Record receiver having plural interactive leaves or a colorless – Having a colorless color-former – developer therefor – or... – Identified color-former
Reexamination Certificate
2002-04-26
2004-03-09
Edwards, N. (Department: 1774)
Record receiver having plural interactive leaves or a colorless
Having a colorless color-former, developer therefor, or...
Identified color-former
C503S215000, C534S558000
Reexamination Certificate
active
06703345
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a diazonium salt, which is important as an synthesis intermediate of an azo dye, an analytical reagent or a constituent material of a heat-sensitive recording material and to a heat-sensitive recording material containing a diazonium salt and a coupler as coloring components and more particularly to a diazonium salt which has no probability of explosion and high storage stability and which results in little stain formation by decomposition and to a heat-sensitive recording material with excellent storage property before printing (raw storage property) and the light-resistance after printing (image storage property).
2. Description of the Related Art
A diazonium salt is known as an important intermediate of an azo dye. A variety of synthesis methods of the azo dye is known and, as described in “New Experimental Chemistry Lecture” (published by Maruzen Co., Ltd., vol. 14-III, pp. 1516-1534), examples thereof include synthesis methods by oxidation reaction, reduction reaction, substitution reaction, addition reaction, condensation reaction, and the like. However, the industrial production method of the azo dye which is widely employed is a synthesis method by azo coupling of a diazonium with a coupler such as aniline, a phenol or the like in terms of the availability of raw materials, the cost, the production yield and the like. Such a method has a risk in which explosion of the diazonium salt may occur during the synthesis process. Consequently, it has been required to develop a stable diazonium salt with little possibility of explosion.
Further, the diazonium salt, as described in Japanese Patent Application Laid-Open (JP-A) No. 11-228517, is used for quantitative analysis of bilirubin, a main component of a bile pigment contained in the body fluid, and regarded as an important compound in the medical and pharmaceutical fields.
The diazonium salt is generally an extremely chemically active compound and easily reacts with a compound having a phenol derivative and an active methylene group so-called coupler to form an azo dye and is also photosensitive and decomposes when exposed to light and loses its activity. Accordingly, the diazonium salt has been utilized in an optical recording material such as diazo copying (“Basis of Photographic-Engineering-Non-Silver Halide Photography”, edited by Japan Photography Associate, published by Corona, 1982, pp. 89-117, pp. 182-201).
Further, nowadays, based on the characteristic in which the diazonium salt decomposes when exposed to light and loses the activity, it is employed in a recording material which requires image fixation and a typical example is a photo-fixation type heat-sensitive recording material proposed in “Journal of Imaging Electronics Associate”, vol. 11, no. 4, 1982, pp. 290-296 (Koji Sato, et al.) It has a recording layer containing the diazonium salt and a coupler and is heated according to image signals so as to cause a reaction of the components contained in the material and so as to form an image and then is exposed to light in order to fix the formed image.
Such a recording material containing the diazonium salt as a coloring component has a disadvantage in which the diazonium salt gradually thermally decomposes even in a dark place since the diozonium salt has an extremely high chemical activity and thus the non-image areas are colored by production of the colored substances by the decomposition and the contrast of the image is decreased. Further, it has another disadvantage in which the image after recording fades under sunlight or light of a fluorescent lamp.
A variety of means for improving such instability of the diazonium salt have been proposed. One of the most efficient means is a method of encapsulating the diazonium salt in microcapsules. Since the diazonium salt is isolated from substances such as water and a base which promote decomposition by encapsulating the diazonium salt, decomposition of the diazonium salt can considerably be suppressed and the shelf-life of a recording material in which the method is employed can remarkably be prolonged (Tomomasa Usami, et al., “Journal of Electrophotography Associate”, vol. 26, no. 2, 1987, pp. 115-125).
A general method for encapsulating the diazonium salt in microcapsules is a method for producing microcapsules by steps of dissolving the diazonium salt in a hydrophobic solvent (an oil phase); adding the oil phase to an aqueous solution containing a water-soluble polymer (a water phase); carrying out emulsification and dispersion by a homogenizer or the like; and polymerizing monomers or a prepolymer included in the oil phase and/or the water phase at the interface to form or deposit a polymer which composes the wall of the microcapsules. Such a method is described in details, for example, in “Microcapsule” (written by Tomoji Kondo, published by The Nikkan Kogyo Shimbun, Ltd. 1970), “Microcapsule” (written by Tamotsu Kondo, et al., Sankyo Shuppan, 1977) and the like. As the material of the capsule wall, cross-linked gelatin, an alginic acid salt, cellulose, urea resin, urethane resin, melamine resin, nylon resin and the like can be used.
In particular, microcapsules having a glass transition temperature slightly higher than a room temperature such as urea resin and urethane resin prevents a substance from permeating the capsule wall at room temperature and allows the substance to pass through the wall at a temperature equal to or higher than the glass transition temperature, so that they are called thermally responsive microcapsules and are extremely useful for heat-sensitive type recording materials. That is, in the case of a heat-sensitive recording material comprising a heat-sensitive recording layer containing thermally respondensive microcapsules containing a diazonium salt and outside of the microcapsules a coupler as coloring components, the diazonium salt can be maintained stably for a long time and a color image can easily be formed by heating it and the formed image can be fixed by light radiation.
To encapsulate the diazonium salt can remarkably improve the stability of a recording material.
Although the stability of a recording material is remarkably improved as described above, instability due to the diazonium salt itself is not completely suppressed and coloration of non-image areas after a long term storage of the recording material is not sufficiently suppressed. Also, there still remains a problem that an image fades even after printing and fixing the image if it is exposed for a long time to a light source.
Present inventors have proposed a variety of diazonium salts as diazo compounds suitable for recording materials (JP-A Nos. 1-80588, 4-59288, 4-197782, 6-328853, 8-31033, 10-337961, 11-105432, 11-342675, and 2000-15935), however depending on the storage conditions of the recording materials, coloration may take place and thus further improvement is required in order to obtain stable images with high grades. On the other hand, lightfastness of images after printing and fixing is insufficient.
SUMMARY OF THE INVENTION
The present invention aims to solve the above-described conventional problems and achieve the following objects.
That is, the objects of the invention are at first to provide a diazonium salt with no probability of explosion, useful for a synthesis intermediate of an azo dye, an analytical reagent, or a constituent material for a heat-sensitive recording material, having a stable storage property, and with little stain formation and secondary to provide a heat-sensitive recording material capable of giving an image which is free from coloration in non-image areas with the lapse of time during storage and thus excellent in whiteness and also scarcely fades when exposed to sunlight, light from a fluorescent lamp or the like and thus excellent in lightfastness.
A first aspect of the invention is a diazonium salt represented by the following general formula (1): General formula (1)
wherein R
1
represents a branched alkyl group; R
2
and R
3
sep
Higuchi Satoshi
Ikeda Kimi
Jinbo Yoshihiro
Kawabuchi Tatsuo
Nagase Hisato
Edwards N.
Sughrue & Mion, PLLC
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