DE2634893A1 - STABILIZED TRANSPARENT RECEIVING MATERIAL FOR THERMOGRAPHIC IMAGE RECORDING - Google Patents

Description

MINNESOTA MINING AND MANUFACTURING COMPANY Saint Paul, Minnesota, V.St.A.

¹¹ Stabilized transparent receiving material for thermographic imaging "

Priority: 4.8.1975, V, St, A., No. 601 717 and 6.7.1976, V., St.A. _r no.702 849

In the unpublished US Pat. No. 3,935,012, a light-sensitive Transmission material that contains the following substances:

(a) a thermally stable compound which can be cleaved photolytically with the formation of hydrogen halide,

(b) an acid-cleavable adduct of a first reactant and an organic compound with a vinyl ether linkage, which yields a reducing agent on cleavage with acid, and

(c) a hydrogen halide acceptor in an amount

which is less than the amount that binds all of the hydrogen halide formed during photolysis.

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Developed during imagewise exposure of this transfer material hydrogen halide, which splits the adduct and releases the reducing agent in the exposed areas. Then will brought this transmission material together with a receiving material, containing a second reactant, e.g. B «a reducible metal soap and an organic reducing agent, such as a steric hindered phenol. After heating this combination, a portion of the metal soap is reduced with that in the exposed areas released reducing agent to elemental metal on the transfer material an image. This speeds up again the heat-induced reduction of the remaining metal soap by the less reactive organic reducing agent, originally present in the receiving material to form a visible image. .

The image record obtained on the receiving material is of good quality. It has been found, however, that this receiving material, which contains a reducible metal soap and an organic reducing agent, exhibits an unacceptable increase in background density when exposed to a conventional overhead projector for an extended period of time, for example at least two hours. During the formation of the image, a small amount of material is transferred from the unexposed areas of the transfer sheet to the receiving material. When the receiving material bearing the image recording is used in a skylight projector, the reducing agent is released in sufficient quantity to result in an increase in the background density.
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The invention is based on the object of a stabilized transparent To provide thermographic imaging receiving material which avoids the increase in background density will. This object is achieved by the invention.

The invention thus provides a stabilized transparent one Receiving material for thermographic imaging consisting of a transparent support coated with a film-forming material Binder, a reducible metal soap and an organic reducing agent, which is characterized in that it additionally about 0.00007 to 0.005 parts by weight per part by weight of the metal soap of a polycyclic aromatic dye • with a development characteristic of at least 150 seconds contains.

The receiving material of the invention carrying an image recording can be used for long periods of time on conventional overhead projectors without appreciable Increase in the optical density of the background areas are exposed. Presumably the polycyclic stabilizes aromatic Dye the receiving material by delaying the reduction the metal soap as a result of the releasing reducing agent in the background areas.

The receiving material of the invention generally consists of. a clear carrier with a coating of a film-forming polymers or resinous binders, a reducible metal soap and an organic reducing agent. If necessary, the coating can also contain a toner for the

L -I

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tallbild, such as phthalazinone, fillers or various other common additives.

The carrier preferably consists of a thin, flexible, transparent plastic film, such as that used for projection images is used.

The reducible metal soap is preferably a silver salt of a long-chain fatty acid, such as silver behenate or silver stearate, used. However, other reducible metal soaps are also suitable, such as iron (III) stearate, gold stearate or cerium stearate « Other suitable reducible metal soaps are also known. "

Examples of the organic reducing agents that can be used in the receiver sheet are pyrogallol, 4-azeloyl-bis-pyrogallol, 4-stearoylpyrogallol, gallacetophenone, di-tert, -butylpyrogallol, Gallic acid anilide, gallic acid methyl ester, gallic acid ethyl ester, gallic acid propyl ester, gallic acid isopropyl ester, gallic acid butyl ester, Gallic acid dodecyl ester, gallic acid, ammonium gallate, 3,4-dihydroxybenzoic acid ethyl ester and -cetyl ester, 2,5-dihydroxybenzoic acid, l-hydroxy-2-naphthoic acid, 2-hydroxy-3-naphthoic acid, phloroglucinol, pyrocatechol, 2,3-dihydroxynaphthalene, 4-lauroylpyrocatechol, Sodium gallate, 3,4-dihydroxybenzaidehyde, 4-methylesculetin, 3 »4-dihydroxybenzoic acid, 2,3-dihydroxybenzoic acid, Hydroquinone, 4,4'-dihydroxydiphenyl, 3,4-dihydroxyphenylacetic acid, 4- (3,4-dihydroxyphenylazo) benzoic acid, 2,2-methylenebis-3,4,5-trihydroxybenzoic acid, o- and p-phenylenediamine, tetra-

