Thermally developable materials with abrasion-resistant backside coatings
View Patent ↗Thermally developable materials including photothermographic and thermographic materials have an outermost backside layer that includes a combination of a polysiloxane and a smectite clay that has been modified with a quaternary ammonium compound. The resulting outermost backside layers exhibit improved abrasion resistance. The materials can also include conductive layers underneath the outermost backside layer.
1. A thermally developable material that comprises a support having on one side thereof, one or more thermally developable imaging layers comprising a binder and in reactive association, a non-photosensitive source of reducible silver ions, and a reducing agent composition for said non-photosensitive source reducible silver ions, and
having disposed on the backside of said support, an outermost backside layer comprising one or more binder polymers, a polysiloxane, and a smectite clay that has been modified with a quaternary ammonium compound, and
said material further comprising a buried backside conductive layer underneath said outermost backside layer.
2. The material of claim 1 said outermost backside layer further comprising amorphous silica particles.
3. The material of claim 2 wherein the standard deviation divided by the mean volume diameter of said amorphous silica particles is less than 0.28.
4. The thermally developable material of claim 2 wherein the mean volume diameter of said amorphous silica particles is at least 3 μm greater than the dry thickness of said outermost backside layer.
5. The thermally developable material of claim 2 wherein said outermost backside layer has a dry thickness of from about 2 to about 2.5 μm and the mean volume diameter of said amorphous silica particles is from about 7 to about 9.5 μm with a standard deviation of less than 2.2 μm.
6. The thermally developable material of claim 2 wherein said silica particles are present in said outermost backside layer in an amount of from about 20 to about 100 mg/m 2 .
7. The material of claim 1 wherein said outermost backside layer comprises a polyvinyl acetal or cellulosic polymer as a binder.
8. The material of claim 1 wherein said outermost backside layer has a dry thickness of from about 1 to about 3 μm.
9. The material of claim 1 wherein said backside conductive layer comprises a metal oxide that is present in said backside conductive layer in an amount of from about 0.05 to about 1 g/m 2 distributed within one or more binder polymers that are present in an amount of from about 15 to about 60 weight %.
10. The material of claim 1 wherein said backside conductive layer has a dry thickness of from about 0.05 to about 1.1 μM.
11. The material of claim 1 wherein said backside conductive layer and said outermost backside layer have been formulated in organic solvents and have been simultaneously coated.
12. The material of claim 1 wherein said outermost backside layer comprises a cellulosic ester polymer and said backside conductive layer comprises a single phase mixture of a polyester and a polyvinyl acetal or a cellulose ester.
13. The material of claim 1 wherein said polysiloxane is present in said outermost layer an amount of about 4 to about 6 weight %.
14. The material of claim 1 wherein said polysiloxane has the following Structure (I):
wherein one or more of the terminal groups of said polysiloxane is methyl or alkylamino.
15. The material of claim 1 wherein the siloxane chain of said polysiloxane contains diphenyl, phenylmethyl, dimethyl, a mixture of phenylmethyl and dimethyl groups, or a mixture of (epoxycyclohexylethyl)methyl and dimethyl groups.
16. The material of claim 1 wherein said non-photosensitive source of reducible silver ions is a silver salt of an aliphatic carboxylic acid or a mixture of silver salts of aliphatic carboxylic acids, at least one of which is silver behenate.
17. The material of claim 1 that is a non-photosensitive thermographic material.
18. The material of claim 1 that is a photothermographic material further comprising a photosensitive silver halide.
19. A black-and-white photothermographic material that comprises a support having on one side thereof, one or more thermally developable imaging layers comprising a binder and in reactive association, a preformed photosensitive silver halide, a non-photosensitive source of reducible silver ions that comprises silver behenate, and a reducing agent composition for said non-photosensitive source reducible silver ions that comprises a hindered phenol, and
having disposed on the backside of said support, a simultaneously coated outermost backside layer and a non-imaging backside conductive layer:
a) said outermost backside layer comprising a film-forming polymer, a polysiloxane, a smectite clay that has been modified with a quaternary ammonium compound, and amorphous silica particles, and
b) said non-imaging backside conductive layer being interposed between and directly adhering said support to said outermost backside layer, said non-imaging backside conductive layer comprising a mixture of two or more polymers that include a first polymer serving to promote adhesion of said backside conductive layer directly to said support, and a second polymer that is different than and forms a single phase mixture with said first polymer, wherein:
1) said backside conductive layer has a water electrode resistivity measured at 21.1° C. and 50% relative humidity of 1×10 12 ohms/sq or less,
2) the total amount of mixture of two or more polymers in said backside conductive layer is at least 15 weight %,
3) said backside conductive layer comprises a conductive non-acicular zinc antimonate,
4) said film-forming polymer of said outermost backside layer is a cellulose acetate butyrate, said second polymer of said backside conductive layer is a cellulose acetate butyrate, and said first polymer is a polyester,
5) said amorphous silica particles are present in an amount of from about 30 to about 70 mg/m 2 of said outermost backside layer,
6) said outermost backside layer has a dry thickness of from about 1 to about 3 μm,
7) the mean volume diameter of said amorphous silica particles is from about 7 to about 9.5 μm with a standard deviation of less than 2.2 μm,
8) said amorphous silica particles extend at least 5 μm above the surface of said dried outermost backside layer,
9) said backside conductive layer has a dry thickness of from about 0.10 to about 0.3 μm, and
10) said polysiloxane chain of said polysiloxane contains diphenyl, phenylmethyl, dimethyl, a mixture of phenylmethyl and dimethyl groups, or a mixture of (epoxycyclohexylethyl)methyl and dimethyl groups.
20. A method of forming a visible image comprising:
(A) imagewise exposing the material of claim 1 that is a photothermographic material to electromagnetic radiation to form a latent image,
(B) simultaneously or sequentially, heating said exposed photothermographic material to develop said latent image into a visible image.
21. The material of claim 7 wherein said polysiloxane is present in an amount of from about 1.5 to about 6% based on the total dry weight of said polyvinyl acetal or cellulosic polymer binder.
22. The material of claim 7 wherein said cellulosic polymer binder is cellulose acetate butyrate and said polysiloxane is present in an amount of from about 1.5 to about 6% based on the total dry weight of said cellulose acetate butyrate binder.