Record receiver having plural interactive leaves or a colorless – Having a colorless color-former – developer therefor – or... – Having nonreactant particles of defined size
Reexamination Certificate
2001-09-07
2003-12-02
Hess, B. Hamilton (Department: 1774)
Record receiver having plural interactive leaves or a colorless
Having a colorless color-former, developer therefor, or...
Having nonreactant particles of defined size
C503S226000, C503S200000
Reexamination Certificate
active
06656880
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a heat-sensitive recording material having a heat-sensitive recording layer on a substrate, and more particularly to a heat-sensitive recording material suitable for recording using a heating element such as a thermal head or the like.
2. Description of Related Art
In recent years, heat-sensitive recording has rapidly grown in popularity, because of benefits such as: 1) no need for development; 2) when paper is used as a substrate, the recording material is very similar to ordinary paper; 3) easy handling; 4) high color density; 5) simple and inexpensive recording devices; 6) no noise during recording; 7) high reliability, meaning low maintenance; and the like.
Against this background, there has also been rapid progress in the shift to color imaging, and demand is high for multi-color heat-sensitive recording materials that can be directly recorded with thermal heads and the like.
In heat-sensitive recording, a recording surface of a heat-sensitive recording material is directly contacted by a heating element such as a thermal head or the like. In this state, heat is generated and the heating causes color development. The heating element is switched between on and off states and an image is thereby recorded. Accordingly, if runnability (transportability) of the recording material during recording is to be improved, or if adhesion of dirt to a surface of the thermal head must be avoided, microparticles, which are inorganic particles or the like, are generally provided at an outermost layer of the recording material, which contacts the thermal head.
However, in order to avoid a reduction in not only heat transmission to the recording material during recording but also image quality, which depends on heat transmitted, a certain amount of contact pressure is applied and the head is pressed against the recording material. As a result, wearing tends to occur. In particular, if there are many high-hardness inorganic particles at the surface of the outermost layer, wearing of the thermal head (head-wearing) is rapid, and durability thereof is greatly reduced. Wearing of the thermal head is particularly noticeable in cases where application of heat is performed at a high temperature to obtain high color density and where heat is applied continuously for multi-color recording.
Wear can be moderated and the durability of the head improved by techniques that reduce the above-described head-wearing. These techniques include reducing contact pressure, and making the surface with which the head contacts softer by using microparticles with a comparatively low hardness or the like. However, these techniques tend to increase amounts of dirt at the thermal head (head-soiling). Head-soiling inhibits the transfer of heat to the recording material, and interferes with homogeneous color formation. Therefore, in order to obtain sharp images with homogeneous density, it is desirable that head-soiling tends not to occur.
Accordingly, head-wearing and head-soiling have a reciprocal relationship, such that when one is improved, the other tends to deteriorate. Until now it has proved difficult to improve both at the same time.
In accordance with the foregoing, a heat-sensitive recording material that can record, stably over long periods, sharp images with excellently homogeneous density, that alleviates head-wearing and does not reduce durability, and that does not lead to a loss of image quality due to head-soiling has been desired.
SUMMARY OF THE INVENTION
The present invention is provided to solve the above-described various problems of the conventional art, and the goal of the present invention is to achieve the following object.
An object of the present invention is to provide a heat-sensitive recording material that is capable of stably recording sharp images with excellently homogeneous density and suppressing head-wearing without causing loss of image quality due to head-soiling.
The inventor of the present invention has performed assiduous investigations into effects of recording surfaces on thermal heads. The inventor has combined results thereof and has discovered that, while the presence of microparticles at the surface contacting the head is essential for runnability, it is necessary that the microparticles have hardness such that head-soiling does not occur and softness (pressure absorbence) such that the head is not scratched.
The present invention is a heat-sensitive recording material having a heat-sensitive recording layer on a substrate, wherein an outermost layer from the substrate contains microparticle-aggregation particles.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A heat-sensitive recording material of the present invention includes microparticle-aggregation particles in an outermost layer, which contacts with a heating element such as a thermal head or the like during recording.
The heat-sensitive recording material of the present invention is described in detail below.
The heat-sensitive recording material of the present invention has, on a substrate, at least a heat-sensitive recording layer. The heat-sensitive recording material preferably also has a protective layer. The heat-sensitive recording material has other layers, such as an intermediate layer and the like, as necessary.
The present invention includes microparticle-aggregation particles in the outermost layer provided on the substrate, that is, the layer disposed furthest from the substrate (which may be a heat-sensitive recording layer or a protective layer). Further, the heat-sensitive recording layer may be a single-color heat-sensitive recording layer formed by a single layer, or may be a multi-color heat-sensitive recording layer in which a plurality of single-color heat-sensitive recording layers that develop mutually different hues are stacked.
Microparticle-Aggregation Particles
The microparticle-aggregation particles are regular or irregular particle aggregations formed by aggregating pluralities of microparticles. More fundamentally, a microparticle-aggregation particle may be a particle in which some microparticles have been mutually chemically bonded (e.g., by siloxane bonds or the like). Alternatively, the microparticle-aggregation particle may be a particle in which some microparticles have been attracted together by interaction forces between individual microparticles or the like, cohered and aggregated, and held together to form a single particle.
The microparticle-aggregation particles also include particles in which pluralities of microparticles have been made into microparticle aggregations by a binder having elasticity and softness, to thereby provide aggregation particles provided with sufficient softness to be pressure-deformable, as described below.
Because the present invention contains the microparticle-aggregation particles (occasionally hereafter referred to as “aggregation particles”) in the outermost layer, which contacts with the thermal head, it is possible for a surface of the outermost layer to have particles that are provided with a certain degree of hardness and with a softness sufficient to allow pressure-deformation when pressure is applied. That is, the particles have sufficient hardness to prevent head-soiling during recording, but do not have sufficient hardness to scratch and wear the head when a pressing force at or exceeding a certain level is applied at the head. Therefore, head-soiling can be avoided, while at the same time wear of the thermal head can be reduced, even in cases of continuous high-density recording, multi-color recording and the like, and thus durability of the head can be greatly improved.
As described earlier, in order to obtain the effects of preventing both head-soiling and head-wearing, it is essential that the microparticle-aggregation particles are present across the whole of the surface of the outermost layer. Specifically, a total surface coverage of the microparticle-aggregation particles is preferably 20 to 90%, and more preferably 30 to 70%.
Consequentl
Fuji Photo Film Co. , Ltd.
Hess B. Hamilton
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