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methylbenzidine, 4,4 ·, 4 "-Dläthylaminotriphenylmethan, ο-, m- and p-aminobenzoic acid, £ X - and ß-naphthol, 4-methoxy-1-hydroxy-dihydronaphthalene and tetrahydroquinoline. These compounds are cyclic or aromatic compounds with an active hydrogen atom on a carbon, oxygen or nitrogen atom, which in turn is bonded to a ring atom. These compounds can when dissolved at moderate temperatures in an aqueous solution of a metal salt in an organic Solvents reduce and precipitate metal ions.

The reducible metal salt and the organic reducing agent are preferably mixed together before coating. However, the two compounds can also be applied separately in adjacent layers, with the aromatic dye must be present in the layer containing the reducible metal salt.

The most varied of film-forming binders are used as binders into consideration, for example cellulose propionate, polyethylene methacrylate, Polyvinyl acetate, vinyl acetate-vinyl chloride copolymers and cellulose acetate butyrate.

The quantitative ratio of reducible metal soap to organic reducing agent in the receiving material can be within a relatively wide range. However, the two compounds must be present in sufficient quantity so that a visible and sharp image is formed when the receiving material in the presence of the reactants, namely, the reducing agent is _L heated, which is supplied from the transfer material. In general -I

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mine the amount of reducible metal soap is about 4 to 12 parts by weight per part by weight of organic reducing agent.

The aromatic dyes used in the present invention for suppression the increase in the optical background density cannot be fully represented by a general formula. However, a simple test could be devised to exactly distinguish the useful and unusable aromatic dyes differs. This test is explained below. A solution is made from the following components:

Cellulose acetate propionate 5 grams

Methyl ethyl ketone 95 grams

aromatic dye to be investigated 0.10 millimoles

4-methoxy-1-naphthol 0.575 millimoles

15 g of this solution are poured into an aluminum dish with a layer height of 12.5 mm and irradiated for 1 hour at a distance of 15 cm with a 150 watt tungsten filament lamp. Thereafter, irradiated solution is poured in a thickness of 50 microns on a hereinafter described, more than 6 month old receiving material and dried at 65 ⁰ C. After drying, the receiving material is heated to 100 ° C. The time taken for the optical density of the receiving material to show an increase of 0.85 is determined. This time is the development characteristic of the dye under study. The dyes which can be used according to the invention show a development characteristic of at least 150, preferably

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at least 300 seconds. The optical density is used with a usual MacBeth Model TD 4o4A densitometer with a yellow filter certainly.

The receiver used for this test is as follows manufactured. A dispersion of silver behenate is made with the following components:

Parts by weight

Silver behenate 12.00 Tetrachlorophthalic anhydride 0.24 Tin (II) stearate 0.0072 Methyl ethyl ketone 87.7528

100.0000

The constituents are mixed with one another for half an hour, then homogenized at 562 kg / cm, then cooled to 27 ° C and homogenized again at 5β2 kg / cm.

