US3705807A

US3705807A - Photosensitive material for radiography

Info

Publication number: US3705807A
Application number: US137179A
Authority: US
Inventors: Vinicio Busatto
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1970-04-24
Filing date: 1971-04-26
Publication date: 1972-12-12
Anticipated expiration: 1989-12-12
Also published as: FR2093449A5; DE2119718A1; CA966352A; DE2119718C3; BE766202A; DE2119718B2; GB1337609A

Abstract

A RADIOGRAPHIC ELEMENT CAPABLE OF BEING HANDLED UNDER YELLOW SAFELIGHTS, THE ELEMENT CONTAINING A FILTER DYE WHICH ITSELF IMPORTS TO THE ELEMENT A DENSITY TO YELLOW LIGHT OF NOT LESS THAN 0.4 AND A DENSITY TO BLUE LIGHT OF NOT GREATER THAN 0.1.

Description

PHOTOSENSITIVE MATERIAL FOR RADIOGRAPHY Filed April 26, 1971 W/ll/fl mam J m H Mm m T 0 W m5 m C m 4 V w/ 1 B 1 United States Patent 3,705,807 PHOTOSENSITIVE MATERIAL FOR RADIOGRAPHY Vinicio Busatto, Savona, Italy, assignor to Minnesota Mining and Manufacturing Company Filed Apr. 26, 1971, Ser. No. 137,179 Claims priority, application Italy, Apr. 24, 1970, 50,263/ 70 Int. Cl. G03c 1/84 US. Cl. 96-84 R 8 Claims ABSTRACT OF THE DISCLOSURE A radiographic element capable of being handled under yellow safelights, the element containing a filter dye which itself imparts to the element a density to yellow light of not less than 0.4 and a density to blue light of not greater than 0.1.

The present invention relates to a photosensitive material for radiographic use.

Radiographic materials which are employed for industrial and for medical uses are often similar. In general, the photosensitive material for industrial radiography is employed to photograph internal parts of metallic bodies; the photosensitive material for medical radiography is generally employed to photograph internal parts of animal bodies, especially the human body.

Frequently the same radiographic material may be used both for industrial as well as for medical radiography. In both cases, X-rays pass through the object to be radiographed and expose, either directly or indirectly, radiographic material. Two reinforcing shields may be employed, one of them placed between the X-ray source and the radiographic film, the other one placed behind the film itself.

Radiographic material, as is known, commonly employs a transparent support (e.g., cellulose triacetate or of polyester), which has an emulsion layer coated on each side and which has protecting layers coated on the emulsion layers, the construction thus having at least five layers including the transparent support layer.

The radiographic, material support generally displays a silght blue coloration, the yellow density (i.e., the density measured with yellow light) which is due to the blue coloration of the film being of the order of 0.13 (Westrex Densitometer filter Status A).

The photosensitive emulsions for radiography are usually based on silver bromo-iodide which have maximum sensitivity to blue-violet radiations and minor sensitivity to the X-rays. Such emulsions show some sensitivity to the blue-green radiations and exhibit low sensitivity to higher wave length radiations (e.g., green or red).

The protective layers are generally of gelatin and of gelatin hardeners such as aldehydes, salt of chromium and aluminum, and mucochloric acid. The protective layers serve to protect the emulsion layers from scratches, etc.

The reinforcing shields such as those referred to above (sometimes referred to as intensifier screens) may be metallic (e.g., lead, tantalum) and saline, the latter referring to a sheet of paper or of plastic material bearing on a face a paste consisting of a dispersion in gelatin, or, in another similar medium, of a product such as lead sulfate, barium sulfate, calcium tungstate, zinc sulfide, the lead struck by X-rays emits slow neutrons which are easily absorbed by the emulsion giving rise for the formation of a latent image. Saline shields emit a blue-violet light for which the photosensitive emulsion for radiography has maximum sensitivity. Lead is used as a shield in the case of radiographic films for industrial use, whereas saline shields are generally used in the case of radiographic films for medical use because less X-ray exposure is required. Saline shields, however, can be employed in industrial radiography as well.

The fact that photosensitive emulsions for radiography exhibit high sensitivity to blue-violet light, some sensitivity to blue-green light and low sensitivity to higher wave length radiations (e.g., green, green-yellow, yellow, orange and red), permits safety lights having wavelengths of from green to red to be used during manufacture and processing of radiographic materials. However, such safety lights must be of low intensity to avoid undue exposure of the radiographic material which may lead to fogging. Particularly useful are those safety lamps having emission maxima at wavelengths of from 580 to 620 m Sodium lamps, for example, have an emission maximum in the range of 580600 m Working at the necessarily low light intensities, however, results in considerable inconvenience for the operator.

The object of the present inveniton is to provide a radiographic material which can be handled under safety lights of high intensity for relatively long periods of time without risk of undue exposure.

