EP0442360A1 - Process for transfer of azo dyes - Google Patents

Abstract

Process for transfer of azo dyestuffs from a support to a plastic-coated paper by diffusion with the aid of an energy source, in which a support is used on which are present one or more azo dyestuffs of the formula <IMAGE> in which   X denotes nitrogen or the radical C-CN   Z denotes oxygen or the radical -CH(R<7>)-, in which R<7> represents hydrogen or C1-C4-alkyl,   R<1> represents hydrogen, substituted or unsubstituted alkyl or substituted or unsubstituted phenyl,   R<2> and R<3> each denote hydrogen or C1-C4-alkyl,   R<4> denotes hydrogen, C1-C10-alkyl, C1-C10-alkoxy or acylamino,   R<5> denotes hydrogen, chlorine, C1-C4-alkyl, C1-C4-alkoxy, C1-C4-alkylthio or substituted or unsubstituted phenyl and   R<6> denotes cyano or the radical -CO-OR<1>, -CO-NHR<1> or -CO-N(R<1>)2, in which R<1> has the abovementioned meaning.

Description

The present invention relates to a new process for transferring azo dyes, which have a thiophene-based diazo component, from a support to a plastic-coated paper using an energy source.

In the thermal transfer printing process, a transfer sheet containing a thermally transferable dye in one or more binders, optionally together with suitable auxiliaries, is supported on a support with an energy source, e.g. with a heating head, heated by short heating impulses (duration: fractions of a second) from the back, whereby the dye migrates from the transfer sheet and diffuses into the surface coating of a recording medium. The main advantage of this method is that it is easy to control the amount of dye to be transferred (and thus the color gradation) by adjusting the energy to be released from the energy source.

• leichte thermische Transferierbarkeit,
• geringe Migration innerhalb oder aus der Oberflächenbeschichtung des Aufnahmemediums bei Raumtemperatur,
• hohe thermische und photochemische Stabilität sowie Resistenz gegen Feuchtigkeit und chemische Stoffe,
• für substraktive Farbmischung die geeigneten Farbtöne aufweisen,
• einen hohen molaren Absorptionskoeffizienten aufweisen,
• bei Lagerung des Transferblattes nicht auskristallisieren,
• technisch leicht zugänglich sein.

In general, the color recording is carried out using the three subtractive primary colors yellow, magenta and cyan (and possibly black). To enable optimal color recording, the dyes must have the following properties:

• easy thermal transferability,
• low migration within or from the surface coating of the recording medium at room temperature,
• high thermal and photochemical stability as well as resistance to moisture and chemical substances,
• have suitable shades for subtractive color mixing,
• have a high molar absorption coefficient,
• do not crystallize when storing the transfer sheet,
• be technically easily accessible.

At the same time, these requirements are difficult to meet.

Therefore, most of the known dyes used for thermal transfer printing do not meet the required profile.

Dyes which are used in thermal transfer printing processes are already known from the prior art. For example, EP-A-216 483 or EP-A-258 856 describes azo dyes which have diazo components based on thiophene and coupling components based on aniline.

Furthermore, disazo dyes based on thiophene and aniline are known from EP-A-218 937 for this purpose.

In addition, EP-A-302 682 teaches the thermal transfer of azo dyes which are derived from 2-aminothiophenes which have a condensed carbonyl group in ring position 5.

The object of the present invention was to provide a method for transferring azo dyes, the dyes being intended to meet the above-mentioned requirements as well as possible.

befinden, in der
X
Stickstoff oder den Rest C-CN
Z
Sauerstoff oder den Rest -CH(R⁷)-, wobei R⁷ für Wasserstoff oder C₁-C₄-Alkyl steht,
R¹
Alkyl, Alkanoyloxylalkyl, Alkoxycarbonyloxyalkyl oder Alkoxycarbonylalkyl, wobei diese Reste jeweils bis zu 15 Kohlenstoffatomen aufweisen und durch Phenyl, C₁-C₄-Alkylphenyl, C₁-C₄-Alkoxyphenyl, Halogenphenyl, Benzyloxy, C₁-C₄-Alkylbenzyloxy, C₁-C₄-Alkoxybenzyloxy, Halogen, Hydroxy oder Cyano substituiert sein können, Wasserstoff, gegebenenfalls durch
C₁-C₁₅-Alkyl, C₁-C₁₅-Alkoxy oder Halogen substituiertes Phenyl oder einen Rest der Formel II

worin

Y

für C₂-C₆-Alkylen,

m

für 1, 2, 3, 4, 5 oder 6 und

R⁸

für C₁-C₄-Alkyl oder gegebenenfalls durch C₁-C₄-Alkyl oder C₁-C₄-Alkoxy substituiertes Phenyl stehen,

