Field of the invention
-
The present invention relates to thermographic recording
materials whose prints have improved image tone.
Background of the invention.
-
Thermal imaging or thermography is a recording process wherein
images are generated by the use of thermal energy. In direct
thermal thermography a visible image pattern is formed by image-wise
heating of a recording material.
-
EP 692 733 discloses a direct thermal recording process
wherein a direct thermal recording material is heated dot-wise and
the direct thermal recording material comprises on a substrate an
imaging layer containing uniformly distributed in a film-forming
polymeric binder (i) one or more substantially light-insensitive
organic silver salts being no double salts, the silver salt(s)
being in thermal working relationship with (ii) an organic reducing
agent therefor, characterized in that the reducing agent is a
benzene compound the benzene nucleus of which is substituted by no
more than two hydroxy groups which are present in 3,4-position on
the nucleus and have in the 1-position of the nucleus a substituent
linked to the nucleus by means of a carbonyl group.
-
EP-A 903 625 discloses a substantially light-insensitive black
and white monosheet thermographic recording material is provided
comprising a support and a thermosensitive element containing a
substantially light-insensitive organic silver salt, a 1,2-dihydroxybenzene-compound
in thermal working relationship therewith
and a binder, characterized in that the 1,2-dihydroxybenzene-compound
is represented by formula (I):
where R is -P(=O)R
1R
2, -SO
xR
3, -CN , -NO
2 or -CR
4=NR
5 when n is 0; R
is -P(=O)R
1R
2, -SO
xR
3, -CN, -NO
2, -CR
4=NR
5 or -COR
6 when n is an
integer; R
1 and R
2 are independently an alkyl, a substituted alkyl,
an aryl, a substituted aryl group, an alkoxy, a substituted alkoxy,
an aryloxy, a substituted aryloxy, a hydroxy group, an amino group
or a substituted amino group; R
3 is an alkyl, a substituted alkyl,
an aryl, a substituted aryl, an amino or a substituted amino group;
R
4 is an alkyl, a substituted alkyl, an aryl or a substituted aryl
group or hydrogen; R
5 is an alkyl, a substituted alkyl, an aryl, a
substituted aryl, a hydroxy, an alkoxy, an aryloxy, an acyl, an
amino or a substituted amino group; R
6 is an alkyl, a substituted
alkyl, an aryl, a substituted aryl, an alkoxy, a substituted
alkoxy, an aryloxy, a substituted aryloxy, a hydroxy, an amino or a
substituted amino group or hydrogen; x is 1, 2 or 3; and the
benzene ring of the 1,2-dihydroxybenzene-compound represented by
the formula (I) may be further substituted.
-
Unpublished European Patent Application Nr. EP01000096.6
disclosed a monosheet black and white substantially light-insensitive
thermographic recording material comprising a
thermosensitive element and a support, the thermosensitive element
containing a substantially light-insensitive organic silver salt, a
3,4-dihydroxybenzene compound in thermal working relationship
therewith and a binder, characterized in that the 3,4-dihydroxybenzene
compound is an aryloxo-3,4-dihydroxybenzene
compound in which the aryl-group is substituted with at least one
substituent having a σm-value greater than 0; or a heteroaryloxo-3,4-dihydroxybenzene
compound in which the heteroaryl group has a
unified aromaticity index IA greater than 53 and is optionally
substituted with at least one group selected from the group
consisting of aryl, hydroxy, carboxy, sulfo, sulfoalkyl, sulfoaryl,
sulfonylalkyl, sulfonylaryl, annulated aryl, annulated heteroaryl,
carboxyalkyl, carboxyaryl, oxoalkyl, oxoaryl, halogen, nitro, cyano
and mercapto-alkyl groups; and a thermographic recording process
therefor.
-
Unpublished European Patent Application Nr. EP01000095.8
disclosed a monosheet black and white substantially light-insensitive
thermographic recording material comprising a
thermosensitive element and a support, the thermosensitive element
containing a substantially light-insensitive organic silver salt, a
1,2-dihydroxybenzene-compound in thermal working relationship
therewith and a binder, characterized in that the 1,2-dihydroxybenzene-compound
is represented by formula (I): R1SO2R2,
wherein R1 is an optionally substituted aryl group and R2 is
selected from the group consisting of a 3,4,5-trihydroxyphenyl
group, a 3-alkoxy-4,5-dihydroxyphenyl group and a 3-aryloxy-4,5-dihydroxyphenyl
group; or the 1,2-dihydroxybenzene-compound is
represented by formula (II): R3COOR4, wherein R3 is a 3-alkoxy-4,5-dihydroxyphenyl
group or a 3-aryloxy-4,5-dihydroxyphenyl group; and
R4 is an alkyl group or an aryl group; and a thermographic
recording process therefor.
-
US 3,028,254 discloses heat-sensitive copy-sheets comprising a
substantially light-insensitive organic silver salt, a reducing
agent therefor and a binder. Specifically in Example 1 molar ratio
of molar hydroxy-equivalents of reducing agents to molar silver-equivalents
of the substantially light-insensitive organic silver
salts of 1.78 and 1.33 are disclosed with respect to 3,3,3',3'-tetramethyl-1,1'-spiro-bis-indane
5,5',6,6'-tetrol and behenyl
pyrogallol and silver behenate; and 3,3,3',3'-tetramethyl-1,1'-spiro-bis-indane
5,5',6,6'-tetrol and silver behenate respectively.
-
US 3,031,329 discloses heat-sensitive copy-sheets comprising a
substantially light-insensitive organic silver salt, a reducing
agent therefor and a binder. Specifically in Examples 1 and 2
molar ratios of molar hydroxy-equivalents of reducing agents to
molar silver-equivalents of the substantially light-insensitive
organic silver salts of 7.29 and 4.13 are disclosed respectively
with respect to 3,3,3',3'-tetramethyl-1,1'-spiro-bis-indane
5,5',6,6'-tetrol, 3,4-dihydroxybenzoic acid and silver behenate;
and methyl gallate and silver behenate respectively.
-
US 3,074,809 discloses heat-sensitive copy-sheets comprising a
substantially light-insensitive organic silver salt, a reducing
agent therefor and a binder. Specifically in Examples 1, 2 and 3
molar ratios of molar hydroxy-equivalents of reducing agents to
molar silver-equivalents of the substantially light-insensitive
organic silver salts of 5.725, 5.725 and 2.310 are disclosed
respectively with respect to hydroquinone and silver behenate;
hydroquinone and silver behenate; and methyl gallate, 2,3-dihydroxybenzoic
acid and silver behenate respectively.
-
US 3,103,881 discloses heat-sensitive copy-sheets comprising a
substantially light-insensitive organic silver salt, a reducing
agent therefor and a binder. Specifically in Example 3 a molar
ratio of molar hydroxy-equivalents of reducing agents to molar
silver-equivalents of the substantially light-insensitive organic
silver salts of 2.95 is disclosed with respect to 3,4-dihydroxybenzoic
acid and silver behenate.
-
US 3,107,174 discloses heat-sensitive copy-sheets comprising a
substantially light-insensitive organic silver salt, a reducing
agent therefor and a binder. Specifically in Example 1 a molar
ratio of molar hydroxy-equivalents of reducing agents to molar
silver-equivalents of the substantially light-insensitive organic
silver salts of 3.29 is disclosed with respect to methyl gallate
and silver behenate.
-
Typical X-ray images with conventional silver halide
radiographic film have an image tone corresponding to CIELAB-values
of a* = -4.62 and b* = -8.86 for D = 1.0 and a* = -2.53 and b* =-4.41
for a density of 2.0 and exhibit excellent archivability both
as regards stability of image density and stability of image tone.
Prints produced with prior art thermographic recording materials
which exhibit acceptable archivability exhibit a reddish image tone
and prior art thermographic recording materials which exhibit
clinically acceptable neutral (a* = b* = 0) to bluish image tone
(a* = 0 to -7; b* < 0) exhibit unacceptable archivability. This
problem is particularly acute if prints are produced with thermal
head printers with a heating time ≤ 15ms. It is desirable to
obtain image tones as close to the image tone typically attained
with silver halide radiographic film as possible.
Aspects of the invention.
-
It is therefore an aspect of the present invention to provide
concepts to enable substantially light-insensitive thermographic
recording materials to be developed whose prints exhibit both
satisfactory archivability and image tone.
-
It is a further aspect of the present invention to provide
concepts to enable substantially light-insensitive thermographic
recording materials to be developed which upon printing with a
thermal head printer with a heating time ≤ 15 ms produce prints
exhibiting both satisfactory archivability and image tone.
-
Further aspects and advantages of the invention will become
apparent from the description hereinafter.
Summary of the invention
-
It has been surprisingly found that with particular classes of
1,2-dihydroxybenzene compound reducing agents, an increase in the
molar ratio of molar equivalents of active hydroxy groups in the
1,2-dihydroxybenzene compound reducing agent or mixtures thereof
with respect to the molar equivalents of organic silver salt or
mixtures thereof above the stoichiometric value of 1.00 had the
unexpected result of reducing both the CIELAB a*-value of prints
produced therewith without the expected prohibitive deterioration
in the archival properties of the prints. This effect was found to
be particularly pronounced when the prints were produced with a
thermal head printer with heating time ≤ 15 ms.
-
The above mentioned aspects of the present invention are
realized by providing a monosheet black and white substantially
light-insensitive thermographic recording material comprising a
thermosensitive element and a support, the thermosensitive element
containing one or more substantially light-insensitive organic
silver salts, one or more reducing agents consisting of one or more
1,2-dihydroxybenzene-compounds in thermal working relationship
therewith and a binder, characterized in that the molar ratio of
molar hydroxy-equivalents of the 1,2-dihydroxybenzene compounds to
molar silver-equivalents of the substantially light-insensitive
organic silver salts is between 1.2 and 6.0; the 1,2-dihydroxybenzene-compounds
have a -(CH=CH)nR group in the 4
position wherein n is zero or an integer and R is a substituent
with a Hammett σp constant > 0.35 and < 0.95 exclusive of a
carboxy-group; and the benzene ring of the 1,2-dihydroxy-compounds
is optionally further substituted with an entity selected from the
group consisting of an alkyl, substituted alkyl, alkenyl, aryl,
heteroaryl, alkoxy, thioalkyl, aryloxy, thioaryl, thioheteroaryl,
acyloxy, thioacyl, amido, sulphonamido and halogen groups, an
annelated aryl ring system and an annelated heteroaryl ring system.
-
The above mentioned aspects of the present invention are also
realized by providing a thermographic recording process for a
monosheet black and white substantially light-insensitive
thermographic recording material according to any of the preceding
claims comprising the steps of: (i) providing the thermographic
recording material; (ii) bringing the thermographic recording
material into the proximity of a heat source; (iii) applying heat
imagewise from the heat source to the thermographic recording
material; and (iv) removing the thermographic recording material
from the proximity of the heat source.
-
Several embodiments are disclosed in the dependent claims.
Detailed description of the invention.
-
According to a first embodiment of the thermographic recording
process, according to the present invention, the heat source is a
thermal head. According to a second embodiment of the
thermographic recording process according to the present invention,
the heat source is a thin film thermal head. According to a third
embodiment of the thermographic recording material according to the
present invention, the heat source is a thin film thermal head
operating with heating time of ≤ 25 ms. According to a fourth
embodiment of the thermographic recording material according to the
present invention, the heat source is a thin film thermal head
operating with heating time of ≤ 15 ms.
Definitions
-
The term alkyl means all variants possible for each number of
carbon atoms in the alkyl group i.e. for three carbon atoms: n-propyl
and isopropyl; for four carbon atoms: n-butyl, isobutyl and
tertiary-butyl; for five carbon atoms: n-pentyl, 1,1-dimethylpropyl,
2,2-dimethylpropyl and 2-methyl-butyl etc.
-
"Annelated" means having a carbon-carbon bond in common with
e.g. annelation of a benzene ring with a naphthalene ring results
in anthracene or phenanthrene depending on which carbon-carbon bond
in the naphthalene ring is common to both the naphthalene ring and
the benzene ring.
-
By substantially light-insensitive is meant not intentionally
light sensitive.
-
Selected values of Hammett σm and Hammett σp substituent
constants are to be found in Advances in Linear Free Energy
Relationships, Edited by N. B. Chapman and J. Shorter, published by
Plenum Press, London in 1972 on pages 28-29. The highest value
reported for the Hammett σm and Hammett σp substituent constants is
regarded as being the Hammett σm and Hammett σp substituent constant
for the purposes of the present invention.
-
The unified aromaticity index IA is described by C.W. Bird in
Tetrahedron, 48(32), 335-340 (1992), which also discloses
aromaticity index values for a large range of aromatic groups.
