DE2246254A1 - ELECTROPHOTOGRAPHIC RECORDING MATERIAL - Google Patents

Description

Kt -., 2113 1 PP-Dr.8.-ih 18 September 1-972

description
to register the

KALLE AKTIENGESELLSCHAFT Wiesbaden-Biebrich

for-a patent

Electrophotographic recording material (addendum to patent application, file number P 22 20 408.6)

The invention relates to an electrophotographic recording material consisting of an electrically conductive one Base material and a photoconductive double layer made of organic materials.

In the main patent (German patent application, file number P 22 20 408.6) a recording material is proposed with a photoconductive double layer made of a homogeneous, color-covering, charge carrier generating, organic dye layer and a transparent cover layer made of insulating, organic materials

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at least one charge-transporting compound.

It has now been found that such a paraffin layer is particularly suitable, consisting of a compound of the general formula

f.

-NH-CO-CH-N = N-A-N = N-CH-CO-NH- / '

CO CO

i ι

CH ₃ CH ₃

consists in what

- A - equals an optionally substituted diphenyl, 2-phenylbenzimidazole or Azobenzene residue, ■

R, R - ,, R ₂ and R-, are each identical or different and are hydrogen, C _{1 -C 1} ^ - alkyl, C ₁ - C ^ - alkoxyI, or halogen
mean.

The diphenyl, 2-phenylbenzimidazole or azobenzene radical is preferably through C-, - C ₁ . - Alkyl, C, - Ck - alkoxyl and / or halogen, in particular chlorine, substituted.

In the attached formula table are compounds suitable according to the invention which, unless otherwise noted, for example from Color Index (CI.) are known,

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_ -7 _mm '

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for example listed. Herein mean:

Formula No. Designation Identification

1 pigment yellow 12 · CI. 21 090

2 pigment orange 16 'CI. 21 I60

3 pigment yellow 17 CI. 21 105

4 Vulcan fast yellow GR CI. 21 100

5 pigment oranges 15 CI. 21 130 '6 Vulcan Fast Yellow R .CI. 21 135

7 Vulcan fast yellow 5 G CI. -21 220

8 Vulcan fast yellow G 'CI. 21 O95

9 Vulcan fast orange GG CI. 21 I65

10 ■ Pigment yellow 63 · CI .. 21 091

11. Pigment yellow 55 CI. 21 Ö96

12 Helio-brilliant yellow GR CI. 20 045

13, permanent yellow NGG CI, 20 040

14 Bis-4 ¹ , 6- (acetoacetanilido-P-azo) -2-

phenylbenzimidazole

analogous to CI. 21 I60

15 4,4'-bis-azo- (2,5-dichloro-2'-methoxy-5 ' methylazobenzene) -bis- (ß-ace- (toacetanilid)

■ 16 4,4'-bis-azo- (2 _J 5 ^f -dichlor- -

5,2 'dimethoxy-azobenzene) -

bis- (β-acetoacetanilide)

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- Ii -

Of these dyes, those listed under numbers 1, 2, 15 and 16 have proven particularly useful.

The trisazo dyes 15 and 16 are made according to the following for connection 16 and with the corresponding starting product also applicable for connection 15 Process made: '. '

34 parts by weight of 4,4'-diamino-2,5'-dichloro-S ^ -dimethoxyazobenzene are stirred in 250 parts by volume of glacial acetic acid and 100 parts by volume of 5 η HCl for about 1 hour. One diazotizes at 0-5 ° C with 4l parts by volume of 5 η sodium nitrite solution and after 1 hour also destroys the excess nitrite Sulfamic acid. In a second vessel, 35 parts by weight of acetoacetanilide are mixed in 500 parts by volume of water and dissolved by adding 110 parts by volume of 2 η sodium hydroxide solution.

The clarified alkaline solution of the coupling component is slowly added dropwise to the solution at 5 ~ 10 ° C of the diazonium salt. After the coupling has ended, the dye suspension is heated to 90 ° C. for 1 hour. Man sucks the brown product, washed with water, slurried again in 500 parts by volume of hot alcohol, sucks off again and dries at 60-700 c. The dye thus obtained possesses the structure according to formula 16 and can be used according to the invention.

