US2035463A - Carrier for records and process of making same - Google Patents

Description

c. J. DIFPEL March 31, 1936.

CARRIER FOR RECORDS AND PROCESS OF MAKING SAME Filed Oct. 12, 1934 Patented Mar. 31, 1936 I 1 some I UNITED STATES PATENT orr cs CARRIER FOR RECORDS AND PROCESS Cornelis Johannes Dippel, Elndhoven, Netherlands, assignor to N. V. Philips Gioeiiampenfabrleken, Eindhoven, Netherlands Application October 12, 1934, Serial No. 8,1 In Great Britain October 27, 19%

11 Claims. (Cl. arc-cc) My invention relates to carriers of records and to the manufacture of same, and more particularly'to carriers for the mechanical recording of optically reproducible vibration tracks.

By a vibration track is meant a record of any type of vibration, obtained on a carrier by cutting, indenting, or like mechanical operation.

My invention will be described in connection with the recordin'g of sound vibrations and picture impulses, the vibration track on the carrier being obtained preferably by a cutting operation with a chisel type of tool, as described on U. S. Patent 1,919,116 to James A. Miller. Such records are usually reproduced optically, for instance by means of photocells and/or are photographicaily copied.

However, it should be well understood that my invention is not limited to the example given for its IIIUStIatiOIL'bUt-BPDHGS broadly 'to mechanically recorded and optically reproducible vibration tracks.

The quality of such mechanically recorded and;

optically reproducible tracks, as will be more fully explained hereafter, depends largely on the material of the layer in which the track is recorded and which is hereinafter referred to as the cutting layer. The best results have been obtained so far with cutting layers formed of gelatin. This material has better cutting prop-- erties and is therefore better adapted for such mechanical recording, than celluloid or other similar photographic materials.

However, even when using gelatin as carriers or cutting layers for such vibration tracks, serious difiicuities exist, and the object of my invention is to eliminate, or at least greatly reduce, such difliculties.

One of the difllculties arises because of the fact that, when generally cutting this material even with a properly sharpened tool, the surface of the vibration track is more or less rough, instead of being smooth. This coarse or rough surface, which appears to the eye as if it were frosted, is not homogeneously transparent, but diffuses the light passing through same.

This roughness or frosted surface of the vibration track affects the passage of light through it, in thesame manner as does a glass plate having a frosted surface, 1. e. causes a loss in the light transmitted through same, as well as a diffusion and deflection of the light rays passing same. As is known, a glass plate or disc having a frosted surface is less transparent to light than is a smooth-surfaced disc of the same dimensions, as its frosted surface can be regarded as hibited by the hydrophil colloids in that state being made up of a large number of small sur= faces forming various angles with each other, which reflect the light in different directions;

, thus a portion of the light is lost by reflection at the surface, and. the light which is allowed 5 to pass through the disc is deflected and difiused.

The coarse or rough condition of the track surface, besides decreasing the translucency oi the track with a resulting loss of light, also results in a non-homogeneous transparency of the track. In reproduction, such reduced translucency of the track decreases the contrast efiect: also the lack of uniformity in translucency of the track causes disturbing ground noises, which are especially bothersome for vibrations of small amplitudes. 7

Furthermore the above stated diffusion and deflection caused by a. rough or frosted track surface, deleteriously influences the quality of the copies obtained from such a track. In order to obtain a good copy of a vibration track of the type discussed, a light beam having parallel rays is used in preference to a beam having dif, fused rays, as in the case of diffused rays the boundary lines of the track do not appear with sumcient sharpness, thus the desired sharp contrast eifect is not obtained. However with a track having a frosted surface, even when using a light beam having parallel rays, the rays are deflected and difiused in their passage through the track; thus the above drawbacks of difiused light again occur.

This roughness of the cut track-surface seems to be due to the adhesiveness or stickiness exin which they are used for recording. This ad-' hesiveness prevents a. cutting tool from removing the material in a. continuous smooth cut. In fact the removal of the material takes place in the form of short individual cuts and with a hopping or jumping movement of the cutting tool.