-
The molar hydroxy-equivalents of a 1,2-dihydroxybenzene
compound is obtained by multiplying the molar concentration of the
1,2-dihydroxybenzene compound by the number of hydroxy-groups
substituents on benzene rings in formula (I) and then adding these
values together. For example ethyl 3,4-dihydroxybenzoate has two
molar hydroxy-equivalents per mole, n-propyl gallate with the
benzene ring substituted with three hydroxy-groups has three molar
hydroxy-equivalents per mole and 3,3,3',3'-tetramethyl-1,1'-spiro-bis-indane
5,5',6,6'-tetrol with two benzene rings each substituted
with two hydroxy-groups has four molar hydroxy-equivalents per
mole.
-
The molar silver-equivalent of a substantially light-insensitive
organic silver salt is obtained by multiplying the
molar concentration of the substantially light-insensitive organic
silver salt by the number of silver-atoms in the particular
substantially light-insensitive organic silver salt e.g. silver
behenate has one molar silver-equivalent per mole and silver
adipate, being a silver salt of a dicarboxylic acid, has two molar
silver-equivalents per mole.
-
The molar ratio of the molar hydroxy-equivalent of the 1,2-dihydroxybenzene
compound to the molar silver-equivalent of the
substantially light-insensitive organic silver salt is obtained by
dividing the molar hydroxy-equivalent of the 1,2-dihydroxybenzene
compound, obtained as described above, by the molar silver-equivalents
of the substantially light-insensitive organic silver
salt, obtained as described above.
-
If more than one 1,2-dihydroxybenzene compound and/or more
than one substantially light-insensitive organic silver salt is
present, the molar ratio of molar hydroxy-equivalents of the 1,2-dihydroxybenzene
compounds to molar silver-equivalents of the
substantially light-insensitive organic silver salts is determined
by dividing the sum of the hydroxy-equivalents of the 1,2-dihydroxybenzene
compounds present by the sum of the silver-equivalents
of the substantially light-insensitive organic silver
salts present.
-
The total line time of a thermal head is the time between the
beginning of the printing of one line of pixels and the beginning
of the printing of the next line of pixels in the printer transport
direction. The total line time is equal to the active line time if
no cooling time is included in the total line time. Should a
cooling time be included in total line time, this cooling time
should be subtracted from the total line time to obtain the active
line time.
-
The heating time of a thermal head is obtained by multiplying
the active line time of the thermal head by the ratio of the length
of the resistance elements in the thermal head in the transport
direction of the printer to the distance between the beginning of
one printing line to the next printing line e.g. for an active line
time of 12ms, a resistance element length in the printer transport
direction of 75 µm and a distance between the beginning of one
printing line to the next printing line of 50 µm, the printing time
is 12 x (75/50) = 18ms. This heating time corresponds to the time
during which the film element experiences heat.
-
Heating in association with the expression a substantially
water-free condition as used herein, means heating at a temperature
of 80 to 250°C. The term "substantially water-free condition" as
used herein 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.
Molar ratio of molar OH-equivalents of the 1,2-dihydroxybenzene
compounds to molar Ag-equivalents of the organic silver salts
-
According to a first embodiment of the substantially light-insensitive
thermographic recording material of the present
invention the molar ratio of molar hydroxy-equivalents of the 1,2-dihydroxybenzene
compounds to molar silver-equivalents of the
substantially light-insensitive organic silver salts is 1.3 to 5.0.
-
According to a second embodiment of the substantially light-insensitive
thermographic recording material of the present
invention the molar ratio of molar hydroxy-equivalents of the 1,2-dihydroxybenzene
compounds to molar silver-equivalents of the
substantially light-insensitive organic silver salts is 1.3 to 4.0.
-
According to a third embodiment of the substantially light-insensitive
thermographic recording material of the present
invention the molar ratio of molar hydroxy-equivalents of the 1,2-dihydroxybenzene
compounds to molar silver-equivalents of the
substantially light-insensitive organic silver salts is 1.5 to 3.5.
-
According to a fourth embodiment of the substantially light-insensitive
thermographic recording material of the present
invention the molar ratio of molar hydroxy-equivalents of the 1,2-dihydroxybenzene
compounds to molar silver-equivalents of the
substantially light-insensitive organic silver salts is 1.5 to 3.0.
-
According to a fifth embodiment of the substantially light-insensitive
thermographic recording material of the present
invention the molar ratio of molar hydroxy-equivalents of the 1,2-dihydroxybenzene
compounds to molar silver-equivalents of the
substantially light-insensitive organic silver salts is 1.5 to 2.5.
-
According to a sixth embodiment of the substantially light-insensitive
thermographic recording material of the present
invention the molar ratio of molar hydroxy-equivalents of the 1,2-dihydroxybenzene
compounds to molar silver-equivalents of the
substantially light-insensitive organic silver salts is 1.3 to 2.0.
1,2-dihydroxybenzene compounds according to formula (I)
-
The 1,2-dihydroxybenzene-compounds used the substantially
light-insensitive thermographic recording material of the present
invention have a -(CH=CH)nR group in the 4 position wherein n is
zero or an integer and R is a substituent with a Hammett σp
constant > 0.35 and < 0.95 exclusive of a carboxy-group; and the
benzene ring of the 1,2-dihydroxy-compounds is optionally further
substituted with an entity selected from the group consisting of an
alkyl, substituted alkyl, alkenyl, aryl, heteroaryl, alkoxy,
thioalkyl, aryloxy, thioaryl, thioheteroaryl, acyloxy, thioacyl,
amido, sulphonamido and halogen groups, an annelated aryl ring
system and an annelated heteroaryl ring system.
-
According to an seventh embodiment of the substantially light-insensitive
thermographic recording material of the present
invention the R group in the 1,2-dihydroxybenzene-compounds is
-P(=O)R1R2, -SOxR3, -CN, -NO2, -CR4=NR5 or -COR6; R1 and R2 are
independently an alkyl, a substituted alkyl, an aryl, a substituted
aryl group, an alkoxy, a substituted alkoxy, an aryloxy, a
substituted aryloxy, a hydroxy group, an amino group or a
substituted amino group; R3 is an alkyl, a substituted alkyl, an
aryl, a substituted aryl, an amino or a substituted amino group; R4
is an alkyl, a substituted alkyl, an aryl or a substituted aryl
group or hydrogen; R5 is an alkyl, a substituted alkyl, an aryl, a
substituted aryl, a hydroxy, an alkoxy, an aryloxy, an acyl, an
amino or a substituted amino group; R6 is a hydrogen atom or an
alkyl, a substituted alkyl, an aryl, an aryl substituted with at
least one substituent having a Hammett σm-constant > 0 and < 0.85,
an alkoxy, a substituted alkoxy, an aryloxy, a substituted aryloxy,
a heteroaryl having a unified aromaticity index greater than 53 or
a substituted heteroaryl group having a unified aromaticity index
greater than 53; and x is 1, 2 or 3.
-
According to an eighth embodiment of the substantially light-insensitive
thermographic recording material of the present
invention the 1,2-dihydroxybenzene-compounds are selected from the
group consisting of 3,4-dihydroxybenzoate alkyl and aryl esters,
3,4-dihydroxybenzophenone, 3,4-dihydroxybenzophenone compounds in
which the benzene ring without hydroxy-group substituents is
substituted with at least one substituent having a Hammett σm-constant
> 0 and < 0.85, 3,4-dihydroxy-acetophenone and 3,4-dihydroxybenzonitrile.
-
According to a ninth embodiment of the substantially light-insensitive
thermographic recording material of the present
invention, the 1,2-dihydroxybenzene compounds according to formula
(I) are selected from the reducing agents disclosed in EP-B 692
733, EP-A 903 625 and unpublished European Patent Application Nr.
EP01000096.6.
-
According to a tenth embodiment of the substantially light-insensitive
thermographic recording material of the present
invention, wherein the thermosensitive element contains more than
one of the 1,2-dihydroxybenzene compounds according to formula (I)
and one of the 1,2-dihydroxybenzene compounds according to formula
(I) is 1,2-dihydroxybenzonitrile.
-
According to an eleventh embodiment of the substantially
light-insensitive thermographic recording material of the present
invention, the 1,2-dihydroxybenzene compounds according to formula
(I) are 3,4-dihydroxybenzonitrile and 3,4-dihydroxybenzophenone.
-
According to a twelfth embodiment of the substantially light-insensitive
thermographic recording material of the present
invention, the 1,2-dihydroxybenzene compounds according to formula
(I) is an alkyl 3,4-dihydroxybenzoate such as ethyl 3,4-dihydroxybenzoate
and n-butyl 3,4-dihydroxybenzoate.
-
Suitable 1,2-dihydroxybenzene compounds according to the
present invention are:
Thermosensitive element
-
The thermosensitive element as used herein is that element
which contains all the ingredients which contribute to image
formation. According to the present invention, the thermosensitive
element contains one or more substantially light-insensitive
organic silver salts, one or more 1,2-dihydroxybenzene-compounds as
reducing agents therefor in thermal working relationship therewith
and a binder. The element may comprise a layer system in which the
above-mentioned ingredients may be dispersed in different layers,
with the proviso that the substantially light-insensitive organic
silver salts are in reactive association with the reducing agents
i.e. 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 organic silver salt so
that reduction to silver can occur.
Organic silver salt
-
According to a thirteenth embodiment of the substantially
light-insensitive thermographic recording material of the present
invention, the organic silver salts are not double organic salts
containing a silver cation associated with a second cation e.g.
magnesium or iron ions.
-
According to a fourteenth embodiment of the substantially
light-insensitive thermographic recording material of the present
invention, at least one of the organic silver salts is a
substantially light-insensitive silver salt of an organic
carboxylic acid.
-
According to a fifteenth embodiment of the substantially
light-insensitive thermographic recording material of the present
invention, at least one of the organic silver salts is a
substantially light-insensitive silver salt of an aliphatic
carboxylic acids known as a fatty acid, 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, as disclosed in
EP-A 964 300.
-
Organic silver salts may be dispersed by standard dispersion
techniques. Ball mills, bead mills, microfluidizers, ultrasonic
apparatuses, rotor stator mixers etc. have been found to be useful
in this regard. Mixtures of organic silver salt dispersions
produced by different techniques may also be used to obtain the
desired thermographic properties e.g. of coarser and more finely
ground dispersions of organic silver salts.
Auxiliary reducing agent
-
Combinations of compounds according to formula (I) with a
further reducing agent may also be used that on heating become
reactive partners in the reduction of the substantially light-insensitive
organic silver salt. According to an sixteenth
embodiment of the substantially light-insensitive thermographic
recording material of the present invention, the thermosensitive
element contains a reducing agent in addition to 1,2-dihydroxybenzene
compounds according to formula (I).
-
According to a seventeenth embodiment of the substantially
light-insensitive thermographic recording material of the present
invention, the thermosensitive element further contains at least
one reducing agent disclosed in unpublished European Patent
Application Nr. EP01000095.8, such as: 4-methyl-3',4',5'-trihydroxy-diphenylsulphone.
Binder of the thermosensitive element
-
The film-forming binder of the thermosensitive element may be
all kinds of natural, modified natural or synthetic resins or
mixtures of such resins, in which the substantially light-insensitive
organic silver salt can be dispersed homogeneously
either in aqueous or solvent media: e.g. cellulose derivatives such
as ethylcellulose, cellulose esters, e.g. cellulose nitrate,
carboxymethylcellulose, starch ethers, galactomannan, polymers
derived from α,β-ethylenically unsaturated compounds such as
polyvinyl chloride, after-chlorinated polyvinyl chloride,
copolymers of vinyl chloride and vinylidene chloride, copolymers of
vinyl chloride and vinyl acetate, polyvinyl acetate and partially
hydrolyzed polyvinyl acetate, polyvinyl alcohol, polyvinyl acetals
that are made from polyvinyl alcohol as starting material in which
only a part of the repeating vinyl alcohol units may have reacted
with an aldehyde, preferably polyvinyl butyral, copolymers of
acrylonitrile and acrylamide, polyacrylic acid esters,
polymethacrylic acid esters, polystyrene and polyethylene or
mixtures thereof.
-
According to an eighteenth embodiment of the substantially
light-insensitive thermographic recording material of the present
invention, the thermosensitive element contains a binder which does
not contain additives or impurities which adversely affect the
thermographic properties of the thermographic recording materials
in which they are used.
Toning agent
-
According to a nineteenth embodiment of the substantially
light-insensitive thermographic recording material of the present
invention, the thermosensitive element further contains a so-called
toning agent organic silver salt in order to obtain a neutral black
image tone in the higher densities and neutral grey in the lower
densities.
-
Suitable toning agents are described in US 3,074,809, US
3,446,648 and US 3,844,797 and US 4,082,901. Other particularly
useful toning agents are the heterocyclic toning compounds of the
benzoxazine dione or naphthoxazine dione type as disclosed in
GB 1,439,478, US 3,951,660 and US 5,599,647.
