EP0444529A1 - Use of dyestuffs for sublimation transfer process - Google Patents

Abstract

Use of water-insoluble monoazo dyes of the formula I <IMAGE> in which R¹ is alkyl with 1 to 6 C atoms, cyclopentyl, cyclohexyl, fluorine, chlorine, bromine, alkoxy with 1 to 4 C atoms or trifluoromethyl, R² alkyl with 1 to 7 C- Atoms, R³ and R <4> independently of one another denote alkyl with 1 to 4 carbon atoms, for the sublimation transfer process.

Description

The invention relates to the use of dyes of a certain constitution for the sublimation transfer process. Some of the dyes used are new and are claimed together with the process for their preparation in the context of the present invention. The invention further relates to a dye carrier for the sublimation transfer process, a process for its preparation and a process for the transfer of dyes.

With the help of the sublimation transfer process, excellent color images can be produced, for example on plastic-coated paper or on plastic foils, based on image information supplied by electronic image sources such as video cameras or video recorders, television screens or computers or electronic still cameras etc. The electronic image information is processed in facsimile devices, copiers or printers which contain a thermal print head with numerous tiny (for example 4 to 16 per mm) heating elements arranged in a row. The digital image information is converted into different heating levels in the thermal print head and fed to the individual heating elements. The heating elements press on the back of a dye carrier, for example an ink ribbon which has a color layer on its front side, in which blocks with a dye of the subtractive primary colors yellow, magenta and cyan and optionally also black are contained in the ribbon direction. The front of the ink ribbon lies with the ink layer on the recording material on which the colored image is to be created. Depending on the heating energy supplied to the heating elements, a proportional amount of dye released from the dye layer and transferred to the recording material. The ink ribbon and recording material are moved past the thermal print head. An image is first transferred line by line in a basic color. The full color spectrum of the image is then generated by sequential transmission of the other two primary colors and, if necessary, additionally of black.

The heating impulses generated by the heating elements are in the range of milliseconds. It is generally believed that dye transfer from the ribbon to the recording material is by sublimation, but other mechanisms of dye transfer, e.g. dye evaporation or dye diffusion. In addition to the term sublimation transfer process, other terms, such as dye diffusion thermal transfer process and thermal transfer printing process, are also used. Of course, numerous modifications are possible to the described principle of the sublimation trans process. For example, the ribbon with the successively arranged three or four color areas of the primary colors can be replaced by three or four color carriers, each with a primary color yellow, magenta, cyan and possibly black.

The gradation of the colors on the finished record is easily influenced in the sublimation transfer process by controlling the heating energy given off by the heating elements, whereby the amount of dye subliming and transferred to the recording material is adjusted. Due to this easy controllability of the color gradations, the sublimation transfer process has advantages over other color transfer processes. On the other hand, however Sublimation transfer processes are only suitable for dyes that meet the special requirements of this process. This primarily includes the requirement that the dye can be sublimed or evaporated easily and without decomposition under the working conditions of the sublimation transfer process, ie in fractions of a second, in order to ensure adequate transfer to the recording material.

With textile transfer printing, a paper with a multicolored design is first printed on a paper printing machine. This design is then reprinted on a suitable textile material, usually polyester, by means of sheet-like exposure to temperatures of 180 to 230 ^o C on presses or transfer printing calenders. In contrast to the sublimation transfer process mentioned at the outset for the production of colored records, the heating times in textile transfer printing are considerably longer and are usually in the range from 20 to 60 seconds. This fact and other differences between textile transfer printing and sublimation transfer processes mean that the dyes which can be used in textile transfer printing are normally not or not optimally suitable for the sublimation transfer process.

A dye suitable for the sublimation transfer process is said to have, for example, the following properties: it should be transferable to the recording material without decomposition in a narrow temperature range within a few milliseconds; its sublimation from the recording material should be as low as possible; its image stability in the recording material should be long and high, in particular the image should be stable against the effects of light, moisture, chemicals, heat, friction and scratches and other environmental influences; he must have a basic shade suitable for three or four color printing and its molecular extinction coefficient should be high; it should be easily soluble in organic solvents and provide uniform records. In addition, the dye is said to be non-toxic and easy to produce and easy to process into a printing ink.

The dyes known for the sublimation transfer process, e.g. C.I. Disperse Red 60, the dyes of US 4,695,288, US 4,764,178, DE-OS 36 38 756 and DE-OS 38 01 545 do not yet sufficiently meet the requirements imposed by the sublimation transfer process.