A binder solution is made up of the following components:

Parts by weight of cellulose acetate butyrate
Polyethylene methacrylate
Methyl ethyl ketone

100.00

7th 50 7, 50 85 00

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_ ₈ _ 2634833. ^Π

A coating composition is then made up of the following ingredients manufactured:

Parts by weight

Silver behenate dispersion 54.5531

Binder Solution 43,6400

Phthalazinone 0.9819

2,6-di-tert-butyl-p-cresol 0.785Ο 4,4 »-Methylene-bis-2,6-di-tert.-

butylphenol " 0.0400

100.0000

The above ingredients are thoroughly mixed together, then by means of a slot die with 87.5 micron slot width on a transparent plastic film cast and 3 minutes at 82 ⁰ C .in the stream of hot air dried. The area applied is 0.70 g / 9.29 dm ² . The clear, transparent coating is coated with a 5 percent solution of cellulose acetate propionate in methyl ethyl ketone to a thickness of microns and dried. A 5 micron thick top layer is left behind.

A preferred class of polycyclic aromatic used Dyes with a development characteristic of at least 150 seconds are oxygen sensitizing dyes, containing at least 2 residues conjugated as part of a single chromophore, each residue of three being linearly catacondensed six-membered aromatic rings with an -OZ group in the meso position, Z a stable monovalent And the -OZ group is a solubilizing group. Preferably at least one auxochromic group is with one

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ORIGINAL INSPECTED

Atoms with an atomic weight of at least 31 attached to the chromophore, the atom being attached directly to the chromophore is. The aforementioned radicals with three linear catacondensed six-membered aromatic rings have the following general formulas

OZ 'OZ'

COO - COO

The aromatic rings can be homocyclic or heterocyclic. Nitrogen atoms are generally used as heteroatoms Question. The dye can be homocyclic and / or heterocyclic

Contains residues of the aforementioned type. These remainders are in conjugation, so that these residues are part of a single chromophore, namely part of the same chromophore. A chromophore is a group of atoms or electrons in a molecule that are essentially responsible for an absorption band; see.

* Theory and Application of ultraviolet Spectroscopy, Jaffe and Orchin, John Wiley & Sons, Inc. (1962). The two residues can be connected to one another or condensed in peri-belling, for example

or

. OZ *

in which the two radicals have atoms in common, or

ORlGHMAL iiväöPECTED 709807/1062

the residues can be linked to one another in conjugation via at least one bridge. The following remnants are used as bridge remnants Question:

(a) At least trivalent atoms that form covalent bonds, such as nitrogen, carbon, sulfur and oxygen atoms;

(b) ligands with 2 or more atoms that are at least bidentate, for example bidentate, tridentate, tetradentate, hexadentate and octadentate ligands; and

(c) covalent single or double bonds.

The size, chemical nature or structure of the bridge remainder is' not of critical importance as long as the two radicals that form the catacondensed aromatic rings are in Conjugation so that they are part of a single chromophore.

The bridge residues can also have a polycyclic, homocyclic or heterocyclic structure. As heteroatoms in the heterocyclic Bridge residues are generally nitrogen, oxygen and sulfur atoms.

There are two remnants of bridges in numerous connections. For example can have two ligands, one ligand and one covalent bond or two covalent bonds in a single compound present as bridge remnants.

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The dyes preferably contain at least one auxochromic group which is bound to the chromophore. These preferred Dyes are described in U.S. Patent 3,819,664. The auxochromes Groups can also consist of one atom or of numerous atoms, provided a heavy atom with an atomic weight of at least 31, which is present as part of the auxochrome group, is directly bound to the chromophoric residue of the dye « An auxochromic group is a group attached to a chromophore that affects the nature of the excited states; See Theory and Application of Ultraviolet Spectroscopy, Jaffe and Orchin, John Wiley & Sons, Ine, (1962) *

Preferred auxochromic atoms are chlorine, bromine, mercury, sulfur, iodine and selenium atoms. Other auxochromic atoms are Phosphorus, arsenic, tellurium, germanium, tin, lead and antimony Auxochromic group can consist of more than one atom provided a heavy atom is included as part of the auxochrome group is present, is bound directly to the chromophoric part of the dye molecule.

The -OZ and -OZ 'groups present in the dyes are also auxochromic groups, but these groups act predominantly as solubilizing groups, d. H. they mainly determine the solubility of the dye in the various solvents, in which the dyes can be dissolved. The chemical structure and the nature of the radicals Z and Z 'is not of crucial.

