Note: Descriptions are shown in the official language in which they were submitted.
)7
The invention relates to diazotype material, more particularly to
- a one-component diazotype material that can be developed by applying a small
amount of developing liquid
c6l /llo~ve~nber ~P, Iq73
The Dutch Patent Application 72 07 099~ describes a process for mak-
ing diazotype copies, in which one-component diazotype material is developed
after imagewise exposure by spreading a buffered, aqueous solution of an azo-
coupling component over the light-sensitive layer, in an amount between 1.,5
and 4.5 cm3 per square metre.
The diazotype paper used in the process according to the patent
application mentioned above consists, in a simple embodiment, of a paper
support that, after a so-called precoat layer has been applied for smoothing
its surface, has been sensitized in such a way that, after drying, the diazon-
ium compound has penetrated into the precoat layer to an average depth of at
most 8 micrometres. The sensitization of the material is accomplished by
applying an adapted concentrated diazo-solution over the precoat layer in an
amount of 2-8 cm3 per square metre.
Due to the fact that, upon development only one side of the diazo-
type paper is wetted with developing liquid and the developing liquid pene-
trates through the precoat layer into the paper support, the diazotype copies
will show a strong curl, in particular immediately after development. To
avoid curling of the copy, the paper support may be provided with a sealing
layer preventing the developing liquid from penetrating into the paper fibres.
Preferably, the sealing layer is applied on either side of the paper support,
because otherwise curling may occur as a consequence of water penetrating into
the paper fibres of the reverse side of the copy. For instance, unless the
reverse side of the diazotype paper is coated with a sealing layer, the just
developed copies will curl during piling, as a consequence of moisture pene-
trating from the image side of one copy into the reverse side of the overlying
copy.
The manufacture of non-curling or almost non-curling diazotype
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paper by providing either side of a paper support with a sealing layer, then
coating one side with a precoat layer and, finally, sensitizing the precoat
layer by applying a small amount of concentrated diazo-solution, is cumber-
some and requires a complex coating machine with long drying paths, when it
is desired to manufacture the material in one machining operation and at high
speed. Due to the fact that the front side of the paper is subjected to
three coating operations and, on the other hand, the reverse side to one oper-
ation only, it may frequently occur that the paper does not remain flat in
the coating machine, in consequence of which an additional treatment of the
reverse side is necessary, thus complicating the manufacture of the diazotype
paper even more.
The manufacture of the diazotype paper is considerably simplified,
if it would be possible to apply the light-sensitive diazonium compound as
well as the further solid components of the sensitizing liquid simultaneously
with the precoat over the sealing layer. However, the choice of the compon-
ents for such a diazotype material is no simple matter, because a lot of
demands, partly contrary to each other, must be met. For instance, the paper
support must be coated with a more or less hydrophobic sealing layer on which
it must be possible, without the aid of an adhesive layer, to apply a very
smooth, more or less hydrophilic light-sensitive layer having sufficient
adhesion both in dry and in moist condition. It should be possible to apply
the components of the light-sensitive layer with sufficient adhesion to the
sealing layer, using a coating liquid that contains no solvents penetrating
deeply into the sealing layer, or swelling it, because the diazonium compound
would otherwise be partly trapped in the sealing layer and be inaccessible
to the developing liquid.
The light-sensitive layer itself may not be too thick, because the
developing liquid, in order to obtain complete development of the diazotype
material, must be able to penetrate through the whole thickness of the layer
but, on the other hand, it must fully absorb the amount of developing liquid
~L066~7
applied, in order to obtain copies feeling dry. Further, substances reducing
the durability of the diazotype material, or the quality or durability of the
diazotype copy to an unacceptable level may, of course, not be incorporated
in the sealing layer and the light-sensitive layer.
