Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
2000-05-31
2002-06-04
Pham, Hai (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S256000
Reexamination Certificate
active
06400390
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an image recording method and to an image recording apparatus.
Heretofore, in order to record an image on the basis of image data, a silver halide photographic material is exposed to a laser beam. Further, in recent years, it has appeared a thermally developable silver halide photosensitive material which is capable of visualizing an image by thermal development without using a liquid process. However, it has been proved that, if it is exposed to a laser beam, interference fringes are generated to produce unevenness of image. This phenomenon will be explained with reference to
FIG. 15
which is a conceptional drawing showing the relation between the cross-section of a film and a laser beam.
As shown in FIG.
15
(
a
), when a laser beam enters the film F, which is composed of a photosensitive layer of a thermally developable silver halide photosensitive material and a supporting member made of a PET film or the like, from its obverse surface F
1
, owing to a part of the beam being reflected by the reverse surface F
2
and returns to the obverse surface F
1
, interference occurs between the beam B
1
which directly enters the photosensitive layer and the beam B
2
which is transmitted through the photosensitive layer, reflected by the surface F
2
and further reflected by the obverse surface F
1
. For this reason, the light quantity which is applied to the photosensitive layer varies depending on the thickness of the film, and as a result of it, the amount of exposure for the thermally developable silver halide photosensitive material varies, to produce unevenness of density.
If the optical path difference &dgr; between the beam directly entering the photosensitive layer and the beam passing through the photosensitive layer after being reflected by the surfaces F
2
and F
1
is an integral multiple of the wavelength of the laser beam, the light quantity applied to the photosensitive layer becomes maximum, and if it is shifted by a half of the wavelength, the light quantity becomes minimum. The reflectance R at the boundary surface between two media having different refractive indices is expressed by the following equation (1):
R=
((
nB−nA
)/(
nB+nA
))
2
(1),
where nA and nB denote the refractive indices of the media being present at the both sides of this boundary surface respectively.
Now, for example, assuming that the refractive indices of the respective layers of the photosensitive material are the same and uniform, and that nA=1 (air) and nB=1.5 (photosensitive material), the reflectance R at the boundary surface between air and the photosensitive layer is 4%. Further, the variation of light quantity (peak to peak) &Dgr;A owing to interference can be expressed by the following equation (2), reaching a large value of 16%:
&Dgr;
A=
4
R
(2).
Actually, as shown in FIG.
15
(
b
), the variation of light quantity owing to interference becomes less than the above-described value, because a laser beam absorption layer is provided at the rear side of the reverse surface F
2
and scattered light s is generated by the silver halide particles included in the photosensitive layer. However, if there is a slight difference of refractive index between the absorption layer and the photosensitive layer, reflection occurs at the boundary surface F
2
of the absorption layer and the supporting member, to make the absorption layer not to contribute to the reduction of interference. Further, because the conventional photosensitive materials have large sized silver halide particles included, and are capable of being provided with multiple absorption layers, interference fringes are difficult to be generated in them, while a thermally developable photosensitive material has finer silver halide particles than the conventional photosensitive materials, and the light scattering in the photosensitive layer is much less than the conventional films, hence, interference becomes remarkable especially in the case of a high-contrast thermally developable photosensitive material having a &ggr; value (film contrast) of 2 or more.
It is possible to prevent the variation of light quantity owing to interference as described in the above by the countermeasures (a) to (c) as follows:
(a) By providing a reflection reducing film on the reverse surface of the supporting member (F
2
), the reflectance by the boundary surface F
2
between the supporting member and the absorption layer is reduced.
(b) The dispersion of the thickness of the supporting member is suppressed to a fraction one over several or less of the wavelength of the laser beam (generally 0.5 to 1.5 &mgr;m).
(c) By making smaller the difference of refractive index between the supporting member and the absorption layer, the reflectance R at the boundary surface F
2
between the supporting member and the absorption layer is made smaller.
However, the countermeasure (a) results in the raise of cost, and is not favorable. Further, concerning the countermeasure (b), it is possible to suppress the dispersion of the medium having a thickness of several &mgr;m, but it is nearly impossible to suppress the dispersion of the medium having a thickness of 100 &mgr;m or more to a value under 1 &mgr;m or smaller. Furthermore, regarding the countermeasure (c) too, because even a difference of refractive index of only 0.05 or smaller makes interference fringes, it is nearly impossible to adjust the difference of the refractive index between the both members to a value under this level.
Further, in the description of the U.S. Pat. No. 4,711,838, it is disclosed a thermally developable silver halide photosensitive material comprising a surface layer diffusing and transmitting the near infrared light which is in the wavelength region of a laser beam, a reverse surface layer diffuse-reflecting or absorbing this near infrared light, and a layer which is provided between the supporting member and the photosensitive layer and diffuse-transmits or absorbs this near infrared light. Heretofore, it is general to suppress interference fringes by devising the photosensitive material itself as described in the above. Further, in the publication of the TOKUHYOHEI 10-500229, it is disclosed that a laser diode is driven by an input signal for the laser diode to which a high-frequency signal is superposed.
However suppression of interference fringes by devising the photosensitive material gives a bad influence to other characteristics of the photosensitive material, for example, visibility after development and cost of the photosensitive material, or it is not sufficient by itself alone as the countermeasure. Further, the superposing of a high-frequency signal to the input signal for the laser diode is technically difficult, makes cost high, and possibly makes the operation all the more unstable, and further, it has the defect that it makes the efficiency of utilizing light about a half. Furthermore, in a high-contrast photosensitive material having a &ggr; value of 2 or larger, the suppression of interference fringes has not been made enough.
SUMMARY OF THE INVENTION
This invention has been made in view of the above-described problems in the conventional technology; it is an object of this invention to provide an image recording method and an image recording apparatus capable of improving the quality of an image which is formed on a photosensitive material, by reducing the interference fringes of the laser beam by a method which is different from conventional ones.
In order to accomplish the above-described subjects, the image recording method of this invention is an image recording method in which an image is formed on a thermally developable silver halide photosensitive material by making a scanning exposure to a laser beam for said photosensitive material, which has a photosensitive layer including a silver salt of an organic acid and silver halide particles having an average particle size of 0.1 &mgr;m or smaller provided on a supporting member having a thick
Tamakoshi Yasuaki
Umeda Toshikazu
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Konica Corporation
Pham Hai
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