JPS6348385A - Material for positive thermography - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to thermographic materials, particularly tenon type materials. This means that such materials are dark or colored before exposure to heat and become colorless or at least lightened when heat is applied.

Technical Background Thermal image forming sheets are used for copying, thermal print pufferfish,
It has been used for thermal recording and thermal labeling. Many of these materials involve thermally increasing the reactivity of two or more components of the color-forming reaction system that do not react at normal temperatures. Reactivity is often enhanced by melting one or both of the reactants that are physically separated from each other. This separation is usually accomplished either by dispersing it in a single coating layer or by placing it in two separate coating layers. Several general classes of chromogenic reactants have been used, two of which are commonly used: a) leuco dyes or spiro2lan compounds capable of reacting with phenolic compounds (e.g., U.S. Pat. No. 3,829; No. 401 and No. 3
, 846,153); b) heavy metal salts of organic acids capable of reacting with the ligand to give colored complexes (e.g., U.S. Pat. Nos. 2.666.654, 3,094,620);
No. 6,296,055, and No. 3,955.6
No. 59).

The transition metal salt class is often preferred commercially because of the thermal stability and near-black color of the resulting images (US Pat. No. 4,531,141). Among the transition metals used, iron, nickel, and cobalt are universally used, and ferric ion appears to be one of the most preferred (U.S. Pat. Nos. 2.666.654 and 3,953,659). No. 4,531,141).

No documentation has been found in the literature regarding thermographic systems with positive working as defined above. Such systems require normally black or deeply colored sheets that become virtually colorless upon exposure to heat.

Although there are many black complexes of iron, they generally do not readily react to become colorless under heat or other stimuli. U.S. Pat. No. 4,533,930 teaches that ferric organothiophosphates, ornotiophosphinates, and organothiophosphonates react with chelating agents to give different colors, usually darker colors. Disclosed. In fact, many of these thiomaterials are themselves essentially black.

The present invention shows how such black thio compounds can be used in the production of positive-working thermographic materials.

SUMMARY OF THE INVENTION The present invention provides (a) dark-colored complexes of ferric iron with ligands selected from organothiophosphates, or-notiophosphinates, and organothiophosphonates; and (b) organophosphates, organophosphines. A tenon-type imaging material is provided which comprises a clear binder in which an acid component selected from acids and organophosphonic acids is dispersed or dissolved. The acid component is derived from the free acid or its salt.

One aspect of the present invention is to provide a thermographic material that responds to heat to provide a colorless image on a dark or black background.

In the detailed description of the invention, formula (I) Fe[82P(OR)2]3' Fe(82FOR)3 R(1) Fe[:82PR2]3 [wherein the two R substituents are individually A ferric complex selected from alkyl, cycloalkyl, alkaryl, and aryl, and substituted versions of these components, provided that this substituent does not result in the formation of a chelating site. is under the influence of heat, the formula (■) M"(-oop(oR')2) M"lnee00PR') R/ (U a )
PR' 2:I M+ (-〇0F(OR')〇-]M+M"(-00P
R'O-:)M+ [wherein the R' substituents are individually alkyl, cycloalkyl, alkaryl, and aryl, as well as substituted versions of these substituents, provided that they ), and M is selected from H, N)(, , Na, and K),
or M"(-00P(OR')2)2 M"[knee00FOR':]2 R'(ffb)M"(-
00PR'2] 2 M"("-00P(OR')O-) M"(-00PR'O-) [where R' is as above and M is selected from Ca and J ] or a salt thereof.

Reactants (1) and (II) may be dispersed as discrete microparticles in a binder and coated as a thin layer on the support, or may be dispersed in separate adjacent layers, or the compounds ( Either I) or (') may be in a solid state in a layer of binder, and the other compound may also be contained in the form of microparticles, or compound (1) and (ff) are in the same layer in solid solution or are adjacent to each other, jj
It may be inside. When heated, metathesis occurs, for example as follows: FeCzP(Ou)2]s+a-(:oopu'
1Fe(OOPR' 2)a+H-(82P(OR)2
:) The factors favoring the progress of this reaction are as follows: a) The oxygen donor is harder than the sulfur donor towards Fe+++ (does not give up electrons easily), which means that the iron complex b) the pKa of the phosphate etc. being lower than the pKa of the thio equivalent also induces replacement of the thio acid component by the oxygen equivalent; C) Oligomeric iron complexes composed of oxygen analogs are relatively inert and drive the reaction forward.

In the selection of R substituents for the thio component when M is H, lower alkyl groups are least preferred because the free acid produced under the influence of heat is volatile and has an unacceptable odor.

In both (1) and (II), tri-substituted variants of the acid component are not effective by themselves in the present invention because they are highly susceptible to hydrolysis and are unstable under normal atmospheric conditions.

The ferric complex of formula (1) may be produced by reacting an aqueous solution of a thioorganophosphorus acid with an aqueous solution of a ferric salt of a strong acid (preferably nitric acid) under acidic conditions. instead,
The two reactants may be dissolved in glacial acetic acid for the reaction.