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The presence of the dyes which can be used according to the invention as dye layers in the electrophotographic material mentioned at the outset means that highly light-sensitive, organic photoconductor layers are obtained which, for example, can be arranged on a cylindrical drum or revolve as an endless belt. The dyes of the invention possess, in addition to the extensive \\ - even groups with electron magnetic appeal, such as cyano, electron system with Donatörsubstituenten - nitro, halogen groups. This combination causes strong, long-wave absorption. In addition, the electron acceptor function causes a rapid transport of the electrons, which has a strong influence on the electrophotographic sensitivity. On the other hand, the extended ^] T ~ electron system, especially in the presence of electron donor substituents, is able to also transport electron gaps, ie so-called defect electrons. Accordingly, the dyes according to the invention in the photoconductive double-layer arrangement have a very high photosensitivity in the visible spectral range. They also have good thermal and photochemical stability, so that, for example, they can be vapor-deposited in vacuo without decomposition and are not subject to any changes even under xerographic conditions. In contrast to conventional single-layer materials with known sensitizers and different from known ones

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Double-layer materials with sensitizers or photoconductors in the top and bottom layers are shown by the double layers according to the invention no signs of fatigue after multiple charging and exposure cycles.

According to the main patent (German patent application, file number P 22 20 408.6), the organic dye layer a thickness ranging from about 0.005 / U to about 2 / U is enough. In the case of those used according to the invention Dyes, the dye layer has a thickness ranging from about 0.01 »to about 2» ». - The layer thicknesses are determined via the respective extinction of the dye layer at an assumed density of the dye of about d = 1. By arranging the dye in a layer, a high concentration of excited Dye molecules reached in the dye layer and at the interface between the dye layer and the top layer.

The structure of the electrophotographic material is shown in FIGS. 1 and 2 attached hereto. In Figure 1 is a Material shown, which consists of an electrically conductive Support 1, the organic dye layer 2 and the organic, transparent cover layer 3 consists. According to FIG. 2, the recording material can also be constructed made of a metallized plastic layer 1.4 as a layer carrier, one that prevents charge carrier initiation in the dark Intermediate layer 5, the organic dye layer 2 and the organic, transparent cover layer 3

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As the electrically conductive carrier material 1 or 1, 4 materials with sufficiently electrically conductive properties are suitable, as they have also been used previously for these purposes. These include, in particular, metal foils made of aluminum, tin or lead or, if necessary, transparent substrates that are vapor-coated or laminated with these metals, such as plastics. Some of the intermediates shown in Figure 2 _ä layer-5 consists of organic material such as polyamide resin or off. a thermally, anodically or chemically generated metal oxide layer, for example from an aluminum oxide layer.

The organic dye layer made from the inventive Dyes are an important part of the electrophotographic material according to the parent application. she essentially determines the spectral photosensitivity of the photoconductive double layer according to the invention. the organic dye layer must be extremely uniform, because only their uniformity guarantees a uniform initiation of charge carriers into the top layer.

To achieve this goal, the dye layers applied using special coating methods. This includes application by mechanical rubbing .des finely powdered dye material into the electrically Conductive carrier material, by chemical deposition, for example of a leuco base to be oxidized, by electrolytic deposition or electrochemical processes or by gun-spray technology.

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However, it is preferably applied by vapor deposition of the dye made in vacuo. This results in a tightly packed, homogeneous application.

The application in a tightly packed arrangement makes it unnecessary to achieve a high level of color coverage make thick layers of dye. The dense packing of the dye molecules and the extremely low layer thickness allow the transport of load carriers in a particularly favorable manner, so that it is completely sufficient if the Charge carriers are only generated at the boundary layer.