-
According to a twentieth embodiment of the substantially
light-insensitive thermographic recording material of the present
invention, the thermosensitive element further contains one or more
toning agents selected from the group consisting of phthalazinone,
benzo[e][1,3]oxazine-2,4-dione, 7-methyl-benzo[e][1,3]oxazine-2,4-dione,
7-methoxy-benzo[e][1,3]oxazine-2,4-dione and 7-(ethylcarbonato)-benzo[e][1,3]oxazine-2,4-dione.
Stabilizers
-
Stabilizers may be incorporated into the substantially light-insensitive
thermographic recording materials of the present
invention in order to obtain improved shelf-life and reduced
fogging.
-
According to a twenty-first embodiment of the substantially
light-insensitive thermographic recording material of the present
invention, the thermosensitive element further contains at least
one stabilizer selected from the group consisting of benzotriazole;
substituted benzotriazoles; tetrazoles; mercaptotetrazoles, such as
1-phenyl-5-mercapto-tetrazole; and aromatic polycarboxylic acids,
such as ortho-phthalic acid, 3-nitro-phthalic acid,
tetrachlorophthalic acid, mellitic acid, pyromellitic acid and
trimellitic acid, and anhydrides thereof.
Polycarboxylic acids and anhydrides thereof
-
According to a twenty-second embodiment of the substantially
light-insensitive thermographic recording material of the present
invention, the thermosensitive element further comprises at least
one optionally substituted aliphatic (saturated as well as
unsaturated aliphatic and also cycloaliphatic) polycarboxylic acid
and/or anhydride thereof in a molar percentage of at least 15 with
respect to all the organic silver salt(s) present and in thermal
working relationship therewith. The polycarboxylic acid may be used
in anhydride form or partially esterified form on the condition
that at least two free carboxylic acids remain or are available in
the heat recording step. According to a twenty-third embodiment of
the substantially light-insensitive thermographic recording
material of the present invention, the thermosensitive element
further contains glutaric acid.
Surfactants and dispersion agents
-
Surfactants and dispersants aid the dispersion of ingredients
or reactants which are insoluble in the particular dispersion
medium. The thermographic recording materials of the present
invention may contain one or more surfactants, which may be
anionic, non-ionic or cationic surfactants and/or one or more
dispersants.
Other additives
-
The recording material may contain in addition to the
ingredients mentioned above other additives such as levelling
agents e.g. BAYSILON™ MA (from BAYER AG, GERMANY).
Support
-
The support for the thermosensitive element according to the
present invention may be transparent, translucent or opaque and is
a thin flexible carrier made of transparent resin film, e.g. made
of a cellulose ester, cellulose triacetate, polypropylene,
polycarbonate or polyester, e.g. polyethylene terephthalate.
-
The support may be in sheet, ribbon or web form and subbed if
need be to improve the adherence to the thereon coated
thermosensitive element. It may be pigmented with a blue pigment
as so-called blue-base. One or more backing layers may be provided
to control physical properties such as curl and static.
Protective layer
-
According to a twenty-fourth embodiment of the substantially
light-insensitive thermographic recording material of the present
invention, the thermosensitive element is provided with a
protective layer to avoid local deformation of the thermosensitive
element and to improve resistance against abrasion.
-
According to a twenty-fifth embodiment of the substantially
light-insensitive thermographic recording material of the present
invention, the thermosensitive element is provided with a
protective layer comprising a binder, which may be solvent-soluble,
solvent-dispersible, water-soluble or water- dispersible.
-
According to a twenty-sixth embodiment of the substantially
light-insensitive thermographic recording material of the present
invention, the thermosensitive element is provided with a
protective layer comprising solvent-soluble polycarbonates as
binders, as described in EP-A 614 769.
-
According to a twenty-seventh embodiment of the substantially
light-insensitive thermographic recording material of the present
invention, the thermosensitive element is provided with a
protective layer comprising a water-soluble or water-dispersible
binder, as coating can be performed from an aqueous composition and
mixing of the protective layer with the immediate underlayer can be
avoided by using a solvent-soluble or solvent-dispersible binder in
the immediate underlayer. The protective layer according to the
present invention may be crosslinked. Crosslinking can be achieved
by using crosslinking agents such as described in WO 95/12495.
Solid or liquid lubricants or combinations thereof are suitable for
improving the slip characteristics of the thermographic recording
materials according to the present invention.
-
According to a twenty-eighth embodiment of the substantially
light-insensitive thermographic recording material of the present
invention, the thermosensitive element is provided with a
protective layer comprising a solid thermomeltable lubricant such
as those described in WO 94/11199. The protective layer of the
thermographic recording material according to the present invention
may comprise a matting agent. According to a twenty-ninth
embodiment of the substantially light-insensitive thermographic
recording material of the present invention, the thermosensitive
element is provided with a protective layer comprising a matting
agent such as described in WO 94/11198, e.g. talc particles, and
optionally protrude from the protective layer.
Backing layer configuration
-
According to a thirtieth embodiment of the substantially
light-insensitive thermographic recording material, according to
the present invention, the support, on the opposite side of the
support to the thermosensitive element, is provided with an
adhesion layer containing an intrinsically conducting polymer. The
adhesion layer contains a binder e.g. a latex binder and a
colloidal pigment e.g. colloidal silica.
-
According to a thirty-first embodiment of the substantially
light-insensitive thermographic recording material, according to
the present invention, the support, on the opposite side of the
support to the thermosensitive element, is provided with an
adhesion layer containing an intrinsically conducting polymer and
the adhesion layer is provided with a backing layer optionally
containing a second intrinsically conducting polymer. The backing
layer contains a binder e.g. poly(vinyl alcohol), poly(methyl
methacrylate) and gelatine, a pigment e.g. colloidal silica, and a
matting agent e.g. silica particles or polymer particles e.g.
poly(methyl methacrylate) particles.
-
According to a thirty-second embodiment of the substantially
light-insensitive thermographic recording material, according to
the present invention, the support, on the opposite side of the
support to the thermosensitive element, is provided with an
adhesion layer containing an intrinsically conducting polymer and
the adhesion layer is provided with a backing layer optionally
containing a second intrinsically conducting polymer and the
intrinsically conducting polymer and/or the second intrinsically
conducting polymer is a polythiophene.
-
According to a thirty-second embodiment of the substantially
light-insensitive thermographic recording material, according to
the present invention, the support, on the opposite side of the
support to the thermosensitive element, is provided with an
adhesion layer containing an intrinsically conducting polymer and
the adhesion layer is provided with a backing layer optionally
containing a second intrinsically conducting polymer and the
intrinsically conducting polymer and/or the second intrinsically
conducting polymer is a polythiophene, which is a polymer or
copolymer of a 3,4-dialkoxythiophene in which said two alkoxy
groups may be the same or different or together represent an
optionally substituted oxy-alkylene-oxy bridge e.g. poly(3,4-ethylenedioxythiophene).
-
It is important that the pH of the dispersion for coating the
outermost layer of the same side of the support as the thermosensitive
element be less than 5 and substantially identical to
that of the dispersion for coating the outermost layer of the side
of the support opposite to that of the thermosensitive element.
This results in a similar surface pH from the outermost layers on
both sides of the support.
Coating
-
The coating of any layer of the recording material 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, U.S.A.
Thermographic processing
-
Thermographic imaging is carried out by the image-wise
application of heat either in analogue fashion by direct exposure
through an image or 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, with a
substantially light-insensitive thermographic material preferably
containing an infra-red absorbing compound, or by direct thermal
imaging with a thermal head.
-
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 into
heat via Joule effect. 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 1.0ms, the pressure
contact of the thermal printhead with the recording material being
e.g. 200-500g/cm2 to ensure a good transfer of heat.
-
In order to avoid direct contact of the thermal printing heads
with the outermost layer on the same side of the support as the
thermosensitive element when this outermost layer is not a
protective layer, the image-wise heating of the recording material
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.
-
Activation of the heating elements can be power-modulated or
pulse-length modulated at constant power. EP-A 654 355 discloses 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. EP-A 622 217 discloses a method for making an image
using a direct thermal imaging element producing improvements in
continuous tone reproduction.
-
Image-wise heating of the recording material can also be
carried out using an electrically resistive ribbon incorporated
into the material. Image- or pattern-wise heating of the recording
material may also proceed by means of pixel-wise modulated ultrasound.
Industrial application
-
Thermographic imaging can be used for the production of
reflection type prints and transparencies, in particular for use in
the medical diagnostic field in which black-imaged transparencies
are widely used in inspection techniques operating with a light
box.
-
The invention is illustrated hereinafter by way of comparative
examples and invention examples. The percentages and ratios given
in these examples are by weight unless otherwise indicated. The
ingredients used in the substantially light-insensitive
thermographic recording materials of the invention and comparative
examples in addition to those disclosed above are given below:
- Ingredients for the backing and adhesion layers:
- POVAL™ 103 = a 98% hydrolyzed poly(vinyl alcohol) from
Kuraray;
- V03/140 = Erkol™ V03/140, a 88% hydrolyzed poly(vinyl
alcohol) from Acetex Europe;
- 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;
- PE40 = PERAPRET™ PE40, a 40% aqueous dispersion of
polyethylene latex from BASF;
- Poligen™ WE7 = a 40% aqueous latex of oxidized polyethylene from
BASF;
- LATEX01 = a 26.8% aqueous latex of a copolymer of 88%
vinylidene chloride, 10% methyl acrylate and 2%
itaconic acid and containing 0.13% Mersolat H;
- LATEX02 = a 20% aqueous poly(methyl methacrylate) latex
with 100 nm particles;
- LATEX03 = a 30% latex of a copolymer of 88% vinylidene
chloride, 10% methyl acrylate and 2% itaconic
acid and 0.75% Hostapon™ T;
- LATEX04 = a 20% aqueous poly(methyl methacrylate) latex
with 50nm particles;
- PEDOT/PSS-1 = a 1.2% aqueous dispersion of poly(3,4-ethyleneoxythiophene)/poly(styrene
sulphonic acid)
(1:2.46 by weight) produced as described in US
5,354,613;
- PEDOT/PSS-2 = homogenized PEDOT/PSS-1;
- Snowtex™ O = a 20% aqueous dispersion of colloidal silica
from Nissan Chemical;
- Kieselsol 100F = a 30% aqueous dispersion of colloidal silica
from BAYER;
- UVONAC = a 10% aqueous solution of acetylated ULTRAVON W;
- Mersolat™ H = a 76% aqueous paste of a sodium pentadecylsulfonate
from BAYER;
- ZONYL™ FSO 100 = a block copolymer of polyethyleneglycol and
polytetrafluoroethylene with the structure:
F(CF2CF2)yCH2CH2O(CH2CH2O)xH, where x = 0 to ca.
15 and y = 1 to ca. 7from DUPONT
- Hostapon™ T = a 40% concentrate of a sodium salt of N-methyl-N-2-sulfoethyl-oleylamide
by HOECHST;
- Arkopal NO 60 = a nonylphenylpolyethylene-glycol from HOECHST;
- OP80 = Akypo™ OP80, an 80% concentrate of an octylphenyl-oxy-polyethyleneglycol(EO
8)acetic acid
from CHEMY;
- MAT01 = Sunsphere™51, a 8.63% dispersion of 5.7 µm
silica particles from Asahi Glass;
- MAT02 = a 20% aqueous dispersion of 6 µm crosslinked beads
of a copolymer of 98% methyl methacrylate and 2%
stearyl methacrylate and 0.4% Arkopal NO 60
produced as described in US 4,861,812;
- Ingredients for thermosensitive element:
- the organic silver salt:
- AgB = silver behenate;
- binders:
- BL5HP = S-LEC BL5HP, a polyvinylbutyral from Sekusui;
- crosslinking agent:
- VL = Desmodur™ VL, a 4,4'-di-isocyanatodiphenylmethane from
BAYER;
- the reducing agent:
- CR01 = methyl gallate (from US 3,031,329 and US 3,107,174);
- CR02 = 3,3,3',3'-tetramethyl-1,1'-spiro-bis-indane 5,5',6,6'-tetrol
(according to US 3,028,254, 3,031,329 and EP 599 369):
- the toning agents:
- T01 = benzo[e][1,3]oxazine-2,4-dione;
- T02 = 7-(ethylcarbonato)-benzo[e][1,3]oxazine-2,4-dione;
- T03 = 7-methyl-benzo[e][1,3]oxazine-2,4-dione;
- the stabilizers:
- S01 = glutaric acid;
- S02 = tetrachlorophthalic acid anhydride;
- S03 = benzotriazole.