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In general, the radicals Z and Z ^{1 are} monovalent radicals which are stable under normal conditions and which do not cause any decomposition of the chromophoric part of the dye. These residues have neither an oxidizing nor a reducing effect on the chromophoric part of the dye, and they do not have an adverse effect on the effectiveness of the compound as a dye. Within these limits, the -OZ and -OZ ¹ groups can be stable derivatives of an inorganic acid, for example they can have the general formula

-OSO ₃ Y,

in the Y a. Alkali, alkaline earth or ammonium ion means, or .. the general formula

-OPO ₃ R ₂ or -OPO ₃ R ₃

have, in which R is a hydrogen atom or a stable organic Represents rest.

As organic radicals for Z and Z ¹ are alkyl, cycloalkyl, substituted alkyl and cycloalkyl radicals, alkenyl, alkynyl or aryl radicals, polycyclic ^ radicals, acyl, alkaryl and aralky radicals, Z and Z ¹ can be identical or to be different. Alkyl radicals with at least one carbon atom are common Z radicals. Low

even

Re-alkyl radicals are preferred, but long-chain alkyl radicals are also used in question. Suitable substituents on the alkyl radicals are all radicals or groups, with the exception of hydrogen atoms and other alkyl radicals.

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In addition to the solubilizing groups -OZ and -OZ ¹ and the auxochromic groups, the dyes can also be substituted by other groups, such as fluorine atoms, nitrile, hydroxy, alkyl, aryl, acyl or alkoxy radicals or polycyclic groups that are stable and which do not cause decomposition of the chromophoric part of the dye.

The dyes used according to the invention can either by independent synthesis or preferably from dye precursors getting produced. For example, Vat Violet 7 (Color Index No. 59321) can be mixed with customary alkylating agents according to the following reaction scheme RX are alkylated:

, OCH.

NaOH ^ RX

OCH.

OCH.

OCH.

RX denotes, for example, an alkyl iodide, alkyl tosylate, alkyl benzene sulfonate or dialkyl sulfate. Examples of other suitable alkylated vat dyes are ethylated Vat Blue 18 (Color Index No. 59815) and ethylated Vat Green 1 (Color Index No. 59825).

For the preparation of compounds of the aforementioned general formula in which R is an optionally substituted allyl or Means propargyl group, two alkylating agents are used

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for example allyl bromide or propargyl bromide or their substituted ones Derivatives used.

To prepare compounds of the above general formula in which R and R ¹ denote cycloalkyl radicals, the dianion can be reacted with activated cycloalkyl halides, such as 2-chlorocyclohexanone, according to the reaction scheme above. The product obtained has the formula

According to Wolff-Kischner, this product can then become a Compound of formula

H
can be reduced · The

Vat dye first in the presence of zinc and an acid,. like acetic acid, reduced and then with a carboxylic acid anhydride, such as acetic anhydride. Various other such dyes can also be known methods.

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Other usable aromatic dyes other than the above Have formula are, for example, octaphenyltetrazaphorphyrin and erythrosine. These dyes also have a development characteristic of at least 150 seconds.

The amount of polycyclic aromatic dye present in the receiving material must be such that it increases the optical background density with longer exposure in a skylight projector is sufficiently suppressed. The tendency the increase in background optical density is inversely proportional the amount of aromatic dye in the receiving material. An effect is thus achieved even with the smallest amounts of the dye. The maximum amount of the dye depends on the solubility limit of the dye in the binder or on the presence of undesirable discoloration of the receiving material through the dye. Within these limits, the preferred amount of aromatic dye is about 0.00007 to 0.005 parts by weight per part by weight of metal soap.

The examples illustrate the invention. Unless otherwise stated, parts are by weight.

example 1

A receiving material is prepared as follows. First, a silver behenate dispersion is made from the following components:

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Parts

Silver behenate 12.00

Tetrachlorophthalic anhydride

(Development modifier) 0.24

Tin (II) stearate 0.0072

Methyl ethyl ketone '87.7528

100.0000

The aforementioned constituents are mixed with one another for 30 minutes, then homogenized at 562 kg / cm, ^{cooled to 27 °} C. and homogenized again at 562 kg / cm.

