical energy
via the Joule effect into heat, which is transferred to the surface of the thermographic
recording material wherein the chemical reaction resulting in the development of a
black and white image takes place. Such thermal printing heads may be used in contact
or close proximity with the recording layer. The operating temperature of common thermal
printheads is in the range of 300 to 400°C and the heating time per picture element
(pixel) may be less than 1.0 ms, the pressure contact of the thermal printhead with
the recording material being e.g. 200-500g/cm
2 to ensure a good transfer of heat.
[0051] In order to avoid direct contact of the thermal printing heads with a recording layer
not provided with an outermost protective layer, the image-wise heating of the recording
layer with the thermal printing heads may proceed through a contacting but removable
resin sheet or web wherefrom during the heating no transfer of recording material
can take place.
[0052] The image signals for modulating the laser beam or current in the micro-resistors
of a thermal printhead are obtained directly e.g. from opto-electronic scanning devices
or from an intermediary storage means, optionally linked to a digital image work station
wherein the image information can be processed to satisfy particular needs. Activation
of the heating elements can be power-modulated or pulse-length modulated at constant
power. EP-A 654 355 describes a method for making an image by image-wise heating by
means of a thermal head having energizable heating elements, wherein the activation
of the heating elements is executed duty cycled pulsewise.
[0053] When used in thermographic recording operating with thermal printheads the thermographic
recording materials are not suitable for reproducing images with fairly large number
of grey levels as is required for continuous tone reproduction. EP-A 622 217 discloses
a method for making an image using a direct thermal imaging element producing improvements
in continuous tone reproduction.
[0054] Image-wise heating of the thermographic recording material can also be carried out
using an electrically resistive ribbon incorporated into the material. Image- or pattern-wise
heating of the thermographic recording material may also proceed by means of pixelwise
modulated ultra-sound, using e.g. an ultrasonic pixel printer as described e.g. in
US-P 4,908,631.
Photothermographic printing
[0055] Photothermographic recording materials, according to the present invention, may be
exposed with radiation of wavelength between an X-ray wavelength and a 5 microns wavelength
with the image either being obtained by pixel-wise exposure with a finely focused
light source, such as a CRT light source; a UV, visible or IR wavelength laser, such
as a He/Ne-laser or an IR-laser diode, e.g. emitting at 780nm, 830nm or 850nm; or
a light emitting diode, for example one emitting at 659nm; or by direct exposure to
the object itself or an image therefrom with appropriate illumination e.g. with UV,
visible or IR light.
[0056] For the thermal development of image-wise exposed photothermographic recording materials,
according to the present invention, any sort of heat source can be used that enables
the recording materials to be uniformly heated to the development temperature in a
time acceptable for the application concerned e.g. contact heating, radiative heating,
microwave heating etc.
Industrial application
[0057] Thermographic recording materials according to the present invention may be used
for both the production of transparencies, for example in the medical diagnostic field
in which black-imaged transparencies are widely used in inspection techniques operating
with a light box, and reflection type prints, for example in the hard copy field.
For such applications the support will be transparent or opaque, i.e. having a white
light reflecting aspect. Should a transparent base be used, the base may be colourless
or coloured, e.g. with a blue colour for medical diagnostic applications.
[0058] While the present invention will hereinafter be described in connection with a preferred
embodiment thereof, it will be understood that it is not intended to limit the invention
to that embodiment. The following examples and comparative examples illustrate the
present invention. The percentages and ratios used in the examples and compositions
of the ingredients are by weight unless otherwise indicated.
