Record receiver having plural interactive leaves or a colorless – Having a colorless color-former – developer therefor – or... – Having nonchromogenic liquid spread-control or...
Reexamination Certificate
2001-05-30
2004-01-20
Hess, Bruce (Department: 1774)
Record receiver having plural interactive leaves or a colorless
Having a colorless color-former, developer therefor, or...
Having nonchromogenic liquid spread-control or...
C503S204000, C503S215000, C503S216000
Reexamination Certificate
active
06680281
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a heat-sensitive recording material which makes use of a color forming reaction between a leuco dye and a developer.
BACKGROUND ART
Heat-sensitive recording materials are well known which make use of the color forming reaction of a lueco dye with a color-developer which develops a color on contact with the leuco dye, such that the two materials are brought into contact with each other by heating to produce a color image. These heat-sensitive recording materials are relatively inexpensive, and recording devices for these materials are compact and relatively easy to maintain. Consequently such recording materials are widely used as recording media for facsimile systems, word processors, various computers and other application.
With the expansion of the scope of application of such heat-sensitive recording materials, diversified performances are demanded, such as enhanced sensitivity of the heat-sensitive recording layer, improved chemical resistance of the recorded portions (=recorded images), stability of the recorded portions with time, capability of multi-color recording of the heat-sensitive recording materials, etc.
The heat-sensitive recording materials in which a leuco dye is contained in microcapsules to enhance resistance of the recorded portions to chemicals or resistance to background fogging are disclosed in Japanese Unexamined Patent Publications Nos. 12695/1982, 214691/1984, 214990/1985, 247987/1992, etc.
Japanese Unexamined Patent Publications Nos. 142025/1997, 263057/1997 and 290565/1997 disclose heat-sensitive recording materials capable of forming distinct multi-color images by using a composite of a leuco dye and a resin.
With these heat-sensitive recording materials as well, further improvement in resistance to chemicals and resistance to background fogging is demanded.
Accordingly, an object of the present invention is to provide a heat-sensitive recording material which is excellent in preservability of the recorded portions and resistance to background fogging.
SUMMARY OF THE INVENTION
As a means for achieving the above object, in a heat-sensitive recording material comprising a support and a heat-sensitive coloring layer formed on the support and containing a leuco dye and a developer, the present invention utilizes, in the heat-sensitive coloring layer, either composite particles each containing a leuco dye in solid resin particle or microcapsules containing a leuco dye and a hydrophobic organic solvent, and N-p-toluenesulfonyl-N′-3-(p-toluenesulfonyloxy)phenylurea as a color developer.
Particularly, the present invention provides a heat-sensitive recording material which comprises a support and a heat-sensitive coloring layer formed on the support and containing a leuco dye and a developer, wherein the leuco dye is either (a) in the form of composite particles each of which contains the leuco dye in a solid resin particle or (b) contained in microcapsules in which a hydrophobic organic solvent is contained, and the developer is N-p-toluenesulfonyl-N′-3-(p-toluenesulfonyloxy)phenylurea.
Further, a heat-sensitive recording material capable of multi-color recording can be obtained by incorporating into the heat-sensitive coloring layer another leuco dye which forms a color different from that formed by the above leuco dye which is in the form of composite particles or contained in microcapsules.
DETAILED DESCRIPTION OF THE INVENTION
In the heat-sensitive coloring layer, the amount of the composite particles containing a leuco dye in solid resin particles or the amount of microcapsules containing a leuco dye and a hydrophobic organic solvent, and the amount of N-p-toluenesulfonyl-N′-3-(p-toluenesulfonyloxy)phenylurea (hereinafter referred to as “a specific developer”) are not specifically limited.
Generally, the amount of said composite particles or said microcapsules is preferably about 5 to about 70% by weight, more preferably about 10 to about 40% by weight, based on the total amount of solids in the heat-sensitive coloring layer (including the amount of the hydrophobic organic solvent in the microcapsules when the microcapsules are used; the same applies hereinafter). The amount of the specific developer is preferably about 5 to about 60% by weight, more preferably about 10 to about 40% by weight, based on the total amount of solids in the heat-sensitive coloring layer.
Composite Particles
Composite particles in which a leuco dye is contained in solid resin particles are known and disclosed, for example, in EP 0 774 363 A1. The disclosure of EP 0 774 363 A1 is incorporated herein by reference. More specifically, composite particles to be used in the present invention are particles in which leuco dye particles are coated with a solid resin or a leuco dye is uniformly dispersed or dissolved in a solid resin.
The average particle diameter of the composite particles is preferably about 0.2 to about 5.0 &mgr;m, more preferably about 1.0 to about 3.0 &mgr;m.
The content of the leuco dye in the composite particles is preferably about 5 to about 70% by weight, more preferably about 15 to about 40% by weight, based on the total weight of the composite particles.
The resin which constitutes the composite particles is not specifically limited and includes, for example, thermoplastic styrene resins, acrylic resins, amide resins, urethane resins, amide-urethane resins, carbonate resins, etc. These resins may be employed alone or as a mixture of two or more. Especially preferred are amide-urethane resins since the use thereof makes it easier to produce composite particles and imparts good resistance to background fogging to the resulting heat-sensitive coloring layer due to excellent heat resistance of said resin.
As composite particles composed of an amide-urethane resin and a leuco dye, preferred are those produced by emulsifying and dispersing in water a solution of a lueco dye (solute) in a polyisocyanate compound (solvent) and then causing a polymerization reaction of the polyisocyanate compound, since they have good heat resistance and therefore are excellent in achieving high resistance to background fogging and easy to produce.
A method for producing composite particles comprises, for example, the steps of dissolving a leuco dye in a polyisocyanate compound serving as a resin-forming material (optionally, containing a polyol compound, a polyamine compound or the like) at a temperature of 60 to 150° C.; cooling the resulting solution if so desired; emulsifying and dispersing the solution in an aqueous media containing as dissolved therein a protective colloid substance such as a polyvinyl alcohol with use of an emulsifier such as a homomixer, an ultrasonic emulsifier, a forced-space-passed mill; adding a reactive substance such as a water soluble polyamine if so desired; and polymerizing the above resin-forming materials to produce composite particles comprising the leuco dye and amide-urethane resin (for example, an amide bond- and urethane bond-containing resin formed by a reaction of an isocyanate compound and water and optionally a polyol or a polyamine).
The proportions of the leuco dye and the polyisocyanate compound are selected in view of better color-forming sensitivity and ease of production, and the polyisocyanate compound is preferably used in an amount of 50 to 2000 parts by weight, more preferably 150 to 600 parts by weight, based on 100 parts by weight of the leuco dye.
The polyisocyanate compound is preferably selected from those which are in the form of a liquid having low viscosity at normal temperatures and which highly dissolve the leuco dye. As such polyisocyanate compounds, particularly preferred are dicyclohexyl-methane-4,4′-diisocyanate, norbornendiisocyanate, hexamethylene diisocyanate, a tris-isocyanulate compound of hexamethylene diisocyanate, etc. because they have low viscosity.
Examples of the polyol compound and the polyamine compound which are optionally added to the polyisocyanate compound acting as solvent are as follows:
Polyol compounds: ethylen
Harunaga Rie
Suzuki Shigeru
Tajiri Masanao
Umemoto Takashi
Hess Bruce
Kubovcik & Kubovcik
Oji Paper Co. Ltd.
LandOfFree
Heat-sensitive recording material does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Heat-sensitive recording material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Heat-sensitive recording material will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3206374