Image-forming method

Details Image-forming method Image-forming method

1999-08-12

2001-12-25

Chea, Thorl (Department: 1752)

Radiation imagery chemistry: process, composition, or product th

Thermographic process

Heat applied after imaging

C430S351000, C430S203000, C430S503000, C430S572000, C430S944000

Reexamination Certificate

active

06333143

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a method for forming an image, and more particularly to a method for forming an image by exposing a heat-development light-sensitive material to light using at least one exposure head having a plurality of exposure light sources.
BACKGROUND OF THE INVENTION
Heat-development light-sensitive material is known in the art, and heat-development light-sensitive materials and their processes are described, for example, in “Shashin Kogaku no Kiso (Higinen Shashin-hen)” (published by Korona-sha, 1982), pages 242 to 255, and in U.S. Pat. No. 4,500,626.
Further, methods wherein, for example, dye images are formed by the coupling reaction of the oxidized product of a developing agent with a coupler are described, for example, in U.S. Pat. No. 3,761,270 and U.S. Pat. No. 4,021,240. Furthermore, methods for forming positive color images by the light-sensitive silver dye bleach process are described, for example, in U.S. Pat. No. 4,235,957.
Further, recently, the method wherein a diffusion dye is released or formed imagewise by heat development and the resultant diffusion dye is transferred to a dye-fixing element is proposed. In this method, by changing the type of the dye-providing compound to be used or the type of the silver halide to be used, a negative dye image, as well as a positive dye image, can be obtained. More details are described, for example, in U.S. Pat. No. 4,500,626, U.S. Pat. No. 4,483,914, U.S. Pat. No. 4,503,137, U.S. Pat. No. 4,559,290, JP-A-58-149049 (“JP-A” means unexamined published Japanese patent application), JP-A-60-133449, JP-A-59-218443, JP-A-61-238056, EP-A-220 746 (A2), the Journal of Technical Disclosure (“Kokai Giho”) 87-6199, EP-A-210 660 (A2), and the like.
With respect to the method for obtaining a positive color image by heat development, various methods have been proposed. For example, U.S. Pat. No. 4,559,290 proposes a method wherein a so-called DRR compound, which has been formed into an oxidized compound incapable of releasing a dye image, is used under the coexistence with a reducing agent or a precursor thereof. In this method, the reducing agent is oxidized in proportion to the exposure amount of a silver halide by heat development, and the above oxidized compound is reduced with the unoxidized remaining reducing agent, to cause a diffusion dye to be released, to form a positive color image. Further, EP-A-220 746 (A) and the Journal of Technical Disclosure (“Kokai Giho”) No. 87-6199 (Vol. 12, No. 22) describe heat-development color light-sensitive materials wherein use is made, as a compound capable of releasing a diffusion dye by the same mechanism, of a compound capable of releasing a diffusion dye by reductive cleavage of the N-X bond, in which X represents an oxygen atom, a nitrogen atom, or a sulfur atom.
Since the heat-development color light-sensitive material can be processed easily and rapidly in comparison with the conventional wet-development light-sensitive material, development can be conducted by means of a small-sized compact apparatus. Accordingly, relatively inexpensive apparatuses as color printers, or color copies of a silver salt color light-sensitive material system, are being developed and sold. To further broaden the application of these apparatuses, it is considered that various improvements are required.
As the exposure light source for these light-sensitive materials, various proposals are made, and as a digital exposure light source, for example, light-emitting diodes (LED), semiconductor lasers (LD), and various fluorescent substances are used. In the case of inexpensive LEDs or the like, scanning exposure is made by using an exposure head having a plurality of arranged elements, for example, to shorten the exposure time. However, in the system wherein exposure is made by using a plurality of elements like this for one light-sensitive layer, there is a problem that uneven density occurs on the image, due to dispersion (scattering) of the amount of light and exposure wavelength among the elements.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an image-forming method that is improved with respect to the unevenness of exposure density resulting from a plurality of exposure light sources.
Other and further objects, features, and advantages of the invention will appear more fully from the following description.
DETAILED DESCRIPTION OF THE INVENTION
The above object of the present invention has been attained by:
(1) A method for forming an image on a light-sensitive material having on a base at least a light-sensitive silver halide emulsion and a binder, which comprises, subjecting at least one light-sensitive layer to exposure to light, by using an exposure head that has a plurality of different light sources for emitting lights in respective specific wavelength regions correspondingly to adjacent exposure picture elements, to form an image, wherein, in the specific wavelength regions from the shortest wavelength to the longest wavelength for the respective plurality of light sources to be used, the change in sensitivity of the light-sensitive material in the spectral sensitivity curve obtained by plotting the sensitivities of the light-sensitive material in terms of the specific wavelength regions including the wavelengths in centers of gravity of respective light sources is 0.01 log E
m or less;
(2) The method for forming an image as stated in the above (1), wherein the light-sensitive material is a heat-development light-sensitive material having on a base at least three silver halide emulsions different in color sensitivity, a binder, and a dye-providing compound;
(3) The method for forming an image as stated in the above (1) or (2), wherein the exposure light sources for emitting lights in specific wavelength regions are LEDs having wavelengths selected in the light emitting wavelength range of the visible region and the infrared region; and
(4) The method for forming an image as stated in the above (1) or (2), wherein the exposure light sources for emitting lights in specific wavelength regions are blue LEDs, green LEDs, and/or red LEDs.
That is, in the present invention, the wavelength dependence of the sensitivity (relative sensitivity) of the light-sensitive material is to be 0.01 log E
m or less in the above specific wavelength regions.
When a plurality of light sources is used, a change (fluctuation) in density occurs because the light emitting wavelength and the amount of light of each of the light sources disperse. Therefore, the amount of light and the wavelength were measured separately and it was attempted to previously take measures for the correction to make them uniform. However, to the contrary to the expectation, the improvement in the unevenness of density was not satisfactory. It was found that this was because the correction became not satisfactory, due to a measurement error of wavelength in the spectral sensitivity region where the change in sensitivity for wavelength was drastic.
It is possible to select light sources of identical wavelengths by choosing previously, but the yield is considerably bad, which is unpreferable in view of the cost.
In the present invention, it has been found that this problem can be solved by designing a flat spectral sensitivity less varying in sensitivity for wavelength, in the range of light emitting wavelength regions used to correspond to respective color sensitivity regions. That is, it is required that the gradient of the sensitivity (in log E unit) for wavelength in the visible range of the density unevenness is 0.01 log E
m or less.
In the exposure system for use in the present invention, for example, a method wherein image information is subjected to scanning exposure by causing light emitting diodes, various lasers (laser diodes, gas lasers, and the like), and the like to emit light through electrical signals can be used (including methods described, for example, in JP-A-2-129625, JP-A-5-176144, JP-A-5-199372, and JP-A-6-127021).
As the image information, use can be made

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