R² und R³
gleich oder verschieden sind und unabhängig voneinander jeweils Wasserstoff oder C₁-C₄-Alkyl,
R⁴
Wasserstoff, C₁-C₁₀-Alkyl, C₁-C₁₀-Alkoxy oder den Rest -NH-COR² oder -NHSO₂R⁸, wobei R² und R⁸ jeweils die obengenannte Bedeutung besitzen,
R⁵
Wasserstoff, Chlor, C₁-C₄-Alkyl, C₁-C₄-Alkoxy, C₁-C₄-Alkylthio oder gegebenenfalls durch C₁-C₄-Alkyl, C₁-C₄-Alkoxy oder Halogen substituiertes Phenyl und
R⁶
Cyano oder den Rest -CO-OR¹, -CO-NHR¹ oder -CO-N(R¹)₂ bedeuten, wobei R¹ jeweils die obengenannte Bedeutung besitzt.It has now been found that the transfer of azo dyes from a support to a plastic-coated paper by diffusion using an energy source is advantageously achieved when using a support on which one or more azo dyes of the formula I

are in the
X
Nitrogen or the rest C-CN
Z
Oxygen or the radical -CH (R⁷) -, where R⁷ is hydrogen or C₁-C₄-alkyl,
R¹
Alkyl, alkanoyloxylalkyl, alkoxycarbonyloxyalkyl or alkoxycarbonylalkyl, these radicals each having up to 15 carbon atoms and by phenyl, C₁-C₄-alkylphenyl, C₁-C₄-alkoxyphenyl, halophenyl, benzyloxy, C₁-C₄-alkylbenzyloxy, C₁-C₄-alkoxybenzyloxy, halogen , Hydroxy or Cyano can be substituted, hydrogen, optionally by
C₁-C₁₅ alkyl, C₁-C₁₅ alkoxy or halogen substituted phenyl or a radical of the formula II

wherein

Y

for C₂-C₆ alkylene,

m

for 1, 2, 3, 4, 5 or 6 and

R⁸

represent C₁-C₄-alkyl or phenyl optionally substituted by C₁-C₄-alkyl or C₁-C₄-alkoxy,

R² and R³
are identical or different and are each independently hydrogen or C₁-C₄alkyl,
R⁴
Is hydrogen, C₁-C₁₀ alkyl, C₁-C₁₀ alkoxy or the radical -NH-COR² or -NHSO₂R⁸, where R² and R⁸ each have the abovementioned meaning,
R⁵
Hydrogen, chlorine, C₁-C₄-alkyl, C₁-C₄-alkoxy, C₁-C₄-alkylthio or optionally substituted by C₁-C₄-alkyl, C₁-C₄-alkoxy or halogen and phenyl
R⁶
Cyano or the radical -CO-OR¹, -CO-NHR¹ or -CO-N (R¹) ₂ mean, where R¹ each has the meaning given above.

All alkyl and alkylene radicals occurring in the above-mentioned formula I can be either straight-chain or branched.

Residues Y in formula I are e.g. Ethylene, 1,2- or 1,3-propylene, 1,2-, 1,3-, 1,4- or 2,3-butylene, pentamethylene, hexamethylene or 2-methylpentamethylene.

Suitable radicals R¹, R², R³, R⁴, R⁵ and R⁷ in formula I are e.g. Methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl or tert-butyl.

R¹ and R⁴ are furthermore, for example pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, 2-methylpentyl, heptyl, octyl, 2-ethylhexyl, isooctyl, nonyl, isononyl, decyl or isodecyl.

