Abstract Disclosed is a heat-sensitive recording material useful in the manufacture of thermal paper and thermal labels. The material comprises a cellulosic or other suitable substrate, a thermally imprintable color-producing layer, and a protective layer over the color-producing layer. It may also include a second protective layer and/or a pressure-sensitive adhesive layer, on the surface of the substrate opposite from the color-producing layer, and a releasable liner covering the adhesive layer. The color-producing layer includes a basic, acid-neutralizing agent for both reducing background discoloration during manufacturing and increasing image definition. The protective layer comprises a polymeric binder which is both ionically and covalently cross-linked to provide improved resistance to hydrophobic and hydrophillic solvents.
A protective coating composition for deposit on thermally sensitive marking material comprising water and the following ingredients in the following parts by weight: ______________________________________
Ingredient Parts by Weight
______________________________________
A covalently and ionically
100
cross-linkable organic, water
soluble resin
covalent cross-linking agent
15 to 30
ionic cross-linking agent
0.1 to 0.4
organic acid catalyst
15 to 25
inert filler particles
50 to 100
surfactant 0.05 to 0.25,
______________________________________ said composition forming a protective layer which is covalently and ionically cross-linked throughout its thickness and which imparts to the marking material resistance to background discoloration and fading on exposure to solvents.
Claim 2
Dependent Claim
100 words
A protective coating composition for deposit on thermally sensitive marking material comprising water and the following ingredients in the following parts by weight: ______________________________________
Ingredient Parts by Weight
______________________________________
A covalently and ionically
100
cross-linkable organic, water
soluble resin
covalent cross-linking agent
15 to 30
ionic cross-linking agent
0.1 to 0.4
organic acid catalyst
15 to 25
inert filler particles
50 to 100
surfactant 0.05 to 0.25,
______________________________________ said composition forming a protective layer which is covalently and ionically cross-linked throughout its thickness and which imparts to the marking material resistance to background discoloration and fading on exposure to solvents.
Claim 3
Dependent Claim
31 words
The composition of claim 1 wherein said organic, water soluble resin comprises a carboxylated polyvinyl alcohol, said covalent cross-linking agent comprises melamine formaldehyde and said ionic cross-linking agent comprises aluminum sulfate.
Claim 4
Dependent Claim
29 words
The composition of claim 1 wherein said organic acid catalyst is selected from the group consisting essentially of fumaric acid, malonic acid, tartaric acid, maleic acid and diglycolic acid.