Silver halide X-ray photosensitive material

A silver halide X-ray photosensitive material has a support bearing thereon a silver halide emulsion layer. The layer has at least three kinds of silver halide emulsions whose photographic characteristics are substantially different from each other. Out of at least three kinds of the silver halide emulsions, at least one of them is a monodisperse emulsion E.sub.1 and at least another one of them is a polydisperse emulsion E.sub.2.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a silver halide X-ray photosensitive material for 
medically diagnostic use, and more particularly to a silver halide X-ray 
photosensitive material having a wide exposure latitude in a specific 
region of the characteristic curve thereof and is so sharp as to be 
convenient for medical diagnoses, and still more particularly to the 
so-called direct X-ray photographic film. 
2. Description of the Prior Art 
When X-ray photographing the regions of an organism with a silver halide 
X-ray photosensitive material (hereinafter simply called an X-ray 
photosensitive material), a high order of diagnosing capability is 
required for early finding a nidus and for avoiding a diagnostic error. 
However, the conventional X-ray photosensitive materials cannot always 
satisfy these requirements. 
To be concrete, the conventional direct X-ray photosensitive materials are 
roughly classified into (a) a high-gamma type, (b) a low-gamma type and 
(c) a medium-gamma type. The high-gamma type materials are, substantially 
poor in the information contents in a low exposure area, though the 
sharpness thereof is relatively good; the low-gamma type materials (b) 
are, on the contrary, poor in sharpness, though the information contents 
in the low exposure area are aboundant, so that it is hard to diagnose; 
and the medium-gamma type materials (c) are merely an average in the 
sharpness as well as in the information contents in the low-exposure area. 
On the characteristic curves drawn when the above-mentioned types of direct 
X-ray photosensitive materials were processed in the undermentioned 
processing conditions, .gamma..sub.1 and .gamma..sub.2 were obtained at 
the points of optical density of 0.50 and 1.50, and at the points of 
optical density of 0.05 and 0.30, respectively. The typical examples of 
the .gamma..sub.1 and .gamma..sub.2 are shown in the following Table-1: 
[Processing Conditions] 
Each type of the materials is to be processed with a roller-transport type 
automatic processor, New QX-1200, manufactured by Konishiroku Photo Ind. 
Co., Ltd. Japan, by making use of Developer-1 given below and by following 
the steps mentioned below: 
______________________________________ 
Developing Step 
Temperature 
Time 
______________________________________ 
Developing 35.degree. C. 
30 sec. 
Fixing 34.degree. C. 
20 sec. 
Washing 33.degree. C. 
18 sec. 
Drying 45.degree. C. 
22 sec. 
______________________________________ 
Developer 
Potassium sulfite 55.0 g 
Hydroquinone 25.0 g 
1-phenyl-3-pyrazolidone 
1.2 g 
Boric acid 10.0 g 
Potassium hydroxide 21.0 g 
Triethylene glycol 17.5 g 
5-methylbenztriazole 
0.04 g 
5-nitrobenzimidazole 
0.11 g 
1-phenyl-5-mercaptotetrazole 
0.015 g 
Glutaraldehyde bisulfite 
15.0 g 
Glacial acetic acid 16.0 g 
Potassium bromide 4.0 g 
Add water to make 1.000 cc 
______________________________________ 
Fixer 
SAKURA Acid Hardening Fixer, XF, manufactured by 
Konishiroku Photo Ind. Co., Ltd., Japan. 
______________________________________ 
TABLE 1 
______________________________________ 
.gamma..sub.1 
.gamma..sub.2 
(D = 0.50-1.50) 
(D = 0.05-0.30) 
______________________________________ 
High-gamma type 
2.6-3.0 0.83-0.96 
Medium-gamma type 
2.4-2.7 0.73-0.82 
Low-gamma type 2.0-2.2 0.68-0.72 
______________________________________ 
There are some instances where the following serious faults or 
disadvantages are practically experienced in X-ray photographing with the 
conventional types of direct X-ray photosensitive materials. Namely, a 
region of an organism most frequently X-rayed is chest, and the important 
parts for chest X-ray reading are blood vessels in lung fields and 
coronary artaries behind a heart. 
Lung fields are in a medium-density area (D=1.3-1.5) and a high sharpness 
is required for reading the blood vessels in the lung fields, and coronary 
arteries are in a low-density area (D=0.05-0.30), and a wide latitude is 
required for reading. 
Conventional X-ray photosensitive materials of high-gamma type do not 
contribute substantially to the efficiency of diagnoses because they take 
the coronary arteries only in extremely low density though they take lung 
fields sharply. On the contrary, when using those of low-gamma type, the 
lung fields are taken unsharply, though the coronary arteries are taken 
reasonably. 
As for the methods of avoiding such disadvantages to diagnoses as mentioned 
above, there is a method of using a double-gamma type of X-ray 
photosensitive materials in which two kinds of polydisperse emulsions each 
having the different gradation (i.e., gamma; .gamma.), and the method is 
naturally limited in the discretionary control of the characteristic curve 
thereof. In addition, there is a proposal of constituting a characteristic 
curve of which the low, midium and high density regions are regulated by 
three kinds of emulsions each different in photographic characteritics, 
and in this proposal, the characteristic curve may be controlled fairly. 
However, if two or more kinds of such polydisperse emulsions are used in 
combination, the value of .gamma. is so sharply lowered that it can hardly 
be put in practical use if it is anything of medical X-ray photosensitive 
materials. 
On the other hand, there is another proposal of preventing a .gamma.-value 
of a mixed emulsion from lowering, by the mixture of monodisperse 
emulsions. In this proposed method, it is found that there are such 
problems as that the information contents in the low-density region of a 
characteristic curve are substantially less, that is, the .gamma.-value is 
raised excessively and the exposure latitude of the low-density region is 
narrowed, and any smooth characteristic curve cannot be obtained. 