3-Hydroxybutyl, 3-Hydroxyheptyl, 10-Hydroxy-1-ethyldecyl, 2-Cyanoethyl, 3-Cyanopropyl, 3-Cyano-2-methylpentyl, 7-Cyanononyl, 7-Cyano-4-methyloctyl, 5-Chlorpentyl, 4-Chlor-1-butylbutyl, 5,5,5-Trifluorpentyl,

Phenyl, 2-Methylphenyl, 4-Butoxyphenyl, 4-Undecylphenyl, 4-Chlorphenyl,

Residues R¹ are, for example, undecyl, dodecyl, tridecyl, isotridecyl (the names isooctyl, isononyl, isodecyl and isotridecyl are trivial names and come from the alcohols obtained after oxosynthesis - see also Ullmann's Encyclopedia of Industrial Chemistry, 4th edition, volume 7 , Pages 215 to 217 and volume 11, pages 435 and 436) tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, benzyl, 1- or 2-phenylethyl,

3-hydroxybutyl, 3-hydroxyheptyl, 10-hydroxy-1-ethyldecyl, 2-cyanoethyl, 3-cyanopropyl, 3-cyano-2-methylpentyl, 7-cyanononyl, 7-cyano-4-methyloctyl, 5-chloropentyl, 4- Chloro-1-butylbutyl, 5,5,5-trifluoropentyl,

Phenyl, 2-methylphenyl, 4-butoxyphenyl, 4-undecylphenyl, 4-chlorophenyl,

R⁴ and R⁵ are also, for example methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy or sec-butoxy.

Residues R⁴ are still e.g. Pentyloxy, isopentyloxy, neopentyloxy, hexyloxy, heptyloxy, octyloxy, 2-ethylhexyloxy, nonyloxy or decyloxy.

Residues R⁵ are still e.g. Methylthio, ethylthio, propylthio, isopropylthio or butylthio.

worin

Y

für C₂-C₄-Alkylen,

m

für 1, 2, 3 oder 4 und

R⁸

für C₁-C₄-Alkyl oder gegebenenfalls durch C₁-C₄-Alkyl oder C₁-C₄-Alkoxy substituiertes Phenyl stehen,

R⁴
Wasserstoff, C₁-C₆-Alkyl, C₁-C₆-Alkoxy oder den Rest -NH-COR² oder -NHSO₂R⁸, wobei R² und R⁸ jeweils die obengenannte Bedeutung besitzen,
R⁵
Wasserstoff, Chlor, C₁-C₄-Alkyl, C₁-C₄-Alkoxy oder Phenyl und
R⁶
Cyano oder den Rest -CO-OR¹, -CO-NHR¹ oder -CO-N(R¹)₂ bedeuten, wobei R¹ jeweils die zuletztgenannte Bedeutung von R¹ besitzt.The process according to the invention is preferred if one uses a carrier on which there are one or more azo dyes of the formula I in which
R¹
Alkyl, alkanoloxyalkyl or alkyloxycarbonylalkyl, where these radicals each have up to 12 carbon atoms and can be substituted by hydroxy or cyano, or a radical of the formula II

wherein

Y

for C₂-C₄ alkylene,

m

for 1, 2, 3 or 4 and

R⁸

represent C₁-C₄-alkyl or phenyl optionally substituted by C₁-C₄-alkyl or C₁-C₄-alkoxy,

R⁴
Is hydrogen, C₁-C₆-alkyl, C₁-C₆-alkoxy or the radical -NH-COR² or -NHSO₂R⁸, where R² and R⁸ each have the abovementioned meaning,
R⁵
Hydrogen, chlorine, C₁-C₄-alkyl, C₁-C₄-alkoxy or phenyl and
R⁶
Cyano or the radical -CO-OR¹, -CO-NHR¹ or -CO-N (R¹) ₂ mean, where R¹ has the latter meaning of R¹.

