Thermosensitive recording sheet

Claim 2

A thermosensitive recording sheet, comprising: a support material; a thermosensitive coloring layer formed on said support material, said thermosensitive coloring layer comprising a colorless or light-colored leuco dye, and an acidic material which develops color in said leuco dye upon application of heat to said thermosensitive coloring layer; and a protective layer formed on said thermosensitive coloring layer, said protective layer comprising a water-soluble polymeric binder and silica powder having an oil absorption of 150% or higher and a bulk density of 5 ml/g or higher, as measured in accordance with Japanese Industrial Standard K 5101.

Claim 3

A thermosensitive recording sheet as claimed in claim 1, wherein the amount of said water-soluble binder agent in said protective layer is in the range of 30 wt. % to 90 wt. % of the total weight of said protective layer, the amount of said silica powder is in the range of 70 wt. % to 10 wt. % of the total weight of said protective layer, and the coating amount of said protective layer is in the range of 1 g/m 2 to 6 g/m 2 .

Claim 4

A thermosensitive recording sheet as claimed in claim 1, wherein said protective layer further comprises a thermo-fusible material in an amount of not more than 20 wt. % of the total weight of said protective layer.

Claim 5

A thermosensitive recording sheet as claimed in claim 3, wherein said thermo-fusible material is selected from the group consisting of higher fatty acid amides; higher fatty acid metallic salts; animal waxes and vegetable waxes; and petroleum waxes.

Claim 6

A thermosensitive recording sheet as claimed in claim 1, wherein said protective layer further comprises an aqueous emulsion of a member selected from the group consisting of styrene-butadiene latex, styrene-acrylic acid ester and vinyl acetate, in an amount of not more than 20 wt. % of the total weight of said protective layer.

Claim 7

A thermosensitive recording sheet as claimed in claim 1, wherein said thermosensitive coloring layer further comprises a filler and a binder agent, the amount of said filler is not more than 3 times by weight the amount of said leuco dye, and the amount of said binder agent is in the range of 3 wt. % to 10 wt. % of the total weight of said thermosensitive coloring layer.

Claim 8

A thermonsensitive recording sheet as claimed in claim 6, wherein said filler in said thermosensitive coloring layer is selected from the group consisting of calcium carbonate, clay, talc, silica, polystyrene and urea-formaldehyde resin.

Claim 9

A thermonsensitive recording sheet as claimed in claim 6, wherein said binder agent in said thermosensitive coloring layer is selected from the group consisting of polyvinyl alcohol, cellulose ether, starch, ammonium polycarboxylates, and alkaline salts of isobutylene-maleic anhydride copolymer; and aqueous emulsions of styrene-butadiene latex, styrene-acrylic acid ester, and vinyl acetate.

Claim 10

A thermosensitive recording sheet as claimed in claim 1, wherein the amount of said acidic material is in the range of 2 to 6 times by weight the amount of said leuco dye in said thermosensitive coloring layer.

Claim 11

A thermosensitive recording sheet as claimed in claim 1, wherein said colorless or light-colored leuco dye is selected from the group consisting of triphenylmethane-type leuco compounds, fluoran-type leuco compounds, phenolthiazine-type leuco compounds, auramine-type leuco compounds and spiropyran-type leuco compounds.

Claim 12

A thermosensitive recording sheet as claimed in claim 1, wherein said acidic material is selected from the group consisting of organic acids and polyvalent metallic salts of organic carboxylic acids.

Claim 13

A thermosensitive recording sheet as claimed in claim 1, wherein said thermosensitive coloring layer further comprises a thermo-fusible material for decreasing the melting point of said leuco dye, said acidic material, or both.

Claim 14

A thermosensitive recording sheet as claimed in claim 12, wherein said thermo-fusible material is selected from the group consisting of higher fatty acid amides, higher fatty acid metallic salts; animal waxes and vegetable waxes; and petroleum waxes.

Claim 15

A thermosensitive recording sheet as claimed in claim 2, wherein said water-soluble binder is selected from the group consisting of polyvinyl alcohol, cellulose ethers, starch, ammonium carboxylates and alkali salts of isobutylene-maleic anhydride.