In the industry skilled in the art, it is well-known that the larger the 
sizes of high-speed silver halide grains of a photographic light-sensitive 
material are, the more a desensitization is freqently caused under a 
mechanical pressure prior to an exposure to light, that is, a pressure 
desensitization. With a medical X-ray film, for example, a pressure 
desensitization is apt to occur, while being handled, by such a crease as 
the so-called knick mark, because of the large film-sizes. Further in 
recent years, as for a medical X-ray photographic system, an automatic 
exposing and processing apparatus equiped with a mechanical transport 
means are popularly used. In such an apparatus, it is hardly avoided to 
affect films by a mechanical force. Especially in a dry condition such as 
winter-time, there frequently cause a pressure desensitization. When 
causing such a phenomenon in some place, there may be a danger of making 
an doctor erroneously diagnose and getting the doctor and his patient into 
a serious trouble. 
With the purpose of improving such pressure desensitization as mentioned 
above, U.S. Pat. Nos. 2,628,167, 2,759,822, 3,445,235 and 2,296,204 
disclose the silver halide photosensitive materials such as those using a 
silver halide emulsion containing thallium or those using dyes. They are, 
however, not satisfactorily improved and are seriously stained with the 
dyes, and it can hardly say that the other ones are always capable of 
satisfactorily displaying the characteristics of silver halide 
photosensitive materials mainly utilizing an ordinary and high 
surface-sensitivity of silver halide grains having a large average grain 
size. 
On the other hand, many attempts are made to improve such pressure 
desensitization by changing the physical properties of the binders of 
silver halide photographic light-sensitive materials. For example, those 
attempts are described in U.S. Pat. Nos. 3,536,491, 3,775,128, 3,003,878, 
2,759,821 and 3,772,032. With those technique, however, any fundamental 
improvement cannot be attained, even though the pressure desensitization 
may be improved, because the surface of a film becomes sticky and the 
physical properties of binders such as the dryness, scratches and the like 
are deteriorated seriously. 
SUMMARY OF THE INVENTION 
Objects of the Invention 
It is an object of the invention to provide an X-ray photosensitive 
material which is high in definition, wide in the exposure latitude of the 
low-density area thereof and high in diagnosing capability. 
Another object of the invention is to provide an X-ray photosensitive 
material in which a pressure desensitization is improved. 
Constitution of the Invention 
The present inventors found that an X-ray photosensitive material capable 
of displaying the photographic characteristics which are fit for the 
objects can reproducibly and easily be prepared by using in combination at 
least three kinds of silver halide emulsions containing a polydisperse and 
monodisperse emulsions and having different photographic characteristics 
from each other. That is to say, such X-ray photosensitive material of the 
invention characteristically comprises at least three kinds of silver 
halide emulsions having substantially different photographic 
characteristics from each other and out of the three kinds thereof at 
least one is a monodisperse emulsion E.sub.1 and at least one is a 
polydisperse emulsion E.sub.2. The objects of the invention can be 
achieved by the above-mentioned constitution.

DETAILED DESCRIPTION OF THE INVENTION 
In this invention, it may be allowed to use more than three kinds of 
emulsions having different photographic characteristics from each other. 
It is however practically good enough to use three kinds of them and it is 
therefore good enough to use a single kind each of monodisperse emulsion 
E.sub.1 and polydisperse emulsion E.sub.2 out of the three kinds of them. 
The rest one may be selected from the disperse emulsions according to the 
characteristics of the above-mentioned two kinds of emulsions E.sub.1, 
E.sub.2. 
In this invention, the words, "substantially different photographic 
characteristics", mean that out of the photographic characteristics 
including sensitivity, gradation, color sensitivity, color rendering 
property, developability, image-sharpness, graininess and the like, at 
least the sensitivity and the gradation are different from each other. 
Monodisperse emulsion E.sub.1 to be used in this invention is a silver 
halide emulsion of which at least 80% and more preferably 95% of the 
grains thereof by number or weight are in a size within .+-.40% and more 
preferably .+-.30% of the average grain size, when the average grain size 
is measured in the following method reported by Trivelli and Smith. 
A further preferable monodisperse emulsion E.sub.1 of the invention is that 
of the variation coefficient of grain sizes of not more than 0.20. An 
average grain size r can be obtained in the following formula; 
##EQU1## 
in which the diameter r of the grains of an emulsion is divided into n 
sections and a grain size and grain number belonging to the first section 
of n sections are designated by ri and ni, respectively. Further a 
standard deviation value s can generally be obtained in the following 
formula; 
##EQU2## 
and a variation coefficient VC can be obtained in the following formula; 
##EQU3## 
Consequently, a monodispersibility to be determined for the emulsions 
relating to this invention is formulated as s/r.ltoreq.0.20. 
Monodisperse silver halide emulsions preferably be used in this invention 
comprise substantially the so-called regular-crystal emulsions. The term, 
regular-crystal emulsion means an emulsion substantially comprising 
crystallized grains in a regular form such as a cube, octahedron, 
tetradecahedron, dodecahedron, sphere or the like. For example, these 
regular-crystal emulsions are described in T. H. James, "The Theory of the 
Photographic Process", 5th edition, published by MacMillan Publication 
Co., Inc., p. 22. 
In this invention, the regular-crystal emulsions include those rounded off 
by a silver halide solvent or the like to such a degree that the original 
form before rounding is recognizable. 
In addition, the term, "polydisperse" means a state where at least 10% by 
number or weight of distributed grains are varied by 40% in size from the 
average grain size when measuring the average grain size in such an 
ordinary method as reported by Trivelli and Smith in "The Photographic 
Journal", No. 79, 1939, pp. 330-338. Emulsions of which 25% of the grains 
at the most are varied in size from the average grain size may preferably 
be used in this invention. 
Polydisperse silver halide emulsion E.sub.2 which is preferably used in 
this invention substantially comprises the so-called twinned crystals. 
Such twinned crystal emulsions are in the tabular, bar, or irregular form, 
and substantially comprise crystallized grains having twinned planes. In 
this invention, they also include those rounded off to the same extent as 
described above. For example, these twinned crystals are also described in 
"The Theory of the Photographic Process", p. 22. 