- Ingredients for the protective layers:
- Ercol 48 20 = Ercol™ 48 20, a polyvinylalcohol from Acetex Europe;
- 26/88 = MOWIOL™ 26/88, a polyvinylalcohol from Clariant
GmbH;
- VP AC 4055 = LEVASIL™ VP AC 4055, a 15% aqueous dispersion of
colloidal silica with a specific surface area of
500m2/g from Bayer AG which had been converted into
the ammonium salt;
- ULTRAVON™ W = a 75-85% concentrate of a sodium arylsulfonate from
Ciba Geigy converted into acid form by passing
through an ion exchange column;
- SYLOID™ 72 = a silica from Grace;
- VPDZ 3/100 = SERVOXYL™ VPDZ 3/100, a mono[isotridecyl polyglycolether
(3EO)] phosphate from Servo Delden
BV);
- VPAZ 100 = SERVOXYL™ VPAZ 100, a mixture of monolauryl and
dilauryl phosphate from Servo Delden B.V.;
- type P3 = MICROACE™ type P3, an Indian talc from Nippon Talc;
- Satintone S = Satintone™ S, a calcined china clay from Engelhard,
USA;
- RILANIT™ GMS = a glycerine monotallow acid ester from Henkel AG;
- TMOS = tetramethylorthosilicate hydrolyzed in the
presence of methanesulfonic acid.
-
COMPARATIVE EXAMPLES 1 to 12 and INVENTION EXAMPLES 1 to 11
Preparation of the thermosensitive element
-
The thermosensitive elements of the substantially light-insensitive
thermographic recording materials of COMPARATIVE
EXAMPLES 1 to 12 and INVENTION EXAMPLES 1 to 11 were produced by
coating a dispersion with the following ingredients in 2-butanone
onto a subbed 168µm thick blue-pigmented polyethylene terephthalate
support with CIELAB a*- and b*- values of -7.9 and -16.6
respectively; and drying at 50°C for 1h in a drying cupboard to
produce layers with the compositions given in Table 1.
Comparative example nr. | Reducing agent | Ratio of molar OH-equivalents to molar Ag-equivalents | AgBeh coverage [g/m2] | BL5HP [g/m2] | T01 mol% vs AgB | T02 mol% vs AgB | S01 mol% vs AgB | S02 mol% vs AgB | S03 mol% vs AgB | Oil [g/m2] |
1 | CR01 | 1.0 | 3.71 | 14.84 | 15 | 5 | 24 | 4.91 | 9.84 | 0.033 |
2 | CR01 | 1.5 | 3.68 | 14.72 | 15 | 5 | 24 | 4.91 | 9.84 | 0.0335 |
3 | CR01 | 2.0 | 3.94 | 15.76 | 15 | 5 | 24 | 4.91 | 9.84 | 0.0351 |
4 | CR02 | 1.0 | 3.71 | 14.84 | 15 | 5 | 24 | 4.91 | 9.84 | 0.033 |
5 | CR02 | 1.5 | 3.63 | 14.52 | 15 | 5 | 24 | 4.91 | 9.84 | 0.0323 |
6 | CR02 | 2.5 | 3.63 | 14.52 | 15 | 5 | 24 | 4.91 | 9.84 | 0.0323 |
7 | I-6 | 1.0 | 3.81 | 15.24 | 15 | 5 | 24 | 4.91 | 9.84 | 0.0339 |
8 | I-6 | 1.0 | 3.50 | 14.00 | 15 | 5 | 24 | 4.91 | 9.84 | 0.0328 |
9 | I-6 | 7.0 | 3.50 | 14.00 | 15 | 5 | 24 | 4.91 | 9.84 | 0.0328 |
10 | I-13 | 1.0 | 3.45 | 13.80 | 15 | 5 | 24 | 4.91 | 9.84 | 0.0339 |
11 | I-13 | 7.0 | 3.60 | 14.40 | 15 | 5 | 24 | 4.91 | 9.84 | 0.0324 |
12 | I-14 | 1.0 | 3.58 | 14.33 | 15 | 5 | 24 | 4.91 | 9.84 | 0.0339 |
Invention example nr |
1 | I-6 | 1.33 | 3.87 | 15.48 | 15 | 5 | 24 | 4.91 | 9.84 | 0.0344 |
2 | I-6 | 1.50 | 3.92 | 15.68 | 15 | 5 | 24 | 4.91 | 9.84 | 0.0349 |
3 | I-6 | 1.75 | 3.87 | 15.48 | 15 | 5 | 24 | 4.91 | 9.84 | 0.0344 |
4 | I-6 | 2.0 | 3.81 | 15.24 | 15 | 5 | 24 | 4.91 | 9.84 | 0.0339 |
5 | I-6 | 2.5 | 3.76 | 15.04 | 15 | 5 | 24 | 4.91 | 9.84 | 0.0335 |
6 | I-6 | 3.0 | 3.48 | 13.92 | 15 | 5 | 24 | 4.91 | 9.84 | 0.0335 |
7 | I-6 | 5.0 | 3.66 | 14.64 | 15 | 5 | 24 | 4.91 | 9.84 | 0.0332 |
8 | I-13 | 3.0 | 3.65 | 14.60 | 15 | 5 | 24 | 4.91 | 9.84 | 0.0337 |
9 | I-13 | 5.0 | 3.54 | 14.16 | 15 | 5 | 24 | 4.91 | 9.84 | 0.0325 |
10 | I-14 | 3.0 | 3.50 | 14.00 | 15 | 5 | 24 | 4.91 | 9.84 | 0.0349 |
11 | I-14 | 5.0 | 3.37 | 13.49 | 15 | 5 | 24 | 4.91 | 9.84 | 0.0344 |
protective layer
-
The thermosensitive elements of the thermographic recording
materials of COMPARATIVE EXAMPLES 1 to 12 and INVENTION EXAMPLES 1
to 11 were then coated with an aqueous composition with the
following ingredients to produce a layer with the following
ingredient coverages as solids after drying:
ERCOL 48 20 | = 2.1g/m2 |
VP AC 4055 | = 1.05g/m2 |
ULTRAVON™ W | = 0.075g/m2 |
SYLOID™ 72 | = 0.09 g/m2 |
VPDZ 3/100 | = 0.075g/m2 |
VPAZ 100 | = 0.075g/m2 |
type P3 | = 0.045g/m2 |
RILANIT™ GMS | = 0.15g/m2 |
TMOS (assuming complete conversion to silica) | = 0.87g/m2 |
-
The pH of the coating composition was adjusted to a pH of 3.8 by
adding IN nitric acid. Those lubricants which were insoluble in
water, were dispersed in a ball mill with, if necessary, the aid of
a dispersion agent. The composition was coated to a wet layer
thickness of 85mm and then dried at 40°C for 15 minutes and
hardened for 7 days at 45°C and a relative humidity of 70% thereby
producing the thermographic recording materials of COMPARATIVE
EXAMPLES 1 to 12 and INVENTION EXAMPLES 1 to 11.
thermographic printing
-
The thermographic recording materials of COMPARATIVE EXAMPLES
1 to 12 and INVENTION EXAMPLES 1 to 11 were printed using a
DRYSTAR™ 4500 printer from AGFA-GEVAERT equipped with a thin film
thermal head with resistor elements 75 µm long in the transport
direction of the printer and 50 µm wide in the direction
perpendicular to the transport direction to print symmetrical
pixels with a resolution of 508 dpi (= 200 dots/cm), adapted to
operate in three modes:
| maximum printing power [mW/pixel] | line time [ms] | heating time [ms] |
DRYSTAR™ 4500 mode 1 | 34 | 12 | 18 |
DRYSTAR™ 4500 mode 2 | 36 | 7 | 10.5 |
DRYSTAR™ 4500 mode 3 | 43.5 | 3.5 | 5.25 |
The thermal head resistors were power-modulated to produce
different image densities.
-
The maximum densities of the images (D
max) measured through a
visible filter with a MACBETH™ TR924 densitometer in the grey scale
step corresponding to a data level of 64 are given in Tables 2 for
COMPARATIVE EXAMPLES 1 to 12 and INVENTION EXAMPLES 1 to 11 for
DRYSTAR™ 4500 printer modes 1, 2 and 3 respectively.
Comparative Example nr. | Reducing agent | Ratio of molar OH-equiv to molar Ag-equiv | Printer mode 1 | Printer mode 2 | Printer mode 3 |
| | | Dmax (vis) | Dmin (vis) | Dmax/AgB coverage [m2/g] | Dmax (vis) | Dmin (vis) | Dmax/AgB coverage [m2/g] | Dmax (vis) | Dmin (vis) | Dmax/AgB coverage [m2/g] |
1 | CR01 | 1.0 | 3.26 | 0.23 | 0.88 | - | - | - | 3.12 | 0.22 | 0.84 |
2 | CR01 | 1.5 | 3.52 | 0.23 | 0.96 | - | - | - | 3.42 | 0.22 | 0.93 |
3 | CR01 | 2.0 | 3.52 | 0.22 | 0.89 | - | - | - | 3.59 | 0.22 | 0.91 |
4 | CR02 | 1.0 | 2.48 | 0.23 | 0.67 | - | - | - | 2.46 | 0.22 | 0.66 |
5 | CR02 | 1.5 | 3.82 | 0.22 | 1.05 | - | - | - | 3.53 | 0.22 | 0.97 |
6 | CR02 | 2.0 | 3.75 | 0.22 | 1.03 | - | - | - | 3.72 | 0.22 | 1.03 |
7 | I-6 | 1.0 | 3.39 | 0.22 | 0.89 | - | - | - | 3.49 | 0.22 | 0.91 |
8 | I-6 | 1.0 | 3.02 | 0.22 | 0.86 | 3.36 | 0.22 | 0.96 | 3.46 | 0.22 | 0.99 |
9 | I-6 | 7.0 | 3.09 | 0.21 | 0.88 | 3.39 | 0.21 | 0.97 | 3.60 | 0.22 | 1.03 |
10 | I-13 | 1.0 | 3.26 | 0.22 | 0.94 | 3.53 | 0.22 | 1.02 | 3.51 | 0.22 | 1.02 |
11 | I-13 | 7.0 | 3.29 | 0.20 | 0.91 | 3.50 | 0.20 | 0.98 | 3.62 | 0.20 | 1.00 |
12 | I-14 | 1.0 | 3.30 | 0.21 | 0.92 | 3.49 | 0.21 | 0.97 | 3.52 | 0.21 | 0.98 |
Invention Example nr. |
1 | I-6 | 1.33 | 3.50 | 0.22 | 0.90 | - | - | - | 3.74 | 0.22 | 0.96 |
2 | I-6 | 1.50 | 3.45 | 0.23 | 0.88 | - | - | - | 3.77 | 0.22 | 0.96 |
3 | I-6 | 1.75 | 3.35 | 0.22 | 0.87 | - | - | - | 3.8 | 0.22 | 0.98 |
4 | I-6 | 2.0 | 3.31 | 0.22 | 0.87 | - | - | - | 3.88 | 0.22 | 1.02 |
5 | I-6 | 2.5 | 3.23 | 0.22 | 0.86 | - | - | - | 3.78 | 0.22 | 1.00 |
6 | I-6 | 3.0 | 3.19 | 0.21 | 0.92 | 3.43 | 0.22 | 0.99 | 3.69 | 0.21 | 1.06 |
7 | I-6 | 5.0 | 3.12 | 0.21 | 0.85 | 3.39 | 0.21 | 0.93 | 3.62 | 0.22 | 0.99 |
8 | I-13 | 3.0 | 3.36 | 0.21 | 0.97 | 3.55 | 0.21 | 0.97 | 3.86 | 0.21 | 1.06 |
9 | I-13 | 5.0 | 3.12 | 0.20 | 0.89 | 3.46 | 0.20 | 0.98 | 3.69 | 0.20 | 1.03 |
10 | I-14 | 3.0 | 3.28 | 0.20 | 0.94 | 3.59 | 0.20 | 1.03 | 3.91 | 0.20 | 1.12 |
11 | I-14 | 5.0 | 3.20 | 0.19 | 0.95 | 3.48 | 0.19 | 1.03 | 3.52 | 0.20 | 1.04 |
Image evaluation
-
The image tone of fresh prints made with the substantially
light-insensitive thermographic recording materials of COMPARATIVE
EXAMPLES 1 to 12 and INVENTION EXAMPLES 1 to 11 using printer modes
1, 2 and 3 was assessed on the basis of the L*, a* and b* CIELAB-values.
The L*, a* and b* CIELAB-values were determined by
spectrophotometric measurements according to ASTM Norm E179-90 in a
R(45/0) geometry with evaluation according to ASTM Norm E308-90.
The b* CIELAB-values changed little between the printer modes and
as a function of the ratio of molar hydroxy-equivalents to molar
silver equivalents. On the other hand, the a* CIELAB-values of
fresh prints of the substantially light-insensitive thermographic
recording materials of COMPARATIVE EXAMPLES 1 to 12 and INVENTION
EXAMPLES 1 to 11 at optical densities, D, of 1.0 and 2.0 given in
Table 3 changed dramatically both with the DRYSTAR™ 4500 printer
mode used and with the ratio of molar hydroxy-equivalents to molar
silver equivalents.
-
In Table 3 a* CIELAB-values are given for D = 1.0 and D = 2.0
for the fresh substantially light-insensitive thermographic
recording materials of COMPARATIVE EXAMPLES 1 to 12 and INVENTION
EXAMPLES 1 to 11 printed in printer mode 1 and the changes in a*
CIELAB-values, Δa*, on changing the printer mode from mode 1 to
mode 2 and mode 1 to mode 3 respectively.