According to the following reaction equations, excitation (1) and charge separation (2) take place in the dye layer:

1. S + hv -i ? S ^x

2. S ^X + S -> * S® + 'S ⁰

with S - dye molecules

S ^x - excited dye molecules and 'S®, * S® - dye radical ions

At the interface between the organic dye layer and the transparent cover layer there are reactions of the excited dye molecules or the charge carriers that have arisen in the form of the dye radical ions with the molecules of the compound causing the charge transport in the top layer possible according to the following equations:

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3 ". S ^x + P ₁ -? 'S ⁰ + ⁴ F ₁ ^

4. S ^x + F ₂ ->"S © + ^r F ₂ ©

5. 'S® + P ₁ - ^ _- S + "F ₁ ⁰

6. 'S® + P ₂ -7 S +' F ₂ ⁰ with F ₁ - donor molecule

F ₂ - acceptor molecule ¹ PJ ^ ₉ 'Pp ^ö - donor or. Acceptor radical ion

Sensitization reactions take place at the interface between the transparent cover layer and the organic one Dye layer instead. The top layer is therefore at least a sensitized, organic photoconductor in the area of the interface, which leads to the surprisingly high photoconductivity leads.

The reactions 3 and 5 then proceed preferentially when as IT - electron system in the top layer a compound is chosen, which can easily donate electrons as a donor compound. This is e.g. with 2,5-Bxs- (4-diethylaminophenyl) -l, 3,4-oxdiazole or polyvinyl carbazole is the case. With a substance in the top layer that easily accepts electrons as an electron acceptor, such as 2,4,7-trinitrofluorenone or N-t-butyl ^ jß-dinitro-naphthalimide, ' Reactions 4 and 6 are preferably possible.

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The special embodiment of the invention now allows that it is sufficient for the effectiveness of the dye if, in addition to its intensive absorption, it only contains either electron-attracting substituents such as ^ C = O, halogen, or electron-repelling substituents such as alkyl or -O- alkyl is, depending on whether it is for the reactions 3, 5 and ¹ J, 6 preferably suitable. The invention allows a further transport of the charge carriers within the densely packed dye layer according to the following reactions, which is facilitated by particularly low energy expenditure:

7. 'S® + S -> S + "S® resp.

8. S + 'S ⁰ ->"S ⁰ + S

In all conventional sensitization processes, on the other hand, the transport via the is in low concentration present dye molecules difficult because of their large distance from each other.

The charge transport in the top layer proceeds analogously with:

9. "P ^ + F ₁ -> F ₁ + 'Fj® (p-conducting) 10.' F ₂ ⁰ + F ₂ -> F ₂ + 'F ₂ ⁰ (n-conducting)

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As a practical consequence of reactions 1-10, _{3 it} follows that when electron donors are used in the cover layer, the double-layer arrangement is negatively charged so that the reactions J >> 5 » 8, 9 can take place. Conversely, layers with electron acceptors in the cover layer are positively charged so that reactions 4, 6, 7 and 10 can take place.

As mentioned, the dye layers are only very thin and accordingly, the dye is only required in a very small amount. Due to the vapor deposition in a high vacuum, however, one is extreme high uniformity of the dye layer ensures how it cannot be easily achieved by conventional coating methods. This evenness is very important contributes to the great sensitivity that characterizes the layers according to the invention, the charge carrier reactions 3 and 4 without local mutual disturbances (recombinations) can expire.

The transparent cover layer has a high electrical Resistance and prevents the electrostatic charge from flowing away in the dark. When exposed, it transports the charges generated in the organic dye layer.

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The transparent cover layer preferably consists of a mixture of an electron donor compound and a binding agent if a negative charge is to be carried out. On the other hand, however, there is the transparent cover layer preferably from a mixture of an electron acceptor compound and a binder, if the electrophotographic recording material according to the invention can be used for positive charging target.

Accordingly, compounds serving for charge transport are used in the transparent cover layer which are known as electron donors or electron acceptors in the field of photoconductors. They are used in connection with binders or adhesion promoters, which with regard to the charge transport, the film properties, the adhesion promotion and surface properties are coordinated with the compound serving for charge transport. Farther Conventional sensitizers or substances which form charge transfer complexes are preferably additionally present. However, these can only be used insofar as the necessary transparency; the top layer is not impaired. Finally, the usual other additives such as leveling agents, plasticizers and adhesion promoters can also be present.

