DE1008571B - Double layer film for black and white photography - Google Patents

Description

The invention relates to a black and white photographic film having on one side one Blank film various halogen silver emulsions are arranged.

Black and white photographic films which have two emulsion layers are well known. In general becomes a more sensitive silver halide emulsion over a less sensitive and finer-grain one Poured emulsion, with a corresponding setting of the blackening curve shape z. B. by appropriate Modification of the intrinsic sensitivities and contrasts as well as the silver content of the two Emulsions is achieved. These measures can reduce the negative amount of the photographic material expanded and the maximum blackening of the shoulder part of the blackening curve increased, since the less sensitive emulsion works in the area of stronger exposure and so for Contributes to density in the shoulder part of the density curve. It is used in this context for example see U.S. Patent 420,130.

Either of the two emulsions in layers of this type can be panchromatically sensitized, if the emulsions can be selected accordingly with regard to their different sensitivities an improved negative range can be achieved. The degree of blackening of the negative is in this case but exaggerated when red-colored objects, for example the flesh tones in portrait flash photography, so that such negatives produce inferior copies.

Accordingly, it is an object of the invention to provide a black and white bilayer photographic film train, which does not have these disadvantages and improves its copying properties are. In particular, the photographic film should have a reduced degree of blackening for red, a sufficient gradient should nevertheless be maintained in the shoulder part of the characteristic curve. The film according to the invention is thus intended to have a reduced degree of blackening for red while maintaining the same the advantages of a larger exposure latitude.

According to the present invention, this object is essentially achieved in that a halide silver emulsion is poured onto one side of a blank film, which emulsion has a certain sensitivity to green, but no noticeable sensitivity to red. The sensitivity for green should be at least one tenth of the sensitivity in the blue spectral range. A second emulsion layer is cast over this first emulsion layer, which layer film has essentially the same sensitivities in the blue, green and red spectral ranges on a double layer
for black and white photography

Applicant:

Eastman Kodak Company,
Rochester, NY (V. St. A.)

Representative: Dr.-Ing. W. Wolff, patent attorney,
Stuttgart-N, Lange Str. 51

Claimed priority:
V. St. v. America from. September 9, 1954

Norman Frederick Beach, Rochester, NY (V. St. A.),
has been named as the inventor

shows. The sensitivity to white light of the outer layer or the layer applied as a second layer should be at least log E = +0.3 greater than the sensitivity for white light of the first cast Emulsion.

The technical terms used in the following description are defined as follows:

The negative circumference is the distance along the exposure abscissa of the blackening curve, in which a corresponding increase in exposure has a substantially uniform increase the result of blackening, d. H. thus the distance of the straight line projected onto the exposure abscissa Part of the blackening curve. Similarly, the terms "exposure latitude" and »Linear exposure range« used. (The terms are under “exposure latitude” and “linear exposure scale "defined in Mees, The Theory of the Photographic Process, 1954, p. 868.)

Below the gradient is the ratio between a certain log Ε interval, Δ log E, the blackening curve and the corresponding blackness

709 509/356

interval AD as it is expressed by the formula *

Δ log E

is defined (Mees, as above, p. 866).

Shoulder gradient is the gradient at any point on the shoulder of the blackening curve.

filter KTr. 58) and 4 for the red spectral range (Wratten filter No. 25). Other suitable sensitivity ratios for the panchromatic layer are, for example, 5 for the blue area, 4 for 5 for the green area and 3 to 5 for the red area. These figures relate only to the speed ratios in each layer itself and not to the ratios from one layer to another.
The sensitivity of the panchromatic external

the abscissa of the blackening curve (see Mees, as above, p. 957).
Wratten filters are light filters of a defined

Under the sensitivity of the ■ photographic

Material is in the present case the reciprocal value 10 layer should be at least log E = + 0.3 greater the inertia of the material to be understood, therefore, as the sensitivity of the orthochromatic

Inner layer, d. H. so, should essentially be two

£ times as large, based on both sensitivities

S = - white light.

¹ 15 In the photographic shown in FIG

Material means 10 a blank film made of acetyl

where k is a constant and i is the inertia (see Mees, cellulose, glass, synthetic resin or another through as above, p. 868). visible material, 11 the orthochromatic and 12

Below the blackening range is the difference between the panchromatic emulsion layer. In general Seeing the maximum and minimum blackening of 20, a layer 13 appears on the back of the blank film photographic image, measured along the blackness, used to prevent halos.

Suitable spectrophotometric curves for the top and bottom emulsion layers are shown in FIG. 2, respectively and 3 respectively.

to understand the spectral transmittance, as shown in FIG. 4 shows a measured on three sample casts in the book "Kodak \ N rat filter", published by Schwärzungskurvenschar. Each of the three samples had two emulsion layers from Eastman Kodak Co., Rochester (New York), the same in each case being described in 1951. panchromatic outer emulsion layer, but

In the present, different inner emulsion layers are intended to be used under spectral range in the case of those blue, green or red spectral ranges. Here, the curve is a test cast with an area that consists of white light from panchromatic inner layer, curve B a

Sample casting with an orthochromatic inner layer and curve C assigned to a sample casting with a non-sensitized inner layer. All 35 samples were radiated with white light! «And developed in the same way.

