Heat-sensitive recording material

Details Heat-sensitive recording material Heat-sensitive recording material

2001-11-13

2003-12-23

Hess, B. Hamilton (Department: 1774)

Record receiver having plural interactive leaves or a colorless

Having a colorless color-former, developer therefor, or...

C503S226000

Reexamination Certificate

active

06667275

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a heat-sensitive recording material and in particular to a heat-sensitive recording material excellent in curling resistance.
2. Description of the Related Art
A heat-sensitive recording material for recording images by applying heat using a thermal head, etc. is relatively inexpensive, and a recording device for the heat-sensitive recording material is simple, highly reliable and maintenance-free. Accordingly, the heat-sensitive recording material is widely used, and in recent years, high performance characteristics such as high image quality and image storability have been achieved.
On the other hand, the heat-sensitive recording material subjected to a change in environmental humidity or to heating during recording has a problem of losing balance in elongation between a front face and a back face of the heat-sensitive recording material and is thus deformed toward one side, resulting in a problem in qualities called curling. This problem has been observed particularly significantly in a multi-layer multicolor heat-sensitive recording material wherein a plurality of heat-sensitive recording layers exhibiting different color hues have been laminated.
Such curling impairs the qualities of the recording material as a product even if higher performance could be achieved in image quality and image storability.
To prevent such curling, the heat-sensitive recording material is provided not only with a heat-sensitive recording layer, a protective layer, etc. but also with a back coat layer on an opposite side (back) of a support, on which the heat-sensitive recording layer and the like are not arranged. For example, JP-A No.8-282112 discloses a heat-sensitive recording material provided with a back coat layer consisting of a single layer on a support, wherein the layer comprises an inorganic lamellar compound. By providing the recording material with the inorganic lamellar compound-containing layer on the other side of the support than the side having the heat-sensitive recording layer, it is certainly possible to prevent curling of the recording material to some degrees. However, in a low-humidity environment, curling cannot be completely prevented, whereby deformation in a curled state occurs, thus deteriorating the qualities of the heat-sensitive recording material. A multicolor heat-sensitive recording material having a thick recording layer consisting of plural layers is also easily curled, and hence encounters a problem with maintaining flatness.
In recent years, various techniques of forming images have been provided. Although coloration of images is advancing and regarded as important, the ability of the material itself to be stable as a recording medium without deterioration in qualities is required along with improvements in performance such as high image quality and image storability. Again because of curling, the range of applications of a material may be limited.
As described above, a heat-sensitive recording material which is capable of preventing curling attributable to a change in environmental humidity during use or to heating during recording, free of deterioration in qualities resulting from deformation of the material, and applicable to a wide variety of fields has not yet been provided.
SUMMARY OF THE INVENTION
To solve various problems in the prior art described above, an object of the present invention is to achieve the following goal. That is, the object of the present invention is to provide a high-quality multicolor heat-sensitive recording material formed of a sheet material or multiple layers or the like, which can prevent curling attributable to an environmental change or heating during recording, is free of deformation of the material, and is applicable to a wide variety of fields.
The means to achieve the object are described as follows:
A mode of the present invention is a heat-sensitive recording material having at least a heat-sensitive recording layer on one side of a support and a back coat layer on the other side, wherein the back coat layer comprises a plurality of layers, and an outermost layer in the back coat layer, which is most remote from the support, contains an inorganic lamellar compound or polyvinyl alcohol.
Another mode of the present invention is a heat-sensitive recording material having at least a heat-sensitive recording layer on one side of a support and a back coat layer on the other side, wherein the back coat layer comprises a plurality of layers, and an outermost layer in the back coat layer, which is most remote from the support, contains an inorganic lamellar compound. It is preferable that the outermost layer further contains gelatin, and it is more preferable that the inorganic lamellar compound is a synthetic mica.
Still another mode of the present invention is a heat-sensitive recording material having at least a heat-sensitive recording layer on one side of a support and a back coat layer on the other side, wherein the back coat layer comprises a plurality of layers, and an outermost layer in the back coat layer, which is most remote from the support, contains polyvinyl alcohol. It is preferable that the outermost layer further contains an inorganic lamellar compound, and it is more preferable that the layer positioned between the outermost layer and the support contains gelatin.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The heat-sensitive recording material of the present invention has a back coat layer consisting of multiple layers on a surface of a support on which a heat-sensitive recording layer is not provided. An outermost layer in the back coat layer, which is most remote from the support, contains an inorganic lamellar compound and/or polyvinyl alcohol.
Hereinafter, the heat-sensitive recording material of the present invention is described in detail. Polyvinyl alcohols as used herein refer to polyvinyl alcohols and/or modified polyvinyl alcohols.
The heat-sensitive recording material of the present invention has at least a heat-sensitive recording layer on one side of a support, which may consist of a single or plural layers and may have other layers such as a protective layer as necessary, and on the other side of the support, may have a back coat layer consisting of plural layers and if necessary additional layers.
(Back Coat Layer)
The back coat layer is formed by laminating two or more layers, and consists of the outermost layer (hereinafter, also called “outermost back layer”) most remote from the support and one or more layers (hereinafter, also called “intermediate back layers”) positioned between the outermost layer and the support.
<Outermost Back Layer>
The outermost back layer contains an inorganic lamellar compound and/or polyvinyl alcohol which serves as a binder, and as necessary additional components.
For example, in an environment with extreme low or high humidity, water in a vapor form is easily released from, or absorbed into, the layer in contact with air. In this case, when water absorption and release is different between the two sides of the support, shrinkage balance is lost, which facilitates curling to occur on one side. Especially in a multicolor heat-sensitive recording material consisting of plural layers, water absorption and release are significantly different between the side having the multi-layered heat-sensitive recording layer and the side not having the layer, and thus shrinkage balance is further lost, which causes serious deformation. However, when the side (back face) not having the heat-sensitive recording layer is provided with a back coat layer consisting of plural layers and the outermost layer thereof contains an inorganic lamellar compound or polyvinyl alcohol, water retained in a layer adjacent to the outermost layer can be blocked by the outermost layer, whereby migration of water across layers upon a change in air humidity can be inhibited and thus the balance in shrinkage between the front and the back can be easily maintained. Further, although water migration is easil

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