i) backing layer ingredients:
[0059]
- KELZAN™ S
- = a xanthan gum from MERCK & CO., Kelco Division, USA, which according to Technical
Bulletin DB-19 is a polysaccharide containing mannose, glucose and glucuronic repeating
units as a mixed potassium, sodium and calcium salt;
- PERAPRET™ PE40
- = a 40% aqueous dispersion of polyethylene latex from BASF;
- LATEX02,
- = a 20% by weight dispersion of polymethyl methacrylate with an average particle size
of 88.8nm prepared as described in US-P 5,354,613;
- LATEX03,
- = a 15% dispersion of a terpolymer of 18 mol% methyl acrylate, 79 mol% potassium salt
of acrylic acid and 3 mol% tetra-allyloxyethane;
- LATEX04
- = a 20% dispersion of a 1µm polymethylmethacrylate latex;
- KIESELSOL™ 100F
- = a colloidal silica from BAYER;
- KIESELSOL™ 300F
- = a colloidal silica from BAYER;
- PLEXIGUM™ M345
- = a polymethylmethacrylate type from ROHM;
ii) thermosensitive element ingredients (in addition to those mentioned above):
[0060]
- AgB
- = silver behenate
- R01
- = ethyl 3,4-dihydroxybenzoate, a reducing agent
- T01
- = benzo[e][1,3]oxazine-2,4-dione, a toning agent
- LATEX 01
- = a terpolymer of 42% butyl acrylate, 53% styrene, 2% itaconic acid and 3% of the
ammonium salt of N-[(4'-sulfobenzamido)-oxo-decyl]methacrylamide.
iii) protective layer ingredients:
[0061]
- POLY01
- = POLYVIOL™ WX48 20, a polyvinylalcohol from WACKER CHEMIE;
- SYLOID™ 72
- = a porous silica from Grace with a similar particle size to SYLOID™ 244;
- SYLOID™ 244
- = a porous silica with a weight averaged particle size of 3.86µm from Grace;
- MICROACE™ P3
- = an Indian talc with a particle size of 4.5µm, from Nippon Talc;
- STEAMIC™OOS
- = a talc with a particle size of 2.8µm, from Talc de Luzenac;
- SERVOXYL™ VPAZ 100
- = a mixture of monolauryl and dilauryl phosphate, from Servo Delden B.V.;
- SERVOXYL™ VPDZ 3/100
- = a mono[isotridecyl polyglycolether (3 EO)] phosphate, from Servo Delden B.V.;
- RILANIT™ GMS
- = a glycerine monotallow acid ester, from Henkel AG;
- LEVASIL™ VP AC 4055
- = 15% aqueous dispersion of colloidal silica with acid groups substantially neutralized
with sodium ions and a specific surface area of 500 m2/g, from Bayer AG;
- china clay
- = China Clay Supreme' a supreme china clay type with a weight averaged particle size
of 0.4µm, Zinchem-Benelux N.V.;
- kaolin
- = DIXIE Clay with a weight averaged particle size of 0.2µm, from R.T. Vanderbilt Company,
Inc.
Preparation of colloidal silica with any acid groups upon acidification substantially
neutralized with ammonium ions
[0062] Colloidal silica with any acid groups upon acidification substantially neutralized
with ammonium ions was prepared from LEVASIL™ VP AC 4055 in a two step process. In
the first step 10L of the acidic ion exchange resin LEWATIT™ S100MB was added to a
mixture of 12L of deionized water and 4L of a 26% aqueous ammonia solution. The dispersion
was then stirred for 90 minutes thereby converting the ion exchange resin into its
ammonium form. The converted ion exchange resin in the ammonium form was then filtered
off and washed with deionized water until the wash-water was neutral. In the second
step 5L of the ion exchange resin in the ammonium form was added to 20L of LEVASIL™
VP AC 4055 and the resulting dispersion stirred for 2 hours. The ion exchange resin
was then filtered off, a further 5L of the ion exchange resin in the ammonium form
added, the dispersion stirred for 2 hours and then the ion exchange resin was filtered
off.
COMPARATIVE EXAMPLES 1 & 2 and INVENTION EXAMPLES 4 & 5
Thermosensitive elements
[0063] In the coating of the thermosensitive elements of COMPARATIVE EXAMPLES 1 & 3 AND
INVENTION EXAMPLES 1 to 6, 175µm thick subbed blue pigmented polyethylene terephthalate
support was coated with an aqueous coating composition which upon drying produced
a thermosensitive element containing the composition given in table 1.