The invention was based on the object of specifying dyes which are outstandingly suitable for the sublimation transfer process in which dyes are transferred from a support to a recording material by brief local heat supply.

worin
R¹ Alkyl mit 1 bis 6 C-Atomen, Cyclopentyl, Cyclohexyl, Fluor, Chlor, Brom, Alkoxy mit 1 bis 4 C-Atomen oder Trifluormethyl,
R² Alkyl mit 1 bis 7 C-Atomen und
R³ und R⁴ unabhängig voneinander Alkyl mit 1 bis 4 C-Atomen
bedeuten.The invention relates to the use of water-insoluble monoazo dyes of the general formula I in the sublimation transfer process

wherein
R¹ alkyl with 1 to 6 carbon atoms, cyclopentyl, cyclohexyl, fluorine, chlorine, bromine, alkoxy with 1 to 4 carbon atoms or trifluoromethyl,
R² alkyl with 1 to 7 carbon atoms and
R³ and R⁴ independently of one another alkyl having 1 to 4 carbon atoms
mean.

The dyes of the formula I used in the sublimation transfer process according to the invention can be used alone, in a mixture with one another or in a mixture with other dyes.

The dyes of the formula I in which R 2 is alkyl having 4 to 7 carbon atoms are new and are claimed in the context of the present invention together with a process for their preparation.

The alkyl and alkoxy radicals can be straight-chain or branched.

Alkyl radicals with 1 to 6 carbon atoms, which in the formula I can represent R 1, are e.g. Methyl, ethyl, propyl, i-propyl, n-butyl, i-butyl, sec-butyl, tert-butyl, n-pentyl, i-pentyl, n-hexyl.

Alkoxy radicals with 1 to 4 carbon atoms, which in the formula I can represent R 1, are e.g. Methoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, sec-butoxy and tert-butoxy.

Alkyl radicals with 1 to 7 carbon atoms, which in the formula I can represent R², are, for example: methyl, ethyl, n-propyl, i-propyl, n-butyl, butyl-2, 2-methylpropyl, n-pentyl, Pentyl-2, pentyl-3, n-hexyl, n-heptyl, heptyl-3, heptyl-4.

Alkyl radicals with 1 to 4 carbon atoms, which in the formula I can represent R³ and R⁴, are: methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl and tert-butyl .

Preferred radicals for R 1 are alkyl radicals with 1 to 3 carbon atoms, alkoxy radicals with 1 to 3 carbon atoms and in particular chlorine and bromine. Preferred radicals R 1 are accordingly: methyl, ethyl, n-propyl, i-propyl, methoxy, ethoxy, n-propoxy, i-propoxy and in particular chlorine and bromine.

The alkyl radicals which represent R 2 preferably have 2 to 6 carbon atoms. Examples of such preferred alkyl radicals for R 2 are: ethyl, n-pentyl, pentyl-2, pentyl-3, n-hexyl and in particular n-propyl, i-propyl, n-butyl, butyl-2 and 2-methylpropyl. The alkyl radicals which represent R² very particularly preferably have 3 or 4 carbon atoms.
R³ is preferably methyl or ethyl.

The radicals R³ and R⁴ are preferably selected such that the sum of the carbon atoms in the radicals R³ and R⁴ is 3, 4, 5 or 6, in particular 3 or 4.

If R¹ is an alkyl or alkoxy radical, the sum of the carbon atoms in the radicals R¹, R², R³ and R⁴ is preferably 6 to 11. If R¹ is fluorine, chlorine, bromine or trifluoromethyl, the sum of the carbon atoms in the for R², R³ and R⁴ are preferably alkyl radicals 5 to 10.

Dyes which are preferably used for the use according to the invention are those with preferred meanings of R¹, R², R³ and R⁴.

in der R¹, R², R³ und R⁴ die vorstehenden Bedeutungen haben, X Cyan oder Halogen und Hal ein Halogenatom, wie Chlor oder insbesondere Brom bedeutet, in an sich bekannter Weise z.B. nach den Angaben der DOS 1 809 920, 1 809 921, den GB-Patentschriften 1 184 825, 1 125 685, der DAS 1 544 563, der DOS 2 310 745, der DAS 2 456 495, der DAS 2 610 675, der DOS 2 724 116, der DOS 2 724 117, der DOS 2 834 137, der DOS 2 341 109, der US-Patentschrift 3 821 195, der DOS 2 715 034 oder der DOS 2 134 896 einer nukleophilen Austauschreaktion unterwirft, wobei als nucleophiles Agenz das Cyanidion CN⁻ eingesetzt wird.The individual dyes of the formula I are prepared by azo dyes of the formula II