Briefly, the present invention relates to a radiographic element which includes a base layer, a silver halide photographic emulsion layer carried on each surface of the base layer, and a protective layer carried by each emulsion layer. The element contains filter dye which is highly absorptive of yellow light (e.g., light at 580- 620 mg) and is highly transmissive of blue light (e.g., light at 410-450 mg). The dye is present in an amount sufiicient to itself impart to the element a density to yellow light of not less than 0.4 and a density to blue light of not more than 0.1. In the preferred embodiment, the dye is distributed in layers of the element such that (a) the base layer provides 15-35% of said density to yellow light, and

(b) the emulsion layers together provide not less than one-half of said density to yellow light which is not not provided by the base layer.

In the most preferred embodiment, the dye is distributed through each of the base, emulsion, and protective layers, the base layer providing 15-35% of said density to yellow light and the emulsion layers together providing at least half of the density to yellow light not provided by the base layer. Preferably, the dye is distributed symmetrically in the element with respect to the base layer.

In particular the filter layers should display an absorption curve with a density minimum in the zone ranging from 360 to 500 m nt, and a maximum in the zone ranging from 580 to 700 m l. The minimum of the absorption curve should substantially correspond to the wave length at which the reinforcing shields are emitting (if reinforcing shields are employed) and the maximum of the absorption curve should substantially correspond to the maximum of the emission curve of the safety lamp employed. Since safety lamps which are especially useful are the sodium lamps, which have an emission maximum ranging between 580 and 600 mg (a zone in which the eye is particularly sensitive), filter layers having a maximum of absorption in the same zone are desired; on the other hand since the most commonly used shields are those ones containing e.g., calcium tungstate (which emits in the zone of 410-450 mg) filter layers having a minimum of absorption in this zone are desired. In general filter layers useful to the present invention objedtives are layers containing a blue filter dye.

Each of the layers composing the radiographic material can be transformed into a filter layer by introduction thereto of a dye having the desirable absorption characteristics.

It has now been found, for example, that in order to easily handle a radiographic material, Without fogging it under a safety light of 2.5 lux (emanated from a sodium lamp filtered through a yellow filter), the radiographic material should have an absorption in the yellow such as that shown in FIG. 1. Suflicient dye is employed in the element so as to itself provide a density to yellow light of not less than 0.4 (to prevent fogging by yellow safelights) and a density to blue light of not more than 0.1 so as to maintain blue light sensitivity of the element. It has further been found that the capacity of a radiographic element to withstand exposure to yellow light and yet retain good blue light sensitivity is also sensitive to the placement of the dye in layers of the element. Thus it has been found that optimum results are obtained when the supporting layer contains dye in an amount sufficient to provide from -35% of the total density of the element to yellow light imparted by dye, and when the emulsion layers together contain dye in and amount suificient to enable these layers to provide at least half of that density to yellow light which is not provided by the supporting layer. Preferably, as noted above, the dye is included within each layer of the element.

The dye in the emulsion and protective layers may be chosen so as to be decolorable in photographic processing baths. If this dye is not decolorable in processing baths, the finished radiograph has a pleasant bluish aspect, and it can be observed for a long time on a negatoscope without causing eye fatigue. On the other hand, if this dye is decolorable in photographic processing baths, then the finished radiograph will be of a lighter bluish hue for viewing. The dye of the supporting layer, of course, is not decolorable.

Blue dyes which are decolorable in photographic processing baths include for instance, the blue dyes described in the US. Pat. No. 3,260,601, and the dyes corresponding to the following structural formulas:

II N Dyes which are not decolorable in the processing baths and which are useful to the objectives of the present in- 4 vention include the euprophthalocyanine (CI 74160) corresponding to the formula:

(5) Methylene Blue (CI 52015) (zinc double chloride) and (6) (CI 52030), (zinc double chloride) Cuprophthalocyanine dyes are preferred. The invention may be better understood by reference to the following illustrative, non-limiting examples:

EXAMPLE 1 2200 g. of a high sensitivity radiographic emulsion containing 5% of gelatin and 1.4 moles of silver halide (98.2% bromide and 1.8% iodide) was prepared.

Thereafter 1820 g. of a coating solution for providing protective layers was prepared:

G. Deionized water 1453.0

Gelatin 71.4 10 g. of silica dispersion in 1000 cc. of a 10% gelatin solution 286.0 Potassium nitrate (aqueous 25% solution) 3.7 "Manoxol N (Hardware and Holden Ltd., sodium dinonylsulfonsuccinate) 2.5 10% mucochloric acid solution in toluated methyl alcohol 3.4 Correction to pH 6 The silver halide emulsion was coated on each face of a transparent blue polyester support having a density equivalent to 0.16 as read on the Westrex Densitometer filter Status A, to provide a silver coverage equivalent to 4.5 g./m. Then over each emulsion layer was coated a protective layer having a thickness of 1.35 The thusprepared is designated material 0 as a reference material.

A No. 1 material was prepared in the same manner as the reference material, except that the 1820 g. of protec tive solution contained 6.84 g. of cuprophthalocyanine added in the form of a 2% aqueous suspension, equivalent to 0.125 g./m. of individual protective layer.

The No. 2 material, according to the present invention, was prepared in the same manner as the reference material except that the 2200 g. of emulsion contained 4.32 g. of cuprophthalocyanine added in the form of a 2% aqueous dispersion equivalent to 0.125 g./m. of emulsion layer.