Further, the grain shape and its sizes can be observed by the use of an 
electron micrographic means or the grain sizes can be obtained by the use 
of a centrifuge type Stokes' diameter measuring instrument. 
A gradient .gamma. is generally determined in the manner that a 
characteristic curve is drawn on a rectangular coordinates system of which 
the coordinate axes of optical density D and exposure logarithm log E are 
graduted with the same unit degrees, and thereon a gradient .gamma. is 
determined by a tan 0 of angle 0 made between a straight line connected 
between two points on the characteristic curve and the axis of log E. 
In this invention, an X-ray photosensitive material in which a pressure 
desensitization is improved by at least three kinds of emulsions 
containing monodisperse emulsion E.sub.1 and polydisperse emulsion 
E.sub.2, in the case that a value of gamma .gamma..sub.1 determined by the 
effective density points of 0.50 and 1.50 on a characteristic curve is 
from 2.7 to 3.3 and a value of gamma .gamma..sub.2 determined by the 
effective density points of 0.05 and 0.30 is from 0.36 to 0.65, and the 
characteristic curves mentioned in this invention are drawn on a 
rectangular coordinates system on which the same unit degrees of optical 
density D and exposure logarithm log E are graduated on the respective 
coordinate axis. 
On the characteristic curve, the above-mentioned .gamma..sub.1 means an 
inclination of a straight line connected between a point of a base 
(support) density+a fog density+effective density 0.50 and a point of the 
base density+the fog density+effective density 1.50, and the 
above-mentioned .gamma..sub.2 means an inclination of a straight line 
connected between a point of the base density+the fog density+effective 
density 0.05 and a point of the base density+the fog density+effective 
density 0.30. 
In a numerical expression, .gamma..sub.1 and .gamma..sub.2 mean tan 0.sub.1 
and tan .theta..sub.2, respectively, provided that the angles made between 
the straight lines and the axes of exposure (i.e., the axes of abscissas) 
represent .theta..sub.1 and .theta..sub.2, respectively. 
In this invention, the above-mentioned polydisperse emulsion E.sub.2 has 
the highest speed among the at least three emulsions used in combination, 
and it is in charge of the toe portion of a characteristic curve, that is, 
it is in charge of an effective density of from 0 to 0.6 which is obtained 
by deducting a fog density and a base density from a density measured, or 
it is in charge of the effective density zero up to 25% of a maximum 
effective density on the characteristic curve. 
Under the conditions of an ordinary process such as Processing Conditions N 
in which the above-mentioned emulsion E.sub.2 is so coated independently 
as to be in a regular thickness (i.e., the emulsion E.sub.2 is coated so 
as to be 2.5 to 3.5 in a maximum effective density), the proper gamma 
value .gamma..sub.0 thereof is from 1 to 3, and the average grain size 
thereof is of the order of 0.8 to 3 .mu.m, preferably 1 to 3 .mu.m. 
In this invention, on the other hand, monodisperse emulsion E.sub.1 has a 
medium speed among the at least three emulsions used in combination, and 
according to the above-mentioned definition, the proper gamma value 
.gamma..sub.0 thereof is from 3 to 5, and the average grain size thereof 
is of the order of 0.5 to 2 .mu.m. It is preferred that such a 
monodisperse emulsion may chiefly be in charge of from 20% to 80% of a 
maximum value of an effective density on a characteristic curve. 
In this invention, other emulsion having relatively minimal speed which is 
in charge of a maximum effective density portion of the characteristic 
curve is used. To be concrete, this emulsion is in charge of a portion 
having not less than 50% of a maximum effective density or a portion 
having an effective density of not less than 1.20. Such emulsion may be so 
selected as to be suitable for the requirements for the characteristics, 
no matter what is selected from either monodisperse emulsions or 
polydisperse emulsions. A value of .gamma..sub.0 is from 3 to 5 if it is a 
monodisperse emulsion, and from 1 to 3 if it is polydisperse emulsion. The 
average grain size of them is from 0.3 to 0.8 .mu.m. 
Providing that the speed of a medium speed emulsion, i.e., a monodisperse 
silver halide emulsion E.sub.1 is regarded as 100, the ratios to the 
speeds of every emulsion are as follows: 
Polydisperse silver halide emulsion E.sub.2 : 
monodisperse silver halide emulsion E.sub.1 : 
other emulsions=(140-300):100:(50-80) 
Further, providing that the speed of the above-mentioned monodisperse 
silver halide emulsion is regarded as 100, the speed of polydisperse 
silver halide emulsion is preferably from 110 to 300. 
[Processing Conditions N] 
(1) How to exposure 
A photosensitive emulsion layer is coated over the both surfaces (or one 
surface) of the transparent base (support) of an X-ray photosensitive 
material so as to be 2.5 to 3.5 in a maximum effective density. The X-ray 
photosensitive material is sandwiched between two pieces of optical wedge 
adjusting the density inclination to be synmetric mirror-reflectionwise, 
and is then exposed to light of 5400.degree. K. in the same quantity from 
both sides at the same time for one tenth of a second. 
(2) How to process 
a. Steps processing is made with the following developer and a 
roller-transport type automatic processor, a New QX-1200 Model, 
manufactured by Konishiroku Photo Ind. Co., Ltd., Japan, and according to 
the following steps: 
______________________________________ 
Temperature 
Time 
______________________________________ 
Developing step 
35.degree. C. 
30 sec. 
Fixing step 34.degree. C. 
20 sec. 
Washing step 33.degree. C. 
18 sec. 
Drying step 45.degree. C. 
22 sec. 
______________________________________ 
b. Processing liquids 
______________________________________ 
Developer 
______________________________________ 
Potassium sulfite 55.0 g 
Hydroquinone 25.0 g 
1-phenyl-3-pyrazolidone 
1.2 g 
Boric acid 10.0 g 
Potassium hydroxide 21.0 g 
Triethylene glycol 17.5 g 
5-methylbenztriazole 
0.04 g 
5-nitrobenzimidazole 
0.11 g 
1-phenyl-5-mercaptotetrazole 
0.015 g 
Glutaraldehyde bisulfite 
15.0 g 
Glacial acetic acid 16.0 g 
Potassium bromide 4.0 g 
Add water to make 1.000 cc 
______________________________________ 
Fixer 
Acid hardening fixer, Sakura XF, manufactured by Konishiroku Photo Ind. 
