GB1568722A - Method of making copies of a master information carrier having information tracks - Google Patents

Description

(54) METHOD OF MAKING COPIES OF A MASTER INFORMATION CARRIER HAVING INFORMATION TRACKS (71) We, N. V. PHILIPS' GLOEILAMPENFABRIEKEN, a limited liability Company, organised and established under the laws of the Kingdom of the Netherlands, of Emmasingel 29, Eindhoven, the Netherlands, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to a method of making copies of a master information carrier having a spiral-like or a concentric circles type information track. Audio and/or video information may be stored in the form of frequency- or phase-modulated signals wherein the structure of the tracks is built up from blocks of variable length which lie in one plane separated by areas of variable 'length which lie in another plane. This type of information carrier is described in British Patent Specification 1,391,541 wherein audio and/or video signals are stored as a topographical structure composed of first areas which all lie in a first plane and are separated by second areas which all lie in the second plane parallel to and spaced from, the first plane by a distance comparable to a wavelength of optical radiation. The information tracks of such carriers have a very fine structure; the length of the said blocks are areas in the one plane in practice, being of the order of 1 pm and the width thereof approximately 0.3 Nm.

It is known from United States Patent Specification 3,381,085 to photographically make copies of information tracks on which coded images are provided in the form of a spiral-like track of variable light transmission which has been written by means of a modulated electron beam. Such an information track has a rather coarse structure. Photographical reproduction thereof does not present any problem.

It has been found, however, that the information tracks of the kind as described in British Patent Specification 1,391,541 cannot be copied as such photographically.

Light scattering during the exposure and the occurrence of deflection phenomena may result, in use, in an annoying back ground noise.

The usual photographic emulsions based on silver halide are too coarse-granular to enable fine details of the information track to be reproduced without losses. Even emulsions of this kind having a very small grain, the so-called Lippman emulsions, proved to be unfit for this purpose.

The aforesaid deflection phenomena is particularly disadvantageous for it is associated with the fact that the wavelength of the light used for making the copy is of the same order of magnitude as the images of the track to be copied. This is very disadvantageous for certain molecular disperse light-sensitive systems where the material used contains an aromatic diazosulphonate, and which material after exposure, is contacted with a solution containing mercurous ions and possibly also silver ions so that physically developable mercury-or silver amalgam nuclei are obtained.

It has also been found that the diazosulphonates are insufficiently resistant to diffusion so that a considerable part of the definition of the original information track may be lost. Moreover, it is not at all obvious to photographically make copies of information tracks of the above-mentioned kind, as obtained, for example, according to the method described in British Patent Specification 1,447,066. According to this method, a photolacquer is provided on an information carrier of disc-form and, by rotation of the disc relative to a puncti-form source of radiation, in particular a beam of radiation provided by a laser, is intermittently exposed and not exposed during variable times corresponding to the information, the photolacquer is developed and the desired information track is etched.

The information track thus formed consists of a relief image. When a copy is to be made herefrom photographically, an image in the carrier is obtained which extends substantially throughout the thickness of the carrier. It is not obvious at all that the whole video and audio information would be transmitted completely by this.

It has surprisingly been found now, however, that excellent copies of master information carriers having a spiral-like information track or a track built up from concentric circles in which audio and/or video information is stored in the form of frequency or phase-modulated signals as blocks of variable lengths which lie in one plane separated by regions of variable lengths which lie in another plane, can be obtained by means of a photographic system known from British Patent Specification 1,227,116.

According to the present invention there is provided a method of making copies of a master information carrier having a spirallike information track or a track built up from concentric circles, in which audio and/or video information is stored in the form of frequency- or phase-modulated signals in the form of blocks of variable lengths which lie in one plane, separated by areas of variable lengths which lie in another plane wherein a photosensitive material consisting of a support layer in which at least the surface is electrically insulating and which layer contains or is coated with a photosensitive compound comprising an aromatic diazothioether of the formula

wherein X is a substituent, n is 0 to 5 and R is a branched or non-branched alkyl group or aralkyl group, is exposed to the information using light, thereby forming a light reaction product, treating this product in the presence of moisture with mercurous ions or with mercurous and silver ions to form mercury or silver amalgam nuclei which are deposited in the form of a physically developable latent image, physically developing said resulting nuclei image to an optical density below D=l above the basic density of the carrier to produce said copies, each copy having the blocks and the areas of the information track contained in a single plane of the support layer.

According to one embodiment of the invention the photosensitive compound is an aromatic diazothioether of the aforesaid formula and wherein X is a substitutent in the benzene ring, n isO, 1,2 or 3 and R is a straight chain or a branched alkyl group or aralkyl group.

By thus developing to a comparatively low density, the above-mentioned interfering deflection images are suppressed. It is surprising in itself that images having such unusual low densities are capable of comprising the full information.

In one embodiment copies are obtained by being manufactured on a carrier material which has a transport support layer thereon.

