US3310479A - Electrolytic recording media - Google Patents

Electrolytic recording media Download PDF

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US3310479A
US3310479A US256543A US25654363A US3310479A US 3310479 A US3310479 A US 3310479A US 256543 A US256543 A US 256543A US 25654363 A US25654363 A US 25654363A US 3310479 A US3310479 A US 3310479A
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recording media
thiourea
electrolytic
media
weight
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US256543A
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Goldstein Amnon
Allan R Mcgreevy
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Fairchild Semiconductor Corp
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Fairchild Camera and Instrument Corp
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Priority to US256543A priority Critical patent/US3310479A/en
Priority to DEF41904A priority patent/DE1201853B/en
Priority to FR962437A priority patent/FR1393448A/en
Priority to CH135664A priority patent/CH488239A/en
Priority to GB3125/64A priority patent/GB1063771A/en
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B41PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41MPRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M5/00Duplicating or marking methods; Sheet materials for use therein
    • B41M5/20Duplicating or marking methods; Sheet materials for use therein using electric current
    • B41M5/205Duplicating or marking methods; Sheet materials for use therein using electric current and an eroding electrode

Definitions

  • This invention rel-ates to electrolytic recording media and to solutions for the preparation of the same. More particularly, it relates to electrolytic recording media and to impregnating solutions containing a tetraborate sensitizer to increase the optical density of the recorded mark and to impart other valuable properties.
  • Electrolytic recording is recording by means of the electrolytic action of an electric current in a suitable electrosensitive medium.
  • the recording current is localized to product marks corresponding to graphic copy scanned at a remote point.
  • electrolytic facsimile recording it is common to dipose a recording sheet or electrolytic recording medium between an anode and a cathode at least one of which is in motion.
  • the electrolytic recording media is also drawn past the electrodes at a regular rate to produce linear recording.
  • Various recording devices incorporating the use of an electrolytic recording media are known and have been described. A suitable device for use in accordance with this invention is described in US. Patent 2,575,959,
  • electrolytic recording media comprise a porous sheet or support such as paper impregnated with electrolytically conductive aqueous solution containing a marking compound and an electrolyte.
  • the preferred marking compounds are polyhydroxy compounds such as oatechol.
  • Other classes of compounds such as aminophenols, organic acids and aldehydes having a polyhydroxylated phenyl group in the molecule, reduced quinones and derivatives of these compounds such as the esters and. amides of the acids or the oximes of the aldehydes are useful.
  • Aryl, alkyl or analkyl substituted analogues of the aminophenols or of the acids, aldehydes or their derivatives may also be employed.
  • Hydroquinone, salicylaldoxime, salicyclic acid, s-alicyclic aldehyde, o-aminophenol, ,hydroxylated aminotoluidines are mentioned as examples of marking compounds othe than polyhydroxy marking compounds.
  • the recording media When the recording media is sandwiched between a cathode and an anode, the latter being formed from iron, stainless steel, vanadium or equivalent metal and a current is passed, the anode dissolves into the conductive solution and reacts with the polyhydroxy compound to form a mark whose tonal quality varies from pale gray to dark black depending on the current intensity.
  • electrolytes which are useful in electrolytic recording media are known. Their function is to impart electric conductivity to the impregnating solution. Their concentration is a particular solution is a matter of choice depending upon the degree of conductivity desired. The concentration may vary from as low as 1% by weight or even lower to as high as the solubility limit of the electrolyte in the solution. The preferred concentration is from about 5% to about 15% by weight.
  • Typical elec troly-tes used in the preparation of electrolyticrecording media include alkali and alkaline earth metal halides and nitrates. The choice of electrolyte is not critical to this invention but sodium or potassium chloride, bromide or nitrate are preferred.
  • polyhydroxy compounds are used in the preparation of electrolytic recording media. These are phenolic compounds capable of reacting with dissolved anode material to produce a mark. One polyhydroxy tion for special purposes.
  • catechol a compound which is widely used is catechol. Others which are useful include pyrogallol, gallic acid, protocatechuic acid and tannic acid. Catechol although widely used is somewhat objectionable because of its high vapor pressure and of late, there has been considerable interest in replacing it in commercial preparations with less volatile marking compounds. Acids and their derivatives such as esters, amides or equivalents are of special interest because of their low volatility. Any of the known polyhydroxy compounds utilized in the preparation of electrolytic recording media can be employed in the practice of this invention.
  • the preferred polyhydroxy compounds used in praparing electrolytic recording media of this invention have at least two adjacent hydroxyl groups and it is believed that formation of the mark involves chelation of the dissolved anode material between these groups. It is not essential however, that the functional groups in the marking compound be adjacent.
  • the marking compound to be useful must be at least somewhat soluble in water, say for example, at least 1% by weight at 20 C. Its concentration is not critical, but may vary from about 1% by weight or even lower up to the maximum of solubility for the particular compound employed. Generally, the concentration varies between about 1.5% and 5% by weight.