Co., Ltd., Japan 
In the invention, any desired characteristic curve can almost freely be 
obtained by controlling the speeds and proper gamma values of at least 
three kinds of the emulsions mentioned above as well as by controlling the 
ratios of the quantity of emulsions used to each other, the thickness 
thereof and the like. 
As for a composition of a silver halide of emulsions relating to this 
invention, anyone of silver bromide, silver iodobromide and silver 
iodobromochloride may be used and among them silver iodobromide is 
preferably used. The silver iodide content thereof is not more than 10 mol 
% and is preferably from 0.1 to 6 mol %. 
It may also be allowed to dope these silver halides with a veriety of metal 
salts for adjusting photographic characteristics, such as an iridium salt 
for improving photoflash exposure characteristics, a rhodium salt for 
adjusting speeds and gamma values, a thallium salt for improving pressure 
resistance, and the like. 
Polydisperse emulsions E.sub.2 relating to this invention can be prepared 
in any publicly known process. They can be prepared by applying such a 
process as a neutral process, an acid process, an ammonia process, a 
normal precipitation process, a reverse precipitation process, a 
double-jet process, a controlled double-jet process, a conversion process, 
a core/shell process, or the like described in, for example, T. H. James, 
"The Theory of the Photographic Process", 4th edition, published by 
Macmillan Publishing Co., Inc., 1977, pp. 38-104, and the like. 
Other examples of polydisperse emulsions E.sub.2 of this invention include 
a silver halide emulsion comprising tabular shaped silver halide grains of 
which grain size is not less than five times as thick as the grain 
thickness. 
Such tabular shaped silver halide grains can be prepared in any process 
publicly known in the industry skilled in the art. 
For example, as described in Hidemaru Sakai's doctoral thesis, "Studies on 
the Preparation Processes of Photodevelopment Type Silver Halide 
Photosensitive Materials", published in October, 1960, and available at 
the Japan National Library, there is a known process in which small 
tabular shaped grains prepared at a high pBr value are added with ungrown 
fine grains precipitated under the same conditions so that the ungrown 
fine grains may be grown. 
There are also known processes such as a process described in, for example, 
Japanese Patent Publication Open to Public Inspection (hereinafter called 
Japanese Patent O.P.I. Publication) No. 113928/1983, in which, in the 
initial stage, grains in a reactor, do not substantially contain any 
iodide ion and the preparation thereof is made at a pBr value of from 0.6 
to 1.6, and then they are grown by adding a silver salt, a bromide or an 
iodide; and such a process as described in Japanese Patent O.P.I. 
Publication No. 127921/1983 in which tabular shaped grains are formed, in 
a pBr atmosphere of not more than 1.3, into seed crystals in which the 
tabular shaped grains are present in the quantity of not less than 40% by 
weight, so that the seed crystals are grown while the pBr value is being 
kept in the previous degree and at the same time the solutions of silver 
and a halogen is being added thereto. 
When preparing a monodisperse emulsion E.sub.1 relating to this invention, 
it is desired to accelerate the rates of adding a water-soluble silver 
salt and a water-soluble halide as the silver halide grains are grown. If 
such adding rates are accelerated, the grain size distribution may further 
be monodispersed and the mixing time may also be shortened. Accordingly, 
these facts lead to advantages in an industrial production and are also 
favorable from the point of view that the possibilities of the structural 
defects caused in silver halide grains may be reduced. 
Processes of accelerating the adding rate include the processes such as 
disclosed in Japanese Patent Examined Publication Nos. 36890/1973 and 
16364/1977 and Japanese Patent O.P.I. Publication No. 142329/1980 in which 
the rates of adding an aqueous solution of a silver salt and an aqueous 
solution of a halide may be allowed to accelerate continuously or 
stepwise. The rate of an adding flux just before new nuclear grains are 
produced is allowed to serve as the highest limit of the above-mentioned 
adding rates. The values of such a highest limit are varied according to a 
temperature, pH, pAg, agitation degree, compositions of silver halide 
grains, solubility, grain sizes, distance between grains, protective 
colloids and the density thereof, and the like. 
The processes of preparing the monodisperse emulsions E.sub.1 relating to 
this invention are publicly known. For example, they are described in 
"Journal of Photographic Science", 12, pp. 242-251, 1963, Japanese Patent 
Examined Publication Nos. 36890/1973 and 16364/1977, Japanese Patent 
O.P.I. Publication Nos. 142329/1980 and 179835/1982, and U.S. Pat. No. 
4,026,668. 
Silver halides to be used in the invention may also be of core/shell type. 
These silver halides may chemically be sensitized with chemical sensitizers 
independently or in combination, including for example, a sulfur 
sensitizer such as sodium thiosulfate, thiourea and the like; a noble 
metal sensitizer such as a gold sensitizer including a gold acid chloride, 
gold trichloride and the like, a palladium sensitizer such as palladium 
chloride, palladium acid chloride and the like, a platinum compound, an 
iridium compound, and the like; a selenium sensitizer such as selenious 
acid, selenourea and the like; a reduction sensitizer such as stannous 
chloride, a polyamine including diethylenetriamine, thiourea dioxide, a 
sulfite, silver nitrate and the like. A variety of sensitizing dyes and 
other additives may be added thereto so as to answer to the purposes. 
Wherein, such a technique or the like as described in "Research 
Disclosure" Nos. 17643 and 18431 may be applied thereto. 
At least three kinds of emulsions to be used in this invention may be used 
in the mixture or laminated independently. 
When chemically sensitizing a silver halide emulsion Em.sub.2 of this 
invention for toe portion of a characteristics curve, (which is preferably 
a polydisperse emulsion E.sub.2 of this invention) and a silver halide 
emulsion Em.sub.1 of this invention for a medium density portion (which is 
preferably a monodisperse emulsion E.sub.1 of this invention), there are 
two processes, that is, one process in which the respective emulsions are 
chemically sensitized separately under optimum conditions, and another 
process in which after mixing up the two emulsions, the mixture is 
chemically sensitized. The preferable process is the former. 