The No. 3 material, according to the present invention, was prepared in the same manner as the reference material, except that the 1820 g. of protective solution contained 4.08 g. of cuprophthalocyanine added in the form of a 2% aqueous dispersion equivalent to 0.075 g./m. of protective layer, and that the 2200 g. of emulsion contained 1.75 g. of cuprophthalocyanine added in the form of a 2% aqueous solution, equivalent to 0.050 g./m. of emulsion layers.

No. 4 material was prepared in the same manner as the reference material, but using a colorless transparent polyester support instead of a colored support and containing in the 1820 g. of protective solution, 9.54 g. of cuprophthalocyanine added in the form of a 2% aqueous solution equivalent to 0.173 g./m. of protective layer in the finished product.

No. material was prepared in the same manner as the reference material except that a transparent colorless support instead of a colored support was used. The 2200 g.

and in a Ferrania F 11 fixing bath having the following composition:

G. Sodium hyposulfite crystals 400 Anhydrous sodium bisulfite 30 Fused sodium acetate 20 Boric acid crystals Potassium alum Water to 1000 cc.

The fog data are indicated in Table No. 2.

The data of the column headed 0 indicate the densities of the unexposed, processed samples. The numbers not in parentheses in the other columns indicate the density of the exposed and processed samples. The data in parentheses indicate the density increase due to exposure of the various samples to yellow light. The density values were measured with a Quantalog Densitometer, TD-102, white light.

of emulsion contained 6.05 g. of cuprophthalocyanine TABLE 2 EXAMPLE 2 added in the form of a 2% aqueous solution equivalent to 0.173 g./m. of emulsion layer in the finished product.

No. 6 material was prepared in the same manner as the reference material except that a transparent colorless support was usedinstead of a colored support. The 1820 g. of protective solution contained 5.72 g. of cuprophthalocyanine added in the form of a 2% aqueous solution equivalent to 0.103 g./m. of protective layer in the finished product, and the 2200 g. of emulsion contained 2.44 g. of cuprophthalocyanine added in the form of a 2% aqueous solution equivalent to 0.070 g./m. of emulsion layer in the finished product.

Table 1 indicates the values of the density to yellow light which is imparted to each of certain layer of the above constructions by the incorporation therein of dye. Measurements were made with a Westrex Densitometer, filter Status A.

TABLE 1 Metol 3 Anhydrous sodium sulfite 5O Hydroquinone 9 Anhydrous sodium carbonate (Soda Solway) 50 Potassium bromide 3 Water to 1000 cc.

A reference material A analogous to the reference material of Example 1 but less sensitive to light was prepared. Then a material B was prepared in the same manner except that to the 1820 g. of protective solution was added 2.72 g. of cuprophthalocyanine (equivalent to 0.050 g./m. of protective layer) and to the 2200 g. of emulsion was added 2.64 g. of cuprophthalocyanine (equivalent to 0.070 g./m. of emulsion layer in the finished product). The two materials were exposed and processed, as described Example 1, and the fog was similarly measured. The resulting data appears in Table 3 as follows:

[O 0 seven? What is claimed is:

1. A radiographic element which includes a base layer, a silver halide photographic emulsion layer carried on each surface of the base layer, and a protective layer carried by each emulsion layer, said element containing filter dye which is highly absorptive of yellow light and highly transmissive of blue light, and which is present in an amount sufiicient to itself impart to said element a density to yellow light of not less than 0.4 and a density to 'blue light of not greater than 0.1.

2. The element of claim 1 wherein said dye is distributed in layers of said element such that the base layer provides from 15% to 35;% of said density to yellow light and said emulsion layers together provide not less than one half of said density to yellow light which is not provided by said base layer.

3. The element of claim 1 wherein said dye is a cuprophthalocyanine dye.

4. The element of claim 2 wherein said dye is included in each of said base, emulsion, and protective layers.

5. The element of claim 2 wherein the dye in said emulsion and protective layers is decolorized in photographic processing solutions.

6. A radiographic element which includes a base layer, a silver halide photographic emulsion layer carried on each surface of the base layer, and a protective layer carried by each emulsion layer, said element containing filter dye which is highly absorptive of yellow light and highly transmissive of blue light and which is present in an amount sufiicient to itself impart to said element a density to yellow light of not less than 0.4 and a density to blue light of not greater than 0.1, the dye in said base layer being non-decolora'ble in photographic processing baths and the dye in other layers of said element being decolorable in photographic processing baths.

7. The radiographic element of claim 6 in which each emulsion layer contains a blue filter dye which is decolorable in photographic processing baths and each protective layer containing a blue filter dye which is decolorable in photographic processing baths.

References Cited UNITED STATES PATENTS 2,112,217 3/1938 B aldsiefen 9684 R 2,489,662 11/1949 Murray 96-84 R 3,237,008 2/1966 Dostes 9684 R 3,260,601 7/1966 Bailey 96-84 R RONALD H. SMITH, Primary Examiner U.S. Cl. X.R. 9682