[0064] In the coating of the thermosensitive elements of COMPARATIVE EXAMPLE 2 and INVENTION
EXAMPLE 7, 175µm thick subbed blue pigmented polyethylene terephthalate support was
coated with an aqueous coating composition and dried at 18 to 20°C for 93s in a stream
of air with a flow rate of 950kg/min to produce the thermosensitive element containing
the composition given in table 1.
Table 1
|
thermosensitive elements |
|
Comparative examples nr 1 & 3 and Invention examples |
Comparative example nr. 2 & Invention example 7 |
AgBeh |
4.92g/m2 |
4.94g/m2 |
GEL05 |
0.67g/m2 |
4.53g/m2 |
GEL06 |
3.45g/m2 |
- |
formaldehyde |
0. 2g/m2 |
- |
Surfactant Nr. S01 |
0.256g/m2 |
0.32g/m2 |
Surfactant Nr. S02 |
0.004g/m2 |
0.004g/m2 |
R01 |
1.00g/m2 |
1.00g/m2 |
T01 |
1.08g/m2 |
1.08g/m2 |
boric acid |
0.31g/m2 |
0.31g/m2 |
Protective layer
[0065] The thermosensitive elements of the thermographic recording materials of INVENTION
EXAMPLES 1 to 7 and COMPARATIVE EXAMPLES 1 to 3 were then coated with a protective
layer having the compositions given in table 2.
Table 2
coverage in g/m2 |
Invention example nr |
Comparative example nr |
|
1-5 |
6 |
7 |
1 |
2 |
3 |
GEL06 |
2.5 |
2.5 |
2.5 |
2.5 |
2.5 |
2.5 |
Colloidal silica in ammonium form |
0.5 |
0.5 |
0.5 |
0.5 |
0.5 |
0.5 |
HCHO |
0.2 |
0.4 |
0.87 |
0.4 |
0.87 |
0.4 |
STEAMIC™ OOS |
0.045 |
0.045 |
0.045 |
0.045 |
0.045 |
0.045 |
SYLOID™ 72 |
0.09 |
0.09 |
0.09 |
0.09 |
0.09 |
0.09 |
RILANIT™ GMS |
0.135 |
0.135 |
0.135 |
0.135 |
0.135 |
0.135 |
SERVOXYL™ VPAZ 100 |
0.06 |
0.06 |
0.06 |
0.06 |
0.06 |
0.06 |
SERVOXYL™ VPDZ 3/100 |
0.075 |
0.075 |
0.075 |
0.075 |
0.075 |
0.075 |
Surfactant Nr. S02 |
0.11 |
0.11 |
0.11 |
0.11 |
0.11 |
0.11 |
[0066] The protective layers of INVENTION EXAMPLES 1 to 7 and COMPARATIVE EXAMPLES 1 to
3 were dried under the conditions given in table 3 to produce protective layers about
3µm thick.
Evaluation of the protective layers
[0067] The protective layers were then subjected to lateral swelling tests whereby from
a sample of thermographic recording materials with dimensions of 0.3 x 2cm
2 the layer combination on the side of the thermographic recording material coated
with the thermosensitive element was detached from the support and its swelling behaviour
in water monitored. After 2 minutes in deionized water at room temperature, the increase
in length of the thermographic recording materials of INVENTION EXAMPLES 1 to 7 and
COMPARATIVE EXAMPLES 1 to 3 was measured This is expressed in table 3 as the % swelling.
[0068] The printability of the thermographic recording materials of INVENTION EXAMPLES 1
to 7 and COMPARATIVE EXAMPLES 1 to 3 was investigated in a thermographic printer.
