Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
1998-10-16
2001-08-14
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
51, 51, 51, 51
Reexamination Certificate
active
06274301
ABSTRACT:
TECHNICAL FIELD
This invention relates to a photothermographic recording element and more particularly, to a photothermographic element having improved tone stability during storage.
BACKGROUND ART
Photothermographic materials which are processed by a thermographic process to form photographic images are disclosed, for example, in U.S. Pat. Nos. 3,152,904 and 3,457,075, D. Morgan and B. Shely, “Thermally Processed Silver Systems” in “Imaging Processes and Materials,” Neblette, 8th Ed., Sturge, V. Walworth and A. Shepp Ed., page 2, 1969.
These photothermographic materials generally contain a reducible silver source (e.g., organic silver salt), a catalytic amount of a photocatalyst (e.g., silver halide), a toner for controlling the tone of silver, and a reducing agent, typically dispersed in an organic binder matrix. Photothermographic materials are stable at room temperature. When they are heated at an elevated temperature (e.g., 80° C. or higher) after exposure, redox reaction takes place between the reducible silver source (functioning as an oxidizing agent) and the reducing agent to form silver. This redox reaction is promoted by the catalysis of a latent image produced by exposure. Silver formed by reaction of the organic silver salt in exposed regions provides black images in contrast to unexposed regions, forming an image.
Recently in the medical field, the imaging technology has made an advance with a focus on the keyword of easy, rapid and Earth-friendly processing. For example, the development of a medical image recording system which is laser exposed and heat developed started, and a dry system discharging a processing solution as little as possible has become widespread. Meanwhile, the laser output means has also made a progress to offer a wider range of choice of lasers, and the demand for visible light lasers is increasing.
For such photographic photosensitive materials, there are known in the art various methods of containing dyestuffs in the photosensitive materials to adjust the tone thereof in order that an image as a whole look in a more black tone, for example, a method of using oil-soluble dyestuffs in photographic silver halide photosensitive materials as described in JP-A 243654/1985, a method of using an emulsified dispersion of specific anthraquinone dyestuffs as described in JP-A 139607/1989, and a method of emulsifying and dispersing a colored dyestuff together with a polymer and introducing the dispersion into an emulsion layer as described in JP-A 289227/1993 and 341441/1993.
However, when dyestuffs are contained in emulsion layers of photothermographic materials by such prior art methods, the dyestuffs can adversely affect photographic properties by increasing the fog by development and reducing the sensitivity beyond the necessity.
Moreover, due to the co-presence of polyhalogenated compounds important as antifoggants for heat development, the dyestuffs can be bleached during storage whereby the image tone is deteriorated or discoloration occurs.
DISCLOSURE OF THE INVENTION
Therefore, an object of the invention is to provide a photothermographic recording element featuring an improved image tone and improved tone stability during storage.
Making extensive investigations, we have completed the invention that achieves the above object.
(1) A photothermographic recording element comprising a transparent support, a binder, a non-photosensitive organic silver salt, a photosensitive silver halide, and a reducing agent, characterized in that
at least one of constituent layers comprises (a) polymeric microparticulates containing a dyestuff, (b) microcapsules containing a dyestuff, and/or (c) an organic or inorganic pigment.
(2) The photothermographic recording element of (1) wherein at least one of constituent layers comprises a toner.
(3) The photothermographic recording element of (1) wherein at least one of constituent layers comprises a polyhalogenated compound.
(4) The photothermographic recording element of (1) comprising as a constituent layer on the transparent support a photosensitive layer containing a photosensitive silver halide and a binder wherein at least one layer of the photo-sensitive layer comprises (a) polymeric microparticulates containing a dyestuff, (b) microcapsules containing a dyestuff, and/or (c) an organic or inorganic pigment, and a polyhalogenated compound.
(5) The photothermographic recording element of (1) wherein (i) polymeric microparticulates containing a dyestuff having at least one absorption peak in the range of 500 to 700 nm, (ii) microcapsules containing a dyestuff having at least one absorption peak in the range of 500 to 700 nm, and/or (iii) an organic or inorganic pigment having at least one absorption peak in the range of 500 to 700 nm is contained.
(6) The photothermographic recording element of (1) wherein an aqueous latex is used as the binder.
BEST MODE FOR CARRYING OUT THE INVENTION
Now the invention is described in detail.
The photothermographic recording element of the invention comprises on a support constituent layers at least one of which comprises (a) polymeric microparticulates containing a dyestuff, (b) microcapsules containing a dyestuff, and/or (c) an organic or inorganic pigment.
By adding a dyestuff in the form contained in polymeric microparticulates or microcapsules or a pigment to a photosensitive element, the element is improved in image tone, and also improved in light fastness in that the discoloration or fading of the image tone by light illumination is eliminated. There is no detrimental influence on photographic properties.
These advantages are enhanced when at least one of the constituent layers contains a polyhalogenated compound as an antifoggant, especially when at least one photosensitive layer containing a photosensitive silver halide, among the constituent layers, comprises (a) polymeric micro-particulates containing a dyestuff, (b) microcapsules containing a dyestuff or (c) an organic or inorganic pigment.
In contrast, if a dyestuff is added as such, the light stability of the image tone is insufficient, and especially in the co-presence of polyhalogenated compounds, substantial discoloration or fading occurs as a result of bleaching of the dyestuff by light illumination.
The dyestuff used in the photosensitive recording element of the invention may be any desired one and selected from, for example, pyrazoloazole, anthraquinone, azo, azomethine, oxonol, carbocyanine, styryl, triphenylmethane, indoaniline, indophenol, and squarylium dyestuffs. Preferred of the dyestuffs used herein are anthraquinone dyestuffs (for example, Compounds 1 to 9 in JP-A 341441/1993, Compounds 3-6 to 3-18 and 3-23 to 3-38 in JP-A 165147/1993), azomethine dyestuffs (for example, Compounds 17 to 47 in JP-A 341441/1993), indoaniline dyestuffs (for example, Compounds 11 to 19 in JP-A 289227/1993, Compound 47 in JP-A 341441/1993 and Compounds 2-10 to 2-11 in JP-A 165147/1993), and azo dyestuffs (for example, Compounds 10 to 16 in JP-A 341441/1993). The amount of these dyestuffs used is determined by the desired quantity of absorption and in general, it is preferred to use the dyestuffs in amounts of 1 &mgr;g to 1 g per square meter of the photosensitive recording element.
Preferably, the dyestuff used herein exhibits a maximum absorption of 0.1 to 2 in the desired range of wavelength.
The dyestuff used herein may have a function of anti-halation or irradiation prevention, and a layer containing the dyestuff may be an anti-halation layer or irradiation-preventing layer.
Where the dyestuff is used herein for the purpose of anti-halation or irradiation prevention, the dyestuff may be any compound as long as it has the desired absorption in the wavelength range and provides an anti-halation layer or irradiation preventing layer with a preferred profile of absorbance spectra. The following compounds are disclosed although the invention is not limited thereto. The dyestuffs used alone include the compounds described in JP-A 56458/1984, 216140/1990, 13295/1995, 11432/1995, U.S. Pat. No. 5,380,635, JP-A 68539/1990,
Fujiwara Itsuo
Okamura Hisashi
Tsuzuki Hirohiko
Yabuki Yoshiharu
Birch & Stewart Kolasch & Birch, LLP
Chea Thorl
Fuji Photo Film Co. , Ltd.
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