A binder solution is made up of the following components: ·

Parts

Cellulose propionate, polyethylene methacrylate, methyl ethyl ketone

100.00

A coating compound is produced from the following components: parts of silver behenate dispersion 54.5851 binder solution 43.6400 phthalazinone (toner for the silver image) 0.9819 2,6-di-tert-butyl-p-cresol 0.7850 butylated Vat Violet 7
(Color Index # 59321) 0.008.0

100.0000 70980 7/1082

7th , 50 7th , 50 85 , 00

The aforementioned ingredients are mixed together thoroughly and then applied to a transparent plastic film with the aid of a slot caster with a slot width of 150 microns. The coating is dried at 82 ° C. for 3 minutes. Of the

Surface application is 0.0013 g / cm. It becomes a clear see-through Coating received. A 5 percent solution of cellulose acetate propionate in methyl ethyl ketone is applied to this coating applied to a thickness of 50 microns and dried. A protective layer 5 microns thick is left behind.

Example 2

A transfer material is made with the following coating compound:

Parts

Cellulose acetate butyrate 7 »887

Methyl ethyl ketone 91.00

equimolar 1: 1 adduct

from 4-methoxy-l-

naphthol and dihydropyran 0.717

Tris (tribromomethyl) -s-triazine 0.58

Perylene (spectral sensitizer) 0.052 Diphenylguanidine (hydrogen bromide

acceptor) 0.016

The coating compound is applied to a transparent polyester film using a caster with a slot width of 75 microns Safety light applied and dried. A transfer photosensitive material is obtained.

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The coated surface of the transfer material is then in contact with a printed original with light-absorbing Parts of the image placed on a reflective white background and exposed in the reflective position with tungsten filament lamps for so long to sensitize the coating in the background areas. The exposure time is generally 12 to 15 seconds.The image areas are also, but to a lesser extent, changed by the absorption of part of the light in the image areas of the original. The exposed transfer material is then placed with its coated surface against the coated surface of the receiving material of Example 1, for example between rollers or plates, and heated to 125 to 140 ° C for 4 to 5 seconds. It becomes a sharp negative of the original received on the receiving material.

The receiving material is exposed for 16 hours in a model ARÖ6 overhead projector. There can be no increase in the optical background density to be established.

When using a receiving material containing no polycyclic aromatic dye, the background optical density increased by 1000% after 16 hours.

Examples 3 to 7

Different receiving materials are made, which are different Contain amounts of polycyclic aromatic dye. First, a stock solution is made up of the following ingredients manufactured:

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Parts

Silver behenate dispersion of

Example 1 54,585

Phthalazinone 0.982

Binder Solution of Example 1 43,585

2,6-di-tert-butyl-p-cresol 0.793

Equal amounts of the aforementioned stock solution, each containing 25 g of silver behenate, are mixed with different amounts

(polycyclic aromatic dye)

butylated Vat Violet f / added. The amounts are below given in Table I.

Table I Example polycyclic dye, g

3 0

4 0.002

5 0.004

6 '0.008

7 0.016-

Each solution is then applied to a 50 micron thick polyester film using a slot caster with a 100 micron slot. The samples are ^{dried at 88 °} C. in the air. A 20 micron thick coating remains, which is provided with a 5 micron thick cellulose acetate butyrate protective layer.

The individual receiving materials will be in contact with beforehand

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exposed photosensitive transfer sheets in Example 2 type described heated. The receiving materials provided with the image recording are then placed under a skylight projector Model AR66 is placed, and the background optical density of each sample is determined after 4, 12 and 30 hours with the initial optical Background Density Compared · Optical density is determined with a MacBeth densitometer and yellow filter. The results are summarized in Table II.

