Granted Patent B2

US 8,470,735 · App. 13/262,701 · Granted Jun 25, 2013

Abstract

Claims (13)

1. A coating solution for a thermosensitive color developing layer, which comprises a colorless or pale-colored electron-donating leuco dye, a hindered phenol compound and, as an electron-accepting developer, a diphenylsulfone derivative represented by the following formula (1):

wherein R 1 is a linear or branched, saturated or unsaturated hydrocarbon group having a carbon number of 1-12, R 2 -R 7 are each independently a halogen atom, or an alkyl group or alkenyl group having a carbon number of 1-12, n, o, p, q, r and s are each an integer of 0 -4, m is an integer of 0-5, and each A is independently a linear or branched, saturated or unsaturated hydrocarbon group having a carbon number of 1-12 and optionally having an ether bond, wherein the aforementioned hindered phenol compound has an average particle size (D50) of not more than 0.5 μm, and

the coating solution has a color tone a* of not less than −4.0 as measured according to JIS Z 8729 and a whiteness W of not less than 62 as measured according to JIS Z 8715.

2. The coating solution according to claim 1 , wherein the hindered phenol compound is a 1,1,3-tris-substituted butane compound represented by the following formula (2):

wherein R 8 , R 11 and R 14 are each independently an alkyl group having a carbon number of 1-8, and R 9 , R 10 , R 12 , R 13 , R 15 and R 16 are each independently a hydrogen atom or an alkyl group having a carbon number of 1-8.

3. The coating solution according to claim 2 , wherein, in the aforementioned formula (2), R 8 , R 11 and R 14 are tert-butyl groups, R 9 , R 12 and R 15 are methyl groups, and R 10 , R 13 and R 16 are hydrogen atoms.

4. The coating solution according to claim 2 , wherein the aforementioned 1,1,3-tris-substituted butane compound of the formula (2) has a crystal structure showing the maximum diffracted X-ray peak within the range of diffraction angle (2θ)=6.4°-6.6°, a second maximum diffracted X-ray peak within the range of one of (2θ)=13.0°-13.2° and (2θ)=19.6°-19.8°, and a third maximum diffracted X-ray peak within the other range, in an X-ray diffraction measurement using CuKαray as an X-ray source.

5. The coating solution according to claim 2 , wherein the aforementioned 1,1,3-tris-substituted butane compound of the formula (2) is an amorphous hindered phenol compound.

6. The coating solution according to claim 1 , wherein the content of the hindered phenol compound is 0.01 part by weight-10 parts by weight, per 1 part by weight of the diphenylsulfone derivative represented by the formula (1).

7. The coating solution according to claim 1 , wherein the aforementioned diphenylsulfone derivative represented by the formula (1) has an average particle size of 0.5 μm-5 μm.

8. The coating solution according to claim 1 , which is prepared using a dispersion obtained by heating a dispersion containing the aforementioned diphenylsulfone derivative represented by the formula (1) at 40° C.-80° C. for 6 hr-72 hr.

9. A thermal recording material comprising a support and a thermosensitive color developing layer formed thereon, wherein the thermosensitive color developing layer is formed with the coating solution according to claim 1 .

10. The thermal recording material according to claim 9 , further comprising a protection layer comprising carboxy-modified polyvinyl alcohol, epichlorohydrin resin and polyamine resin/polyamide resin on the thermosensitive color developing layer.

Assignments (8)