The copy of the information track may be made as reflection against a reflecting surface present. The unblackened parts of the carrier will reflect the light substantially unattenuatedly, while the image parts absorb twice: once for the reflected light.

For this purpose, the reflective surface may be a reflecting metal layer, for example a vapour-deposited aluminium layer.

Embodiments of the invention will now be described by way of example with reference to the ensuing examples: Example 1 Plates of polymethylmethacrylate having a diameter of 340 mm and a thickness of 1 mm are cleaned and then provided with a layer of cellulose acetobutyrate. For this purpose at 7.5 solution of this material (in the form of "Tenite II" of Eastman Kodak; Tenite II is a registered Trade Mark) in a mixture of solvents of methylglycolacetate ethanol in a volume ratio of 8:2 is distributed over the surface by means of centrifuging at a speed of 275 rpm for 1 minute. The layer is dried in the horizontal position for 1 hour at 700C in a furnace having forced air circulation. The dried layer has a thickness of 4 ,um. The cellulose acetobutyrate layer is made hydrophilic by saponification and then made photosensitive by means of the following treatment steps: a) soaking for 5 minutes in a 6.5V solution of 20"C of KOH in a methanol-water mixture in a volume ratio 8:2.

b) soaking for 1 minute in a 9% solution of lactic acid in a methanol-water mixture (8:2) c) soaking for 1 minute in a 1% solution in demineralized water of "Lissapol N", a condensation product of ethylene oxide with alkyl phenols, (The word, "Lissapol" is a registered Trade Mark), d) rinsing for 5 minutes in running demineralized water e) 3xsoaking for 1 minute in propanol-l f) soaking for 3 minutes in a 0.1 molar solution of 3.5 dichloro - 4 dimethylaminobenzene diazothiotertiarybutylether in propanol - 1, after which the adhering liquid is flung away for 1 minute at a speed of 100 rpm. The thickness of the resulting photosensitive layer is 2 ,um. The material is stored in a nitrogen atmosphere. The exposure is carried out by means of a high pressure mercury lamp. For that purpose, a photosensitive plate in a cassette is brought in very close contact with the information carrier to be copied consisting of a glass plate having a chromium layer in which the video and audio information is recorded.

The exposure is carried out with a 125 W HPR lamp for 40 seconds at a distance of 1 metre. In the light path a correction filter with a density D=l is placed so as to obtain a homogeneous exposure.

After the exposure the plate is kept immersed in a nuclei-forming bath for 2 seconds, which bath contains per litre 0.0025 mol (Hg2(NO3)2 0.025 mol AgNO3 and 0.01 mol HNO3, is then rinsed in demineralized water for 4 seconds and developed for 45 seconds in a developer which is kept at 20"C and has the composition per litre: 0.05 mol ferrous ammonium sulphate 0.01 mol ferric nitrate 0.01 mole silver nitrate 0.03 mol citric acid 0.02% "Armac 12D" (The word, "Armac" is a registered Trade Mark) and 0.02% "Lissapol N", rinsed in demineralized water for 60 seconds, in propanol - 1 for 60 seconds and finally dried in a dust-free cupboard. The achieved density is D=0.3.

On the image side of the copy an aluminium layer is vapour-deposited and the photographic image is read as a reflection image from the rear side. The quality of the image and the sound cannot be distinguished from that of the original.

"Armac 12D" is an anionic wetting agent which consists of dodecylamine acetate for approximately 90%, of tetradecylamine acetate for approximately 9% and of acetates of higher alkylamines for the remainder.

Example 2 Glass plates having a diameter of 340 mm and a thickness of 5 mm are cleaned and then provided with a layer of chromium approximately 45 A thick, by vapour deposition. Hereon an approximately 25 A thick TiO2 layer is provided by dipping the plates in a 2.5% solution of titanium acetyl acetonate in propanol - 2, drawing them up slowly and then heating them at 200"C. The plates are covered with a celluloseacetobutyrate layer, made photosensitive, nucleated and developed in the manner as described in the preceding example. The exposure time and/or development time are chosen to be one third to one quarter shorter because the chromium layer already present during the exposure may give rise, in use, to unwanted noise effects. The density cannot be measured directly due to the presence of the chromium layer; it is estimated to have a value D=0.2. The copy made in this manner can be read directly in reflection from the front side. The quality of the small image and the sound cannot be distinguished from that of the original.

According to this method it is possible to provide a plate on both sides with an information track.

WHAT WE CLAIM IS: 1. A method of making copies for master information carrier having a spiral-like information track or a track built up from concentric circles, in which audio and/or video information is stored in the form of frequency- or phase-modulated signals in the form of blocks of variable lengths which lie in one plane, separated by areas of variable lengths which lie in another plane wherein a photosensitive material consisting of a support layer in which at least the surface is electrically insulating and which layer contains or is coated with a photosensitive compound comprising an aromatic diazothioether of the formula

wherein X is a substituent, n is 0 to 5 and R is a branched or non-branched alkyl group or aralkyl group, is exposed to the information using light, thereby forming a light reaction product, treating this product in the presence of moisture with mercurous ions or with mercurous and silver ions to form mercury or silver amalgam nuclei which are deposited in the form of a physically developable latent image, physically developing said resulting nuclei image to an optical density below D=l above the basic density of the carrier to produce said copies each copy having the blocks and the areas of the information track contained in a single plane of the support layer.