The extent of blackening of the curve assigned to sample A in FIG. 4 is so great that when copies are made on the copier material commonly available

4 and 5 typical blackening curves of 40 are produced, the heavily exposed areas »blok sample casts, which are marked with white light or with red light, so that the details on the bright Light were irradiated. Bodies get lost. This is due to

The film according to the invention has on a ren that the blackening range of the negative protrudes beyond the side of two superposed halogen silver blackening range of the copy material on emulsions. The first, that is, the closest to 45. If an unsensitized lower layer is located in the emulsion layer, curve C shows that this gives the school a halosilver gelatin layer, preferably a tergradient lower and the negative circumference from bromosilver- Gelatin layer, which takes in a known manner, so that there is a loss in the details with a dye for the green spectral range of the strongly exposed areas as well as in the negative. The sensitivity in this respect occurs.

Rich should be at least a tenth of the sensitivity, but if an orthochromatic lower layer

Liability in the blue spectral range for which is used, the blackness range of the emulsion has an inherent sensitivity, and negative is sufficiently reduced that the blackness should preferably be equal to the sensitivity in the range of a conventional copying material without a blue spectral range. Over this emulsion layer 55 loss of negative volume is not exceeded. with or without the interposition of an intermediate This advantage is particularly important in the photographic layer of a halogen silver gelatin emulsion, pre-graphing flesh tones that have a strong red light, preferably a bromide silver gelatin emulsion, and which accordingly reflect the negatives that are in is panchromatically negative in the usual way, especially when using flash light. Block the sensitivity of this emulsion 6 _{U lighting.}

In the blue, green or red spectral range, this advantage should be clearly significant in FIG. 5 be the same. licher. The figure shows the blackening curves of the

Suitable spectral sensitivity ratios for the same as for the determination of curves A and B in the first or orthochromatic layer are 10 materials used for FIG Light be-1 for the green spectral range (Wratten filters were irradiated. The blackening range of curve B No. 58). A suitable spectral sensitivity ratio is considerably lower than that of curve A, nits for the second or panchromatic layer are, from which it follows that a blocking or up-6 for the blue spectral range (Wratten filters pound in the negative when photographing red no. 47) , 5 for the green spectral range (Wratten 70 light-reflecting objects are absent. Simultaneously

the Wratten filters No. 47, 58 and 25 (Mees, as above, pp. 860 and 861), see also Figs. 2 and 3.

The drawings show in

Fig. 1 is a cross-section of a film according to the invention, in

Figures 2 and 3 each show typical spectrophotometric curves of the top and bottom layers of the film, respectively, in

the negative size of the negative film is not reduced.

The following example illustrates the production of a film according to the invention.

5 example

On a blank sheet of acetylcelhilose, which is in the is underlaid in the usual way and which has a protective backing layer, a silver bromide gelatin emulsion layer was used potted that with l.r-diethyl-ijy-cyanine iodide plus Γ, 2-diethylthia-2'-cyanine iodide was optically sensitized and had a spectral sensitivity ratio of blue to green like 10: 1.

A silver bromide gelatin emulsion was poured onto the dried orthochromatic emulsion, which was sensitized with 2,2'-diethyl-8-methyl-thiacarbocyanin iodide and which had a sensitivity ratio from green to red like 6: 5 had. The panchromatic emulsion sensitivity was about log E = + 1.5 greater than that of the orthochromatic emulsion.

At the thickness at which they were cast, the two emulsions had roughly the same contrast in the straight part of the blackening curve.

The film thus produced was washed with any suitable developing solution, for example with a Kodak DK-50 developer.

Copies of this film can be made on any suitable material such as Velox paper (Trade name) for contact copies or on Kodabromide paper (trade name) for projection copies, getting produced.

The film produced according to the invention has the following advantages:

1. Larger negative amount in relation to one Film having a non-sensitized lower layer.

2. For 'objects with a greater red light reflection no overexposure occurs with the itself consequent loss of detail in the copies, as is the case with materials, the two have panchromatically sensitized emulsions.

3. Objects with a greater red light reflection can with a reasonable division of the Blackening can be recorded without reducing the capacity for considerably darker parts of the Object is lost.

On the basis of the description, the person skilled in the art is always able to understand the inventive concept to adapt to the current circumstances.

Claims (3)

Patent claims: 1. Double layer film for black and white photography, in which two halogen silver emulsions are arranged on one side of a blank film, thereby characterized in that the emulsion layer arranged in the vicinity of the support has a sensitivity in the green spectral range of at least one tenth of the sensitivity in the blue spectral range and has essentially no sensitivity in the red spectral region and that the The emulsion layer lying further from the blank film has essentially the same sensitivity in blue, green and red spectral range, the sensitivity of this layer to white Light is at least log E = + 0.3 higher than the sensitivity of the layer arranged in the vicinity of the blank film (for white light). 2. Film according to claim 1, characterized in that the arranged in the vicinity of the blank film Emulsion layer in the green spectral range has a sensitivity which is essentially the sensitivity in the blue spectral range is the same. 3. Film according to claim 1 and 2, characterized in that on one side of an acetyl cellulose blank film two bromide silver gelatin emulsion layers are arranged, with the emulsion arranged in the vicinity of the carrier spectral sensitivity ratio of blue to green such as about 10: 1 and in the red spectral range has essentially no sensitivity, while the outer lying from the blank film Emulsion layer has a spectral sensitivity ratio of blue to green to red, such as 6: 5: 4 and the sensitivity of this emulsion layer to white light by at least log E = + 0.3 is higher than the sensitivity of those placed near the blank film Layer (for white light). 1 sheet of drawings © 70ΐ 509/356 5.