-
In the CIELAB-system a negative CIELAB a*-value indicates a
greenish image-tone becoming greener as a* becomes more negative, a
positive a*-value indicating a reddish image-tone becoming redder
as a* becomes more positive. A negative CIELAB b*-value indicates a
bluish tone which becomes increasingly bluer as b* becomes more
negative and a positive b*-value indicates a yellowish image-tone
becoming more yellow as b* becomes more positive. In terms of the
visual perception of an image as a whole, the image tone of
elements of the image with a density of 1.0 have a stronger effect
than the image tone of elements with lower or higher optical
density.
-
In general with the DRYSTAR™ 4500 printer in mode 1
thermographic recording materials with all the reducing agents
investigated surprisingly exhibited CIELAB a*-values which very
strongly decreased with increasing ratio of molar hydroxy-equivalents
to molar silver-equivalents in the range 1.0 to about
3.0. Above a ratio of 3.0 the change in CIELAB a*-value was much
lower.
-
Fresh prints obtained with the substantially light-insensitive
thermographic recording materials with all the reducing agents
investigated surprisingly exhibited CIELAB a*-values which strongly
increased as the heating time was reduced from 18 ms in printer
mode 1 to 10.5 ms in printer mode 2 to 5.25 ms in printer mode 3.
This effect was surprisingly ameliorated by increasing the ratio of
molar hydroxy-equivalents to molar silver-equivalents. For example
in the case of substantially light-insensitive recording materials
with reducing agent I-6, the shift in a* CIELAB-value in going from
printer mode 1 to printer mode 3 was a prohibitive ca. + 11.5 at D
= 1.0 for a ratio of molar hydroxy-equivalents to molar silver-equivalents
of 1.0 (COMPARATIVE EXAMPLES 7 and 8) and was only
-0.23 at D = 1.0 for a ratio of molar hydroxy-equivalents to molar
silver-equivalents of 7.0 (COMPARATIVE EXAMPLE 9).
-
Such an effect is only usable for substantially light-insensitive
thermographic recording materials with reducing agents
which upon printing with DRYSTAR™ 4500 printer in mode 1 produce
prints with acceptable image tones. Table 4 summarizes the a* and
b* CIELAB values obtained with the substantially light-insensitive
thermographic recording materials of COMPARATIVE EXAMPLES 1 to 12
and INVENTION EXAMPLES 1 to 11.
(DRYSTAR™ 4500 printer mode 1) : |
Comparative Example nr. | Reducing agent | Ratio of molar OH-equivalents to molar Ag-equivalents | fresh print CIELAB values: |
| | | D=1.0 | D = 2.0 |
| | | a* | b* | a* | b* |
1 | CR01 | 1.0 | +4.74 | +4.15 | +11.45 | +7.57 |
2 | CR01 | 1.5 | +1.12 | +2.10 | +6.36 | +4.90 |
3 | CR01 | 2.0 | -0.77 | +1.01 | +3.88 | +3.82 |
4 | CR02 | 1.0 | +27.03 | +32.06 | +29.54 | +13.85 |
5 | CR02 | 1.5 | +1.12 | -5.31 | +5.78 | -0.89 |
6 | CR02 | 2.0 | -1.45 | -4.00 | +3.45 | -0.44 |
7 | I-6 | 1.0 | -2.08 | -8.65 | +2.21 | -5.44 |
8 | I-6 | 1.0 | -3.05 | -8.02 | +1.60 | -5.37 |
9 | I-6 | 7.0 | -4.64 | -5.3 | -2.04 | -4.49 |
10 | I-13 | 1.0 | -2.66 | -7.40 | +1.63 | -5.49 |
11 | I-13 | 7.0 | -3.95 | -3.34 | -1.53 | -2.37 |
12 | I-14 | 1.0 | -2.06 | -7.53 | +2.43 | -5.70 |
Invention Example nr. |
1 | I-6 | 1.33 | -3.80 | -8.93 | +0.13 | -6.40 |
2 | I-6 | 1.50 | -4.24 | -8.73 | -0.51 | -6.70 |
3 | I-6 | 1.75 | -4.53 | -8.33 | -1.20 | -6.73 |
4 | I-6 | 2.0 | -4.67 | -8.21 | -1.56 | -6.92 |
5 | I-6 | 2.5 | -4.68 | -7.57 | -1.94 | -6.69 |
6 | I-6 | 3.0 | -4.89 | -6.49 | -2.08 | -5.85 |
7 | I-6 | 5.0 | -4.64 | -5.71 | -2.03 | -5.14 |
8 | I-13 | 3.0 | -4.21 | -4.94 | -1.64 | -4.32 |
9 | I-13 | 5.0 | -3.86 | -3.61 | -1.39 | -2.67 |
10 | I-14 | 3.0 | -4.50 | -4.08 | -1.46 | -3.70 |
11 | I-14 | 5.0 | -4.48 | -2.50 | -1.16 | -1.70 |
-
Table 4 shows that substantially light-insensitive thermographic
recording materials of INVENTION EXAMPLES 1 to 11 and COMPARATIVE
EXAMPLES 9 and 11 with reducing agents I-6, I-13 and I-14, exhibit
neutral to bluish image tones. However, this is clearly not the
case for the substantially light-insensitive thermographic
recording materials of COMPARATIVE EXAMPLES 1 to 6 with reducing
agents CR01 and CR02, which exhibited strongly reddish image tones.
Archivability tests
-
Simulated long-term archivability tests were performed by heating
prints produced with the DRYSTAR™ 4500 printer in modes 1, 2 and 3
with the substantially light-insensitive thermographic recording
materials of COMPARATIVE EXAMPLES 1 to 12 and INVENTION EXAMPLES 1
to 11 to heating at 57°C in 34% relative humidity for 3 days in the
dark and the CIELAB b*-values were determined for densities of 1.0
and 2.0. The changes in b* CIELAB-values for densities of 1.0 and
2.0 for printer modes 1, 2 and 3 are given in Table 5.
-
The present invention is demarcated with respect to the prior art
by the surprising decrease in a* CIELAB-values with increasing ratio
of molar hydroxy-equivalents to molar silver-equivalents together with
the deterioration in archivability for a ratio of molar hydroxy-equivalents
to molar silver-equivalents of 7.0, see the Δb* CIELAB-values
for COMPARATIVE EXAMPLE 9 and COMPARATIVE EXAMPLE 11 compared
with those for INVENTION EXAMPLES 7 and 9 respectively for printer
modes 1, 2 and 3.
COMPARATIVE EXAMPLE 13 and INVENTION EXAMPLES 12 and 13
Preparation of the thermosensitive element
-
The thermosensitive elements of the substantially light-insensitive
thermographic recording materials of COMPARATIVE
EXAMPLE 13 and INVENTION EXAMPLES 12 and 13 were produced by
coating a dispersion with the following ingredients in 2-butanone
onto a subbed 168µm thick blue-pigmented polyethylene terephthalate
support with CIELAB a*- and b*- values of -7.9 and -16.6
respectively; and drying at 75°C (temperature of the dry air) for 7
minutes to produce layers with the compositions given in Table 6.
Comparative example nr | Reducing agent | Ratio of molar OH-equivalents to molar Ag-equivalents | AgBeh coverage [g/m2] | BL5HP [g/m2] | T01 mol% vs AgB | T02 mol% vs AgB | S01 mol% vs AgB | S02 mol% vs AgB | S03 mol% vs AgB | Oil [g/m2] |
13 | I-1
I-13 | 0.6 +
0.4 | 4.93 | 19.71 | 15 | 5 | 22 | 4.92 | 9.80 | 0.048 |
Invention example nr |
12 | I-1
I-13 | 0.8 +
0.50 | 4.98 | 19.92 | 15 | 5 | 22 | 4.92 | 9.80 | 0.048 |
13 | I-1
I-13 | 1.00 +
0.60 | 4.93 | 19.71 | 15 | 5 | 22 | 4.92 | 9.80 | 0.048 |
-
The thermosensitive elements of the thermographic recording
materials of COMPARATIVE EXAMPLE 13 and INVENTION EXAMPLES 12 and
13 were coated with a protective layer as described for the
thermographic recording materials of COMPARATIVE EXAMPLES 1 to 12
and INVENTION EXAMPLES 1 to 11 and the resulting thermographic
recording materials hardened for 7 days at 45°C thereby producing
the thermographic recording materials of COMPARATIVE EXAMPLE 13 and
INVENTION EXAMPLES 12 and 13.
Thermographic evaluation
-
The fresh thermographic recording materials of COMPARATIVE
EXAMPLE 13 and INVENTION EXAMPLES 12 and 13 were printed with
DRYSTAR™ 4500 printer mode 3 and evaluated as described for the
thermographic recording materials of COMPARATIVE EXAMPLES 1 to 12
and INVENTION EXAMPLES 1 to 11. The results are summarized in
Table 7.
-
The image tone obtained with the thermographic recording
material containing reducing agents I-1 and I-13 in an overall
ratio of molar hydroxy-equivalents to molar silver equivalents of
1.0 (COMPARATIVE EXAMPLE 13) was reddish, as can be seen be the
positive CIELAB a*-value for D = 2.0, whereas the image tone of the
substantially light-insensitive thermographic recording materials
of INVENTION EXAMPLES 12 and 13 were close to that of a typical X-ray
image with conventional silver halide radiographic film.
(DRYSTAR™ 4500 printer mode 3): |
Comparative Example nr | Reducing agent | Ratio of molar OH-equivalents to molar Ag-equivalents | Dmax (vis) | Dmin (vis) | Dmax/AgB coverage [m2/g] | fresh print CIELAB values |
| | | | | | D=1.0 | D = 2.0 |
| | | | | | a* | b* | a* | b* |
13 | I-1
I-13 | 0.60 +
0.40 | 3.28 | 0.23 | 0.66 | -0.36 | -7.17 | +1.81 | -6.09 |
Invention example nr |
12 | I-1
I-13 | 0.80 +
0.50 | 3.41 | 0.23 | 0.69 | -2.32 | -7.25 | -0.04 | -6.30 |
13 | I-1
I-13 | 1.00 +
0.60 | 3.51 | 0.23 | 0.61 | -3.10 | -7.03 | -0.88 | -5.80 |
Archivability tests
-
Simulated long-term archivability tests were performed by heating
prints produced with the thermographic recording materials of
COMPARATIVE EXAMPLES 13 and INVENTION EXAMPLES 12 and 13 to heating at
57°C in 34% relative humidity for 3 days in the dark and the CIELAB
a*- and b*- values were determined for densities of 1.0 and 2.0 are
summarized for prints produced with the DRYSTAR™ 4500 printer in mode
3 in Table 8.
-
The changes in image tone during the archivability tests were
much smaller for the substantially light-insensitive thermographic
recording materials of INVENTION EXAMPLES 12 and 13 than for the
substantially light-insensitive thermographic recording materials of
INVENTION EXAMPLES 1-11, but these materials had the drawback that the
D
max achieved per unit silver behenate coverage was significantly
lower than for the substantially light-insensitive thermographic
recording materials of INVENTION EXAMPLES 1-11.
(DRYSTAR™ 4500 printer mode 3): |
Comparative Example nr | Reducing agent | Ratio of molar OH-equivalents to molar Ag-equivalents | Δ CIELAB values of fresh prints after heating for 3d at 57°C/34%RH for: | ΔD after heating for 3d/57°C /34%RH for |
| | | D= 1.0 | D = 2.0 | ΔD for D=1.0 | ΔD for D=2.0 |
| | | Δa* | Δb* | Δa* | Δb* |
13 | I-1
I-13 | 0.60 +
0.40 | +0.17 | +0.91 | -0.65 | +1.26 | +0.17 | +0.16 |
Invention example nr |
12 | I-1
I-13 | 0.80 +
0.50 | +0.33 | -0.69 | -0.24 | +0.25 | +0.16 | +0.18 |
13 | I-1
I-13 | 1.00 +
0.60 | +0.31 | -1.35 | -0.18 | -0.30 | +0.17 | +0.20 |
COMPARATIVE EXAMPLES 14 and 15 and INVENTION EXAMPLES 14 and 15
Preparation of the thermosensitive element
-
The thermosensitive elements of the substantially light-insensitive
thermographic recording materials of COMPARATIVE
EXAMPLES 14 and 15 and INVENTION EXAMPLES 14 and 15 were produced
by coating a dispersion with the following ingredients in 2-butanone
onto a subbed 168µm non-pigmented polyethylene
terephthalate support; and drying at 50°C for 1 hour to produce
layers with the compositions given in Table 9.