2. A method of making one or more copies of a master information carrier according to Claim 1 in which formula X is a substituent in the benzene ring, R is as defined in Claim 1 and n is 0, 1, 2 or 3.

3. A method as claimed in Claim 1 or Claim 2, characterised in that the carrier has a transport support layer and the copy of the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. thickness of the resulting photosensitive layer is 2 ,um. The material is stored in a nitrogen atmosphere. The exposure is carried out by means of a high pressure mercury lamp. For that purpose, a photosensitive plate in a cassette is brought in very close contact with the information carrier to be copied consisting of a glass plate having a chromium layer in which the video and audio information is recorded. The exposure is carried out with a 125 W HPR lamp for 40 seconds at a distance of 1 metre. In the light path a correction filter with a density D=l is placed so as to obtain a homogeneous exposure. After the exposure the plate is kept immersed in a nuclei-forming bath for 2 seconds, which bath contains per litre 0.0025 mol (Hg2(NO3)2 0.025 mol AgNO3 and 0.01 mol HNO3, is then rinsed in demineralized water for 4 seconds and developed for 45 seconds in a developer which is kept at 20"C and has the composition per litre: 0.05 mol ferrous ammonium sulphate 0.01 mol ferric nitrate 0.01 mole silver nitrate 0.03 mol citric acid 0.02% "Armac 12D" (The word, "Armac" is a registered Trade Mark) and 0.02% "Lissapol N", rinsed in demineralized water for 60 seconds, in propanol - 1 for 60 seconds and finally dried in a dust-free cupboard. The achieved density is D=0.3. On the image side of the copy an aluminium layer is vapour-deposited and the photographic image is read as a reflection image from the rear side. The quality of the image and the sound cannot be distinguished from that of the original. "Armac 12D" is an anionic wetting agent which consists of dodecylamine acetate for approximately 90%, of tetradecylamine acetate for approximately 9% and of acetates of higher alkylamines for the remainder. Example 2 Glass plates having a diameter of 340 mm and a thickness of 5 mm are cleaned and then provided with a layer of chromium approximately 45 A thick, by vapour deposition. Hereon an approximately 25 A thick TiO2 layer is provided by dipping the plates in a 2.5% solution of titanium acetyl acetonate in propanol - 2, drawing them up slowly and then heating them at 200"C. The plates are covered with a celluloseacetobutyrate layer, made photosensitive, nucleated and developed in the manner as described in the preceding example. The exposure time and/or development time are chosen to be one third to one quarter shorter because the chromium layer already present during the exposure may give rise, in use, to unwanted noise effects. The density cannot be measured directly due to the presence of the chromium layer; it is estimated to have a value D=0.2. The copy made in this manner can be read directly in reflection from the front side. The quality of the small image and the sound cannot be distinguished from that of the original. According to this method it is possible to provide a plate on both sides with an information track. WHAT WE CLAIM IS:

1. A method of making copies for master information carrier having a spiral-like information track or a track built up from concentric circles, in which audio and/or video information is stored in the form of frequency- or phase-modulated signals in the form of blocks of variable lengths which lie in one plane, separated by areas of variable lengths which lie in another plane wherein a photosensitive material consisting of a support layer in which at least the surface is electrically insulating and which layer contains or is coated with a photosensitive compound comprising an aromatic diazothioether of the formula

wherein X is a substituent, n is 0 to 5 and R is a branched or non-branched alkyl group or aralkyl group, is exposed to the information using light, thereby forming a light reaction product, treating this product in the presence of moisture with mercurous ions or with mercurous and silver ions to form mercury or silver amalgam nuclei which are deposited in the form of a physically developable latent image, physically developing said resulting nuclei image to an optical density below D=l above the basic density of the carrier to produce said copies each copy having the blocks and the areas of the information track contained in a single plane of the support layer.

2. A method of making one or more copies of a master information carrier according to Claim 1 in which formula X is a substituent in the benzene ring, R is as defined in Claim 1 and n is 0, 1, 2 or 3.

3. A method as claimed in Claim 1 or Claim 2, characterised in that the carrier has a transport support layer and the copy of the

information track is made by reflection against a reflective surface present.

4. A method as claimed in Claim 3, characterised in that the reflective surface present is a reflecting metal layer.

5. Copies of information carriers manufactured - according to any of the preceding Claims.

6. A method of making one or more copies of an information carrier according to Claim 1 substantially as hereinbefore described.

7. A copy of an information carrier according to Claim 1 substantially as hereinbefore described.