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Compounds serving as charge transport are present especially those organic compounds that are a have an extended Jj electron system. These include both monomeric and polymeric aromatic compounds . ·

The monomers used are in particular those which have at least one dialkylamino group or two alkoxy groups. Heterocyclic compounds such as oxdiazole derivatives, which are mentioned in German patent 1,058,836, have proven particularly useful. This includes, in particular, the 2 _J 5-bis (4-diethylaminophenyl) oxdiazole-1,3> 4 Other suitable monomeric electron donor compounds are, for example, triphenylamine derivatives, more highly condensed aromatic compounds such as anthracene, benzocondensed heterocycles, pyrazoline or imidazole derivatives; this also includes triazole and oxazole derivatives, as disclosed in German patents 1,060,260 and 1,120,875. . ■

Examples of polymers are vinyl aromatic polymers such as polyvinyl anthracene, polyacenaphthylene, or copolymers of N-vinyl carbazole and styrene, vinyl acetate, Vinyl chloride, suitable ^. Have particularly proven themselves

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- 14 -? 2 A 6 2 5 Λ

Poly-N-vinylcarbazole or copolymers of N-vinylcarbazole with an N-vinylcarbazole content of at least about hO%. Formaldehyde condensation products with various aromatics, such as condensates of formaldehyde and 3-bromopyrene, are also suitable.

In addition to these compounds, which are predominantly p-conducting, there are also n-conducting Connections used. These so-called electron acceptors are, for example, from German patent specification 1 127 known. In particular, compounds such as 2,4,7-trinitrofluorenone have proven themselves or N-t-BUtyl-3> 6-dinitronaphthalimid.

In terms of flexibility, film properties and adhesive strength, natural or synthetic resins are used as binders suitable. These include in particular polyester resins such as those sold under the name Dynapol ^ (Dynamit Nobel), Vitel ^ 'j (Goodyear) are on the market and mixed polyesters from iso- and terephthalic acid with glycol. Also silicone resins, as they are known under the name Silicone Resin SR the General Electric Comp, or Dow 8O4 from Dow Corning Comp., USA, which are known and represent three-dimensionally crosslinked phenylmethylsiloxanes, have proven to be suitable

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proven. Furthermore, copolymers of styrene are ■

and maleic anhydride, such as those known under the name Lytron ^, Monsanto Chemical Comp, USA, but also poly carbonate resins such as those known under the name Lexan Grade ^ 'from General Electric Comp., USA, or post-chlorinated polyvinyl chlorides such as Rhenoflex ^ ^R 'from Rheinpreussen AG, or chlorinated polypropylene such as Hostaflex ^ ^R ' (Farbwerke Hoechst), can be used well.

The mixing ratio of the charge transporting compound to the binder can vary. However, due to the requirement for maximum photosensitivity, ie,. the largest possible proportion of charge-transporting compound, and after crystallization to be avoided, ie the largest possible proportion of binder, relatively certain limits are set. A mixing ratio of about 1: 1 parts by weight has proven to be preferred, but ratios between about 3: 1 to 1: 4 or greater are also suitable in some cases. . _; -

The conventional sensitizers that can also be used can advantageously promote charge transport. You can also generate charge carriers in the transparent cover layer. Examples of sensitizers that can be used are Rhodamine B extra , Schultz, Dye Tables, Volume I, 7th Edition, 1931, No. 864, Page 365, Brilliant _{Green 5} No. 76O, Page 314 ₃ Crystal Violet, No. 785, Page 329, Viktoria Reinblau, No. , 822, page 347 and cryptoeyanine, no. 927., page 397 ,. can be used. In the same way as the sensitizers, added compounds can also have an effect

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the charge-transporting compound is charge-transfer complexes form. This can further increase the photosensitivity of the double layers described can be achieved. The amount of the added sensitizer or the compound forming the charge transfer complex is dimensioned so that the resulting donor-acceptor complex with its charge-transfer band is still sufficient is transparent to light absorbed by the underlying organic dye layer. As such · Electron acceptors are, for example, compounds such as 3,5- or 3> 4-dinitro-behzoic acid, tetrachlorophthalic anhydride, 2,4,7-trinitrofluorenone, 3 »6-dinitronaphthal- * acid anhydride and N-substituted imides of 3 »6-dinitronaphthalic acid in question. The optimal concentration range is a molar donor / acceptor ratio of about 10: 1 to about 100: 1 and vice versa.