Photosensitive materials of this invention can be variously constructed. 
For example, (1) the above-mentioned silver halide emulsion Em.sub.2 for a 
toe portion and silver halide emulsion Em.sub.1 for a medium density 
portion are mixed up in an appropriate proportion, and the mixture thereof 
is coated on a base (support), and a protective gelatin-layer is then 
provided thereon. The coated layer is allowed to contain a remaining 
emulsion of this invention; (2) silver halide emulsion Em.sub.1 for a 
medium density portion is coated to be a layer on a base and silver halide 
emulsion Em.sub.2 for a toe portion is provided thereon to be a layer, and 
a protective gelatin-layer is further provided thereon. Either Em.sub.1 or 
Em.sub.2 is allowed to contain a remaining emulsion of this invention; (3) 
silver halide emulsion Em.sub.2 for a toe portion is coated to be a layer 
on a base and silver halide emulsion Em.sub.1 for a medium density portion 
is coated thereon to be a layer, and a protective gelatin-layer is further 
coated thereon. Either Em.sub.1 or Em.sub.2 is allowed to contain a 
remaining emulsion of this invention; or (4) In the above-mentioned 
constructions from (1) through (3), a dye-layer is provided between the 
base and the emulsion layer so that any crossover rays can be cut. 
The silver halide weight proportion of silver halide emulsion Em.sub.2 for 
a toe portion to silver halide emulsion Em.sub.1 for a medium density 
portion to be used in this invention is preferably from 3:97 to 35:65 and 
more preferably from 5:95 to 25:75. 
At least three kinds of silver halide emulsions of this invention are to be 
used in silver halide photographic photosensitive materials for X-ray 
photographic use. When these three kinds of emulsions are a high-speed 
emulsion (i.e., a polydisperse emulsion E.sub.2), a medium-speed emulsion 
(i.e., a monodisperse emulsion E.sub.1), and a low-speed emulsion (i.e., 
either of a polydisperse emulsion and a monodisperse emulsion may be 
used), the content ratio by weight of these emulsions is 10-120:100:10-90 
and preferably 30-100:100:50-80, respectively. 
How to laminate such emulsion layers may be determined, taking the speed, 
coating thickness, developability, light permeability and the like of each 
emulsion into consideration. 
Hydrophilic colloids to be used independently or in combination in relation 
to this invention include not only gelatin but also a variety of gelatin 
derivatives such as a gelatin derivative prepared by the interaction of 
gelatin and an aromatic sulfonyl chloride, an acid chloride, an acid 
anhydride, an isocyanate, an 1,4-diketone, a gelatin derivative prepared 
by the interaction of gelatin and a trimellitic acid anhydride, a gelatin 
derivative prepared by the interaction of gelatin and an organic acid 
containing an active gelatin, a gelatin derivative prepared by the 
interaction of gelatin and an aromatic glycidyl ether, a gelatin 
derivative prepared by the interaction of gelatin and maleimide, maleamic 
acid, an unsaturated aliphatic diamide or the like, a sulfalkylated 
gelatin, a polyoxyalkylated gelatin derivative, a high polymer grafted 
gelatin, a synthetic hydrophilic high polymer substance, and a natural 
hydrophilic high polymer substance other than gelatin, such as casein, 
agar, and an alginic polysaccharide. 
Emulsions relating to this invention may be added with a variety of popular 
additives so as to meet the purposes. These additives include, for 
example, a stabilizer or an antifoggant such as an azaindene, a triazole, 
a tetrazole, an imidazolium salt, a tetrazolium salt, a polyhydroxy 
compound and the like; a hardener such as those of an aldehyde, an 
aziridine, an inoxazole, a vinyl sulfone, an acryloyl, an albodiimide, a 
maleimide, a methanesulfonic acid ester, a triazine and the like; a 
development accelerator such as benzyl alcohol, a polyoxyethylene compound 
and the like; an image stabilizer such as those of a chroman, a coumaran, 
a bisphenol, and a phosphorous acid ester; and a lubricant such as a wax, 
a glyceride of a higher fatty acid, a higher alcohol ester of a higher 
fatty acid; and the like. There can also be used a surface active agent 
such as a coating aid, a permeability improving agent for a processing 
liquid or the like, a defoaming agent, or a material for controlling a 
variety of physical properties of a photosensitive material, such as 
various kinds of those of anion type, cation type, non-ion type or 
amphoteric type. Effective antistatic agents include a diacetyl cellulose, 
a styrene perfluoralkyl sodium maleate copolymer, an alkali salt of a 
reactant prepared by the interaction of p-aminobenzene sulfonic acid and a 
styrene-maleic acid anhydride copolymer. Matting agents include, for 
example, methyl polymethacrylate, polystyrene, an alkali-soluble polymer, 
and the like; and a colloidal silicon oxide may further be used. Latexes 
to be added for improving the physical properties of a layer include, for 
example, a copolymer of an acrylic acid ester, a vinyl ester or the like 
and a monomer having other ethylene group. Gelatin plasticizers include, 
for example, glycerol and a glycol compound. Thickening agents include, 
for example, a styrene-sodium maleate copolymer, an alkylvinyl 
ether-maleic acid copolymer and the like. 
Bases (supports) relating to this invention include, for example, a glass 
plate, a cellulose acetate film, a cellulose nitrate film, a 
polyvinylacetal film, a polypropylene film, a polyester film such as a 
polyethylene terephthalate film, a polystyrene film and the like. These 
bases may suitably be selected in accordance with the purposes or the 
forms of the use. 
These bases may be sublayered if occasion demands. 
A variety of coating methods may be used for coating the component layers 
of a photosensitive material relating to the invention. For example, they 
include, for example, an impregnation method, on air-knife method, a 
curtain method, and an extrusion method using such a hopper as described 
in U.S. Pat. No. 2,681,294. Simultaneous double or multiple layer coating 
may also be made, if preferred, in such a method as described in U.S. Pat. 