The printer was equipped with a thin film thermal head with a resolution of 300 dpi
and was operated with a line time of 19ms (the line time being the time needed for
printing one line). During this line time the printhead received constant power. The
average printing power, being the total amount of electrical input energy during one
line time divided by the line time and by the surface area of the heat-generating
resistors was 1.6 mJ/dot being sufficient to obtain maximum optical density in each
of the substantially light-insensitive thermographic recording materials of INVENTION
EXAMPLES 1 to 7. The print quality was visually evaluated on the basis of the following
print characteristics:
printing characteristics |
print quality |
protective layer scoured off by the printing head |
poor |
printing quality good, appearance of protective layer acceptable |
good |
printing quality good, appearance of protective layer good |
excellent |
[0069] The degree of lateral swelling of the layer composition of the thermographic recording
materials of COMPARATIVE EXAMPLES 1 to 3 of above 15% are characteristic of gelatin
in the sol-form, whereas that of the layer composition of the thermographic recording
material of INVENTION EXAMPLES 3, 6 and 7 with a lateral swelling of 13% is characteristic
of a mixture of gelatin in the gel-form with gelatin in the sol-form and that of the
layer composition of the thermographic recording material of INVENTION EXAMPLES 1,
2, 4 and 5 with a lateral swelling of between 6 and 10% is characteristic of gelatin
substantially in the gel-form.
[0070] The protective layers of the thermographic recording materials of COMPARATIVE EXAMPLES
1 to 3 exhibited poor print quality due to the protective layer becoming detached
from the thermosensitive element whereas the thermographic recording materials of
INVENTION EXAMPLES 1 to 7 exhibited an excellent print quality. It is therefore evident
that for protective layer thicknesses of about 3µm, the adhesion of protective layers
with exclusively sol-gelatin is poor, whereas it is satisfactory with gelatin consisting
either of a mixture of sol and gel gelatin or of substantially gel-gelatin.
Table 3
comparative example nr |
air temperature during drying [°C] |
lateral swelling [%] |
print quality |
1 |
21 |
21 |
poor |
2 |
25 |
20 |
poor |
3 |
25 |
17 |
poor |
Invention example nr |
|
|
|
1 |
12 |
9.7 |
excellent |
2 |
12 |
6.1 |
excellent |
3 |
12 |
12.7 |
excellent |
4 |
12 |
6.4 |
excellent |
5 |
12 |
6.7 |
excellent |
6 |
17 |
13 |
excellent |
7 |
17 |
13 |
excellent |
INVENTION EXAMPLES 8 to 10
Thermosensitive elements
[0071] The thermosensitive elements of INVENTION EXAMPLES 8 to 10 were coated on a 175µm
thick subbed polyethylene terephthalate support coated with the following composition:
AgBeh |
4.92g/m2 |
GEL06 |
3.96g/m2 |
formaldehyde |
0.2g/m2 |
Surfactant Nr. S01 |
0.39g/m2 |
Surfactant Nr. S02 |
0.004g/m2 |
R01 |
1.0g/m2 |
T01 |
0.55g/m2 |
boric acid |
0.085g/m2 |
(NH4)2B4O7.10H2O |
0.242g/m2 |
Protective layer
[0072] The thermosensitive elements of the thermographic recording materials of INVENTION
EXAMPLES 8 to 10 were then coated with an aqueous coating composition and dried at
an air temperature of 12°C to produce protective layers with the compositions given
in table 4. The protective layers of INVENTION EXAMPLES 1 to 7 and COMPARATIVE EXAMPLES
1 to 3 were dried to produce protective layers about 7µm thick.
Table 4
coverage in g/m2 |
Invention example nr 8 |
Invention example nr 9 |
Invention example nr 10 |
Gelatin type |
GEL06 |
GEL01 |
GEL02 |
Gelatin coverage |
4.29 |
4.29 |
4.29 |
Colloidal silica in ammonium form |
1.34 |
1.34 |
1.34 |
HCHO |
0.34 |
0.34 |
0.34 |
STEAMIC™ OOS |
0.08 |
0.08 |
0.08 |
SYLOID™ 72 |
0.15 |
0.15 |
0.15 |
RILANIT™ GMS |
0.23 |
0.23 |
0.23 |
SERVOXYL™ VPAZ 100 |
0.1 |
0.1 |
0.1 |
SERVOXYL™ VPDZ 3/100 |
0.13 |
0.13 |
0.13 |
Surfactant Nr. S03 |
0.13 |
0.13 |
0.13 |
Surfactant Nr. S02 |
0.19 |
0.19 |
0.19 |
Thermographic evaluation
[0073] The thermographic recording materials were printed as described for the thermographic
recording materials of COMPARATIVE EXAMPLES 1 to 3 and INVENTION EXAMPLES 1 to 7.