In addition to the transparency of the top layer, its layer thickness is also an important parameter for optimum photosensitivity: Layer thicknesses between about 5 and about 20 , w have proven to be particularly suitable. It has been shown, however, that when monomeric or polymeric, charge-transporting compounds are used in binders, the thickness ranges fluctuate. The ranges for monomeric compounds are more towards greater thickness, while when using polymeric, charge-transporting compounds

Thicknesses in the range of about 5-15 / u are sufficient » With layer thicknesses below about 5 / U can use

lower maximum charging amount can be expected.

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The sole addition of adhesion promoters as binders, especially to polymeric, charge-transporting compounds, already shows good photosensitivity. Here, for example, low molecular weight polyester resin, such as e.g. Adhesive 49 000 from Du Pont, particularly proven,

In the manner described, the cover layers have the property of being highly charged with a small dark discharge to enable. While with all conventional sensitization h an increase in "photosensitivity is linked to an increase in the dark current, the arrangement according to the invention can prevent this parallelism. This means that these layers can be used both in electrophotographic copiers with low copying speed and very low lamp energy as even in those with high copying speeds and correspondingly higher lamp powers.

The invention is illustrated by the following examples, the values of which are compiled in the table below, explained in more detail.

The dyes listed below in a vacuum pumping unit are used for producing photoconductive bilayers' (type Al the company. Pfeiffer, Wetzlar) _s have been measured directly on the base at 10 ~ ^ to 10 Torr, at the temperatures indicated ,, and the specified duration vapor-deposited onto a 90 u thick aluminum foil installed at a distance of approx. 15 cm

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(A lead pad was used for example No. 19).

The dye layers have a thickness that is over that Absorbance measured, is approximately in the range from 0.01 to 2 µ.

For this purpose, the dyes are applied simultaneously to a transparent polyester film and an aluminized one Vaporized polyester film. This results in identical layers on different substrates. The on. the transparent one The layer applied to the film is used to determine the extinction, the other to measure the electrophotographic Sensitivity. Assuming one

c 4

Extinction coefficients of C ^ "1.0. 10 and a density of the dye of d = 1 are calculated using the formula

Thickness (., U) = 10-JE. M. d " ¹ (with E - measured absorbance, M - molecular weight) with measured absorbance of 0.28 or 1.85 at 505 nm for the dyes according to formulas 1 and 2 thicknesses of 0.18 or 1.1» u.

The sensitivities of these layers produced for thickness measurement to the light of the xenon lamp with HQj.5

/ u W / cm are 46 and 40 m / sec half-life of the light discharge and a charge of 810 or -560 volts after coating the dye layer with 6, u stronger

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Top layer To, which will be described later.

To test the electrophotographic properties, transparent cover layers of approx. 5-6 Ω thick are applied to the dye layer. For this purpose, 1 part by weight of 2,4,7-trinitrofluorenone, 1 part by weight of polyester resin, for example Dynapol ^v; , L 206 of Dynamit Nobel Troisdorf (TNP) ₃ or 1 part by weight of 2,5-bis- (4-diethylaminophenyl) -oxdiazole-1,3 _s ^ > 1 part by weight of a copolymer of styrene and maleic anhydride, for example Lytron ^ '820 of Monsanto Corp., USA (To) _s or 1 part by weight of Nt-butyl-3 _s 6-dinitro-naphthalic acid imide and 1 part by weight of polyester resin Dynapol L 206 (DNI), in some cases, as indicated, with the addition of sensitizer in the indicated concentration with regard to the pest body content , centrifuged as a 20% solution in tetrahydrofuran and then dried for 2-3 minutes at 120 ° C.

To compare the photosensitivity are the same Cover layers produced analogously on an aluminum foil (zero layers), which show that according to the invention Increase photosensitivity by more than a factor of 100.

To measure the photosensitivity, the respective

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Photoconductor layer charged to a positive or negative voltage, whereby it was passed three times through a charging device, for example type AG 56 from Kalle AG, setting 7.5 kV. The respective layer is then exposed using an XBO 150 xenon lamp from Osram. The light intensity in the measuring plane is uniformly approx. 270 yuW / cm ² . The level of charge (V) and the photo-induced light decay curve of the photoconductor layer are measured in a 6IO B electrometer from Keithley Instruments, USA, using a probe according to the method described by Arneth and Lorenz in Reprographie 3. 99 ”(1963). The photoconductor layer is characterized by the level of charge and the time (T 1/2) after which half of the charge V / 2 is reached.