  • Oxidants such as potassium chlorate have also been employed to enhance the intensity of oxidation marks.
  • Electrolytic recording media once prepared are generally not used immediately but are stored while still wet with the impregnating solution in sealed containers to retard evaporation.
  • Stabilizers generally used are thiocarbonyl compounds suhc as thiourea, alkyl derivatives of thiourea and dithioburet. Of these thiourea is preferred,
  • the stabilizers In addition to stabilizing the compositions, the stabilizers also stabilize the recorded mark. Thus, when stabilizers are used there is less tendency for the mark to fade or discolor on prolonged standing.
  • compositions prepared in accordance with this invention manifest a pH within the operable range. However, certain of them may be occasionally improved by adjusting the pH to a particular value. This may be effected by adding the base or the acid of the salt employed as the electrolyte. Thus, if sodium chloride is used as the electrolyte, the pH may be adjusted when desired with sodium hydroxide or hydrochloric acid.
  • the preferred acidifier for use in this invention is oxalic acid.
  • Other mineral acids or organic acids such as hydrochloric, nitric, sulfuric, citric, itaconic, formic and maleic acid for example are also useful.
  • the use of an acidifier is not essential since many impregnating solutions with a pH in the above disclosed range can be prepared without additional acids.
  • Antifringing agents are used as an aid for maintaining sharp detail in the mark.
  • Typical antifringing agents include alkali metal phosphates and pyrophosph'ates such as monosodium and disodium phosphate and pyrophosphate and their potassium analogues.
  • the use of antifringing agents is not essential for the recording media described herein but when utilized, they are generally present at a concentration of from about 0.01% to about 0.3% by weight.
  • novel electrolytic recording media and impregnating solutions for their preparation are provided.
  • the solution is an electrolytically conducting solution containing an electrolyte and a marking compound as described above together with a tetraborate sensitizer.
  • Any tetraborate salt which is suificiently soluble in the impregnating solution to provide concentrations of up to by weight on an anhydrous basis at room temperature is suitable as a sensitizer.
  • Sodium tetraborate is preferred.
  • Many tetraborates exist as hydrates. Pentahydrates and decahydrates of sodium tetraborate are well known. Potassium tetraborate exists as both pentaand octahydrate.
  • either hydrated or anhydrous forms of tetraborate can be used and when reference is made to a tetraborate it is specifically intended to include both anhydrous and hydrated forms.
  • concentration of sensitizer is not critical. Useful results are obtained at concentrations as low as 1% -by Weight or even lower and are similarly obtained Preferred concentrations are from about 2% to about 7% by Weight on an anhydrous basis. Acidifiers, stabilizers and antifringing agents can be employed as desired.
  • Electrolytic recording media prepared as described herein have a number of advantages over media prepared by prior known methods. Of these, the most important for many applications is the fact that the recorded image is extremely stable and shows little or no fading or yellowing even after prolonged standing. In side by side tests in which the results obtained with media prepared by prior art methods were compared with the results obtained using similar media prepared by the methods of this invention, it was found that after a month of storage, the image on the prior art media had faded considerably especially in the lighter areas and these had also developed a yellow tinge. In contrast, the image on the media of this invention was still sharp and clear.
  • Avalanching is a well known and recognized phenonemon. It is overmarking in certain areas of the medium and causes non-uniform shading of the mark. Much better tonal quality of the mark than is possible with prior known recording media can be achieved 4, over a wide range of current densities and recording speeds.
  • tetraborate sensitization takes place independently of this property.
  • oxidation marks optical density is improved by the addition of an oxidizing agent such as potassium chlorate to the impregnating solution and increases with increasing concentration.
  • oxidizing agents have no effect on other types of marks. These latter marks are known as precipitation marks.
  • Tetraborate sensitizers improve the optical density of both oxidation and precipitation marks.
  • Impregnating solutions for use in this invention are prepared by dissolving the various ingredients in water. Several sample solutions are shown hereinafter.
  • Electrolytic recording media may be prepared by passing a orous support through a bath containing the impregnating solution. Approximately 2.5 to 3 cubic centimeters of the solution is generally required per square foot of support. The solution is distributed evenly throughout the support. Any excess may be removed by compression for example between pressure rolls. When ready. for use, the electrolytic recording media will contain about 40% impregnating solution by weight. As aforesaid, the media are generally stored in sealed containers until needed.
  • a wet web comprising a porous sheet impregnated with an electrolytically conducting aqueous solution containing at least 1% by weight of a phenolic marking compound together with from about 1% to about 10% by weight based on the anhydrous salt of a tetraborate sensitizer.
  • a web as in claim 2 in which the polyhydroxy marking compound is selected from the group consisting of catechol, pyrogallol, gallic acid, gallamide, methyl gallate, protocatechuic acid, and tannic acid.
  • a wet web as in claim 1 wherein the tetraborate is sodium tetraborate.