As is well known from regular metal working practice, such an intermittent cutting process, causes a greater cutting resistance and thus requires greater power than does smooth; continuous cutting.

This increased viscosity or stickiness may also cause a complete dislodgement and removal, by the cutting tool, of dirt or other particles with which the recording material is contaminated. Due to the fact that these articles are carried along by the cutting tool, so that its cutting edge is deformed during thefurther recording operation, a 'considerable distortion of the boundary 55 lines of the track and the optical reproduction of such a track may occur.

It seems that this hopping or jumping move- .ment of the tool and the resulting irregular cutting of the material are due to the fact that the very high pressures exerted by the cutting tool upon the, recording material, during the recording or cutting operation, causes water to be pressed out of the material forming the cutting layer which increases the viscosity or stickiness of the layer at the cutting edge. This increase in viscosity at, the cutting edge is also irregular and in general causes the cutting layer to offer a greater resistance to the cutting tool than does a material having a uniform cutting resistance which permits a uniform removal ofthe material by the tool.

I have found that the difiiculties referred to above can be considerably reduced when according to my invention care is taken that the water contents of the gelatin layer are such that it is in equilibrium with a relative degree of humidity lying between 20 to 50%. The meaning of this will be explained hereinafter. In order that the invention may be clearly understood and readily I a film carrying a mechanically-recorded vibration track, which can be reproduced by means of light passing through same, and illustrates the advantages obtained with my invention;

Fig. 4 is a sectional view of the film of Fig. 3 taken along the line IV-IV, also showing the cutting tool while cutting the track.

I have found that the water contents of the gelatin are of great importance for its cutting properties. For every kind of gelatin two limits for the water contents can be given between which the cutting performance can be made with good results. Below the under limit the material is too brittle and above the upper limit it is-too sticky which causes the above-mentioned difliculties.

Furthermore I have found that the water contents of gelatin depend upon the relative degree of humidity of the surrounding medium and are nearly. independent of temperature. This relation is for different kinds of gelatin not quite the same, but shows a characteristic conformity. In Fig. 1 a oocalled swelling isotherm for a predetermined kind of gelatin is shown. The relative degree of humidity of the surrounding medium (9/90) is set out along the abscissa axis and the water contents of the gelatin as ordinates. The relative degree of humidity of the medium is the ratio between the existing pressure of the water-vapour in the medium (p) and the saturatlon pressure of the water vapour at this temperature (m). The degree of humidity may be expressed by a proportional number or in percents; both being commonly used. The term swelling isotherm expresses that the curve is determined by constant temperature and that the increase of the water contents stands in close connection to the increase in volume of the gelatin. The curve shows for every relative degree of humidity of the medium the water contents of the gelatin in the state ofequilibrium.

From Fig. 1 it can be concluded that beginning with absolute dryness of. the gelatin the water contents of the material increase rather rapidly in relation to the increase of the relative humidity. After reaching a relative degree of humidity of about 0.2 the water absorption occurs more slowly, whereas after reaching a relative degree of humidity of 0.7 thespecific increase of the water contents is very great.

' To make the matter more clear, it may be remarked that if gelatin with predetermined water a relatively long time before the state of equilibrium is obtained. For determining curves as shown in the accompanying figures, a long time of observation is necessary. The adjustment of the water contents of the gelatin to the relative degree of humidity requires less time, when the condition of the gelatin is determined by a point of the upper steep part of the curve than if the condition is determined by a point on a lower part of the curve. The material becomes more sensitive to moisture if the condition of the gelatin is determined by a point on the upper steep part of the curve. One may Say that the water bound up to a state of equilibrium with a relative degree of humidity of about 0.7 is more strongly bound than is the water bound above this point.

Whereas the curve from Fig. 1 refers to gelatin in powder state, the curves in Fig. 2 refer to two kinds of gelatin in plate form. For this specimen ofgelatin and treated in the state in which it is used for cutting purposes, the specific increase of the water contents increases already if the relative degreeof humidity surpasses 0.55.