The invention provides for a diazotype material of the desired
composition which meets the requirements with respect to durability and
quality of the copy, and which, according to the developing method described
in the Dutch Patent Application 72 07 099, can be developed fast and compl,ete-
ly, whereby copies feeling immediately dry are obtained. The diazotype
material according to the invention comprises a paper support, the same side
of which is coated successively with a sealing layer containing as a film-
forming binder polyvinyl acetate, or a copolymer of styrene with butadiene,
and a light-sensitive layer having a dry weight of at most 8 g/m2 and com-
prising a diazonium compound, polyvinyl alcohol with a degree of hydrolysis
over 75% and starch particles, whereby the weight ratio starch particles to
polyvinyl alcohol is from 5 - 20:1. Upon development in the process accord-
ing to the Dutch Patent Application 72 07 099 the diazotype material accord-
ing to the invention produces strong copies, feeling dry to the touch almost
immediately and showing no or no appreciable curl.
In another aspect, the invention provides a process for the
manufacture of copies, in which a diazotype material is imagewise exposed and
then developed by spreading 1.5 to 4.5 cm3 per square metre of developing
liquid over the light-sensitive side of the diazotype material, character-
ized in that the diazotype material comprises a paper support, the same
side of which is coated successively with a sealing layer containing as a
film-forming binder polyvinyl acetate, or a copolymer of styrene with
butadiene, and a light-sensitive layer having a dry weight of at most 8 g
per square metre and comprising a diazonium compound, polyvinyl alcohol
with a degree of hydrolysis of at least 75% and starch particles, whereby
the weight ratio;polyvinyl alcohol to starch particles is from 1 : 5 to 20.
~ _ 3 _
1066~07
The paper support is coated with a sealing layer containing
as a binder polyvinyl acetate or a copolymer of styrene with butadiene.
The sealing layer can be applied to the support using a solution of the
film-forming binder but, preferably, it is formed by means of a dispersion
of the binder in water, or in a mixture of water with one or more water-
miscible organic solvents, for example alcohols, ketones, glycol, and
glycol esters. To sized papers the sealing layer is preferably applied
from an aqueous dispersion, whereas on well-milled papers, such as natural~
transparent paper,the sealing layer is often advantageously formed from a
dispersion of the binder in a mixture(of water and an organic solvent. The
mixtures of water with organic solvent may contain up to 75% by volume of
1~66107
organic solvent but, in general, mixtures containing no more than 50% by
volume of organic solvent are used. To form a dense coating, the dispersion
layer applied is dried at increased temperature.
For the formation of the sealing layer, suitable aqueous dispersions
of polyvinyl acetate and copolymers of styrene with butadiene are commercially
available. If the sealing layer on the support material is formed using a
polyvinyl acetate dispersion, a cross-linking agent is preferably added to
the dispersion, and the polyvinyl acetate coating is cross-linked by heating
it at 130-180C for some time. It has appeared that this cross-linking
improves the adhesive properties of the polyvinyl acetate coating for the
light-sensitive layer subsequently to be applied. Moreover, the penetration
of the sensitizing liquid into the polyvinyl acetate coating is reduced to a
minimum. The familiar products can be used as cross-linking agent, such as
paraformaldehyde, glyoxal, and water-soluble, optionally modified, condensat-
ion products of urea and melamine with formaldehyde, for example dimethylol-
urea, dimethylolmelamine, hexamethylolmelamine, dimethyloltetramethoxymethyl-
melamine and hexamethoxymethylmelamine. A very suitable cross-linking agent
is hexamethoxymethylmelamine.
Paraformaldehyde and glyoxal are not preferably used, because they
generally have an adverse effect on the durability of the diazotype material.
Used as cross-linking catalysts are acids or acid salts, for example
hydrochloric acid, sulphuric acid, formic acid, acetic acid, benzenesulphonic
acids such as p-toluene sulphonic acid, ammonium chloride, ammonium sulphate
and aluminium sulphate.
In addition to the film-forming binder, the sealing layer may con-
tain one or more fillers, in order to make it more susceptible to the sensit-
izing liquid to be applied, and to improve the adherence of the light-sensit-
ive layer. The filler content may not be so high that the sealing layer be-
comes water-permeable. In general the weight ratio filler to binder in the
sealing layer lies under 1 : 1 and preferably it is from 0.25 - 0.75 : 1.