No. 2,761,791 or British Pat. No. 837,095. 
EFFECTS OF THE INVENTION 
According to this invention, an optimum characteristic curve can be 
obtained by making a good use of the characteristics of at least three 
kinds of emulsions so as to meet the conditions of a region to be 
subjected to diagnose. 
According to this invention, the exposure latitude ranges of both high 
density and low density regions can be satisfied at the same time, so that 
an X-ray photosensitive material capable of displaying a high 
diagnosability can be provided and particularly the defects of the 
conventional types of X-ray photosensitive materials caused in chest X-ray 
photography can be eliminated, and, in addition, an X-ray photosensitive 
material improved in a pressure desensitization can be provided. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Now, this invention will further be described with reference to the 
following preferred embodiments thereof and it is to be understood that 
this invention shall not be limited to the embodiments. 
EXAMPLE 1 
In a single-jet method and a full-ammonia method, a twinned-crystal type 
silver iodobromide emulsion E-1 containing silver iodide of 2 mol % and 
having an average grain size of 1.03 .mu.m and s/r=0.28 was prepared. 
Emulsion E-2 similar to E-1 was also prepared except that the average 
grain size thereof was 1.5 .mu.m, and s/r=0.25. And, Emulsion E-3 similar 
to E-1 was further prepared except that the average grain size thereof was 
0.5 .mu.m and s/r=0.32. 
Next, in a controlled double-jet method, two kinds of monodisperse silver 
iodobromide emulsion containing silver iodide of 2 mol % were prepared. 
One emulsion E-4 comprising rounded hexahedral perfect-crystals was so 
prepared as to have the average grain size of 0.65 .mu.m and s/r=0.162, 
and the other emulsion E-5 was prepared in the same manner as in E-4, 
except that the average grain size was 1.18 .mu.m and s/r=0.123. 
The above-mentioned emulsions were gold sulfur-sensitized under the optimum 
conditions, respectively. 
Each X-ray photosensitive material sample was prepared respectively in such 
a manner as shown in Table-1 that each of the emulsions was mixed in a 
prescribed combination, and each of the mixture thereof was added with 
additives, which are known in the industry skilled in the art, such as 
stabilizer, antifoggant, coating aid and the like in the same quantity, 
and each of the mixed emulsion was coated on the both surfaces of a 
polyethyleneterephthalate base so that the amount of silver can be 73 mg 
per dm.sup.2, respectively. These samples interposed between two sheets of 
intensifying screen for regular type use were exposed to X-rays through an 
aluminium wedge at 90 KVP of a tube voltage and 100 mA of a tube current 
for 0.06 seconds. The exposed samples were developed with an automatic 
processor, QX-1200 Model manufactured by Konishiroku Photo Ind. Co., Ltd., 
Japan, using a developer, which is the same developer as described in page 
3. The obtained characteristic curves I-(1), I-(2), and I-(3) are shown in 
FIG. 1. The characteristic curve I-(3) relating to this invention proves 
that the speed is high, the expression in a toe portion is satisfactory, a 
region between the density values of 1 and 2 provides a favorable gamma 
value and the region can be expressed sharply. In I-(2) which used only 
the polydisperse emulsions in combination, the gamma values are lowered 
markedly, and in I-(1), the information of the toe portion becomes 
unsatisfactory. 
TABLE 1 
______________________________________ 
Mixture Proportion (by weight) 
Curve No. 
E-1 E-2 E-3 E-4 E-5 
______________________________________ 
I-(1) 100 -- -- -- -- For Comparison 
I-(2) 50 20 30 -- -- For Comparison 
I-(3) -- 20 -- 30 50 This Invention 
______________________________________ 
EXAMPLE-2 
FIG. 2 illustrates the respective characteristic curves, II-(1), II-(2) and 
II-(3) of an emulsion given in Example-1 in which two kinds of 
monodisperse emulsions are used in combination, another emulsion given in 
Example-1, in which two kinds of polydisperse emulsions are used in 
combination and a further emulsion of this invention given in Example-1, 
in which three kinds of emulsions are used in combination. Table-2 
illustrates every combinations of the emulsions and the proportion of 
every mixture of the emulsions. 
The characteristic curve II-(3) of the emulsion of this invention proves to 
have a satisfactorily high speed in the foot region and a high gamma value 
of from 1.0 to 2.5 in density, and the characteristic curve is an ideal 
one for medical use. 
TABLE 2 
______________________________________ 
Mixture Proportion (by weight) 
Curve No. 
E-1 E-2 E-3 E-4 E-5 
______________________________________ 
II-(1) -- -- -- 25 75 For Comparison 
II-(2) 60 -- 40 -- -- For Comparison 
II-(3) -- 20 -- 30 50 This Invention 
______________________________________ 
EXAMPLE-3 
FIG. 3 illustrates the characteristic curves of the respective emulsions 
given in Example-1, in which the combination thereof and the mixture 
proportion thereof were changed as shown in Table-3. It is easy to change 
a characteristic curve freely by changing a mixture proportion as shown in 
Table-3. 
TABLE 3 
______________________________________ 
Mixture Proportion (by weight) 
Curve No. 
E-2 E-4 E-5 E-3 
______________________________________ 
III-(1) 10 30 60 -- For Comparison 
III-(2) 30 -- 50 20 For Comparison 
III-(3) 20 30 50 -- This Invention 
______________________________________ 
EXAMPLE-4 
Silver iodobromide monodisperse emulsion in regular octahedral form having 
the average grain size of 1.05 .mu.m was prepared in the manner that a 
potassium bromide solution containing potassium iodide of 2.0 mol % and an 
ammoniacal silver nitrate solution were added in an aqueous gelatin 
solution in a double-jet method with increasing the flow rate. Further, 
the emulsion was covered with pure silver bromide shells by adding an 
ammoniacal silver nitrate solution and a potassium bromide solution in a 
double-jet method. In course of the process, the pAg was kept at 10.0 and 
the pH was gradually lowered from 9.0 to 8.0. The emulsion thus obtained 
is called Emulsion [A]. Emulsion [A] was a perfectly crystallized 
monodisperse emulsion in octahedral form having the average grain size of 
1.25 .mu.m and s/r=0.15. 