As can be seen from the different curves the absolute water contents depend upon the state (powder or plate) in whichit is treated as well as upon the defilements or additions, which it contains. All curves, however, have a similar form, and have the common property that between a relative degree of humidity lying between 0.2 to 0.5 the steepness of the curve is minimum. It has been shown that in this field the cutting properties are best. If the condition of the gelatine is determined by a point of the From the characteristic shape of the swelling isotherms of the different kinds of gelatin and from the corresponding different cutting properties, it may be supposed that the condition of the gelatin in the three parts of the curve is different. The condition of the gelatin in which it is suitable for cutting purposes is defined by the relative degree of humidity with which the water contents are in equilibrium, whereas the limits of the absolute water contents vary according to the state in which it is used and of the additions. Preferably the gelatin used has water contents in equilibrium with a relative degree of humidity of about 0.3 to 0.4 or 30 to 40%. The surrounding medium is not essential and may be air or another gas or mixture, provided it does not chemically affect the gelatin. The cutting conditions of the recording layer may be further improved by combining the measures according to the invention and those described in my copending U. S. patent ap- 1934, now Patent No. 2,019,215, in which I pro- 10 contents is brought into an atmosphere with an I r arbitrary relative degree of-humidity it requires pose to add to the gelatin 9. sulphonated castor oil. The effect of this is,'that the sensitivity to mois-' ture is highly decreased, so that it can longer be exposed to atmospheric conditions without losing taking place during the preparation of the carrier. For instance, thecarrier can be subjected to drying by passing over it a current of gas having a very low water content and with the carrier preferably moving in direction opposite to the flow of the gas; or the carrier can be passed through a space which is maintained at a definite, low. degree of humidity-the degree of humidity and the time of drying depending mainly upon the material of the carrier for example of the kind of gelatin used.

Furthermore, water which is not strongly bound can be removed from the carrier in other ways, for instance, by passing the carrier, in an air-dry state,- through a bath of alcohol whereby a suitable selection of the concentration of the alcohol removes the less strongly bound water to the desired extent.

Of course carriers established in the manner set out above, due to the fact that'they are specially prepared, have water contents, which in general are not in equilibrium with the relative degree of humidity of the atmosphere or in other words, the water vapour pressure of the gelatin does not correspond to the water vapour pressure prevailing in the atmosphere. There-. .fore to prevent a change in their water pressure,

the carriers according to the invention are preferably protected to prevent a change in their water content, for instance by wrapping them in waterproof material up to the time they are used for recording. However, as the rate of absorp tion or liberation of water is quite slow, as said already before, no diiiiculties arise because of any absorption or liberation of water by the carrier, which may take place during the relatively short time required for the cutting operation.

In one embodiment of the invention, the drying of the carrier, in which the cutting layer may comprise a. gelatin of medium hardness of the type used in photography, can be carried .out as follows: Atmospheric air is filtered and sucked into a drying device, where it is cooled below its dew point, and from the dew point and the temperature of the air its degree of humidity is determined. Thereupon the air is heated so as to reduce its humidity to the desired low value. The so dehumidifled air is then used for drying the recording material. Good results have been obtained by passing air so treated, at a rate of about 30 cubic meters per hour through a space having a cross sectional area of about 40 cm. by 40 cm., which space contains the material to be dried at such a temperature that the relative degree of humidity of the air is about 30 to when it enters the space.

The carrier shown in Figs. 3 and 4 consists of three superimposed layers. The base or supporting layer 9 is made of a suitable transparent material, for instance ofcelluloid. The second or cutting layer 2 is also of transparent material. The material of this layer is gelatin, this being the layer into which the track is cut and with which my invention is primarily concerned. The top layer 3 is the covering layer and is a comparatively. thin opaque layer applied to layer 2. The tool used for the recording is shown as a chisel M, having two cutting edges 4-4, which enclose with each other an angle 20:, of about By moving the chisel perpendicular to .the surface of the carrier in accordance with the amplitudes of the vibrations to be recorded, a vibration track is cut into the carrier, the width of which varies with the amplitudes of the vibration to be recorded, said width variations being an amplification of the amplitudes of the chisel.

In the vibration track so obtained, even the high frequency vibrations have sufficiently large amplitudes and thus can be better recorded, than by other. known methods.