Table II

Percentage increase in the optical background density

4 hours 12 hours 30 hours 3 200 500 1000 4th 130 150 220 5 85 140 230 6th 50 75 100 7th 0 0 15th

Example 8

According to Example 1, a receiving material is prepared using the same amount of ferric stearate in place of silver behenate. The transfer material according to Example 2 is used to transfer an image onto the receiving material. It becomes a blue picture with a yellowish background. After exposure in a skylight projector, the background density remains for a long time !Stable. _

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Example 9

According to Example 8, a receiving material is prepared and provided with an image. Instead of iron (III) stearate is a same amount of gold stearate is used. A dark purple-tinged image is obtained on a light purple-colored background. The background density remains stable even after prolonged exposure with a skylight projector.

Example 10

According to Example 8, a receiving material is prepared and provided with an image. Instead of iron (III) stearate, a equivalent amount of cerium stearate used. A blue image on a colorless background is obtained. Even after long exposure with a skylight projector the background density remains stable, '

Example 11

According to Example 1, a receiving material is prepared and provided with an image, instead of the 2,5-di-tert-butyl-p-cresol however, 0.785 parts by weight of 4,4'-methylene-bis-2,6-di-tert-butylphenol used. After the image was formed on the receiver according to Example 2, a dense black image was obtained obtain. The background density remains stable even after prolonged exposure in a skylight projector.

When this example is repeated, but in the absence of butylated Vat Violet 7 (color index No. 59321) in the receiving material, the background density increases tenfold after about 12 hours of exposure in the overhead projector. ^J

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Examples 12 and 13

Two receiving materials are made according to Example 1, however one sample (Example 12) contains no polycyclic aromatic dye and the other sample (Example 13) one Ethylated Vat Blue 18 instead of butylated Vat Violet 7. After an image has been formed on the receiving material, see FIG Example 1 a dense black image is obtained. The background density after exposure in a skylight projector will be determined after different times. The results are summarized in Table III.

initially Table III Background density 12th 0
0 hours example 0.10
0.07 ü hours .5 *
, 11 0.16
0.08 12th
13th

Examples 14 and 15

Two receiving materials are prepared according to Example 1, but one sample (Example I ² I) contains no polycyclic aromatic dye and the other sample (Example 15) contains octaphenyltetrazaporphyrin instead of butylated Vat Violet 7. After the formation of the image on the receiving material according to Example 2 is this is exposed for a long time in a skylight projector and the background density is determined at different times. The results are summarized in Table IV.

9-807.7 ^ 1.06 2

initially Table IV 12th 1
0 hours example 0.06
0.06 Background density , 15
, 09 4 hours 14th
15th 0.14
0.07

Claims (9)

Claims 1 «Stabilized transparent receiving material for thermographic Image recording from a transparent support with a coating of a film-forming binder, a reducible one Metal soap and an organic reducing agent, characterized by an additional content from 0.00007 to 0.005 parts by weight per part by weight of the metal soap of a polycyclic aromatic dye having a Development characteristic of at least 150 seconds. 2. Receiving material according to claim 1, characterized in that the dye at least two residues in conjugation as part of a single chromophore, each residue consisting of three linear catacondensed six-membered aromatic rings with an -OZ group in the meso position, Z is a more stable one is a monovalent residue and the -OZ group represents a solubilizing group * 3. Receiving material according to claim 1 and 2, characterized in that that the dye has the general formula I CD in which R and R ^{1 are} lower alkyl radicals. 709807/106 2 4, receiving material according to claim 3, characterized in that R and R ^{1 represent} butyl groups. 5 · receiving material according to claim 1, characterized in that the dye is octaphenyltetrazaporphyrin or erythrosine. 6. Receiving material according to claim 1, characterized in that the reducible metal soap is silver behenate, silver stearate, iron (III) stearate, gold stearate or cerstearate is » 7. receiving material according to claim 1, characterized in that the organic reducing agent is a sterically hindered phenol is. 8. Receiving material according to claim 7, characterized in that the phenol is 4-methoxy-1-naphthol, 2,6-di-tert-butyl-p-cresol
or 4,4'-methylene-bis-2,6-di-tert-butylphenol. 9. receiving material according to claim 1, characterized in that the dye is an ethylated Vat Blue 18 (Color Index No. 59815). 7 0 9807/1062