Description

United States Patent 3,310,479 ELECTROLYTIC RECORDING MEDIA Amnon Goldstein, Forest Hills, and Allan R. McGreevy,
Elmhurst, N.Y., assignors to Fairchild Camera & In-
strument Corporation, Syosset, N.Y., a corporation of New York No Drawing. Filed Feb. 6, 1963, Ser. No. 256,543
9 Claims. (Cl. 2042) This invention rel-ates to electrolytic recording media and to solutions for the preparation of the same. More particularly, it relates to electrolytic recording media and to impregnating solutions containing a tetraborate sensitizer to increase the optical density of the recorded mark and to impart other valuable properties.
Electrolytic recording is recording by means of the electrolytic action of an electric current in a suitable electrosensitive medium. The recording current is localized to product marks corresponding to graphic copy scanned at a remote point. In electrolytic facsimile recording it is common to dipose a recording sheet or electrolytic recording medium between an anode and a cathode at least one of which is in motion. The electrolytic recording media is also drawn past the electrodes at a regular rate to produce linear recording. Various recording devices incorporating the use of an electrolytic recording media are known and have been described. A suitable device for use in accordance with this invention is described in US. Patent 2,575,959,
Various electrolytic recording media have been described. They comprise a porous sheet or support such as paper impregnated with electrolytically conductive aqueous solution containing a marking compound and an electrolyte. The preferred marking compounds are polyhydroxy compounds such as oatechol. Other classes of compounds such as aminophenols, organic acids and aldehydes having a polyhydroxylated phenyl group in the molecule, reduced quinones and derivatives of these compounds such as the esters and. amides of the acids or the oximes of the aldehydes are useful. Aryl, alkyl or analkyl substituted analogues of the aminophenols or of the acids, aldehydes or their derivatives may also be employed. Hydroquinone, salicylaldoxime, salicyclic acid, s-alicyclic aldehyde, o-aminophenol, ,hydroxylated aminotoluidines are mentioned as examples of marking compounds othe than polyhydroxy marking compounds.
While it is preferred to utilize polyhydroxy compounds in the practice of this invention, it is specifically intended to include other marking compounds .such as those described above within the scope of the invention. With this in mind, the invention will be specifically described and illustrated with reference to polyhydroxy compounds for ease of understanding and simplicity of description.
When the recording media is sandwiched between a cathode and an anode, the latter being formed from iron, stainless steel, vanadium or equivalent metal and a current is passed, the anode dissolves into the conductive solution and reacts with the polyhydroxy compound to form a mark whose tonal quality varies from pale gray to dark black depending on the current intensity.
Several electrolytes which are useful in electrolytic recording media are known. Their function is to impart electric conductivity to the impregnating solution. Their concentration is a particular solution is a matter of choice depending upon the degree of conductivity desired. The concentration may vary from as low as 1% by weight or even lower to as high as the solubility limit of the electrolyte in the solution. The preferred concentration is from about 5% to about 15% by weight. Typical elec troly-tes used in the preparation of electrolyticrecording media include alkali and alkaline earth metal halides and nitrates. The choice of electrolyte is not critical to this invention but sodium or potassium chloride, bromide or nitrate are preferred.
A wide variety of polyhydroxy compounds are used in the preparation of electrolytic recording media. These are phenolic compounds capable of reacting with dissolved anode material to produce a mark. One polyhydroxy tion for special purposes.
compound which is widely used is catechol. Others which are useful include pyrogallol, gallic acid, protocatechuic acid and tannic acid. Catechol although widely used is somewhat objectionable because of its high vapor pressure and of late, there has been considerable interest in replacing it in commercial preparations with less volatile marking compounds. Acids and their derivatives such as esters, amides or equivalents are of special interest because of their low volatility. Any of the known polyhydroxy compounds utilized in the preparation of electrolytic recording media can be employed in the practice of this invention.
The preferred polyhydroxy compounds used in praparing electrolytic recording media of this invention have at least two adjacent hydroxyl groups and it is believed that formation of the mark involves chelation of the dissolved anode material between these groups. It is not essential however, that the functional groups in the marking compound be adjacent.
The marking compound to be useful must be at least somewhat soluble in water, say for example, at least 1% by weight at 20 C. Its concentration is not critical, but may vary from about 1% by weight or even lower up to the maximum of solubility for the particular compound employed. Generally, the concentration varies between about 1.5% and 5% by weight.