The minimum densities, D
min, of the prints given in table 5 were measured through a blue filter with a MACBETH™
TR924 densitometer in the grey scale step corresponding to data levels of 0. The D
min values of the prints produced with the thermographic recording materials of INVENTION
EXAMPLES 8 to 10 were found to be strongly dependent upon the type of gelatin used
in the protective layer and in particular upon the chloride ion concentration in the
gelatin as can be seen from the results in table 5.
Table 5
Invention example nr |
gelatin |
printing after hardening for 5d at 40°C Dmin blue |
ΔDmin blue after 3d at 30°C/85%RH |
|
type |
Cl- concentration in ppm |
|
|
8 |
GEL06 |
<40 |
0.13 |
+0.07 |
9 |
GEL01 |
5300 |
0.21 |
+0.43 |
10 |
GEL02 |
2900 |
0.20 |
+0.45 |
INVENTION EXAMPLES 11 to 14 and COMPARATIVE EXAMPLES 4 and 5
[0074] The thermosensitive element described for INVENTION EXAMPLES 8 to 10 was coated with
an aqueous coating composition and dried at an air temperature of 12°C to produce
the thermographic recording materials of INVENTION EXAMPLES 11 to 14 and COMPARATIVE
EXAMPLES 4 & 5 having protective layers with the compositions given in table 6.
Table 6
coverage in g/m2 |
Invention example nr |
Comparative example nr |
|
11 |
12 |
13 |
14 |
4 |
5 |
GEL06 |
4.29 |
4.29 |
4.29 |
4.29 |
4.29 |
5.63 |
Colloidal silica in ammonium form |
1.34 |
1.61 |
- |
- |
- |
- |
LEVASIL VP AC 4055 |
- |
- |
1.34 |
1.61 |
- |
- |
STEAMIC™ OOS |
0.08 |
0.08 |
0.08 |
0.08 |
0.08 |
0.08 |
SYLOID™ 244 |
0.15 |
0.15 |
0.15 |
0.15 |
0.15 |
0.15 |
RILANIT™ GMS |
0.23 |
0.23 |
0.23 |
0.23 |
0.23 |
0.23 |
SERVOXYL™ VPAZ 100 |
0.1 |
0.1 |
0.1 |
0.1 |
0.1 |
0.1 |
SERVOXYL™ VPDZ 3/100 |
0.13 |
0.13 |
0.13 |
0.13 |
0.13 |
0.13 |
Surfactant Nr. S03 |
0.13 |
0.13 |
0.13 |
0.13 |
0.13 |
0.13 |
Surfactant Nr. S02 |
0.19 |
0.19 |
0.19 |
0.19 |
0.19 |
0.19 |
HCHO |
0.34 |
0.34 |
0.34 |
0.34 |
0.34 |
0.34 |
[0075] The printing behaviour was evaluated on the thermographic recording materials of
INVENTION EXAMPLES 11 to 14 and COMPARATIVE EXAMPLES 4 and 5 after hardening for 5
days at 40°C as described for the thermographic recording materials of INVENTION EXAMPLES
1 to 7 and COMPARATIVE EXAMPLES 1 to 3. The results are given in table 9.
Table 9
Invention example nr |
coating weight of GEL06 [g/m2] |
coating weight of colloidal silica in ammonium form [g/m2] |
coating weight of LEVASIL VP AC 4055 [g/m2] |
% by weight of inorganic particles |
Printing quality |
11 |
4.29 |
1.34 |
- |
19.2 |
good |
12 |
4.29 |
1.61 |
- |
22.2 |
good |
13 |
4.29 |
- |
1.34 |
19.2 |
excellent |
14 |
4.29 |
- |
1.61 |
22.2 |
excellent |
Comparative example nr |
|
|
|
|
|
4 |
4.29 |
- |
- |
- |
poor |
5 |
5.63 |
- |
- |
- |
poor |
[0076] The results show that the thermographic recording materials of INVENTION EXAMPLES
11 to 14 with gelatin-containing protective layers with non-opacifying inorganic particles
with a weight averaged particle size below 1µm in concentrations of 19 and 22% by
weight with respect to the weight of the protective layer i.e. colloidal silica in
ammonium form and LEVASIL™ VP AC 4055 exhibited good or excellent print quality, whereas
the thermographic recording materials of COMPARATIVE EXAMPLES 4 and 5 with gelatin-containing
protective layers without such sub-micron inorganic particles a exhibited poor print
quality.