On the other hand, Emulsion [B] was prepared by treating a silver 
iodobromide emulsion having the same halide composition as in Emulsion [A] 
in a normal precipitation method. This Emulsion [B] was a twinned crystal 
type polydisperse emulsion having the average grain size of 1.25 .mu.m 
(i.e., 15% by number of grains were made oversize by not less than 40% of 
the average grain size. 
A solution containing 12 g of gelatin, 0.3 g of potassium bromide and 720 
cc of water and being kept at 70.degree. C. was added at the same time 
with a solution containing 36 g of silver nitrate in 240 cc of water and a 
solution containing 25.4 g of potassium bromide in 240 cc of water by 
taking 30 seconds, and then an Ostwald ripening process was applied, and 
thereby an emulsion comprising fine and tabular shaped grains was 
obtained. 
To the emulsion was added further with an aqueous silver nitrate solution 
and an aqueous potassium bromide solution containing potassium iodide of 
2.0 mol % in a double-jet method. In course of adding these solutions, the 
pAg and pH values were kept at 0.8 and 2.0, respectively. The obtained 
tabular shaped grains were 1.65 .mu.m in the average grain size and 12.0 
in the ratio of the thickness to the grain size. The twinned crystal 
emulsion thus obtained is called Emulsion [C], (i.e., 13% by number of 
grains will be made oversize by not less than 40% of the average grain 
size). 
Further, a perfectly crystallized octahedral monodisperse emulsion of 1.65 
.mu.m in the average grain size and s/r=0.13 was prepared in the same 
process as taken in Emulsion [A]. The emulsion thus obtained is 
hereinafter called Emulsion [D]. 
Still further, a twinned crystal type polydisperse emulsion (hereinafter 
called Emulsion [E] of 1.65 .mu.m in the average grain size was prepared 
in the same process as taken in Emulsion [B]. (In Emulsion [E], 18% by 
number of grains will be made oversize by not less than 40% of the average 
grain size.). 
Finally, a perfectly crystallized octahedral monodisperse emulsion, 
(hereinafter called Emulsion [F]), of 0.70 .mu.m in the average grain size 
and s/r=0.12 was prepared in the same process as taken in Emulsion [A]. 
After desalting, these emulsions were gold-sensitized and sulfur-sensitized 
and were then stabilized by adding 
4-hydroxy-b-methyl-1,3,3a,7-tetrazaindene, so that these emulsions were 
selectively mixed as shown in Table-4. After each of the emulsions was 
added with general type of additives for photographic use such as a 
spreading agent, a hardener and the like, the emulsions were coated 
respectively on the both surfaces of a blue-dyed and sublayered 
polyethyleneterephthalate film base so that the amount of silver may be 30 
mg per 100 cm.sup.2, and dried. Thus, the sample (Nos. 1-17) of 
photosensitive materials for X-ray photographic use were prepared. 
Sensitometry of each of these samples was made under the aforementioned 
processing conditions N. The processor used was a roller-transport type 
automatic processor, Model New QX-1200 manufactured by Konishiroku Photo 
Ind. Co., Ltd., Japan. 
The evaluation values of the sharpness were expressed by the values of 1.0, 
1.5, 2.0 lines per mm on the respective optical transfer function (OTF) 
curves. The measurement of the OFT of each sample was made in such a 
manner that an OTF measurement chart having thereon lead-made rectangular 
waveforms of from 0.8 to 10 lines per mm was brought into contact with the 
back surface of a fluorescent screen on this side and an exposure was made 
to X-rays so that a total density of both sample surfaces of the regions 
remaining uncovered with the lead-made rectangular waveforms may be 1.0, 
and the back side emulsion layer was pealed off, and the waveformed 
pattern on the other surface was measured by scanning perpendicularly to 
the rectangular waveforms with a Sakura Microdensitometer Model M-5 
manufactured by Konishiroku Photo Ind. Co., Ltd., Japan. The aperture size 
at this time was 230 .mu.m in the parallel direction by 25 .mu.m in the 
perpendicular direction, and the magnification ratio was 100 times. 
When evaluating an exposure latitude, an optical density was expressed by 
the logarithmic exposure difference between a fog density plus 0.05 and 
the fog density plus 0.30. 
On the other hand, a pressure desensitization was measured as follows: 
Each sample was kept constant for about 12 hours, at the temperature of 
25.degree. C. and at the relative humidity of 50%, and under these 
conditions it was bent at an angle of about 280.degree. C. Three minutes 
after it was bent, an exposure was made to light through an optical wedge 
for 10.sup.-2 seconds by means of a tungsten light source, and was 
processed similarly to the aforementioned process with Developer-1. 
The pressure desensitization was evaluated as follows: 
After obtaining the results of blackened density at several points between 
0.5 and 1.5 of the blackened density, the density difference between a 
pressure-desensitized area caused by bending and an area unbent is 
designated by D, and the .DELTA.D was divided by each of the density D so 
as to obtain an average value .DELTA.D/D. This average value was used as 
the standard of pressure desensitization caused by bending. Accordingly, 
the less this value is, the less a pressure desensitization is. 
Table-4 shows the results thereof. 