Various additives such as stabilizers, acidifiers and antifringing agents may be added to the impregnating solu- Many examples .areknown. Oxidants such as potassium chlorate have also been employed to enhance the intensity of oxidation marks.
Electrolytic recording media once prepared are generally not used immediately but are stored while still wet with the impregnating solution in sealed containers to retard evaporation. Unfortunately, during storage there is a tendency for the compositions to degrade. It has been the practice of the art to include relatively small amounts of stabilizers to retard this degradation. Stabilizers generally used are thiocarbonyl compounds suhc as thiourea, alkyl derivatives of thiourea and dithioburet. Of these thiourea is preferred,
In addition to stabilizing the compositions, the stabilizers also stabilize the recorded mark. Thus, when stabilizers are used there is less tendency for the mark to fade or discolor on prolonged standing.
It is aspecial advantage of the impregnating solutions and recording media of this invention that smaller amounts of stabilizer can be utilized than has heretofore been necessary. In fact because of the remarkable stability of the media, it is often possible to omit the stabilizer completely especially in high volume operations where the media will be used within a relatively short time, i.e. one to two months after preparation. If the media is to be stored for a longer period or if it is essential that the mark remain clear and readable for a long time, it is best, however, to use a. stabilizer. Generally, as little as 0.1% by weight will be used. Useful results are obtained at concentrations of from about 0.05% to about 1.0% by weight.
at the maximum of solubility of the sensitizers.
objectionable for many purposes. The preferred range is from 2 to 5. Compositions prepared in accordance with this invention manifest a pH within the operable range. However, certain of them may be occasionally improved by adjusting the pH to a particular value. This may be effected by adding the base or the acid of the salt employed as the electrolyte. Thus, if sodium chloride is used as the electrolyte, the pH may be adjusted when desired with sodium hydroxide or hydrochloric acid.
The preferred acidifier for use in this invention is oxalic acid. Other mineral acids or organic acids such as hydrochloric, nitric, sulfuric, citric, itaconic, formic and maleic acid for example are also useful. The use of an acidifier is not essential since many impregnating solutions with a pH in the above disclosed range can be prepared without additional acids.
Antifringing agents are used as an aid for maintaining sharp detail in the mark. Typical antifringing agents include alkali metal phosphates and pyrophosph'ates such as monosodium and disodium phosphate and pyrophosphate and their potassium analogues. The use of antifringing agents is not essential for the recording media described herein but when utilized, they are generally present at a concentration of from about 0.01% to about 0.3% by weight.
In accordance with this invention novel electrolytic recording media and impregnating solutions for their preparation are provided. The solution is an electrolytically conducting solution containing an electrolyte and a marking compound as described above together with a tetraborate sensitizer. Any tetraborate salt which is suificiently soluble in the impregnating solution to provide concentrations of up to by weight on an anhydrous basis at room temperature is suitable as a sensitizer. Sodium tetraborate is preferred. Many tetraborates exist as hydrates. Pentahydrates and decahydrates of sodium tetraborate are well known. Potassium tetraborate exists as both pentaand octahydrate. For this invention, either hydrated or anhydrous forms of tetraborate can be used and when reference is made to a tetraborate it is specifically intended to include both anhydrous and hydrated forms. The concentration of sensitizer is not critical. Useful results are obtained at concentrations as low as 1% -by Weight or even lower and are similarly obtained Preferred concentrations are from about 2% to about 7% by Weight on an anhydrous basis. Acidifiers, stabilizers and antifringing agents can be employed as desired.
Electrolytic recording media prepared as described herein have a number of advantages over media prepared by prior known methods. Of these, the most important for many applications is the fact that the recorded image is extremely stable and shows little or no fading or yellowing even after prolonged standing. In side by side tests in which the results obtained with media prepared by prior art methods were compared with the results obtained using similar media prepared by the methods of this invention, it was found that after a month of storage, the image on the prior art media had faded considerably especially in the lighter areas and these had also developed a yellow tinge. In contrast, the image on the media of this invention was still sharp and clear. These results were achieved despite the fact that the rior art impregnating solution contained 0.25 gram of thiourea stabilizer per 100 cubic centimeters of solution, whereas the solution used to prepare the media of this invention contained less than one-half of this quantity.