INVENTION EXAMPLES 15 to 21
[0077] The thermosensitive element described for INVENTION EXAMPLES 8 to 10 was coated with
an aqueous coating composition and dried at an air temperature of 12°C to produce
the thermographic recording materials of INVENTION EXAMPLES 15 to 21 having protective
layers with the compositions given in table 8.
Table 8
coverage in g/m2 |
Invention example number |
|
15 |
16 |
17 |
18 |
19 |
20 |
21 |
GEL06 |
4.29 |
4.22 |
3.94 |
3.66 |
3.38 |
3.10 |
2.82 |
Colloidal silica in ammonium form |
1.34 |
1.41 |
1.69 |
1.97 |
2.25 |
2.53 |
2.82 |
STEAMIC™ OOS |
0.08 |
0.08 |
0.08 |
0.08 |
0.08 |
0.08 |
0.08 |
SYLOID™ 244 |
0.15 |
0.15 |
0.15 |
0.15 |
0.15 |
0.15 |
0.15 |
RILANIT™ GMS |
0.23 |
0.23 |
0.23 |
0.23 |
0.23 |
0.23 |
0.23 |
SERVOXYL™ VPAZ 100 |
0.1 |
0.1 |
0.1 |
0.1 |
0.1 |
0.1 |
0.1 |
SERVOXYL™ VPDZ 3/100 |
0.13 |
0.13 |
0.13 |
0.13 |
0.13 |
0.13 |
0.13 |
Surfactant Nr. S03 |
0.13 |
0.13 |
0.13 |
0.13 |
0.13 |
0.13 |
0.13 |
Surfactant Nr. S02 |
0.19 |
0.19 |
0.19 |
0.19 |
0.19 |
0.19 |
0.19 |
HCHO |
0.34 |
0.34 |
0.34 |
0.34 |
0.34 |
0.34 |
0.34 |
[0078] The printing behaviour was evaluated on the thermographic recording materials of
INVENTION EXAMPLES 15 to 21 after hardening for 5 days at 40°C as described for the
thermographic recording materials of INVENTION EXAMPLES 1 to 7 and COMPARATIVE EXAMPLES
1 to 3. The results are given in table 11.
[0079] The results of table 11 show that the thermographic recording materials of INVENTION
EXAMPLES 15 to 21 with gelatin-containing protective layers with 19.2 to 40.3 % by
weight of non-opacifying inorganic particles with a weight averaged particle size
below 1µm with respect to the weight of the protective layer i.e. colloidal silica
in ammonium form all exhibited good print quality.
Table 11
Invention example nr |
coating weight of GEL06 [g/m2] |
colloidal silica in ammonium form |
print quality |
|
|
coating weight [g/m2] |
% by wt in protective layer |
|
15 |
4.29 |
1.34 |
19.2 |
good |
16 |
4.22 |
1.41 |
20.2 |
good |
17 |
3.94 |
1.69 |
24.2 |
good |
18 |
3.66 |
1.97 |
28.2 |
good |
19 |
3.38 |
2.25 |
32.2 |
good |
20 |
3.10 |
2.53 |
36.2 |
good |
21 |
2.82 |
2.82 |
40.3 |
good |
INVENTION EXAMPLES 22 to 27
[0080] The thermosensitive element described for INVENTION EXAMPLES 8 to 10 was coated with
an aqueous coating composition and dried at an air temperature of 12°C to produce
the thermographic recording materials of INVENTION EXAMPLES 22 to 27 having protective
layers with the compositions given in table 12.