This - tends to reduce nitric acid production during the reaction, which in turn results in the production of ferrous ions; this slowly begins to catalyze the reaction that reduces the counter ion NO3- to N02/N2O4, producing undesirable reaction products. Rapid reactions (reaction times less than 30 minutes), ammonium salts of organothiophosphorus acids, or the addition of sodium acetate which reacts with nitric acid prevent this problem from occurring.

Suitable binders for the present invention are acrylic polymers such as acrylates, methacrylates and copolymers thereof, vinyl resins, styrene resins, cellulose resins, polyester resins, urethanes, alkyl resins, silicones, and epoxy resins. - Generally, they must be miscible with non-aqueous solvents and have a melting point above the reaction temperature of the ferric complex with the organophosphorus acid or its salt.

A coating composition suitable for making thermal recording sheets can be prepared by dissolving the ferric complex (1) in a solvent such as acetone, methyl ethyl ketone, or ethanol, and adding a polymeric binder to this solution. The solution obtained is first coated onto a support by means of a wire-wound bar. The acid (II) is dissolved in a suitable solvent as described above and the polymeric binder is added and stirred until dissolved. This solution is then coated onto the first dry coating and dried. In some cases, the interlayer may be coated to reduce the reactivity at room temperature (by selecting reactants I and I to have low room temperature reactivity, or Both reactants can be dissolved in the same polymer layer by mixing and coating at a temperature of <). Alternatively, microparticles of the reactants dispersed in a solvent that does not dissolve the reactants can reduce the number of coating layers to one while reducing reactivity at room temperature.

The coatable composition coated onto a suitable substrate can be dried at a temperature below the thermal reaction temperature.

The substrates used are transparent, opalescent or opaque polymeric films, paper (which may optionally have a white or colored surface coating), glass, ceramic. Reaction temperature (preferably 60-200
0C, more preferably 80-150C) and must be stable and non-deformable.

Imaging using these materials can be accomplished by a variety of well-known thermal imaging techniques. These include the use of focused infrared rays, the use of a thermal printing spatula P, and the use of a method of uniformly irradiating the original document with infrared rays that are absorbed by the characters on the document in close contact with each other.

The invention will now be illustrated by examples.

Example 1 (Green-Black) Preparation of a colorless thermal imaging construct Fe (32P(-0
-ethyl)2]3[Fe(NO3)3.9H2 in acetic acid
0 and diethyldithiophosphate] was coated onto a polyester film with a wire-wound parr to a wet thickness of 1.4 mils and allowed to air dry. The upper surface of this coating was 1.5 g in 10 g of cell E in ethanol.
A 1.4 mil film of the solution of -dodecyl phosphate was coated. A coating with a reflective optical density of 1.9 was obtained. Thermal imaging resulted in a clear, virtually colorless image (reflection optical density 0.3).

Example 2 Reversing the layers of the coating of Example 1 resulted in a similarly functioning construct.

Coatings made as in Examples 1 or 2 using ethylphosphonic acid, phenylphosphonic acid, and phenylphosphonic acid gave images with lower coloration.

Claims (7)

[Claims] (1) a) a dark colored complex of ferric iron with a ligand selected from organothiophosphates, organothiophosphinates, and organothiophosphonates; and b) selected from organophosphates, organophosphinates, and organophosphonates. 1. A positive-working thermographic material having in thermographically reactive combination a source of a component selected from the group consisting of a free acid containing the component and a salt of the acid. (2) The dark colored complex has the general formula Fe[S_2P(OR)_2]_3 Fe[S_2POR]_3 and Fe[S_2PR_2]_3 [wherein the two R substituents are individually alkyl, cycloalkyl, alkyl aryl, and aryl, and substituted versions of the same, provided that the substituent does not result in the formation of a chelating moiety. A positive thermography material according to claim 1. (3) The source of the component is common M^+[^-OOP(OR')_2] M^+[^-OOPOR'] M^+[^-OOPR'] M^+[^-OOP (OR')O^-]M^+M^+[
-OOPR'O^-]M^+ [wherein the R' substituent is individually alkyl, cycloalkyl, alkaryl, and aryl, and substituted versions of these substituents (provided that the substituent is provided that no formation of chelating moieties occurs);
and M is selected from H, NH_4, Na, and K],
and M^+^+[^-OOP(OR')_2]_2▲ formula,
There are chemical formulas, tables, etc. ▼ M^+^+ [^-OOPR'_2]_2 M^+^+ [^-OOP(OR')O^-] M^+^+
[^-OOPR'O^-] wherein R' is as defined above and M is selected from Ca and Mg. type thermographic material. (4) The positive-working thermographic material according to claim 1, further comprising at least one binder in which the complex and the source are independently dissolved or dispersed. (5) A positive thermographic sheet, characterized in that one surface of a substrate is coated with at least one layer of the thermographic material according to claim 4. (6) The positive-working thermographic sheet according to claim 5, comprising a first layer containing the complex and a second layer containing the source of the component. (7) The positive thermography sheet according to claim 6, further comprising an intermediate layer made of a binder located between the first layer and the second layer.