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EP-4126557-B1 - THERMOSENSITIVE RECORDING MEDIUM AND METHOD FOR PRODUCING THERMOSENSITIVE RECORDING MEDIUM

EP4126557B1EP 4126557 B1EP4126557 B1EP 4126557B1EP-4126557-B1

Inventors

  • SUGIURA, Kaito
  • SHIMIZU, KENJI

Dates

Publication Date
20260506
Application Date
20210309

Claims (11)

  1. A thermosensitive recording medium (1) comprising: a support (11); a first underlayer (12A) disposed on or above the support (11); a second underlayer (12B) disposed on or above the first underlayer (12A); and a thermosensitive recording layer (13) disposed on or above the second underlayer (12B), wherein the thermosensitive recording layer (13) comprises a leuco dye, a color developer, and a binder resin, wherein the second underlayer (12B) and the thermosensitive recording layer (13) are formed by simultaneous curtain coating, and surface smoothness of a surface of the thermosensitive recording layer (13), measured by means of an Oken-type smoothness tester according to JIS P-8155, is thereby 1,000 s or greater.
  2. The thermosensitive recording medium (1) according to claim 1, wherein the surface smoothness is 1,600 s or greater.
  3. The thermosensitive recording medium (1) according to claim 1 or 2, wherein the surface smoothness is 2,000 s or greater.
  4. The thermosensitive recording medium (1) according to any one of claims 1 to 3, wherein the first underlayer (12A), or the second underlayer (12B), or both the first underlayer (12A) and the second underlayer (12B) include a pigment and a binder resin.
  5. The thermosensitive recording medium (1) according to claim 4, wherein the pigment included in the first underlayer (12A) is calcined kaolin.
  6. The thermosensitive recording medium (1) according to claim 4 or 5, wherein the second underlayer (12B) includes hollow filler, the hollow filler comprising particles, each particle including a shell of a thermoplastic resin, voids inside the shell, and air or another gas in each void.
  7. The thermosensitive recording medium (1) according to any one of claims 4 to 6, wherein the binder resin of the first underlayer (12A), or the binder resin of the second underlayer (12B), or both the binder resin of the first underlayer (12A) and the binder resin of the second underlayer (12B) include polyvinyl alcohol and a styrene-butadiene copolymer.
  8. The thermosensitive recording medium (1) according to claim 1, wherein the first underlayer (12A) is formed by rod-blade coating.
  9. The thermosensitive recording medium (1) according to claim 1, wherein the first underlayer (12A) includes hollow filler, the hollow filler comprising particles, each particle including a shell of a thermoplastic resin, voids inside the shell, and air or another gas in each void, and an average porosity of the hollow filler is 71% or greater but 95% or less.
  10. A method for producing a thermosensitive recording medium (1), the method comprising: forming a first underlayer (12A) on or above a support (11); forming a second underlayer (12B) on or above the first underlayer (12A); and forming a thermosensitive recording layer (13) on or above the second underlayer (12B), the thermosensitive recording layer (13) comprising a leuco dye, a color developer, and a binder resin, wherein the forming the second underlayer (12B) and the forming the thermosensitive recording layer (13) are performed by simultaneous curtain coating, and surface smoothness of a surface of the thermosensitive recording layer (13), measured by means of an Oken-type smoothness tester according to JIS P-8155, is 1,000 s or greater.
  11. The method according to claim 10, the method comprising forming the first underlayer (12A) by rod-blade coating.

Description

[Technical Field] The present invention relates to a thermosensitive recording medium, and a method for producing a thermosensitive recording medium. [Background Art] Thermosensitive recording media is widely used in various fields, such as a POS field for fresh food products, packed meals, and premade meals; a copying field for books and documents; a telecommunication field, such as facsimiles; a ticketing field for ticket machines, and receipts; and packaging tags for the aviation industry. In recent years, to achieve the higher qualities (e.g. high sensitivity and high image quality) of thermosensitive recording media has been desired to match with versatility of use and high performances of devices for use. In the art, proposed is a thermosensitive recording medium in which a first underlayer, a second underlayer, and a thermosensitive recording layer are separately formed by rod coating or blade coating (see, for example, PTL 1). Moreover, proposed is a thermosensitive recording medium in which a first underlayer and a second underlayer are formed by simultaneous curtain coating, and a thermosensitive recording layer is separately formed on the second underlayer by blade coating (see, for example, PTL 2). EP0992364A2 discloses a heat-sensitive recording material including on a support thereof a heat-sensitive color developing layer containing an electron donative colorless dye and an electron acceptive compound, a first intermediate layer, whose main components are an inorganic pigment and a binder, and a second intermediate layer on the first intermediate layer, which second intermediate layer having an inorganic pigment and a binder as main components, are sequentially laminated between the support and the heat-sensitive color developing layer, such that Oken type smoothness of the first intermediate layer is not less than 700 seconds, and density of the second intermediate layer is not more than 1.0. US 2010/0062936 A1 discloses a thermosensitive recording material which can be produced through high-speed coating, which is excellent in head-matching property, and which can provide a printed image having good waterproofness, while maintaining high sensitivity and high storage stability, which material includes a support, an under layer laid over the support, the under layer containing a plastic hollow particle, a thermosensitive colordeveloping layer laid over the under layer, the thermosensitive color-developing layer containing a leuco dye and a developer, wherein two or more layers including the thermosensitive color-developing layer are formed through simultaneous coating by a curtain coating method. [Citation List] [Patent Literature] [PTL 1] Japanese Patent No. 4793385[PTL 2] Japanese Unexamined Patent Application Publication No. 2011-255554 [Summary of Invention] [Technical Problem] The present invention has an object to provide a thermosensitive recording medium having excellent sensitivity and precision. [Solution to Problem] According to one aspect of the present invention, a thermosensitive recording medium according to claim 1 is provided. [Advantageous Effects of Invention] The present invention can provide a thermosensitive recording medium having excellent sensitivity and precision. [Brief Description of Drawings] [FIG. 1] FIG. 1 is a schematic view illustrating formation of a second underlayer and a thermosensitive recording layer by simultaneous curtain coating in the method for producing a thermosensitive recording medium of the present invention.[FIG. 2A] FIG. 2A is a schematic view illustrating one example of the thermosensitive recording medium of the presentinvention.[FIG. 2B] FIG. 2B is a schematic view illustrating another example of the thermosensitive recording medium of the present invention.[FIG. 2C] FIG. 2C is a schematic view illustrating another example of the thermosensitive recording medium of the present invention. [Description of Embodiments] (Thermosensitive recording medium) The thermosensitive recording medium of the present invention includes a support, a first underlayer disposed on or above the support, a second underlayer disposed on or above the first underlayer, and a thermosensitive recording layer disposed on or above the second underlayer. The thermosensitive recording medium may further include a protective layer, an adhesive layer, and other layers according to the necessity. The second underlayer and the thermosensitive recording layer are formed by simultaneous curtain coating. Surface smoothness of a surface of the thermosensitive recording medium is 1,000 s or greater. The second underlayer and the thermosensitive recording layer are formed by simultaneous curtain coating. The simultaneous curtain coating is a method where two or more coating liquids, such as a thermosensitive recording layer coating liquid are simultaneously applied as curtain films from separate heads, or two or more coating outlets in one head. Since the second underlayer and th