10~6107
The familiar products can be used as fillers, such as clay, kaolin, diatoma-
ceous earth, talcum, silica, barium sulphate~ titanium dioxide, zinc oxide
and aluminium oxide. A preferred filler is silica with a particle size under
10 micrometres. The use of this filler in the sealing layer proves to have a
favourable effect on the complete development of the diazotype material and
the brilliancy of the azo-dyestuff. The sealing layer must fully cover the
paper surface. The weight of the sealing layer to be applied depends largely
on the surface roughness of the paper.
For papers with a smooth surface the application of a sealing layer
having a dry weight of 2-5 g per square metre will mostly suffice. Papers
with a rough surface require the application of a thicker layer but, in most
cases, the layer need not be thicker than equivalent to a dry weight from 8
to 10 g per square metre.
Highly suitable sealing layers according to the invention are
filler-free polyvinyl acetate layers applied from an aqueous dispersion, which
have been cross-linked, preferably with hexamethoxymethylmelamine, as well as
filler-containing layers from a copolymer of styrene with butadiene, which
copolymer contains 50-75% by weight of styrene and 50-25% by weight of buta-
diene, whereby the weight ratio filler to binder is from 0.25 - 0.75 : 1, and
the filler preferably is silica with a particle size under 10 micrometres.
The sealing layer is coated with a light-sensitive layer which con-
tains at least a light-sensitive diazonium compound and, moreover, polyvinyl
alcohol and starch particles in the weight ratio of 1 to 5-20. The degree of
hydrolysis of the polyvinyl alcohol must at least amount to 75% and, prefer-
ably, it amounts to at least 98%. Further, high-molecular polyvinyl alcohols
are preferred to low-molecular products, because they possess a higher bind-
ing capacity. Particularly preferred are high-molecular polyvinyl alcohols
with a degree of hydrolysis of at least 98%, of which a 4 per cent aqueous
solution of 20C has a viscosity of at least 25 centipoises. The light-
sensitive layer contains as a filler starch particles, whereby the weight
~6.610~7.
ratio starch particles to polyvinyl alcohol is from 5-20 : 1. If the weight
ratio starch to polyvinyl alcohol is higher than 20 : 1 the adherence of the
light-sensitive layer to the sealing layer will be insufficient, especially
in moist condition, immediately after development of the diazotype material.
If the weight ratio starch to polyvinyl alcohol is smaller than
5 : 1 the ability of the light-sensitive layer to absorb the developer, and
the velocity with which the developer penetrates into the light-sensitive'
layer become too low, as a result of which the developing speed of the diazo-
type material decreases too much and copies that do not immediately feel dry
are obtained. The starch particles may consist of wheat starch, maize starch
and rice starch, e.g. rice starch is preferably used, because this product
has an intenser whiteness than other starch products, and because, thanks to
a relatively low spread in particle size, smoother layers can be obtained
with it.
The light-sensitive diazonium compound is selected from the diazon-
ium compounds known for application in the diazotype process. In general,
these are benzene diazonium compounds carrying, in 4-position, a tertiary
amino group, a secondary acylamino group, a phenyl group or an etherified
mercapto group and, in one or two of the other positions, a halogen atom, an
alkyl, alkoxy, phenoxy or tertiary acylamino group or a combination of these
substituents. Preferably, a diazonium compound having such a high coupling
activity that the diazotype material can be developed with a neutral to weakly
acid buffered phloro-glucinol solution, is used. Suitable activity coupling
diazonium compounds are described, inter alia, in the British Patent Specifi-
cations 919,037, 919,812, 1,045,242, 1,064,128 and 1,064,129, as well as in
the Belgian Patent Specifications 657,907, 665,368 and 661,008.
If for the development of the diazotype material an alkaline develop-
ing liquid is used, more slowly coupling diazonium compounds, for instance
the diazonium compounds described in the British Patent Specifications 867,630,
875,307, 888,598, 919,037; the French Patent Specifica~ions 1,269,874,
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1066107
1,269,875, 1,269,876; the Belgian Patent Specification 574,785; the Dutch
Patent Application 69 12 554, published February 22, 1971 and the German
Patent Application 2,003,508 published July 9, 1970 may also be used for
the sensitization of the diazotype material.