in which R¹, R², R³ and R⁴ have the above meanings, X is cyan or halogen and Hal is a halogen atom, such as chlorine or in particular bromine, in a manner known per se, for example according to DOS 1 809 920, 1 809 921 GB Patents 1 184 825, 1 125 685, DAS 1 544 563, DOS 2 310 745, DAS 2 456 495, DAS 2 610 675, DOS 2 724 116, DOS 2 724 117, DOS 2 834 137, DOS 2 341 109, US Pat. No. 3,821 195, DOS 2 715 034 or DOS 2 134 896 is subjected to a nucleophilic exchange reaction, the cyanide ion CN⁻ being used as the nucleophilic agent.

Inert organic solvents are used as solvents for the exchange reaction, e.g. Nitrobenzene or glycol or diglycol monomethyl ether or diglycol monoethyl ether or mixtures of such solvents with one another and with tertiary organic nitrogen bases, dipolar aprotic solvents such as e.g. Methylpyrrolidone, pyridine, dimethylformamide or dimethyl sulfoxide, dicyandialkylthioether, water or aqueous systems consisting of water and a water-immiscible organic solvent (such as nitrobenzene), preferably in the presence of a wetting or. Dispersant or a known phase transfer catalyst, or aqueous systems of water and a water-soluble, inert organic solvent, e.g. Ethylene glycol or dimethylformamide.

The presence of organic, basic nitrogen compounds, such as e.g. Pyridine and pyridine bases.

The reaction temperatures are usually between 20 and 150 ^o C.

The nucleophilic agent CN⁻ is the reaction in the form of an optionally complex metal cyanide, such as an alkali or alkaline earth cyanide, zinc cyanide, alkali cyanozincate or ferrate, but preferably in the form of copper-I-cyanide or in the form of a copper-I-cyanide-forming system. The use of a combination of alkali metal cyanide with copper-I-cyanide has proven particularly useful, the weight ratio of alkali metal and copper salt being able to be varied within wide limits. The common range of the weight ratio of alkali metal cyanide / copper-I-cyanide is 5: 95 to 95: 5. The positive mutual influence of the components can also be determined outside these limits. Of course, it is also possible for the copper-I-cyanide in turn to be formed by a system forming copper-I-cyanide, e.g. a combination of alkali cyanide with another copper salt, preferably copper-I salt, e.g. a copper-I-halide.

mit einer Kupplungskomponente der allgemeinen Formel IV

worin R¹, R², R³, R⁴, X und Hal die bereits genannten Bedeutungen besitzen, gekuppelt wird.The dyes of the formula II required for the preparation of the dyes of the formula I can be prepared by adding a diazonium compound of an aromatic amine of the general formula III

with a coupling component of the general formula IV

wherein R¹, R², R³, R⁴, X and Hal have the meanings already mentioned, is coupled.

Solutions of diazonium compounds are known from the amines of the general formula II in a manner known per se by the action of nitrous acid or other systems forming nitrosonium ions in an acidic aqueous medium, a lower alkane carboxylic acid, such as, for example, formic acid, acetic acid or propionic acid or a mixture thereof or an organic solvent Get temperatures from 0 to 40 ^o C.

The coupling is also carried out in a manner known per se by combining the solution of the diazonium compound obtained with a solution of the coupling component at temperatures of 0 to 40 ^° C., preferably 0 to 25 ^° C., in a suitable solvent, such as an alkanol with 1 to 4 C atoms, dimethylformamide, preferably in water acidified with sulfuric acid, hydrochloric acid or phosphoric acid or an optionally water-containing lower alkane carboxylic acid or a lower alkane carboxylic acid mixture, if appropriate also in the presence of an alkanol which is miscible with water to a limited extent. In some cases it may be useful to buffer the pH during the coupling, for example by adding sodium acetate. The coupling is complete after a few hours and the dye of the formula I can be isolated and dried as usual.

The required starting compounds of the general formulas II and III can be prepared from known commercial products by known processes.

The dyes of the formula I used according to the invention for the sublimation transfer process are distinguished, in particular, by the following advantages over the dyes previously used for this purpose: better and similar sublimation ability, higher light fastness, higher solubilities in organic solvents, such as in MEK (methyl ethyl ketone) and toluene, less resublimation from the recording material.