Claim 16

A thermosensitive recording sheet, comprising: a support material; a thermosensitive coloring layer formed on said support material, said thermosensitive coloring layer consisting essentially of an amount of a colorless or light-colored leuco dye effective to form a colored image on said coloring layer, said leuco dye being selected from the group consisting of triphenylmethane, fluoran, phenothiazine, auramine and spiropyran-type leuco compounds, and an amount by weight of an acidic material in the range of from 2 to 6 times the amount of weight of said leuco dye, said acidic material being effective to develop color in said leuco dye upon application of heat to said thermosensitive coloring layer, said acidic material being an organic acid or polyvalent metallic salt of an organic carboxylic acid; and a protective layer formed on said thermosensitve coloring layer, said protective layer consisting essentially of 30 to 90 wt. % of a water-soluble polymeric binder, and 70 to 10 wt. % of silica powder having (1) a bulk density of 5 ml/g or higher as measured by filling a 30 ml sample receiver with said silica powder, measuring the weight F in grams of silica powder contained in said sample receiver, and then determining the bulk density E according to the formula E=30/F, said silica powder also having (2) an oil absorption percent amount G of 150% or higher as measured by adding boiled linseed oil dropwise to a sample of said silica powder on a glass plate while kneading the resulting mixture until the sample becomes putty-like and can be rolled up in a spiral shape, then measuring the amount H of oil added, in ml, and determining the oil absorption G according to the formula G=(H/S)×100, wherein S is the weight of said sample, said protective layer having an amount of coated solids in the range of 1 to 6 g/m 2 .

Claim 17

A thermosensitive recording sheet, comprising: a support material; a thermosensitive coloring layer formed on said support material, said thermosensitive coloring layer consisting essentially of an amount of a colorless or light-colored leuco dye effective to form a colored image on said coloring layer, said leuco dye being selected from the group consisting of triphenylmethane, fluoran, phenothiazine, auramine and spiropyran-type leuco compounds, and an amount by weight of an acidic material in the range of from 2 to 6 times the amount of weight of said leuco dye, said acidic material being effective to develop color in said leuco dye upon application of heat to said thermosensitive coloring layer, said acidic material being an organic acid or polyvalent metallic salt of an organic carboxylic acid; and a protective layer formed on said thermosensitve coloring layer, said protective layer consisting essentially of 30 to 90 wt. % of a water-soluble polymeric binder, and 70 to 10 wt. % of silica powder having (1) a bulk density of 5 ml/g or higher as measured by filling a 30 ml sample receiver with said silica powder, measuring the weight F in grams of silica powder contained in said sample receiver, and then determining the bulk density E according to the formula E=30/F, said silica powder also having (2) an oil absorption percent amount G of 150% or higher as measured by adding boiled linseed oil dropwise to a sample of said silica powder on a glass plate while kneading the resulting mixture until the sample becomes putty-like and can be rolled up in a spiral shape, then measuring the amount H of oil added, in ml, and determining the oil absorption G according to the formula G=(H/S)×100, wherein S is the weight of said sample, said protective layer having an amount of coated solids in the range of 1 to 6 g/m 2 .

Claim 18

A thermosensitive recording sheet as claimed in claim 15, wherein said water-soluble binder is selected from the group consisting of polyvinyl alcohol, cellulose ethers, starch, ammonium carboxylates and alkali salts of isobutylene-maleic anhydride.

Claim 19

A thermosensitive recording sheet as claimed in claim 15, wherein said protective layer further contains a thermo-fusible material in an amount of not more than 20 wt. %, said thermo-fusible material being selected from the group consisting of higher fatty acid amides and derivatives thereof, higher fatty acid metallic salts, animal waxes, vegetable waxes and petroleum waxes.

Claim 20

A thermosensitive recording sheet as claimed in claim 17, wherein said theromsensitive coloring layer further contains a filler in an amount of not more than 3 times the amount by weight of said leuco dye, said filler being selected from the group consisting of calcium carbonate, caly, talc, silica, polystyrene and urea-formaldehyde resin, and said thermosensitve coloring layer also further comprises a binder in an amount in the range of 3 to 10 wt. %, said binder being selected from the group consisting of polyvinyl alcohol, cellulose ether, starch, ammonium polycarboxylates, alkali salts of isobutylene-maleic anhydride copolymers, and aqueous emulsions of styrene-butadiene latex, styrene-acrylic acid ester and vinyl acetate.

Claim 21

A thermosensitive recording sheet as claimed in claim 18, wherein said thermosensitive coloring layer further comprises an amount of a thermo-fusible material effective to decrease the melting point of at least one of said leuco dye and said acidic material, said thermo-fusible material being selected from the group consisting of higher fatty acid amides, higher fatty acid metallic salts, animal waxes, vegetable waxes and petroleum waxes.

Claim 22

A thermosensitive recording sheet as claimed in claim 15, wherein said protective layer further contains an aqueous emulsion of a member selected from the group consisting of styrene-butadiene latex, styrene-acrylic acid ester and vinyl acetate in an amount of not more than 20 wt. %.