TABLE 4 
__________________________________________________________________________ 
Exposure 
Pressure 
Sample 
Mixture Proportion (%) of Emulsions 
Gamma 1 
Gamma 2 OTF (lines/mm) 
Latitude 
Desensitization 
No. [A] 
[B] 
[C] 
[D] 
[E] 
[F] 
D = 0.5-1.5 
D = 0.05-0.30 
1.0 
1.5 2.0 
D = 0.05-0.30 
------.DELTA.D/D 
__________________________________________________________________________ 
1 100 
0 0 0 0 0 3.50 0.89 0.96 
0.76 
0.55 
0.28 0.30 
2 0 100 
0 0 0 0 2.80 0.76 0.94 
0.71 
0.47 
0.33 0.18 
3 90 0 10 0 0 0 3.15 0.39 0.96 
0.75 
0.53 
0.64 0.20 
4 90 0 0 10 0 0 3.10 0.42 0.95 
0.74 
0.51 
0.59 0.22 
5 90 0 0 0 10 0 3.12 0.40 0.95 
0.74 
0.51 
0.62 0.20 
6 80 0 20 0 0 0 2.90 0.47 0.95 
0.73 
0.50 
0.53 0.18 
7 80 0 0 20 0 0 2.80 0.56 0.94 
0.71 
0.47 
0.45 0.20 
8 80 0 0 0 20 0 2.86 0.51 0.94 
0.72 
0.48 
0.49 0.18 
9 0 90 10 0 0 0 2.55 0.38 0.92 
0.68 
0.42 
0.65 0.16 
10 0 90 0 10 0 0 2.50 0.42 0.90 
0.65 
0.37 
0.60 0.19 
11 0 90 0 0 10 0 2.53 0.40 0.91 
0.66 
0.40 
0.63 0.17 
12 0 80 20 0 0 0 2.30 0.46 0.89 
0.64 
0.38 
0.54 0.15 
13 0 80 0 20 0 0 2.21 0.56 0.86 
0.59 
0.30 
0.45 0.16 
14 0 80 0 0 20 0 2.25 0.51 0.88 
0.62 
0.35 
0.49 0.14 
15 70 0 30 0 0 0 2.60 0.50 0.93 
0.68 
0.42 
0.50 0.19 
16 70 0 0 30 0 0 2.52 0.57 0.92 
0.65 
0.39 
0.44 0.19 
17 70 0 0 0 30 0 2.55 0.53 0.91 
0.67 
0.41 
0.47 0.18 
18 60 0 0 0 20 20 2.50 0.52 0.91 
0.68 
0.37 
0.50 0.12 
19 60 20 0 0 0 20 2.53 0.40 0.87 
0.58 
0.30 
0.55 0.13 
20 60 0 20 0 0 20 2.51 0.38 0.90 
0.60 
0.41 
0.58 0.12 
__________________________________________________________________________ 
As is abviously understandable from Table-4, the sample Nos. 18, 19 and 20 
each relating to this invention can display the excellent characteristics 
against pressure desensitization. 
EXAMPLE-5 
Emulsion [G] was prepared similarly to Emulsion [A] of Example-4, except 
only that the pAg was kept at 9.0. Emulsion [G] was a cubic monodisperse 
emulsion having the average grain size of 1.25 .mu.m and s/r=0.13. 
Emulsion [G] and Emulsions [B] through [F] were chemically sensitized 
similarly to the case of Example-4 and were added with a variety of 
additives. Then, the mixed emulsions shown in Table-5 were multilayered on 
both surface of a blue-dyed polyethyleneterephthalate film base as shown 
also in Table-5, and Samples Nos. 21 through 37 of photosensitive 
materials for X-ray photographic use were thus prepared. 
The sensitometry, image quality and pressure desensitization of each of 
these samples were evaluated as in Example-4, and the results thereof are 
shown in Table-5. 
TABLE 5 
__________________________________________________________________________ 
Exposure 
Mixture Proportion (%) of 
Multicoat Gamma 1 
Gamma 2 Latitude 
Pressure 
Sample 
Emulsions Upper 
Lower 
D = D = OTF (lines/mm) 
D = Desensitization 
No. [G] 
[B] 
[C] 
[D] 
[E] 
[F] 
emulsion 
emulsion 
0.5-1.5 
0.05-0.30 
1.0 
1.5 
2.0 
0.05-0.30 
------.DELTA.D/D 
__________________________________________________________________________ 
21 100 
0 0 0 0 0 -- -- 3.53 0.89 0.96 
0.76 
0.55 
0.28 0.28 
22 0 100 
0 0 0 0 -- -- 2.80 0.76 0.94 
0.71 
0.47 
0.33 0.18 
23 80 0 20 0 0 0 F C 2.96 0.47 0.95 
0.74 
0.51 
0.53 0.18 
24 80 0 0 20 0 0 F D 2.91 0.57 0.93 
0.71 
0.48 
0.44 0.19 
25 80 0 0 0 20 0 F E 2.93 0.52 0.94 
0.73 
0.50 
0.48 0.18 
26 80 0 20 0 0 0 C F 2.90 0.45 0.95 
0.73 
0.50 
0.55 0.17 
27 80 0 0 20 0 0 D F 2.85 0.54 0.93 
0.69 
0.47 
0.46 0.18 
28 80 0 0 0 20 0 E F 2.87 0.44 0.94 
0.71 
0.49 
0.57 0.17 
29 0 80 20 0 0 0 B C 2.38 0.47 0.90 
0.65 
0.39 
0.53 0.15 
30 0 80 0 20 0 0 B D 2.33 0.58 0.88 
0.63 
0.36 
0.43 0.16 
31 0 80 0 0 20 0 B E 2.36 0.53 0.89 
0.64 
0.38 
0.47 0.14 
32 0 80 20 0 0 0 C B 2.27 0.45 0.88 
0.63 
0.37 
0.55 0.14 
33 0 80 0 20 0 0 D B 2.23 0.54 0.86 
0.61 
0.33 
0.46 0.15 
34 0 80 0 0 20 0 E B 2.25 0.49 0.87 
0.62 
0.35 
0.51 0.13 
G 
35 60 0 0 0 20 20 F 2.50 0.51 0.91 
0.68 
0.38 
0.50 0.11 
E 
G 
36 60 20 0 0 0 20 F 2.53 0.40 0.88 
0.59 
0.31 
0.55 0.12 
B 
G 
37 60 0 20 0 0 20 F 2.52 0.37 0.90 
0.60 
0.42 
0.58 0.12 
C 
__________________________________________________________________________ 
As is obviously understandable from Table-5, Sample Nos. 35, 36 and 37 each 
can display the excellent characteristics against pressure desensitization 
.