While cutting, the chisel removes portions of both the layer. 2 and the layer 3. The covering layer 3 merely serves to provide a diiference in translucency of the track and of the back-ground so as to permit reproduction by means of passing light. 'I'hecovering layer 3 may consist of a very thin opaque layer of paint, or dye, offeringa practically negligible cutting resistance to the chisel. The actual cutting layer is layer 2, and the track can be cut into this layer before the covering layer is applied thereto, in which case an opaque coating is applied either to the surface of the cut track or the"background around the cording to my invention, as has been previously stated shows a more or less coarse surface of at least part of the vibration track.

If viewed under a microscopethe track surface appears more or less granular, as is indicated in the left side of Fig. 3.

Due to the roughness or coarseness of the track surface, as has been fully explained, the desired sharp contrast effect is not obtained, and also loss of light and ground noises result.

Furthermore, due to the adhesiveness or stickiness of the materialof the cutting layer, particles of the layer at the edges or boundaries of the track for example dirt particles may be dislodged and carried away by the cutting tool as indicated at 5, which causes an irregular boundary line, and

consequently distortions in the reproduction or copying of the record.

All the above dimculties are avoided or greatly reduced by processing the material of the cutting layer, so as to remove all the water therefrom which is not strongly bound, by one of the above stated dehydrating steps.

While I have described my invention in a specific application, it can be applied generally in 'the mechanical recording of optically reproducichanical recording of an optically reproducible vibration track, the process which comprises, ap-

plying to a carrier a cutting layer formed of gela- I moisture content.

3. In the manufacture of carriers for the mechanical recording of, an optically reproducible vibration track, the process which comprises applying to a carrier-a cutting layerformed of gelatin,-and reducing from said gelatin the water contents to such a degree that it becomes in equilibrium with a relative degree of humidity of 20 to 50%.

4, Invthe manufacture of carriers for the mechanical recording of an optically reproducible vibration track, the process which comprises applying to a carrier a cutting layer formed of gelatin, and reducing from said gelatin the water contents to such a degree that it becomes in equilibrium with a relative degree of humidity of 30 to 40%.

5. In the manufacture of carriers for the mechanical recording of an optically reproducible T vibration track, the process, which comprises applying to a carrier a cutting layer formed of gelatin, reducing from said gelatin the water contents to such a degree that it becomes in equilibrium with a relative degree of humidity of 20 to 50%, and protecting prior to using said carrier to prevent a change in its water contents.

6. In the manufacture of carriers forthe mechanical recording of an optically reproducible vibration track, the process which comprises applying to a carrier 9. cutting layer formed of gelatin, reducing from said gelatin the water contents to such a degree that it becomes in equilibrium with a relative degree of humidity of to 40%, and protecting prior to using said carrier to prevent a change in its water contents '1. In the manufacture of carriers for the mechanical'recording of an optically reproducible vibration track the process which comprises, apply ng to a carrier a'cutting layer formed of gelatin, and removing the excess water from the cutting layer by passing said carrier through a current of dry gas, by moving it in a direction opposite to that of the flow of said gas current.

8. In the manufacture of carriers for the mechanical recording of an optically reproducible vibration track, the process comprising the steps, applying to a carrier a cutting layer formed of gelatin; sucking filtered air from the atmosphere into a drying device, cooling said air below its dew point, heating said air up to such a temperature that its relative degree of humidity is about 30 'to and passing said carrier through a current of said dried air in a direction opposite to the flow of said air current.

9. In the manufacture of carriers for the mechanical recording of an optically reproducible vibration track, the process which comprises applying to a carrier :3. cutting layer formed of gelatin, and removing the excess water from the cutting layer by passing said carrier through an 7 alcohol bath.

10. A carrier for the mechanical recording of an optically reproducible vibration track, comprising a cutting layer of gelatin with such water contents that'it is in equilibrium with a relative degree of hunrdity of 20 to 50%.

11. A carrier for the mechanical recording of an optically reproducible vibration track, comprising a cutting layer of a gelatin with such water' contents that it is in equilibrium with a relative degree of humidity of 30 to 40%.

" a Commms JOHANNES DIPPEL.

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