The auxiliary agents usually applied in diazotype materials such
as acid stabilizers~ for example citric acid, tartaric acid, boric acid,
benzene and naphthalene sulphonic acid, anti-yellowing agents and developing
accelerators, may be used in the light-sensitive layer.
The light-sensitive layer is applied over the sealing layer by means
of an aqueous liquid, preferably containing a wetting agent. To prevent the
diazonium compound from being trapped in the sealing layer no or no essential
amounts of substances, for example organic solvents or swelling agents, caus-
ing strong penetration of the sensitizing liquid into the sealing layer, are
incorporated in the sensitizing liquid.
The light-sensitive layer applied has a dry weight of at most 8 g
per square metre, which corresponds with a layer thickness not exceeding
approximately 8 micrometres. Preferably, the dry weight of the light-sensitive
layer is from 3 to 6 g per square metre,
This layer, notwithstanding its slight thickness, is able to fully
absorb 1.5 - 4.5 cm3 per square metre of developing liquid, so that upon
development of the diazotype material according to the process referred to
before, copies feeling dry are obtained almost immediately. Preferably, also
the reverse side of the diazotype material according to the invention is
provided with a sealing layer. Also this layer is preferably applied to the
paper support from an aqueous liquid. The composition of this sealing layer
may be equal to that of the front layer. However, the reverse layer can also
be formed with th0 aid of other, more or less hydrophobic, film-forming sub-
stances, such as for example polyacrylates, polymethacrylates, polyvinyl
chloride, copolymers of acrylates with methacrylates, of vinyl chloride with
vinyl acetate, of styrene with acrylonitrile and, optionally, butadiene, and
of acrylonitrile with butadiene.
~066~07
A filler can also be incorporated in the reverse layer, e.g. to
improve the drafting characteristics of the layer. Besides ordinary opaque
paper, the support of the diazotype material according to the invention may
be natural transparent paper or transparentized paper. As a sealing layer
is applied between the support and the light-sensitive layer, extremely high
demands, for example with respect to the degree of sizing and pH of the sur-
face, need not be made upon the support.
The diazotype material according to the invention can, of course,
als-o be developed in the conventional way, whereby the developing liquid is
applied onto the light-sensitive side or on either side of the diazotype
material, and the amount of liquid applied is 6 cm3 or more per square metre
per side.
In addition to the diazonium compound, an azo-coupling component
or a mixture of azo-coupling components may be incorporated in the light-
sensitive layer of the diazotype material according to the invention. The
two-component diazotype material thus obtained can be developed by spreading
a small amount of alkaline developing liquid, which need not contain any azo-
coupling component now, over the light-sensitive side of the diazotype mater-
ial. The two-component diazotype material is suitable, e.g., for being
developed according to the process described in the United States Patent
Specification 3,446,620, whereby concentrated amine solution is spread to an
amount of approximately 3 cm3 per square metre over the light-sensitive layer.
It stands to reason that this two-component diazotype material can also be
developed in the conventional way, by the action of ammonia vapour or other
alkaline vapours.
Example 1
White base paper for the diazotype process of 80 g/m2 was provided
on either side with a sealing layer having a dry weight of 4 - 4.5 g per
square metre, using a liquid of the following composition:
60 ml of a 50 per cent aqueous dispersion of polyvinyl
acetate
~ ~6:~Q7
2.5 ml of hexamcthoxyllletllylmelamine
0.2 g of p-toluene sulphonic acid
water up to 100 ml.
The layers were dried and cross-linked by heating thom at 150-lS0C
for 30 seconds.
One side of the coated support was then provided with a light-sensi-
tive layer, using a liquid of the following composition:
2 g of 4-dimethylamino-3-(4'-chlorophenoxy)-6-chlorobenzene
diazonium hydrogen-sulphate
2 g of high-molecular polyvinyl alcohol with a degree of
hydrolysis of 98% (Elvanol 72-60*of Du Pont de Nemours and
Co., U.S.A.)
g of rich starch
ml of n-propanol
water up to 100 ml.