There is practically no streaking of the image with the media of this invention. Moreover, the avalanche effect is also negligible. Avalanching is a well known and recognized phenonemon. It is overmarking in certain areas of the medium and causes non-uniform shading of the mark. Much better tonal quality of the mark than is possible with prior known recording media can be achieved 4, over a wide range of current densities and recording speeds.
The exact mechanism by which tetraborate sensitization takes place is not known. Although tetraborates are oxidizing agents, sensitization takes place independently of this property. There are two types of marks recognized in the recording art. These are oxidation marks and precipitation marks. With oxidation marks optical density is improved by the addition of an oxidizing agent such as potassium chlorate to the impregnating solution and increases with increasing concentration. The presence of oxidizing agents has no effect on other types of marks. These latter marks are known as precipitation marks. Tetraborate sensitizers improve the optical density of both oxidation and precipitation marks.
Impregnating solutions for use in this invention are prepared by dissolving the various ingredients in water. Several sample solutions are shown hereinafter.
Electrolytic recording media may be prepared by passing a orous support through a bath containing the impregnating solution. Approximately 2.5 to 3 cubic centimeters of the solution is generally required per square foot of support. The solution is distributed evenly throughout the support. Any excess may be removed by compression for example between pressure rolls. When ready. for use, the electrolytic recording media will contain about 40% impregnating solution by weight. As aforesaid, the media are generally stored in sealed containers until needed.
The following sample solutions are given by way of example and are not intended as limitations of this invention many apparent variations of which are possible without departing from the spirit and scope thereof. In each of the solutions, the indicated quantities of the various ingredients are dissolved in cc. of water. Useful electrolytic media applicable to low, medium and high speed recording may be prepared from any of them by adjusting the pH to form 1 to 6 as described above and impregnating a suitable porous support such as paper.
Grams NaNO 10.0 Catechol 4.5 Na2B407.10H2O 4-0 Oxalic acid 0.125 Thiourea 0.1
. B NaCl 16.0 Gallic acid 2.0
N212B4O7-10H2O Thiourea 0.5
. C Tannic acid 1.5 NaCl 8.0 Na B O .10H O 2.5 Thiourea 0.1
NaCl 7.0 Pyrogallol 2.0 Na2HPO4 Na2B O7- Thiourea 0.1
E Methyl gallate 1.0 NaCl 8.0 Na B O .10H O 2.5 Thiourea 0.1
NaCl 8.0
' Gallamide 1.0 Na HPO 0.1 Na B4O7.10H O Thiourea 0.1
G KNO 12.0 Catechol 4.5 Na2B4O7 2.2 Citric acid 0.125 Thiourea 0.1
H NaBr 3.0 Gallic acid 2.0 K B O .8H O 3.0 N-ethyl thiourea 0.7
1 NaCl 16.0 Gallic acid 2.0 Na2B407 7.0 Thiourea 0.5
J 7 NaCl 7.0 Pyrogallol 2.0 N34P207 Na2B4O pH20 2.0 Thiourea 0.2
K KNO 12.0 Pyrog allol 4.5 Na2B407 Thiourea 0.15
L NaNO 10.0 Catech-ol 4.5 Na B O .5H O 4.0 Itaconic acid 0.12
M NaCl a 16.0 Gallic acid 2.0 K B O .5H O 7.0
N NaNO 10.0
C-atechol 5.0 Na2B4O7.10H O H 30 (con.) 0.125 Thiourea 0.05
O NaCl 7.0 Gallic acid 2.0 NH4P207 3-0 N212B407-10H20 2-0 Thiourea 1.0
P NaCl 8.0 Gallamide 1.0 Na HPO 0.05 Na2B407. Thiourea 0.1
Q N-aBr 3.0 Gallic acid 2.0 K2B407.8H20 10.0 N-ethyl thiourea 0.7
R NaCl 8.0 Gallamide 1.0 NaH2PO4 Na2B4O7.10H O V 2.5 Thiourea 0.1
What is claimed is:
1. For use in electrolytic facsimile recording, a wet web comprising a porous sheet impregnated with an electrolytically conducting aqueous solution containing at least 1% by weight of a phenolic marking compound together with from about 1% to about 10% by weight based on the anhydrous salt of a tetraborate sensitizer.
2. A web as in claim 1 in which the marking compound is a polyhydroxy phenolic marking compound.
3. A web as in claim 2 in which the polyhydroxy marking compound is selected from the group consisting of catechol, pyrogallol, gallic acid, gallamide, methyl gallate, protocatechuic acid, and tannic acid.
4. A web as in claim 1 wherein the electrolytically conducting solution contains from about 0.05 to 1% by weight of a thiocarbonyl stabilizer.
5. A web as in claim 4 wherein the stabilizer is thiourea. 1
6. A wet web as in claim 1 in which the pH of the electrolytically conducting solution is maintained between 1 and 6 by the presence of an acidifier.
7. A wet web as in claim 6 in which the 'aeidifier is selected from the group consisting of hydrochloric, nitric, sulfuric, citric, itaconic, formic, maleic and oxalic acids.
8. A wet web as in claim 1 in which the electrolytically conducting solution contains from 0.01 to 0.3% by Weight of an antifringing agent selected from the group consisting of alkali metal, phosphates and pyrophosphates.
9. A wet web as in claim 1 wherein the tetraborate is sodium tetraborate.
References Cited by the Examiner UNITED STATES, PATENTS 2,367,113 1/ 1945 Gibney 204-2 3,152,903 10/1964 Shepard et al 96-64 OTHER REFERENCES The Condensed Chemical Dictionary, Sixth Edition, Reinhold Company, p. 1036 relied on.
HOWARD S. WILLIAMS, Primary Examiner.
JOHN H. MACK, Examiner.
W. VAN SISE, Assistant Examiner.