Table 12
coverage in g/m2 |
Invention example number |
|
22 |
23 |
24 |
25 |
26 |
27 |
Gelatin GEL06 |
4.29 |
4.29 |
4.29 |
3.66 |
3.38 |
3.10 |
Colloidal silica in ammonium form |
1.34 |
- |
- |
1.34 |
0.5 |
0.5 |
china clay |
- |
1.50 |
- |
- |
1.0 |
- |
kaolin |
- |
- |
1.50 |
- |
- |
1.0 |
STEAMIC™OOS |
0.08 |
0.08 |
0.08 |
0.08 |
0.08 |
0.08 |
SYLOID™244 |
0.15 |
0.15 |
0.15 |
0.15 |
0.15 |
0.15 |
RILANIT™GMS |
0.23 |
0.23 |
0.23 |
0.23 |
0.23 |
0.23 |
SERVOXYL™VPAZ 100 |
0.1 |
0.1 |
0.1 |
0.1 |
0.1 |
0.1 |
SERVOXYL™ VPDZ 3/100 |
0.13 |
0.13 |
0.13 |
0.13 |
0.13 |
0.13 |
Surfactant Nr. S03 |
0.13 |
0.13 |
0.13 |
0.13 |
0.13 |
0.13 |
Surfactant Nr. S02 |
0.19 |
0.19 |
0.19 |
0.19 |
0.19 |
0.19 |
HCHO |
0.34 |
0.34 |
0.34 |
0.34 |
0.34 |
0.34 |
[0081] The printing behaviour was evaluated on the thermographic recording materials of
INVENTION EXAMPLES 22 to 27 after hardening for 5 days at 40°C as described for the
thermographic recording materials of INVENTION EXAMPLES 1 to 7 and COMPARATIVE EXAMPLES
1 to 3. The results are given in table 13.
Table 13
Invention example nr |
coating weight of GEL06 [g/m2] |
coating weight of colloidal silica in ammonium form[g/m2] |
coating weight of china clay[g/m2] |
coating weight of kaolin [g/m2] |
% by weight of inorganic particles |
Printing quality |
22 |
4.29 |
1.34 |
- |
|
19.2 |
good |
23 |
4.29 |
- |
1.5 |
- |
21.0 |
good |
24 |
4.29 |
- |
- |
1.5 |
21.0 |
good |
25 |
4.29 |
1.34 |
- |
- |
19.2 |
good |
26 |
4.29 |
0.5 |
1.0 |
- |
21.0 |
good |
27 |
4.29 |
0.5 |
- |
1.0 |
21.0 |
good |
[0082] The results of table 13 show that the thermographic recording materials of INVENTION
EXAMPLES 22 to 27 with gelatin-containing protective layers with different non-opacifying
inorganic particles with a weight averaged particle size below 1µm in concentrations
of 19 and 21% by weight with respect to the weight of the protective layer i.e. colloidal
silica in ammonium form, china clay and kaolin all exhibited good print quality.