The light-sensitive layer had a dry weight of approximately 4 g/m2.
The diazotype material thus obtained was exposed under a line
original until all the diazonium compound underneath the white areas of the
original had been bleached out.
The exposed material was then developed in a developing device as
described in the Dutch Patent Application 72 07 099, whereby developing liquid
to an amount of approximately 3.5 cm3 per square metre was applied to the
light-sensitive side.
The developing liquid contained per litre:
29 g of phloroglucinol
89 g of succinic acid,
potassium hydroxide to bring the pH of the liquid on 6.0, and water.
A copy with a strong, blac~ imagc on a clear background was obtain-
ed. The copy showcd no curl and folt dry to the touch almost immediately.
Example 2
Baso paper or the diazotype process of 80 g/m was providcd on
cither side wi~h a sealing laycr having a dry weigllt of approxima~cly 2 g
* Trade Mark
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1066107.
per square metre, using a liquid of the following composition:
ml of a 50 per cent aqueous dispersion of a copolymer of
60% by weight of styrene witll 40% by weight of butadiene
ml of water.
One side of the support was then coated with a light-sensitive
layer having a dry weight of 5 g per square metre, using the sensitizing
liquid described in Example 1, with the proviso that it now contained 7.5 ml
of n-propanol. The diazotype material obtained was exposed imagewise and
developed in the way described in Example 1.
The development of the material proceeded quickly. The copy showed
no curl, it immediately felt dry to the touch, and yielded a strong, black
image on a clear background.
Example 3
Base paper for the diazotype process of 65 g/m2 was provided on
either side with a sealing layer having a dry weight of approximately 7 g per
square metre, using a liquid of the following composition:
60 ml of a 50 per cent aqueous dispersion of polyvinyl acetate
40 ml of water.
One side of the support was coated with a light-sensitive layer
having a dry weight of approximately 4 g per square metre, by means of a
liquid containing:
3.2 g of 4-N-methyl-N-cyclohexylamino-3-methoxy-2-N-methyl-N-
ethoxycarbonylamino benzene diazonium-chlorozincate
0.6 g of citric acid
3 g of polyvinyl alcGhol having a degree of hydrolysis of
approximately 77% (Gohsenol KH 17*of Nippon Gohsei, Osaka,
Japan)
g of rich starch
ml of n-propaJIol
water up to 100 ml.
The diazotype material was exposed imagewise and dcvelopcd in thc
way described in Examp]e 1. A strong, non-curling copy i~nediately feeling
* Trade Mark
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L
1~66i~7
dry, and showing a black image on a white background was obtained.
Example 4
Base paper for the diazotype process of 65 g/m was provided on one
side with a sealing layer having a dry weight of 5 g per square metre, using
a liquid of the following composition:
ml of a 50 per cent aqueous dispersion of a copolymer of 70%
by weight of styrene and 30% by weight of butadiene
8 g of amorphous silica with a primary particle size of 30
nanometres
ml of water.
The reverse side of the paper was then provided with a sealing layer
having a dry weight of 4 g per square metre, using a 35 per cent aqueous
dispersion of polyvinyl acetate. The front side of the paper was then coated
with a light-sensitive layer having a dry weight of 7 g per square metre,
using a liquid containing:
1.8 g of 4-N-benzoylamino-2-N-methyl-N-ethoxycarbonylamino-5-
methoxy-benzene diazonium-chlorozincate
0.4 g of citric acid
2 g of high-molecular polyvinyl alochol with a degree of
hydrolysis of approximately 98%
g of wheat starch
0.5 g of saponine
water up to 100 ml.
The diazotype material was then exposed imagewise and developed in
the way described in Example 1.
A strong copy with a brown image on a white background was obtained.
The development of the material proceeded quickly. The copy did not curl and
it immediately felt dry.
Example 5
Natural transparent paper of 75 g/m2 was provided on either side
with a sealing layer having a dry weight of approximately 2.5 g per square
metre, using a liquid of the following composition:
i107
ml of a 50 per ce'nt aqueous dispersion of a coyol~mer of 60%
by weight of styrene with 40% by weig}-t of butadiene
ml of ethanol.
