A thermosensitive recording medium 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 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.

There is provided a heat-sensitive transfer recording medium which is able to better suppress the occurrence of abnormal transfer during high-speed printing using a high-speed printer of sublimation transfer type and is able to improve transfer sensitivity in high-speed printing. The heat-sensitive transfer recording medium includes a base (10), a heat-resistant lubricating layer (20) formed on one surface of the base (10), an underlying layer (30) formed on the other surface of the base (10), and a dye layer (40) formed on a surface of the underlying layer (30), which is on the other side of a surface facing the base (10). In the heat-sensitive transfer recording medium, the underlying layer (30) has a major component that is a copolymer of polyester having a sulfonic group on a side chain and acrylic having at least one of a glycidyl group and a carboxyl group.

Disclosed is a heat-sensitive recording material comprising at least an undercoat layer and a heat-sensitive recording layer in this order on a support, the undercoat layer containing an inorganic pigment, hollow particles, and a binder, the heat-sensitive recording layer containing a leuco dye, developers, and a binder, the heat-sensitive recording layer containing a first developer and a second developer as the developers, the heat-sensitive recording layer containing an N,N-diarylurea-based compound represented by formula (1) as the second developer:

##STR00001## wherein R.sub.2 represents a C.sub.1-12 alkyl group, a C.sub.7-12 aralkyl group, or a C.sub.6-12 aryl group, the aralkyl group and aryl group may be substituted with a C.sub.1-12 alkyl group, a C.sub.1-12 alkoxy group, a C.sub.6-12 aryl group, or a halogen atom, and a plurality of R.sub.2s may be the same or different; and A.sub.1 represents a hydrogen atom or a C.sub.1-4 alkyl group, and a plurality of A.sub.1s may be the same or different.

There is disclosed a heat-sensitive recording material including an undercoat layer formed on one surface of a support and a heat-sensitive recording layer formed on the undercoat layer. The heat-sensitive recording layer contains a leuco dye and a coloring agent. The undercoat layer contains hollow particles and a binding resin. A maximum particle diameter (D100) of the hollow particles is 10 to 30 m. A particle diameter (D50) of the hollow particles at cumulative 50 volume % is 4.0 to 15 m. A ratio D100/D50 of the maximum particle diameter (D100) of the hollow particles to the particle diameter (D50) of the hollow particles at cumulative 50 volume % is 1.8 to 3.0. A volume percentage of the hollow particles having particle diameters of 2.0 m or less is 1% or less.

A heat-sensitive recording material including at least an undercoat layer and a heat-sensitive recording layer in this order on a support, the undercoat layer containing hollow particles and a binder, the heat-sensitive recording layer containing a leuco dye and a developer, the heat-sensitive recording material containing a compound represented by the following formula (1) as a first developer of the heat-sensitive recording layer:

##STR00001##

Disclosed is a heat-sensitive recording material comprising an undercoat layer and a heat-sensitive recording layer in this order on a support, the undercoat layer containing hollow particles, a binder, and an inorganic pigment I, the heat-sensitive recording layer containing a leuco dye, a developer, and an inorganic pigment II, and the heat-sensitive recording layer containing an N,N-diarylurea-based compound represented by the following formula (1): ##STR00001## wherein R.sub.2s may be the same or different, and each represents C.sub.1-12 alkyl, C.sub.7-12 aralkyl, or C.sub.6-12 aryl, and the aralkyl and the aryl may be each substituted with C.sub.1-12 alkyl, C.sub.1-12 alkoxy, C.sub.6-12 aryl, or halogen; A.sub.1s may be the same or different, and each represents hydrogen or C.sub.1-4 alkyl, as the developer, and a pigment with an oil absorption of 130 ml/100 g or less as the inorganic pigment II.

The present disclosure is a thermal transfer sheet including a substrate and a transfer layer, the transfer layer containing a luster pigment, wherein, when an image of the sheet is taken from a side on which the transfer layer is present, the image is analyzed, dark and light portions of the analyzed image are inverted, automatic thresholding is performed in order to determine a threshold value of a brightness distribution, binary representation is subsequently performed, and the number and the total area of the black portions and the total area of the white portions are calculated, the ratio of the total area of the black portions to the total area of the white portions is 0.03 to 0.5, and the black portions have an average area of 100 to 300 m.sup.2.