INVENTION EXAMPLES 28 and 29
Backside layers
[0083] A 175µm thick polyethylene terephthalate support coated on both sides with subbing
layer 01 was coated on one side with backside layer B01 with the following composition:
KELZAN™ S |
10mg/m2 |
polyethylenedioxythiophene |
5mg/m2 |
polystyrene sulfonic acid |
10mg/m2 |
Surfactant Nr. S04 |
21mg/m2 |
PERAPRET™ PE40 |
10mg/m2 |
KIESOLSOL™ 100F |
20mg/m2 |
PMMA latex |
200mg/m2 |
LATEX02 |
30mg/m2 |
[0084] A 175µm thick polyethylene terephthalate support coated on both sides with subbing
layer 01 was also coated on one side with backside layer packet B02. First a layer
with the following composition was coated:
GEL07 |
380mg/m2 |
KIESELSOL 300F |
340.7mg/m2 |
Surfactant Mr. S04 |
13.3mg/m2 |
Surfactant Nr. S05 |
6.7mg/m2 |
2-methyl-2,4-pentanediol |
22.2mg/m2 |
Trimethylolpropane |
11.1mg/m2 |
PMMA latex |
1mg/m2 |
then with a layer with the following composition:
GEL05 |
300mg/m2 |
LATEX 03 |
450mg/m2 |
Surfactant Mr. S07 |
3mg/m2 |
Surfactant Mr. S08 |
1mg/m2 |
Polystyrene sulfonic acid |
8mg/m2 |
and finally with a layer of composition:
GEL08 |
1266mg/m2 |
GEL09 |
100mg/m2 |
GEL10 |
130mg/m2 |
Surfactant Nr. S06 |
<5 mg/m2 |
Surfactant Nr. S07 |
80mg/m2 |
Surfactant Mr. S08 |
3mg/m2 |
anti-bacterial agent |
50mg/m2 |
L1ATEX04 |
100mg/m2 |
PLEXIGUM™ M345 |
50mg/m2 |
dioctadecyl phthalate |
5mg/m2 |
formaldehyde |
106mg/m2 |
sodium sulphate |
1mg/m2 |
Thermosensitive element
[0085] A 175µm thick polyethylene terephthalate support with an uncoated subbing layer 01
on one side and backing layer B01 on the other was used for the thermographic recording
material of INVENTION EXAMPLE 28 and a 175µm thick polyethylene terephthalate support
with uncoated subbing layer 01 on one side and backing layer B02 on the other was
used for the thermographic recording material of INVENTION EXAMPLE 29.
[0086] A thermosensitive element of the following composition was applied in each case to
the side coated with subbing layer 01:
|
thermosensitive element of INVENTION EXAMPLE 28 |
thermosensitive element of INVENTION EXAMPLE 29 |
AgB |
5.031g/m2 |
5.268g/m2 |
Surfactant Nr. S01 |
0.503g/m2 |
0.527g/m2 |
GEL05 |
2.660g/m2 |
2.785g/m2 |
LATEX 01 |
1.843g/m2 |
1.929g/m2 |
R01 |
0.956g/m2 |
1.001g/m2 |
T01 |
1.132g/m2 |
1.185g/m2 |
Boric acid |
0.325g/m2 |
0.340g/m2 |
HCHO |
0.192g/m2 |
0.201g/m2 |
Protective layers
[0087] The thermosensitive elements of the thermographic recording
[0088] materials of INVENTION EXAMPLES 28 and 29 were then coated with a protective layer
with the following composition:
GEL06 |
4.29g/m2 |
colloidal silica in ammonium form |
1.34g/m2 |
STEAMIC™ OOS |
0.08g/m2 |
SYLOID™ 72 |
0.15g/m2 |
RILANIT™ GMS |
0.23g/m2 |
SERVOXYL™ VPDZ 3/100 |
0.10g/m2 |
SERVOXYL™ VPAZ 100 |
0.13g/m2 |
Surfactant Nr. S03 |
0.13g/m2 |
Surfactant Nr. S02 |
0.19g/m2 |
Formaldehyde |
0.34g/m2 |
Curl evaluation experiments
[0089] Curl evaluation experiments were carried out by hanging 24x30 cm
2 sheets for 4 hours at 20°C and 10% and 85% relative humidity respectively in analogy
with ISO Norm 4330 - 1979 (E) and then evaluating the degree of curl with a curl-meter
The curl values in table 14 are the reciprocal of the curl radius in metres.
Table 14
Invention example number |
curl at room temperature & 10% RH |
Curl at room temperature & 85% relative humidity (RH) |
28 |
>10 |
5 |
29 |
10 |
3.7 |
[0090] From these tests it is clear that the thermographic recording material with the gelatin
backing layer INVENTION EXAMPLE 29 exhibits significantly less curl than the thermographic
recording material with the polymethylmethacrylate-based backing layer of INVENTION
EXAMPLE 28.
[0091] Having described in detail preferred embodiments of the current invention, it will
now be apparent to those skilled in the art that numerous modifications can be made
therein without departing from the scope of the invention as defined in the following
claims.