Heat transfer sheet

Details Heat transfer sheet Heat transfer sheet

2001-02-14

2003-04-01

Hess, Bruce H. (Department: 1774)

Record receiver having plural interactive leaves or a colorless

Having plural interactive leaves

C428S195100, C428S913000

Reexamination Certificate

active

06541420

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a heat transfer sheet which can be used for wide range laser recording devices, and with which a transfer image having no deterioration in image quality due to fogging and the like can be obtained.
2. Description of the Related Art
Carbon black, which has absorption in a wide wavelength range, has frequently been used as a light-heat conversion substance included in a light-heat conversion layer of a heat transfer sheet because it can be accommodated to various laser recording devices, as disclosed in Japanese Patent Application Laid-Open (JP-A) No. 5-169861, JP-A No. 9-76637, and JP-A No. 11-321099.
However, because there is a tendency for fine particles of carbon black to agglomerate at the time of application, there has been the possibility for the quality of the transfer image to deteriorate. Further, there has been the possibility for the carbon black to be transferred to the material to which transfer is made due to fusion and ablasion at the time of recording, thus generating fogging and lowering image quality.
SUMMARY OF THE INVENTION
The present invention has been devised in consideration of the above facts. An object of the present invention is to provide a heat transfer sheet which can be accommodated to laser recording devices of varied wavelengths but which does not lower the image quality of a transfer image.
In order to solve the above problems, the present invention provides a heat transfer sheet comprising a light-heat conversion layer having an infrared absorption colorant and an image forming layer sequentially disposed on a support, wherein an optical density in a 600 nm to 1000 nm range of the light-heat conversion layer is within a range of 0.3 to 2.0.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will hereinafter be described in detail.
The heat transfer sheet of the present invention has on a support a light-heat conversion layer and an image forming layer in this order. As long as the support has good dimensional stability and can withstand heat at the time of image formation, anything may be used. Specifically, the film or the sheet disclosed at the lower left column of page 2, lines 12 to 18 of Japanese Patent Application Laid-Open (JP-A) No. 63-193886 can be used.
Further, if an image is to be formed by irradiating a laser from the support side, it is preferable that the support is transparent. If an image is to be formed by irradiating a laser from the image forming layer side, it is not particularly necessary for the support to be transparent.
The support may have a cushion property in order to raise adhesion with the material to which transfer is made. In this case, it is favorable if a material having a low elastic modulus or a material having rubber elasticity is used. Specifically, examples include an elastomer such as natural rubber, acrylate rubber, butyl rubber, nitrile rubber, butadiene rubber, isoprene rubber, styrene-butadiene rubber, chloroprene rubber, urethane rubber, silicone rubber, acrylic rubber, fluorine-contained rubber, neoprene rubber, chlorosulfonated polyethylene, epichlorohydrine, EPDM, urethane elastomer; and resins having a small modulus of elasticity among polyethylene, polypropylene, polybutadiene, polybutene, impact resistant ABS resin, polyurethane, ABS resin, acetate, cellulose acetate, amide resin, polytetrafluoroethylene, nitro-cellulose, polystyrene, epoxy resin, phenol-formaldehyde resin, polyester, impact resistant acrylic resin, styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, acrylonitrile-butadiene copolymer, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, plasticizer-added vinyl chloride resin, vinylidene chloride resin, polyvinyl chloride, and polyvinylidene chloride. Further, a shape-memory resin such as a styrene hybrid polymer, in which polynorbornene or a polybutadiene unit and a polystyrene unit have been compounded, may also be used.
A material having a low modulus of elasticity as described above or a material having rubber elasticity may also be combined in the base material of the support.
Although there are no particular restrictions on the thickness of the support, the thickness is generally 2 &mgr;m to 300 &mgr;m and preferably 5 &mgr;m to 200 &mgr;m. Although the thickness of a support having a cushion property varies in accordance with a number of factors such as the type of resin or elastomer to be used, the suction force at the time of adhesion, the particle diameter of the mat material, and the amount of mat material to be used, it is ordinarily 10 &mgr;m to 100 &mgr;m.
At the side of the support opposite the side provided with a light-heat conversion layer, a backcoat layer may be provided in order to endow the support with such functions as motion stability, heat resistance, and an antistatic property.
The backcoat layer can be formed by applying on the surface of the support a coating liquid for the backcoat layer obtained by dissolving in a solvent a resin such as nitrocellulose or a coating liquid for the backcoat layer obtained by dissolving or dispersing in a solvent a binder resin and 20 &mgr;m to 30 &mgr;m fine particles.
A cushion layer may be disposed on the support under the light-heat conversion layer. The cushion layer may not be necessary if the support has a cushion property. When dimensional stability is required or when materials having a low modulus of elasticity are used, it is preferable to dispose a cushion layer on a support without a cushion property rather than forming a support having a cushion property. Materials cited for the purpose of forming a support with a cushion property can be used as the materials for the cushion layer.
Although the thickness of the cushion layer varies in accordance with a number of factors such as the type of resin or elastomer to be used, the suction force at the time of adhesion, the particle diameter of the mat material, and the amount of mat material to be used, it is usually 10 &mgr;m to 100 &mgr;m.
The cushion layer can be formed by applying a coating liquid in which the material is dissolved or dispersed like a latex in one of various types of solvents by coating methods such as a blade coater, a roll coater, a bar coater, a curtain coater, or a gravure coater, or by an extrusion lamination method or the like.
By providing a cushion layer, adhesion is improved but the time required for decompression when vacuum adhesion is performed does not change much, and a sudden decompression triggers the generation of air pockets. In order to sufficiently ensure adhesion and reduce the time required for vacuum adhesion, it is preferable to roughen the heat transfer sheet.
As a method of roughening the heat transfer sheet, the surface of the cushion layer may be subjected to a roughening treatment, in advance, and then the light-heat conversion layer and the image forming layer are disposed thereon. A method in which a mat material is incorporated in the surface of the heat transfer sheet may also be employed.
The degree to which the cushion layer is roughened is determined in accordance with the elasticity of the cushion layer, film thickness, pressure applied (degree of vacuum), the surface roughness of the heat transfer sheet, the particle diameter of the mat material, and the amount of the mat material.
Roughening the surface of the cushion layer is also dependent upon the materials which form the cushion layer, but the surface roughness Ra is preferably of a range of 0.3 &mgr;m to 10 &mgr;m. A similar range is preferable when roughening the surface of the heat transfer sheet.
An infrared absorption pigment is used as a light-heat conversion substance in the light-heat conversion layer. Examples of infrared absorption pigments which can used include phthalocyanine pigments, naphthalocyanine pigments, squalilium pigments, indorenin dyes, cyanine dyes, nitroso compounds and their metallic complex salts, polymethine pigments, thiol-nickel salts, triallyl methane pigments, immonium pigments, naphthoquinone pigmen

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