The dye carriers required for the dye transfer in the sublimation transfer process are produced in a manner known per se. The dye of the formula I used, optionally in a mixture with one or more other dyes of the formula I and / or in a mixture with one or more other dyes, together with a binder or thickener, for example in water or in an organic solvent, processed into a printing ink. Suitable organic solvents are, for example, methyl ethyl ketone, toluene, butanol or chlorobenzene. The printing ink can contain the dye in dispersed and / or preferably in dissolved form. In the case of a dispersed dye, its particle size is expediently equal to or less than 1 μm. Suitable binders or thickeners are, for example: methyl or ethyl cellulose, polymers of acrylic acid and methacrylic acid, polystyrene, polycarbonates, polysulfones, polyether sulfones, polyester resins etc. 3 to 7 microns applied to an inert carrier and then dried. After drying, the thickness of the dye layer can be, for example, 0.1 to 5 μm. Suitable inert carrier materials consist, for example, of paper, such as capacitor paper, tissue paper, art paper or plastic. For example, plastic films made of polyester, such as polyethylene terephthalate, polyamide, polyimide or polyaramide, are suitable. The carrier material can, for example, have a thickness of 3 to 50 µm and must be tight and should have a high thermal conductivity. In addition to the constituents already mentioned, the printing ink can also contain further constituents, such as, for example, dispersants, antioxidants and / or viscosity regulators, etc. If necessary, the dye carrier contains other layers in a known manner, for example a heat-resistant sliding layer on the back to improve the running properties and heat resistance compared to the heating elements of the thermal print head.

Films made of thermally stable plastics, in particular polyester, are suitable as recording materials and are capable of absorbing the dyes to be transferred. Furthermore, as recording materials e.g. Suitable papers and the like, which are coated with the aforementioned plastics, in particular polyester.

In the process for the transfer of dyes by the sublimation transfer process, the dyes are removed from the support by brief, e.g. local heat supply in the range of milliseconds, e.g. sublimed or evaporated via the heating elements of a thermal print head and transferred to the recording material.

In the sublimation transfer process, the dyes used according to the invention provide strong, yellowish red to reddish violet colored dots or images with very good fastness properties and low resublimation.

The dye sublimation temperature can be determined quickly and easily as follows:
An inert carrier, for example blotting paper or filter paper, is immersed in a, for example 0.25%, solution of the dye to be tested in an organic solvent, for example in ethyl acetate. The dip dyeing thus produced is air-dried. The colored carrier is briefly heated on a Kofler heating bench in the temperature range from 100 to 200 ^o C and the subliming dye is transferred to a polyester film located a short distance (less than 1 mm) above it. The amount of dye migrated into the polyester film can be determined photometrically. The sublimation temperature is the temperature at which a clear coloration on the film can be seen visually.

Example 1:

in 99,75 g Ethylacetat 1 Minute lang eingetaucht und dann an der Luft getrocknet. Die Prüfung der Thermosublimation nach dem oben beschriebenen Verfahren zeigt einen Sublimationsbeginn bei 160^oC. .A filter paper strip (Binzer quality, AA, smooth, approx. 70 g / m²) is placed in a solution of 0.25 g of the dye of the formula

dipped in 99.75 g of ethyl acetate for 1 minute and then air dried. The examination of the thermal sublimation according to the method described above shows a start of sublimation at 160 ^o C.

The dye is made as follows:
8.5 g of sodium cyanide and 28 g of copper-I-cyanide are introduced in succession at 70 to 75 ^° C. in 200 ml of dimethyl sulfoxide and the mixture is stirred for 1/2 hour. Then 106 g of the dibromo precursor of the formula II in which X and Hal are bromine, R¹ is chlorine, R² is n-propyl, R³ is methyl and R⁴ is ethyl, and the batch is 110 to Heated to 112 ^o C, slowly cooled and filtered at 30 ^o C After washing with 50 ml of dimethyl sulfoxide, 7.5% ammonia water and water and drying to constant weight, 64 g of the dye are obtained, which dissolves in ethyl acetate with a red color.

The other dyes according to the invention and used according to the invention are prepared analogously.

Example 2:

zeigt einen Sublimationsbeginn bei 160^oC.The thermal sublimation test of a paper dip dyeing prepared as described in Example 1 using the dye of the formula

shows a start of sublimation at 160 ^o C.