befinden, in der
X
Stickstoff oder den Rest C-CN,
R¹
C₁-C₆-Alkyl oder einen Rest der Formel III

worin

n

für 1 oder 2 und

R⁸

für C₁-C₄-Alkyl stehen,

R⁴
Wasserstoff, Methyl, Methoxy oder C₂-C₅-Alkanoylamino und
R⁶
Cyano oder den Rest -CO-OR¹ bedeuten, wobei R¹ die zuletztgenannte Bedeutung besitzt.The new process is particularly preferred if one uses a carrier on which one or more azo dyes of the formula Ia

are in the
X
Nitrogen or the rest C-CN,
R¹
C₁-C₆ alkyl or a radical of formula III

wherein

n

for 1 or 2 and

R⁸

represent C₁-C₄-alkyl,

R⁴
Hydrogen, methyl, methoxy or C₂-C₅ alkanoylamino and
R⁶
Cyano or the radical -CO-OR¹ mean, wherein R¹ has the latter meaning.

The dyes of the formula I are known from EP-A-201 896 or can be obtained by the methods mentioned there.

Compared to the dyes used in the known processes, the dyes transferred in the process according to the invention are generally distinguished by improved migration properties in the recording medium at room temperature, easier thermal transferability, higher photochemical stability, easier technical accessibility, better resistance to moisture and chemical substances, higher color strength , better solubility, higher color purity and higher thermal stability.

It is also surprising that the dyes of the formula I are readily transferable, even though they have a relatively high molecular weight.

To prepare the dye carriers required for the process, the dyes are in a suitable organic solvent, for example chlorobenzene, isobutanol, methyl ethyl ketone, methylene chloride, toluene, tetrahydrofuran or mixtures thereof, processed with one or more binders, optionally with the addition of auxiliaries, to form a printing ink. This contains the dye preferably in a molecularly dispersed, dissolved form. The printing ink can be applied to the inert support using a doctor blade and the dyeing can be dried in air.

All resins or polymer materials which are soluble in organic solvents and are capable of binding the dye to the inert support in an abrasion-resistant manner are suitable as binders. Preference is given to binders which, after the printing ink has dried in air, absorb the dye in the form of a clear, transparent film without the dye crystallizing out visibly.

Examples of such binders are cellulose derivatives, e.g. Methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, hydroxypropyl cellulose, cellulose acetate or cellulose acetobutyrate, starch, alginates, alkyd resin, vinyl resin, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyrate or polyvinyl pyrrolidone. Polymers and copolymers of acrylates or their derivatives, such as polyacrylic acid, polymethyl methacrylate or styrene-acrylate copolymers, polyester resins, polyamide resins, polyurethane resins or natural CH resins, such as gum arabic, are also suitable as binders. Other suitable binders are e.g. in DE-A-3 524 519.

Preferred binders are ethyl cellulose, ethyl hydroxyethyl cellulose or polyvinyl butyrate.

The ratio of binder to dye preferably varies between 5: 1 and 1: 1.

Auxiliaries, such as are specified in EP-A-227 092, EP-A-192 435 or the patent applications cited therein, are also suitable as auxiliaries, in addition, in particular, organic additives which cause the transfer dyes to crystallize out during storage and when the ink ribbon is heated prevent, e.g. Chlolesterol or vanillin.

Inert carriers are e.g. Tissue, blotting or glassine paper or plastic films with good heat resistance, e.g. optionally metal-coated polyester, polyamide or polyimide.

The inert carrier is optionally additionally coated with a slip layer on the side facing the thermal head in order to prevent the thermal head from sticking to the carrier material. Suitable lubricants are described, for example, in EP-A-216 483 or EP-A-227 095. The thickness of the dye carrier is generally 3 to 30 microns, preferably 5 to 10 microns.

In principle, all temperature-stable plastic layers with an affinity for the dyes to be transferred, whose glass transition temperature should be below 150 ° C, e.g. modified polycarbonates or polyester. Suitable formulations for the receiver layer composition are e.g. in EP-A-227 094, EP-A-133 012, EP-A-133 011, EP-A-111 004, JP-A-199 997/1986, JP-A-283 595/1986, JP- A-237 694/1986 or JP-A-127 392/1986 described in detail.

The transmission takes place by means of an energy source, e.g. by means of a laser or by means of a thermal head which must be able to be heated to a temperature of ≧ 300 ° C. so that the dye transfer can take place in the time range t: 0 <t <15 msec. The dye migrates from the transfer sheet and diffuses into the surface coating of the recording medium.