The abbreviations used for the sensitizers used are:

RhB = Rhodamine B extra BG = brilliant green

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Tabel

Serial Dye vapor deposition top layer Sensi- Photosensitivity No. according to bilizer

Formula min / ° C % ' Tl / 2 V

O - - To - 2100 - 420. O - -. TNF 11000 + 500 1 1 4/300 TNF 0.3 RhB 135 + 690 2 1 2/300 TNF 0.3 RhB 155 +1200 3 1 2/300 DNI - - 130 +1400 4th 1 2/300 To 0.15 BG 57 - 600 VJl 1 4/300 Td 0.3 RhB ' 32. -1300 6th 1 4/300 To 0.3 RhB 23 -II50 7th 2 2/320 TNF - 59 + 45O 8th 2 4/320 To 0.3 RhB • 65 - 730 9 3 2/310 TNF - 170 + 65O 10 4th 3/310 , To 135 - 620 11 12th 5/360 TNF 0.3 RhB 380 . + 940 12th 14th 4/330 TNF - - 120 +1450 13th 15th 4/280 TNF 0.3 RhB 78 + 500 14th 15th 4/280 TNF 0 ₉ 3 RhB 58 ■ j- 48.0 15th 15th 4/280 To 63 -1100 16 16 4/330 TNF '0.3 RhB 82 4- 520 17th 16 4/330 To 0, 0 5 BG 76 -1100 18th Io 4/330 ' To 76 - 940 19th 2 4/320 TNF 40 + 330

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Claims (9)

Claims Electrophotographic recording material made of an electrically conductive carrier material with a photoconductive double layer made of organic materials, which consists of a homogeneous, color-covering, charge carrier generating, organic dye layer and one transparent cover layer made of insulating, organic materials with at least one charge-transporting Connection exists, according to German patent application, file number P 22 20 i | O8.6, characterized in that the organic pigment layer made from a compound of the general formula ⁷ ^ ^v '-NH-CO-CH-N = NAN = N-CH-CO-NH \ j / HXl Ou wu η - η η H - η ωι υυ hut. co co I I CH ₃ CH, consists in what - A - is an optionally substituted diphenyl, 2-phenylbenzimidazole or azobenzene radical and R, R _1, Rp ^{and R} 3 are each identical or different and are hydrogen, C ₁ - C ^ - alkyl, C ₁ - C ₁₁ - Alkoxy I or halogen
mean. 40981 3/1019 2. Recording material Bach claim I _9, characterized in that - A - through C ₁ .- C ^ - alkyl _s . . ' ■ C_ - Cj. - Is substituted by alkoxyl and / or halogen. 3. Recording material according to Claims 1 and 2 _S, characterized in that methyl _s methoxy groups and / or chlorine are present as substituents and η is 1 or 2. '4. Recording material according to Claims 1 and 2 _S, characterized in that the organic dye layer consists of Pigment Yellow 12, CI. 21 09O ₃ ordered * 5. Recording material according to Claims 1 and 2 _S, characterized in that the organic.Färstoffschicht made of pigment orange 16, CI. 21 16O ₅ consists of » 6. Recording material according to claims 1 and 2 _a, characterized in that the organic dye layer of 4.4 ^t -Bis-azo- (2,5-dichloro - 2 ^t -niethoxy-5 ^t -methyl - azobenzene) -bis- ( β - acetoaeetanilid) consists of ° 7. Recording material according to Claims 1 and 2 _S, characterized in that the 'organic dye layer from 4,4'-bis-azo- (2,5 '-diehlor-5,2 -dimethoxy-azobenzene) -bis- ( β - acetoaeetanilid). 4098 13/1019 - 2k - 8. Recording material according to Claims 1 to 6, characterized in that the organic paraffin layer has a thickness between about 0.01 and 2 µ. 9. Recording material according to claims 1 to J, characterized in that the organic dye layer made of metal foil made of aluminum or lead or applied to plastics vapor-coated or laminated with these metals