One side of the paper thus coated was then providcd with a light-
sensitive layer having a dry weight of approximately 5 g pcr square metre,
by means of a liquid containing:
2.7 g of 4-N-benzoylamino-2-N-methyl-N-ethoxycarbonylamino-5-
methoxy-benzene diazoniumhydrogensulphate
3 g of high-molecular polyvinyl alcohol with a degree of
hydrolysis over 98% (Gohsenol N~126)
g of rich starch
0.5 g of saponine.
The diazotype material was exposed under a line original until the
diazonium compound underneath the white areas of the original had just been
bleached out and, subsequently, developed in the l~ay described in Example l.
The development of the material proceeded quickly. The copy did
not curl and it immediately felt dry. It showed a strong brown image on a
clear background, and could be used as an intermediate original for further
copying on diazotype paper.
Example 6
~l.'hite base paper of 65 g1m2 was provided on one side with a sealing
layer having a dry weight of approximately 6 g per square metre~ using liquid
of the following composition:
40 ml of a 50 per cent aqueous dispersion of a copolymer of 60%
by weight of styrene with ~0% by weight of butadiene
5 g of clay
60 ml of water.
The reverse side of the paper was then provided with a sealing layer
having a dry weight of 3 g per square metre, using an aqueous polyvinyl chlor-
ide dispersion (Lutofan 300 D*of B.A.S.F., Ludwigs1lafen/Rhci1l, Gcrmany).
; The front sidc of the paper was then coated Wit}l a light-sensitive
layer having a dry weight of 4 g per square metre, by means of a ]iquid con-
* Trade Mark
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~066107
taining:
2 g of 4-morpholino-2,5-dibutoxy-benzene diazoniumhydrogcn-
sulpllate
2 g of polyvinyl alcohol with a dcgree of hydrolysis of 98%
~Elvanol 72-60)*
g of corn starch
ml of n-propanol.
The diazotype material thus obtained was exposed imagewise under a
line original and then developed in the way described in Example 1, using now
a developer of the composition:
10.8 g of phloroglucinol
13 g of resorcinol
g of thiourea
g of sorbitol
100 g of potassium tetraborate (5 aq.)
3 g of isopropylnaphthalene sulphonic acid
1,000 ml of water.
The copy showed a strong image on a clear background. It did not
curl and felt dry to the touch almost immediately.
Example 7
Base paper for the diazotype process of 90 g/m2 was provided with
a sealing layer having a dry weight of approximately 5 g per square metre,
by means of a liquid containing:
40 ml of an aqueous 50 per cent dispersion of a copolymer of
65% by weight of styrene with 35% by weight of butadiene
12 g of silica with a particle size under 10 micrometres
60 ml of water.
The reverse side of the paper was then provided with a sealing layer
having a dry weight of 3.5 g per square metre, by means of a liquid contain-
ing:
ml of ~n aqueous 50 per ccnt dispersion of a copolymcr of
65% by weight of styrenc with 35% by weight of butadiene
* Trade Mark
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~066~07
7 g of rich starch
ml of water.
The front side o the paper was thcn coated with a light-scnsitive
layer having a dry weight of approximately 3.5 g per square metre, by means
of a liquid containing:
1 g of 4-N-ethyl-N-(2'-hydroxyethyl)amino-benzene diazonium-
chlorozincate
3 g of tartaric acid
1 g of 2,3-dihydroxynaphthalene-6-sulphonic acid (sodium salt)
2 g of high-molecular polyvinyl alcohol with a degree of hydroly-
sis over 98% (Gohsenol NH26
20 g of rice starch
7 ml of n-propanol
water up to 100 ml.
~ The sheet of the diazotype material thus obtained was exposed under
a line original and then developed by spreading over the light-sensitive layer
of the paper approximately 3 ml per square metre of developing liquid having
the following composition: -
48 ml of triethanolamine
43.5 ml of diethyleneglycol monomethylether
8.5 ml of oleic acid.
The copy obtained showed a blue image on a clear background.
Trade Mark
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