Further details of the preparation can be found in the following examples, in which information on percentages, unless stated otherwise, relates to the weight.

Transfer of the dyes

• A) Allgemeines Rezept für die Beschichtung der Träger mit Farbstoff: 1 g Bindemittel wurde in 8 ml Toluol/Ethanol (8:2 v/v) bei 40 bis 50 °C gelöst. Dazu wurde eine Lösung aus 0,25 g Farbstoff in 5 ml Tetrahydrofuran eingerührt. Die so erhaltene Druckpaste wurde mit einer 80 µm Rakel auf eine Polyesterfolie (Dicke: 6 bis 10 µm) abgezogen und mit einem Fön getrocknet.
• B) Prüfung auf thermische Transferierbarkeit
  Die verwendeten Farbstoffe wurden in der folgenden Weise geprüft:
  Die den zu prüfenden Farbstoff in der Beschichtungsmasse (Vorderseite) enthaltende Polyesterfolie (Geber) wurde mit der Vorderseite auf kommerziell erhältliches Hitachi Color Video Print Paper (Nehmer) gelegt und aufgedrückt. Geber/Nehmer wurden dann mit Aluminiumfolie umwickelt und zwischen zwei beheizten Platten bei verschiedener Temperatur T (im Temperaturintervall 70°C < T < 120°C) erhitzt. Die in die glänzende Kunststoffschicht des Nehmers diffundierte Farbstoffmenge ist proportional der optischen Dichte (= Extinktion A). Letztere wurde photometrisch bestimmt. Trägt man den Logarithmus der im Temperaturintervall zwischen 80 und 110°C gemessenen Extinktion A der angefärbten Nehmerpapiere gegen die zugehörige reziproke absolute Temperatur auf, so erhält man Geraden, aus deren Steigung die Aktivierungsenergie ΔE_T für das Transferexperiment berechnet wird:
  
  Zur vollständigen Charakterisierung wurde aus den Auftragungen zusätzlich die Temperatur T*[°C] entnommen, bei der die Extinktion A der angefärbten Nehmerpapiere den Wert 1 erreicht.
  Die in den folgenden Tabellen genannten Farbstoffe wurden nach A) verarbeitet und die erhaltenen, mit Farbstoff beschichteten Träger nach B) auf das Transferverhalten geprüft. In den Tabellen sind jeweils die Thermotransferparameter T* und ΔE_T, die Absorptionsmaxima der Farbstoffe λ_max (gemessen in Methylenchlorid) und die verwendeten Bindemittel aufgeführt.
  Dabei gelten folgende Abkürzungen:

  B =

  Bindemittel
  EC = Ethylcellulose
  MS = Mischung aus Polyvinylbutyrat:EC = 2:1
  V = Polyester

In order to be able to check the transfer behavior of the dyes quantitatively and easily, the thermal transfer was carried out with large-area heating jaws instead of a thermal head, the transfer temperature varying in the range from 70 ° C <T <120 ° C and the transfer time being set at 2 minutes.

• A) General recipe for coating the support with dye: 1 g of binder was dissolved in 8 ml of toluene / ethanol (8: 2 v / v) at 40 to 50 ° C. For this purpose, a solution of 0.25 g of dye was stirred into 5 ml of tetrahydrofuran. The printing paste thus obtained was drawn off onto a polyester film (thickness: 6 to 10 μm) using an 80 μm doctor blade and dried using a hairdryer.
• B) Testing for thermal transferability
  The dyes used were tested in the following way:
  The polyester film (donor) containing the dye to be tested in the coating material (front) was placed with the front on commercially available Hitachi Color Video Print Paper (recipient) and pressed. The encoder / receiver was then wrapped with aluminum foil and heated between two heated plates at different temperatures T (in the temperature interval 70 ° C <T <120 ° C). The amount of dye diffused into the glossy plastic layer of the receiver is proportional to the optical density (= extinction A). The latter was determined photometrically. If one plots the logarithm of the extinction A of the stained receiving paper measured in the temperature interval between 80 and 110 ° C against the associated reciprocal absolute temperature, straight lines are obtained, from whose slope the activation energy ΔE _{T is} calculated for the transfer experiment:
  