Comparative example nr. | Reducing agent | Ratio of molar OH-equivalents to molar Ag-equivalents | AgBeh coverage [g/m2] | BL5HP [g/m2] | T01 mol% vs AgB | T02 mol% vs AgB | S01 mol% vs AgB | S02 mol% vs AgB | S03 mol% vs AgB | Oil [g/m2] |
14 | I-6 | 1.0 | 4.1 | 16.4 | 15 | 5 | 24 | 4.92 | 9.80 | 0.048 |
15 | I-6 | 1.0 | 4.0 | 16.0 | 15 | 5 | 26 | 4.92 | 9.80 | 0.048 |
Invention example nr. |
14 | I-6 | 1.5 | 4.0 | 16.0 | 15 | 5 | 24 | 4.92 | 9.80 | 0.048 |
15 | I-6 | 1.5 | 4.0 | 16.0 | 15 | 5 | 26 | 4.92 | 9.80 | 0.048 |
thermographic printing
-
The fresh thermographic recording materials of COMPARATIVE
EXAMPLES 14 and 15 and INVENTION EXAMPLES 14 and 15 were printed
using a DRYSTAR™ 2000 printer from AGFA-GEVAERT equipped with a
thin film thermal head with resistor elements 152 µm long in the
transport direction of the printer and 85 µm wide in the direction
perpendicular to the transport direction to print symmetrical
pixels (85 µm x 85 µm) with a resolution of 300 dpi (= 118
dots/cm), adapted to operate in two modes:
| maximum printing power [mW/pixel] | line time [ms] | heating time [ms] |
DRYSTAR™ 2000 mode 1 | 104 | 12 | 21.5 |
DRYSTAR™ 2000 mode 2 | 104 | 7.1 | 12.7 |
During printing the printhead was separated from the imaging layer
by a thin intermediate material contacted with a slipping layer of
a separable 5mm thick polyethylene terephthalate ribbon coated
successively with a subbing layer, heat-resistant layer and the
slipping layer (anti-friction layer) giving a ribbon with a total
thickness of 6mm. During the line time the print head received
constant power. The thermal head resistors were power-modulated to
produce different image densities.
-
The prints produced were evaluated as described for the
thermographic recording materials of COMPARATIVE EXAMPLES 1 to 12
and INVENTION EXAMPLES 1 to 11. The results are summarized in
Tables 10 and 11 for DRYSTAR™ 2000 printer modes 1 and 2
respectively.
(DRYSTAR™ 2000 printer mode 1): |
Comparative Example nr. | Reducing agent | Ratio of molar OH-equivalents to molar Ag-equivalents | CIELAB values for fresh prints |
| | | D = 0.5 | D = 1.0 | D = 1.5 | D = 2.0 |
| | | a* | b* | a* | b* | a* | b* | a* | b* |
14 | I-6 | 1.0 | +1.01 | -0.57 | +1.72 | -4.96 | +1.63 | -7.14 | +2.24 | -7.28 |
15 | I-6 | 1.0 | +0.79 | -1.89 | +1.39 | -5.36 | +1.95 | -6.79 | +1.64 | -6.72 |
Invention example nr. |
14 | I-6 | 1.5 | +0.3 | +2.12 | -0.13 | -2.27 | -0.20 | -5.07 | -0.36 | -6.75 |
15 | I-6 | 1.5 | -0.1 | +0.75 | -0.77 | -3.16 | -1.49 | -5.48 | -1.28 | -6.64 |
(DRYSTAR™ 2000 printer mode 2): |
Comparative Example nr. | Reducing agent | Ratio of molar OH-equivalents to molar Ag-equivalents | CIELAB values for fresh prints |
| | | D = 0.5 | D = 1.0 | D = 1.5 | D = 2.0 |
| | | a* | b* | a* | b* | a* | b* | a* | b* |
14 | I-6 | 1.0 | +3.12 | -1.39 | +5.16 | -7.25 | +4.6 | -8.22 | +6.93 | -7.59 |
15 | I-6 | 1.0 | +3.33 | -3.10 | +5.11 | -7.16 | +5.69 | -8.28 | +4.21 | -8.05 |
Invention example nr. |
14 | I-6 | 1.5 | +0.66 | -0.16 | +1.55 | -5.15 | +1.47 | -7.67 | +1.87 | -7.89 |
15 | I-6 | 1.5 | +0.37 | -1.13 | +0.70 | -6.03 | +0.59 | -8.19 | +1.02 | -8.03 |
A desirable image tone was obtained with the thermographic
recording materials containing reducing agent I-6 upon printing
with the DRYSTAR™ 2000 printer mode 1 for a ratio of molar hydroxy-equivalents
to molar silver equivalents of 1.5, despite the
thermographic materials having been coated on a non-pigmented
support, whereas thermographic recording materials containing
reducing agents I-6 upon printing with the DRYSTAR™ 2000 printer
mode 2 for a ratio of molar hydroxy-equivalents to molar silver
equivalents of 1.0 exhibited prohibitively reddish images as can be
seen from the pronouncedly positive CIELAB a*-values.
-
A desirable image tone was obtained with the thermographic
recording materials containing reducing agents I-6 upon printing
with the DRYSTAR™ 2000 printer mode 2 for a ratio of molar hydroxy-equivalents
to molar silver equivalents of 1.5, despite the
thermographic materials having been coated on a non-pigmented
support, whereas thermographic recording materials containing
reducing agents I-6 upon printing with the DRYSTAR™ 2000 printer
mode 2 for a ratio of molar hydroxy-equivalents to molar silver
equivalents of 1.0 exhibited prohibitively reddish images as can be
seen from the pronouncedly positive CIELAB a*-values.
archivability tests
-
Simulated long-term archivability tests were performed by heating
prints produced with the thermographic recording materials of
COMPARATIVE EXAMPLES 14 and 15 and INVENTION EXAMPLES 14 and 15 to
heating at 45°C in 70% relative humidity for 4 days in the dark and
the CIELAB a*- and b*- values determined for densities of 0.5, 1.0 and
1.5 are summarized for prints produced with DRYSTAR™ 2000 printer mode
1 and DRYSTAR™ 2000 printer mode 2 in Tables 12 and 13 respectively.
(DRYSTAR™ 2000 printer mode 1) : |
Comparative Example nr. | Reducing agent | Ratio of molar OH-equivalents to molar Ag-equivalents | CIELAB values for prints after 4d/45°C/70%RH: |
| | | D = 0.5 | D = 1.0 | D = 1.5 | D = 2.0 |
| | | a* | b* | a* | b* | a* | b* | a* | b* |
14 | I-6 | 1.0 | +2.44 | +0.76 | +4.31 | -2.19 | +1.54 | -4.09 | +1.10 | -4.36 |
15 | I-6 | 1.0 | +2.09 | -0.47 | +3.44 | -2.42 | +1.30 | -3.60 | +0.42 | -3.73 |
Invention example nr. |
14 | I-6 | 1.5 | +0.74 | -0.48 | +0.63 | -3.52 | -0.02 | -5.48 | -0.81 | -5.66 |
15 | I-6 | 1.5 | +0.22 | -1.21 | +0.16 | -3.61 | -1.56 | -5.37 | -1.36 | -5.22 |
-
Prints produced with DRYSTAR™ 2000 printer mode 1 with the
substantially light-insensitive thermographic recording materials
of INVENTION EXAMPLES 14 and 15 with a ratio of molar hydroxy-equivalents
to molar silver equivalents of 1.5 exhibited marginally
acceptable image tones after 4 days at 45°C and 70% relative
humidity in the dark, whereas prints produced with the
substantially light-insensitive thermographic recording materials
of COMPARATIVE EXAMPLES 14 and 15 with a ratio of molar hydroxy-equivalents
to molar silver equivalents of 1.0 were very reddish
for densities of both 0.5 and 1.0.
(DRYSTAR™ 2000 printer mode 2): |
ComparAtive Example nr. | Reducing agent | Ratio of molar OH-equivalents to molar Ag-equivalents | CIELAB values for prints after 4d/45°C/70%RH: |
| | | D = 0.5 | D = 1.0 | D = 1.5 | D = 2.0 |
| | | a* | b* | a* | b* | a* | b* | a* | b* |
14 | I-6 | 1.0 | +5.19 | +1.97 | +5.87 | -2.80 | +4.51 | -3.93 | +5.90 | -3.67 |
15 | I-6 | 1.0 | +4.93 | +0.59 | +5.58 | -2.51 | +8.25 | -3.95 | +2.30 | -4.80 |
Invention example nr. |
14 | I-6 | 1.5 | +2.71 | -0.20 | +3.22 | -4.03 | +2.07 | -5.24 | +1.31 | -5.65 |
15 | I-6 | 1.5 | +2.21 | -0.72 | +2.03 | -4.61 | +1.32 | -6.36 | +0.51 | -5.69 |
-
Prints produced with DRYSTAR™ 2000 printer mode 2 with the
substantially light-insensitive thermographic recording materials
of INVENTION EXAMPLES 14 and 15 with a ratio of molar hydroxy-equivalents
to molar silver equivalents of 1.5 exhibited a much
less reddish image tone after 4 days at 45°C and 70% relative
humidity in the dark, than those produced with the substantially
light-insensitive thermographic recording materials of COMPARATIVE
EXAMPLES 14 and 15 with a ratio of molar hydroxy-equivalents to
molar silver equivalents of 1.0 were extremely red at all
densities.
COMPARATIVE EXAMPLE 16
preparation of the subbed support
-
The subbed support was prepared by coating a 175 µm thick blue-pigmented
polyethylene terephthalate support with L*, a* and b*
CIELAB-values of 86.7, -8.2 and -18.2 respectively and a density
through a visible filter determined with a MacBeth™ 924 of 0.19 on
both sides with a layer with an aqueous ethanol dispersion
containing the following ingredients to produce the following
ingredient coverages as solids after drying:
| Coverage [mg/m2] |
LATEX01: | 162.2 |
Kieselsol 100F: | 40.0 |
Mersolat™ H | 0.85 |
UVONAC | 4.0 |
coating of backing layer
-
A backing layer was then applied to one side of the subbed support
with an aqueous ammoniacal N-methyl-pyrrolidinone dispersion
containing the following ingredients to produce the following
ingredient coverages as solids after drying:
| Coverage [mg/m2] |
Kelzan™ S | 10 |
PEDOT/PSS-1 | 15 |
UVONAC | 21 |
Kieselsol 100F | 20 |
Perapret™ | 10 |
LATEX02 | 200 |
MAT02 | 30 |
preparation of the thermosensitive element
-
The thermosensitive elements of the substantially light-insensitive
thermographic recording materials of COMPARATIVE
EXAMPLE 16 was produced by coating a dispersion with the following
ingredients in 2-butanone to a wet thickness of 95 µm onto the side
of the subbed support opposite to that to which the backing layer
had been applied, and drying at 85°C for 5 minutes to produce a
layer with the following composition:
| Coverage [g/m2] | mol% vs AgB |
AgB | 3.809 | 100 |
BL5HP | 15.202 | - |
I-6 | 0.768 | 49.50 |
T01 | 0.209 | 15.06 |
T02 | 0.107 | 5.02 |
S01 | 0.271 | 24.08 |
S02 | 0.120 | 4.94 |
S03 | 0.100 | 9.85 |
Oil | 0.025 | - |
protective layer
-
The thermosensitive elements of the thermographic recording
material of COMPARATIVE EXAMPLE 16 was produced by coating an
aqueous dispersion with the following ingredients onto the
thermosensitive element to give a layer with the following
ingredient coverages as solids after drying:
ERCOL 48 20 | = 2.1g/m2 |
VP AC 4055 | = 1.05g/m2 |
ULTRAVON™ W | = 0.075g/m2 |
SYLOID™ 72 | = 0.09 g/m2 |
VPDZ 3/100 | = 0.075g/m2 |
VPAZ 100 | = 0.075g/m2 |
type P3 | = 0.045g/m2 |
RILANIT™ GMS | = 0.15g/m2 |
TMOS (assuming that the tetramethylorthosilicate is completely converted to SiO2 | = 0.87g/m2 |
The pH of the coating composition was adjusted to a pH of 3.8 by
adding IN nitric acid. Those lubricants which were insoluble in
water, were dispersed in a ball mill with, if necessary, the aid of
a dispersion agent. The composition was coated to a wet layer
thickness of 85 µm and then dried at 40°C for 15 minutes and
hardened for 11 days at 45°C thereby producing the thermographic
recording material of COMPARATIVE EXAMPLE 16.
thermographic evaluation
-
The fresh thermographic recording materials of COMPARATIVE
EXAMPLE 16 was printed with DRYSTAR™ 4500 printer modes 1, 2 and 3
and evaluated as described for the thermographic recording
materials of COMPARATIVE EXAMPLES 1 to 12 and INVENTION EXAMPLES 1
to 11. The results are summarized in Table 14.
