FR2458397A1 - THERMOSENSIBLE RECORDING MATERIAL CONSISTING OF COLORLESS CHROMOGEN AND ELECTRON ABSORPTION SUBSTANCE, AND PROCESS FOR PREPARING THE SAME - Google Patents

Abstract

THE OBJECT OF THE INVENTION IS A THERMOSENSITIVE RECORDING MATERIAL AND A PROCESS FOR THE PRODUCTION OF SUCH MATERIAL. IT INCLUDES A SUPPORT SHEET COATED WITH A SENSITIVELY COLORLESS REACTIVE LAYER CONTAINING A CHROMOGENIC COMPOUND (FOR EXAMPLE CRYSTALLIZED PURPLE LACTONE) AND AN ELECTRON ABSORBING SUBSTANCE IN THE FORM OF A RESOL HAVING A MELTING POINT OF MORE THAN 250C; PREFERREDLY, RESOL IS A REACTION PRODUCT OF HEXAMETHYLENETETRAMINE AND 4,4-DIISOPROPYLIDENEDIPHENOL. THE RECORDING MATERIAL IS LIGHT RESISTANT AND IS NOT AFFECTED BY PLASTICIZERS USED IN OFFICE EQUIPMENT WITHOUT ADHESION TO HOT PEN OR THERMAL PRINTING HEAD DURING RECORDING.

Description

The present invention relates to a heat-sensitive material for recording

  for use in thermosensitive recording processes, including thermal printing in electronic calculators and electronic computer terminal equipment. The recording material comprises a base material coated with a colorless or substantially colorless reactive layer capable of producing a distinct color

  visible during heat marking.

  Reactive coatings containing a chromogenic compound are already known.

  colorless gene which, by reaction with an electron-absorbing substance, causes a visible color to appear. According to British Patent 1,135,540,

  a lactone of crystallized vinlet is used as the chromogenic compound

  colorless gene and a diphenol, a triphenol or a polymer thereof

  as an electron absorbing substance.

  These two reactive components are dispersed in a polyvinyl alcohol film. British Patent 1,479,542 describes chromogenic compounds containing a lactone, a lactam, a sultone or a spiropyran ring which can develop a visible color by

  reaction with an organic acid or a phenol when heating the product.

  It has been found that heat-sensitive recording materials using the above compounds nevertheless pose a number of stability problems, since neither the coating,

  neither the resulting thermal recording is light resistant.

  Already after two months, the coating undergoes an alteration of hue

  and the thermal markings show a clear reduction of the tests.

  Another problem with known recording materials is their sensitivity to plasticizers which are commonly used

  in office articles; for example transparent folders in chlo

  plasticized polyvinyl chloride may not be used as envelopes for such recording materials without the risk of

hue of these materials.

  The present invention solves the stated problems by using a resol as an electron absorbing compound. The colorless color-forming compound is selected from those commonly used for chemically reactive papers which contain, for example, a lactone or a spiropyran ring. A non-limiting example is a lactone of crystallized violet. The resol according to the invention has a melting point greater than 250 ° C and is ui. reaction product of hexamethylenetetramine and 4,4'-diisopropylidene diphenol. The high melt temperature of the resol removes all risks of hot stylus adhesion or thermal recording during recording, which is a well known problem if the recording material contains acids

  organic or phenols with low melting points.

  After preparation, the resonate is spray dried and then dispersed together with the chromogenic compound in an aqueous solution containing a water-soluble binder, such as carboxymethylcellulose.

(CMC) with addition of glyoxal.

  During the drying process, the glyoxal reacts with the CMC

  which makes the binder insoluble and resistant to moisture.

  To set the reaction temperature of the recording material

  the reactive coating according to the invention may also contain ingredients

  waxy materials with a melting point of 90 to 160 C. It has been found that

  fatty acid amide waxes are particularly suitable.

  For economic reasons, the thermally reactive coating can contain

  include fillers such as calcium carbonate, talc, starch,

  calcium stearate or another metal salt of fatty acid.

  It has also been found that a stabilizing action can be obtained

  analogous to the use of a resol according to the invention, based on hexagonal

  methylene tetramine and 4,4'-diisopropylidene diphenol, where the coating

  This reagent contains a salt of the above-mentioned chemical compounds.

  * 20 The following examples describe the preparation of the resol and the

  implementing the invention in a more complete manner. All proportion

tions are by weight.

EXAMPLE 1

  Preparation of Hexamethylenetetramine Resolve .................... 7, 4diisopropylidene-diphenol.20 Ethanol 90% ............. ................ 72 Sodium hydroxide. 1

_ _ _

  The components are di-isout in ethanol and then boiled

  under reflux for one hour. The resole formed by elutriation is purified.

  An even more pure solution can be achieved by recrystallization

in ethanol.

  The resol is finely ground in a disintegrator.

EXAMPLE 2

  Preparation of the thermoreactive coating

245839?

  A - Resol according to Example 1 ...... 13.5 Carboxymethylcellulose ....... 0.6 Calcium stearate .......... 3.5 Ethylene-bis-steamamide. ....... 8.0 Water ...

  ..................... 74.4 The ingredients are milled in a ball mill for four hours. B - Lactone of crystallized purple .....

43 Carboxymethylcellulose ............

2 Water ...............................

The ingredients are milled in a ball mill for four hours. 45 parts of mixture A, 2 parts of mixture B, 42 parts of 10% carboxymethylcellulose and 11 parts of glyoxal are mixed, then the composition is applied in the form of a coating to a suitable support, which can be paper weighing 50 g / m, in an amount to establish a solid layer of a thermoreactive coating weighing 4 to 9 g / m2 after evaporation of water in a DDD: heated drying chamber.

Claims (8)

  1. Heat-sensitive recording material comprising a sheet of   base, coated with a colorless or virtually colorless reactive layer   a colorless colorless compound and an electrolyte absorbing substance.   trons, said ingredients reacting under the action of heat to produce a visible color, characterized in that said electron-absorbing substance is a resol having a higher melting point; at 250 C.   2. Material according to claim 1, characterized in that the resolves   is a reaction product of hexamethylene tetramine and 4,4'diisopropyl-   lidenediphenyl, or a salt of such a reaction product.   3. Material according to claim 1 or 2, characterized in that the chromogenic compound is chosen from those normally used in thermosensitive recording materials, for example those containing a lactone or a spiropyran ring, for example a lactone of crystallized violet.   4. Material according to any one of claims 1 to 3,   characterized in that the base sheet coating also comprises   waxy ingredients with a melting point of 90 to 160 C.   5. Material according to claim 4, characterized in that the ingredient   The waxy fiber is selected from fatty acid amides.   6. Process for the preparation of a heat-sensitive recording material   as defined in any one of claims 1 to 5,   characterized in that the resol and the chromogenic compound are applied to the base sheet in the form of an aqueous dispersion containing a water-soluble binder. 7. Method according to claim 6, characterized in that the   water-soluble binder is a carboxymethylcellulose supplemented with glyoxal.   8. Process according to claim 6 or 7, characterized in that the resol and the chromogenic compound are dispersed separately in water containing carboxymethylcellulose, and then the two are mixed together. dispersions as well as glyoxal.