  For complete characterization, the temperature T * [° C] was additionally taken from the plots at which the extinction A of the colored receiving papers reached the value 1.
  The dyes mentioned in the following tables were processed according to A) and the resulting dye-coated carrier according to B) was tested for the transfer behavior. The tables show the thermal transfer parameters T * and ΔE _T , the absorption maxima of the dyes λ _max (measured in methylene chloride) and the binders used.
  The following abbreviations apply:

  B =

  binder
  EC = ethyl cellulose
  MS = mixture of polyvinyl butyrate: EC = 2: 1
  V = polyester

Claims (3)

Process for transferring azo dyes from a support to paper coated with plastic by diffusion with the aid of an energy source, characterized in that a support is used on which one or more azo dyes of the formula I

are in the
X
Nitrogen or the rest C-CN
Z
Oxygen or the radical -CH (R⁷) -, where R⁷ is hydrogen or C₁-C₄-alkyl,
R¹
Alkyl, alkanoyloxylalkyl, alkoxycarbonyloxyalkyl or alkoxycarbonylalkyl, these radicals each having up to 15 carbon atoms and by phenyl, C₁-C₄-alkylphenyl, C₁-C₄-alkoxyphenyl, halophenyl, benzyloxy, C₁-C₄-alkylbenzyloxy, C₁-C₄-alkoxybenzyloxy, halogen , Hydroxy or cyano may be substituted, hydrogen, phenyl optionally substituted by C₁-C₁₅ alkyl, C₁-C₁₅ alkoxy or halogen, or a radical of the formula II

wherein Y for C₂-C₆ alkylene, m for 1, 2, 3, 4, 5 or 6 and R⁸ is C₁-C₄-alkyl or phenyl optionally substituted by C₁-C₄-alkyl or C₁-C₄-alkoxy, R² and R³
are identical or different and are each independently hydrogen or C₁-C₄alkyl,
R⁴
Is hydrogen, C₁-C₁₀ alkyl, C₁-C₁₀ alkoxy or the radical -NH-COR² or -NHSO₂R⁸, where R² and R⁸ each have the abovementioned meaning,
R⁵
Hydrogen, chlorine, C₁-C₄-alkyl, C₁-C₄-alkoxy, C₁-C₄-alkylthio or optionally substituted by C₁-C₄-alkyl, C₁-C₄-alkoxy or halogen and phenyl
R⁶
Cyano or the radical -CO-OR¹, -CO-NHR¹ or -CO-N (R¹) ₂ mean, where R¹ each has the meaning given above. A method according to claim 1, characterized in that there are one or more azo dyes of the formula I in which
R¹
Alkyl, alkanoyloxyalkyl or alkyloxycarbonylalkyl, where these radicals each have up to 12 carbon atoms and can be substituted by hydroxy or cyano, or a radical of the formula II

wherein Y for C₂-C₄ alkylene, m for 1, 2, 3 or 4 and R⁸ is C₁-C₄-alkyl or phenyl optionally substituted by C₁-C₄-alkyl or C₁-C₄-alkoxy, R⁴
Is hydrogen, C₁-C₆-alkyl, C₁-C₆-alkoxy or the radical -NH-COR² or -NHSO₂R⁸, where R² and R⁸ each have the meaning given in claim 1,
R⁵
Hydrogen, chlorine, C₁-C₄-alkyl, C₁-C₄-alkoxy or phenyl and
R⁶
Cyano or the radical -CO-OR¹, -CO-NHR¹ or -CO-N (R¹) ₂ mean, where R¹ each has the meaning given above. Process according to claim 1, characterized in that one or more azo dyes of the formula Ia

are in the
X
Nitrogen or the rest C-CN,
R¹
C₁-C₆ alkyl or a radical of formula III

wherein n for 1 or 2 and R⁸ is C₁-C₄ alkyl, R⁴
Hydrogen, methyl, methoxy or C₂-C₅ alkanoylamino and
R⁶
Cyano or the radical -CO-OR¹ mean, wherein R¹ has the meaning given above.