DRYSTAR 4500 mode | Ratio of molar hydroxy-equivalents to molar silver equivalents | Dmax (vis) | Dmin (vis) | Dmax/AgB coverage [m2/g] | fresh print CIELAB values: |
| | | | | D=1.0 | D = 2.0 |
| | | | | a* | b* | a* | b* |
1 | 0.99 | 3.05 | 0.22 | 0.80 | -4.66 | -9.39 | -1.11 | -5.61 |
2 | 0.99 | 3.15 | 0.22 | 0.83 | -2.69 | -10.87 | 1.66 | -7.85 |
3 | 0.99 | 3.35 | 0.22 | 0.88 | 2.72 | -13.20 | 6.79 | -9.84 |
It is clear from the CIELAB values that, for a ratio of molar
hydroxy-equivalents to molar silver equivalents of 1.0 outside the
scope of the present invention, there is an undesirable shift in
image tone to positive values of a* i.e. to a reddish image tone
with fresh films from DRYSTAR™ 4500 Printer mode 1 to modes 2 and 3
for a density of 2.0. These very strong positive shifts in CIELAB
a* values from DRYSTAR™ 4500 Printer mode 1 to modes 2 and 3 are
shown in Table 15.
| Mode 1 | a*/mode2 -a*/mode1 | a*/mode3 -a*/mode1 |
| a* | Δa*(2/1) | Δa*(3/1) |
Fresh print CIELAB values for D=1.0 | -4.66 | 1.97 | 7.38 |
Fresh print CIELAB values for D=2.0 | -1.11 | 2.77 | 7.90 |
This demonstrates the strong effect of variation of the line and
heating times on CIELAB a* values in rendering the image tone
increasingly red with decreasing line time and heating time.
archivability tests
-
Simulated long-term archivability tests were performed by
heating prints produced with the DRYSTAR™ 4500 printer in modes 1,
2 and 3 with the substantially light-insensitive thermographic
recording material of COMPARATIVE EXAMPLE 16 to heating at 57°C in
34% relative humidity for 3 days in the dark and the CIELAB b*-values
were determined for densities of 1.0 and 2.0. The changes
in a* and b* CIELAB-values for densities of 1.0 and 2.0 for printer
modes 1, 2 and 3 are given in Table 16.
DRYSTAR 4500 PRINTER mode | Ratio of molar hydroxy-equivalents to molar silver equivalents | Δ CIELAB values of fresh prints after heating for 3d at 57°C/34% RH for: | ΔD after heating for 3d at 57°C/34%RH |
| | D= 1.0 | D = 2.0 |
| | Δa* | Δb* | Δa* | Δb* | ΔD for D=1.0 | ΔD for D=2.0 |
1 | 1.00 | 2.88 | 6.45 | -0.62 | 3.77 | 0.35 | 0.30 |
2 | 1.00 | 2.50 | 10.12 | -1.50 | 5.98 | 0.31 | 0.31 |
3 | 1.00 | -0.47 | 12.40 | -2.87 | 6.87 | 0.16 | 0.28 |
There is a considerable decrease in ΔD at D=1.0 upon changing the
printer mode of a DRYSTAR™ 4500 printer from mode 1 to mode 2 and
mode 3 i.e. upon decreasing the line time and heating time. There
is also an strong increase in Δb* value as can be seen from Table
17.
DRYSTAR™ 4500 Printer | change in b* CIELAB value, Δb*, of fresh prints after heating for 3d at 57°C/34% RH for: |
| D= 1.0 | D = 2.0 |
mode 1 | 6.45 | 3.77 |
mode 2 | 10.12 | 5.98 |
mode 3 | 12.40 | 6.87 |
INVENTION EXAMPLES 16 to 18
preparation of the subbed support
-
The subbed support was prepared by coating a 168 µm thick blue-pigmented
polyethylene terephthalate support with L*, a* and b*
CIELAB-values of 86.7, -8.2 and -18.2 respectively and a density
through a visible filter determined with a MacBeth™ 924 of 0.19 on
one side with a non-antistatic layer with an aqueous dispersion
containing the following ingredients to produce the following
ingredient coverages as solids after drying:
| Coverage [mg/m2] |
LATEX03: | 151 |
Kieselsol 100F: | 35 |
Mersolat™ H | 0.75 |
and on the other side with an antistatic layer with an aqueous
dispersion containing the following ingredients to produce the
following ingredient coverages as solids after drying:
| Coverage [mg/m2] |
PEDOT/PSS-2: | 2.58 |
LATEX03: | 147.3 |
Sorbitol(evaporated during drying): | 24.7 |
Kieselsol 100F: | 16.4 |
Mersolat™ H | 0.74 |
preparation of backing layer
-
The backing layer of the thermographic recording materials of
INVENTION EXAMPLES 16 to 18 were prepared by producing a 13.2% by
weight aqueous solution of POVAL™ 103 by adding 264 g to 1736 g of
cold deionized water, heating to 95°C and maintaining this
temperature for 30 minutes before cooling to room temperature.
This solution was then mixed with 1067.6 g of deionized water
followed by 130.7 mL of a 5% solution of OP80 with mixing, then
1978.5 g of Snowtex™ O with mixing and finally 45.85 g of MAT01
with mixing. The pH of the resulting dispersion was 4.8 and was
adjusted to a pH of 3.5 with IN nitric acid before coating to a wet
thickness of 40 µm on the antistatic subbing layer of the support.
The resulting layer was dried with heated air with a temperature of
140°C with the following composition as solids after drying:
POVAL 103 | = 2.123g/m2 |
OP 80 | = 0.053g/m2 |
Snowtex™ O | = 3.183g/m2 |
Sunsphere H51 | = 0.032g/m2 |
preparation of the thermosensitive element
-
The thermosensitive element of the substantially light-insensitive
thermographic recording materials of INVENTION EXAMPLES 16 to 18
was produced by coating a dispersion to a wet thickness of 95 µm
with the following ingredients in 2-butanone onto the opposite side
of the support to which the backing layer had been applied, and
drying at 85°C for 5 minutes to produce a layer with the following
composition:
| Coverage [g/m2] | mol% vs AgB |
AgB | 4.149 | 100 |
BL5HP | 16.596 | - |
I-1 | 0.438 | 35.00 |
I-13 | 0.894 | 45.00 |
T03 | 0.246 | 15.06 |
S01 | 0.294 | 24.00 |
S02 | 0.130 | 4.91 |
S03 | 0.109 | 9.84 |
VL | 0.185 | - |
Oil | 0.037 | - |
coating of protective layer
-
The thermosensitive elements of the thermographic recording
materials of INVENTION EXAMPLES 16 to 18 were then coated with an
aqueous dispersion with the following ingredients onto the
thermosensitive element with the protective layers with the
ingredient coverages as solids after drying given for the
thermographic recording materials for INVENTION EXAMPLES 16 to 18
in Table 18.
-
The pH of the coating composition was adjusted to a pH of
3.8 by adding IN nitric acid. Those lubricants which were insoluble
in water, were dispersed in a ball mill with, if necessary, the aid
of a dispersion agent. The composition was coated to a wet layer
thickness of 85 µm and then dried at 40°C for 15 minutes and
hardened for 7 days at 50°C thereby producing the thermographic
recording materials of INVENTION EXAMPLES 16 to 18.
| Invention Example nr 16 | Invention Example nr 17 | Invention Example nr 18 |
ERCOL 48 20 [g/m2] | 2.1 | 2.1 | - |
26/88 [g/m2] | - | - | 2.1 |
VP AC 4055 [g/m2] | 1.05 | 1.05 | 1.05 |
ULTRAVON™ W [g/m2] | 0.075 | 0.075 | 0.075 |
SYLOID™ 72 [g/m2] | 0.09 | 0.09 | 0.09 |
VPDZ 3/100 [g/m2] | 0.075 | 0.075 | 0.075 |
VPAZ 100 [g/m2] | 0.075 | 0.075 | 0.075 |
Satintone 5 [g/m2] | - | 0.100 | 0.100 |
type P3 [g/m2] | 0.045 | - | - |
RILANIT™GMS [g/m2] | 0.15 | 0.15 | 0.15 |
TMOS [g/m2] | 0.87 | 0.87 | 0.87 |
thermographic evaluation
-
The fresh thermographic recording materials of COMPARATIVE EXAMPLE
16 was printed with DRYSTAR™ 4500 printer modes 1, 2 and 3 and
evaluated as described for the thermographic recording materials of
COMPARATIVE EXAMPLES 1 to 12 and INVENTION EXAMPLES 1 to 11. The
results are summarized in Table 19.
Invention Example nr | DRYSTAR 4500 Printer mode | Ratio of molar OH-equivalents to molar Ag-equivalents | Dmax (vis) | Dmin (vis) | Dmax/AgB coverage [m2/g] | fresh print CIELAB values: |
| | | | | | D=1.0 | D = 2.0 |
. | | | | | | a* | b* | a* | b* |
16 | 1 | 1.6 | 3.11 | 0.22 | 0.75 | -4.76 | -3.48 | -2.04 | -1.50 |
| 2 | 1.6 | 3.04 | 0.22 | 0.73 | -5.49 | -5.02 | -2.72 | -2.54 |
| 3 | 1.6 | 3.02 | 0.22 | 0.73 | -5.05 | -8.26 | -2.53 | -5.65 |
17 | 1 | 1.6 | 3.05 | 0.22 | 0.73 | -4.77 | -4.10 | -2.02 | -1.90 |
| 2 | 1.6 | 3.01 | 0.22 | 0.73 | -5.51 | -5.74 | -2.74 | -2.99 |
| 3 | 1.6 | 3.02 | 0.22 | 0.73 | -4.83 | -8.85 | -2.26 | -5.95 |
18 | 1 | 1.6 | 3.11 | 0.22 | 0.75 | -4.72 | -3.39 | -1.95 | -1.33 |
| 2 | 1.6 | 3.07 | 0.22 | 0.74 | -5.46 | -4.89 | -2.52 | -2.42 |
| 3 | 1.6 | 3.05 | 0.22 | 0.73 | -4.59 | -8.26 | -1.79 | -5.75 |
-
It is clear from the CIELAB values that, for a ratio of molar
hydroxy-equivalents to molar silver equivalents of 1.6 within the
scope of the present invention, the shift in b* values from
DRYSTAR™ 4500 Printer mode 1 to modes 2 and 3 are to increased
negativity i.e. to desirably increased bluer image tone for
densities of 1.0 and 2.0. The even smaller shifts in CIELAB a*
values from DRYSTAR™ 4500 Printer mode 1 to modes 2 and 3 are shown
in Table 20.
Invention Example nr. | Ratio of molar OH-equiv. to molar Ag-equiv. | Fresh print CIELAB values for D=1.0: | Fresh print CIELAB values for D = 2.0: |
| | mode 1 | a*/mode2 - a*/mode1 | a*/mode3 - a*/mode1 | mode 1 | a*/mode2 - a*/mode1 | a*/mode3 - a*/mode1 |
| | a* | Δa*(2/1) | Δa*(3/1) | a* | Δa*(2/1) | Δa*(3/1) |
16 | 1.60 | -4.76 | -0.73 | -0.29 | -2.04 | -0.68 | -0.49 |
17 | 1.60 | -4.77 | -0.74 | -0.06 | -2.02 | -0.72 | -0.24 |
18 | 1.60 | -4.72 | -0.74 | 0.13 | -1.95 | -0.57 | 0.16 |
-
This demonstrates the advantageous effect of the present
invention in surprisingly allowing the same material to be used
with printers used with widely differing line and heating times
without a negative effect on image tone.
Archivability tests
-
Simulated long-term archivability tests were performed by
heating prints produced with the DRYSTAR™ 4500 printer in modes 1,
2 and 3 with the substantially light-insensitive thermographic
recording materials of INVENTION EXAMPLES 16 to 19 to heating at
57°C in 34% relative humidity for 3 days in the dark and the CIELAB
a*- and b*-values were determined for densities of 1.0 and 2.0.
The changes in a* and b* CIELAB-values for densities of 1.0 and 2.0
for printer modes 1, 2 and 3 are given in Table 21.
Invention Example nr. | DRYSTAR 4500 Printer mode | Ratio of molar hydroxy-equivalents to molar silver equivalents | Δ CIELAB values of fresh prints after heating for 3d at 57°C/34% RH for: | ΔD after heating for 3d/57°C/34%RH |
| | | D= 1.0 | D = 2.0 | ΔD for D=1.0 | ΔD for D=2.0 |
| | | Δa* | Δb* | Δa* | Δb* |
16 | 1 | 1.60 | -1.29 | 1.85 | -0.88 | 0.40 | 0.29 | 0.20 |
| 2 | 1.60 | 0.11 | 1.94 | -0.43 | 0.59 | 0.31 | 0.24 |
| 3 | 1.60 | 0.75 | 3.78 | 0.06 | 2.03 | 0.22 | 0.25 |
17 | 1 | 1.60 | -1.67 | 2.01 | -0.97 | 0.38 | 0.29 | 0.20 |
| 2 | 1.60 | 0.01 | 2.18 | -0.47 | 0.57 | 0.31 | 0.24 |
| 3 | 1.60 | 0.56 | 2.60 | -0.04 | 1.72 | 0.11 | 0.24 |
18 | 1 | 1.60 | -1.66 | 1.59 | -0.90 | 0.01 | 0.26 | 0.17 |
| 2 | 1.60 | -0.27 | 1.53 | -0.60 | 0.21 | 0.29 | 0.22 |
| 3 | 1.60 | 0.30 | 2.63 | -0.25 | 1.38 | 0.10 | 0.23 |
-
There is little change in a* CIELAB-value during the
archivability tests whether the prints were produced using DRYSTAR™
4500 Printer modes 1, 2 or 3. The changes in b* CIELAB-values were
larger for prints produced using DRYSTAR™ 4500 Printer modes 1, 2
or 3 and increased in the order mode 1, mode 2 and mode 3, i.e.
with decreasing line and heating times, as can be seen in Table 22,
which is extracted from Table 21.