Example 3:

zeigt einen Sublimationsbeginn bei 165^oC.Testing the thermal sublimation of a paper dip dyeing as described in Example 1 using the dye of the formula

shows a sublimation beginning at 165 ^o C.

Example 4

10 parts by weight of the dye of Example 1 are processed with 10 parts by weight of cellulose acetate and 80 parts by weight of MEK (methyl ethyl ketone) to form a homogeneous printing ink, and this is drawn off on paper with a 6 μm doctor blade and dried.

The transfer support thus produced is brought into contact with the recording material with its color layer side and a recording is transferred from the back of the transfer support using a conventional heating head. 8 points / mm are transmitted within 8 msec with an electrical output of 0.25 watts / heating element.

The record of bluish-red color obtained is clear and distinct and has excellent fastness properties.

The following table lists further dyes used in accordance with the invention with similarly good sublimation behavior and good fastness level. If no details are given for the specified residues, e.g. i-or sek.- are present, it is normal unbranched residues. The dyes are prepared analogously to the production process mentioned in Example 1.

In the table in the last column, the shade is given which is obtained in the sublimation transfer process on paper coated with polyester. The information used here means:
1 = bluish red
2 = red
3 = yellowish red
4 = reddish violet

Claims (10)

Use of water-insoluble monoazo dyes for the sublimation trans process, characterized in that a dye of the general formula I

wherein
R¹ alkyl with 1 to 6 carbon atoms, cyclopentyl, cyclohexyl, fluorine, chlorine, bromine, alkoxy with 1 to 4 carbon atoms or trifluoromethyl,
R² alkyl with 1 to 7 carbon atoms,
R³ and R⁴ independently of one another alkyl having 1 to 4 carbon atoms
mean,
or a mixture of dyes of the formula I, optionally in a mixture with other dyes, is used. Use according to claim 1, characterized in that R¹ is alkyl with 1 to 3 C atoms, alkoxy with 1 to 3 C atoms, chlorine or bromine. Use according to claim 1 and / or 2, characterized in that R¹ is chlorine or bromine. Use according to one or more of claims 1 to 3, characterized in that R² is alkyl with 2 to 6 carbon atoms. Use according to one or more of claims 1 to 4, characterized in that R² is alkyl with 3 or 4 carbon atoms. Use according to one or more of claims 1 to 5, characterized in that R¹ is an alkyl or alkoxy radical and the sum of the carbon atoms in the radicals R¹, R², R³ and R⁴ is 6 to 11, or that R¹ is fluorine, chlorine, bromine or trifluoromethyl and the sum of the carbon atoms in the alkyl radicals representing R², R³ and R⁴ is 5 to 10. Dye carrier for the sublimation transfer process, characterized in that it is coated with a layer which contains a dye of the general formula I,

wherein
R¹ alkyl with 1 to 6 carbon atoms, cyclopentyl, cyclohexyl, fluorine, chlorine, bromine, alkoxy with 1 to 4 carbon atoms or trifluoromethyl,
R² alkyl with 1 to 7 carbon atoms,
R³ and R⁴ independently of one another alkyl having 1 to 4 carbon atoms
mean,
or a mixture of such dyes, optionally in a mixture with other dyes. Process for transferring dyes from a support by briefly applying local heat to a recording material, characterized in that a support is used on which a dye of the general formula I

wherein
R¹ alkyl with 1 to 6 carbon atoms, cyclopentyl, cyclohexyl, fluorine, chlorine, bromine, alkoxy with 1 to 4 carbon atoms or trifluoromethyl,
R² alkyl with 1 to 7 carbon atoms,
R³ and R⁴ independently of one another alkyl having 1 to 4 carbon atoms
mean,
or a mixture of such dyes, optionally in a mixture with other dyes, is applied. Water-insoluble monoazo dyes of the general formula I

wherein
R¹ alkyl with 1 to 6 carbon atoms, cyclopentyl, cyclohexyl, fluorine, chlorine, bromine, alkoxy with 1 to 4 carbon atoms or trifluoromethyl,
R² alkyl with 4 to 7 carbon atoms,
R³ and R⁴ independently of one another alkyl having 1 to 4 carbon atoms
mean, A process for the preparation of azo dyes of the formula I of claim 9, characterized in that an azo dye of the formula II

3rd
in which R¹, R², R³ and R⁴ have the meanings given in Claim 9 and X is cyan or halogen and Hal is a halogen, is subjected to a nucleophilic exchange reaction in a manner known per se, the cyanide ion being used as the nucleophilic agent.