Invention Example nr. | Ratio of molar hydroxy-equivalents to molar silver equivalents | change in CIELAB values of fresh prints after heating for 3d at 57°C/34% RH for: |
| | D= 1.0 | D = 2.0 |
| | mode 1 | mode 2 | mode 3 | mode 1 | mode 2 | mode 3 |
| | Δb* | Δb* | Δb* | Δb* | Δb* | Δb* |
16 | 1.60 | 1.85 | 1.94 | 3.78 | 0.40 | 0.59 | 2.03 |
17 | 1.60 | 2.01 | 2.18 | 2.60 | 0.38 | 0.57 | 1.72 |
18 | 1.60 | 1.59 | 1.53 | 2.63 | 0.01 | 0.21 | 1.38 |
However, the changes in b* CIELAB-values were acceptable even in
the case of prints produced with DRYSTAR™ 4500 Printer mode 3 with
the lowest line and heating times.
INVENTION EXAMPLE 19
-
The thermographic recording material of INVENTION EXAMPLE 19
was identical to that of INVENTION EXAMPLE 16 except that the
POVAL™103 was replaced by ERKOL™ V03/140 and had the following
ingredient coverages as solids after drying:
V03/140 | = 2.123g/m2 |
OP 80 | = 0.053g/m2 |
Snowtex™ O | = 3.183g/m2 |
Sunsphere H51 | = 0.032g/m2 |
thermographic evaluation
-
The fresh thermographic recording materials of INVENTION EXAMPLE 19
was printed with DRYSTAR™ 4500 printer modes 1, 2 and 3 and
evaluated as described for the thermographic recording materials of
COMPARATIVE EXAMPLES 1 to 12 and INVENTION EXAMPLES 1 to 11. The
results are summarized in Table 23.
DRYSTAR 4500 Printer mode | Ratio of molar OH-equivalents to molar Ag-equivalents | Dmax (vis) | Dmin (vis) | Dmax/AgB coverage [m2/g] | fresh print CIELAB values: |
| | | | | D=1.0 | D = 2.0 |
| | | | | a* | b* | a* | b* |
1 | 1.6 | 3.07 | 0.22 | 0.74 | -4.66 | -3.27 | -1.93 | -0.92 |
2 | 1.6 | 3.02 | 0.22 | 0.73 | -5.41 | -4.87 | -2.54 | -2.20 |
3 | 1.6 | 3.04 | 0.22 | 0.73 | -4.44 | -8.33 | -1.83 | -5.75 |
-
It is clear from the CIELAB values that, for a ratio of molar
hydroxy-equivalents to molar silver equivalents of 1.6 within the
scope of the present invention, the shift in b* values from
DRYSTAR™ 4500 Printer mode 1 to modes 2 and 3 are to increased
negativity i.e. to desirably increased bluer image tone for
densities of 1.0 and 2.0. The even smaller shifts in CIELAB a*
values from DRYSTAR™ 4500 Printer mode 1 to modes 2 and 3 are shown
in Table 24.
Ratio of molar OH-equiv. to molar Ag-equiv. | Fresh print CIELAB values for D=1.0: | Fresh print CIELAB values for D = 2.0: |
| mode 1 | a*/mode2 - a*/mode1 | a*/mode3 - a*/mode1 | mode 1 | a*/mode2 - a*/mode1 | a*/mode3 - a*/mode1 |
| a* | Δa*(2/1) | Δa*(3/1) | a* | Δa*(2/1) | Δa*(3/1) |
1.60 | -4.66 | -0.75 | 0.22 | -1.93 | -0.61 | 0.10 |
This demonstrates the advantageous effect of the present invention
in surprisingly allowing the same material to be used with printers
used with widely differing line and heating times without a
negative effect on image tone.
Archivability tests
-
Simulated long-term archivability tests were performed by
heating prints produced with the DRYSTAR™ 4500 printer in modes 1,
2 and 3 with the substantially light-insensitive thermographic
recording materials of INVENTION EXAMPLE 19 to heating at 57°C in
34% relative humidity for 3 days in the dark and the CIELAB a*- and
b*-values were determined for densities of 1.0 and 2.0. The
changes in a* and b* CIELAB-values for densities of 1.0 and 2.0 for
printer modes 1, 2 and 3 are given in Table 25.
DRYSTAR 4500 Printer mode | Ratio of molar hydroxy-equivalents to molar silver equivalents | Δ CIELAB values of fresh prints after heating for 3d at 57°C/34% RH for: | ΔD after heating for 3d/57°C/34%RH |
| | D= 1.0 | D = 2.0 | ΔD for D=1.0 | ΔD for D=2.0 |
| | Δa* | Δb* | Δa* | Δb* |
1 | 1.60 | -1.62 | 1.97 | -0.90 | 0.17 | 0.25 | 0.18 |
2 | 1.60 | -0.14 | 1.44 | -0.63 | 0.36 | 0.26 | 0.23 |
3 | 1.60 | 0.15 | 3.35 | -0.34 | 1.69 | 0.24 | 0.26 |
-
There is little change in a* CIELAB-value during the
archivability tests whether the prints were produced using DRYSTAR™
4500 Printer modes 1, 2 or 3. The changes in b* CIELAB-values were
larger for prints produced using DRYSTAR™ 4500 Printer modes 1, 2
or 3 and increased in the order mode 1, mode 2 and mode 3, i.e.
with decreasing line and heating times, as can be seen in Table 26,
which is extracted from Table 25.
Ratio of molar hydroxy-equivalents to molar silver equivalents | change in CIELAB values of fresh prints after heating for 3d at 57°C/34% RH for: |
| D= 1.0 | D = 2.0 |
| mode 1 | mode 2 | mode 3 | mode 1 | mode 2 | mode 3 |
| Δb* | Δb* | Δb* | Δb* | Δb* | Δb* |
1.60 | 1.97 | 1.44 | 3.35 | 0.17 | 0.36 | 1.69 |
However, the changes in b* CIELAB-values were acceptable even in
the case of prints produced with DRYSTAR™ 4500 Printer mode 3 with
the lowest line and heating times.
INVENTION EXAMPLE 20
preparation of the subbed support
-
The subbed support was prepared by coating a 175 µm thick blue-pigmented
polyethylene terephthalate support with L*, a* and b*
CIELAB-values of 86.7, -8.2 and -18.2 respectively and a density
through a visible filter determined with a MacBeth™ 924 of 0.19
with the non-antistatic and antistatic subbing layers described for
the support of INVENTION EXAMPLES 16 to 18.
Coating of backing layer
-
A backing layer was applied to the antistatic layer of the support
with an aqueous dispersion containing the following ingredients to
produce the following ingredient coverages as solids after drying:
| Coverage [mg/m2] |
KELZAN™ S | 10 |
PEDT/PSS-2 | 12 |
Zonyl™ FSO 100 | 21 |
Kieselsol 100F | 20 |
Poligen™ WE7 | 10 |
LATEX04 | 1000 |
MAT01 | 30 |
Preparation of the thermosensitive element
-
The thermosensitive elements of the substantially light-insensitive
thermographic recording materials of INVENTION EXAMPLE 20 was
produced by coating a dispersion with the following ingredients in
2-butanone onto the opposite site of the support to the backing
layer, and drying at 85°C for 5 minutes to produce layers with the
following composition:
| Coverage [g/m2] | mol% vs AgB |
AgB | 4.10 | 100 |
BL5HP | 16.40 | - |
I-1 | 0.37 | 29.67 |
I-6 | 0.81 | 48.34 |
T02 | 0.12 | 5.00 |
T03 | 0.26 | 15.00 |
S01 | 0.29 | 23.98 |
S02 | 0.13 | 4.94 |
S03 | 0.11 | 9.85 |
Oil | 0.036 | - |
The thermosensitive element was coated with the same protective
layer as described for COMPARATIVE EXAMPLE 16.
thermographic evaluation
-
The fresh thermographic recording materials of INVENTION EXAMPLE 20
was printed with DRYSTAR™ 4500 printer modes 1, 2 and 3 and
evaluated as described for the thermographic recording materials of
COMPARATIVE EXAMPLES 1 to 12 and INVENTION EXAMPLES 1 to 11. The
results are summarized in Table 27.
DRYSTAR 4500 printer mode | Ratio of molar hydroxy-equivalents to molar silver equivalents | Dmax (vis) | Dmin (vis) | Dmax/AgB coverage [m2/g] | fresh print CIELAB values: |
| | | | | D=1.0 | D = 2.0 |
| | | | | a* | b* | a* | b* |
1 | 1.56 | 3.05 | 0.22 | 0.74 | -4.03 | -6.89 | -2.01 | -4.80 |
2 | 1.56 | 2.95 | 0.22 | 0.72 | -4.66 | -8.08 | -2.20 | -5.50 |
3 | 1.56 | 3.18 | 0.22 | 0.78 | -3.70 | -10.77 | -0.81 | -8.07 |
It is clear from the CIELAB values that, for a ratio of molar
hydroxy-equivalents to molar silver equivalents of 1.56 within the
scope of the present invention, the shift in b* values from
DRYSTAR™ 4500 Printer mode 1 to modes 2 and 3 are to increased
negativity i.e. to desirably increased bluer image tone for
densities of 1.0 and 2.0. The even smaller shifts in CIELAB a*
values from DRYSTAR™ 4500 Printer mode 1 to modes 2 and 3 are shown
in Table 28.
| Mode 1 | a*/mode 2 - a*/mode 1 | a*/mode 3 - a*/mode 1 |
| a* | Δa*(2/1) | Δa*(3/1) |
Fresh print CIELAB values for D=1.0 | -4.03 | -0.63 | 0.33 |
Fresh print CIELAB values for D=2.0 | -2.01 | -0.19 | 1.20 |
This demonstrates the advantageous effect of the present invention
in surprisingly allowing the same material to be used printers used
with widely differing line and heating times without a negative
effect on image tone.
Archivability tests
-
Simulated long-term archivability tests were performed by
heating prints produced with the DRYSTAR™ 4500 printer in modes 1,
2 and 3 with the substantially light-insensitive thermographic
recording material of INVENTION EXAMPLE 20 to heating at 57°C in
34% relative humidity for 3 days in the dark and the CIELAB a*- and
b*-values were determined for densities of 1.0 and 2.0. The
changes in a* and b* CIELAB-values for densities of 1.0 and 2.0 for
printer modes 1, 2 and 3 are given in Table 29.
-
The change in a* CIELAB-value for prints produced using
DRYSTAR™ 4500 Printer modes 1, 2 or 3 were not insubstantial and
varied with the mode used, but not in the order mode 1, mode 2 and
mode 3, i.e. there was no consistent increase with decreasing line
and heating times.
DRYSTAR 4500 PRINTER mode | Ratio of molar hydroxy-equivalents to molar silver equivalents | Δ CIELAB values of fresh prints after heating for 3d at 57°C/34% RH for: | ΔD after heating for 3d at 57°C/34%RH |
| | D= 1.0 | D = 2.0 | ΔD for D=1.0 | ΔD for D=2.0 |
| | Δa* | Δb* | Δa* | Δb* |
1 | 1.56 | 0.65 | 1.44 | 0.35 | -0.64 | 0.45 | 0.54 |
2 | 1.56 | 2.35 | 1.51 | 0.95 | 0.46 | 0.48 | 0.58 |
3 | 1.56 | 1.94 | 3.49 | 0.46 | 2.95 | 0.44 | 0.54 |
The change in b* CIELAB-value for prints produced using DRYSTAR™ 4500
Printer modes 1, 2 or 3 during the archivability tests increased in
the order mode 1, mode 2 and mode 3, i.e. there with decreasing line
and heating times, as can be seen in Table 30, which is extracted from
Table 29.
DRYSTAR 4500 Printer | change in b* CIELAB value, Δb*, of fresh prints after heating for 3d at 57°C/34% RH for: |
| D= 1.0 | D = 2.0 |
mode 1 | 1.44 | -0.64 |
mode 2 | 1.51 | 0.46 |
mode 3 | 3.49 | 2.95 |
However, the changes in b* CIELAB-values were acceptable even in
the case of prints produced with DRYSTAR™ 4500 Printer mode 3 with
the lowest line and heating times.
-
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.