Claims (1)

1. FOR USE IN ELECTROLYTIC FACSIMILE RECORDING, A WET WEB COMPRISING A POROUS SHEET IMPREGNATED WITH AN ELECTROLYTICALLY CONDUCTING AQUEOUS SOLUTION CONTAINING AT LEAST 1% BY WEIGHT OF A PHENOLIC MARKING COMPOUND TOGETHER WITH FROM ABOUT 1% TO ABOUT 10% BY WEIGHT BASED ON THE ANHYDROUS SALT OF A TETRABORATE SENSITIZER.
US256543A 1963-02-06 1963-02-06 Electrolytic recording media Expired - Lifetime US3310479A (en)

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DEF41904A DE1201853B (en) 1963-02-06 1964-02-01 Electrolytic recording medium
FR962437A FR1393448A (en) 1963-02-06 1964-02-03 Electrolytic recording medium
CH135664A CH488239A (en) 1963-02-06 1964-02-05 Electrolytic recording medium
GB3125/64A GB1063771A (en) 1963-02-06 1964-02-06 Electrolytic recording media

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3493481A (en) * 1966-10-27 1970-02-03 Photocircuits Corp Method of testing printed circuit boards

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3444055A (en) * 1966-10-27 1969-05-13 Hogan Faximile Corp Electrolytic recording medium

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2367113A (en) * 1941-02-06 1945-01-09 Bell Telephone Labor Inc Electrographic recording medium
US3152903A (en) * 1959-04-30 1964-10-13 Minnesota Mining & Mfg Reproduction system

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2367113A (en) * 1941-02-06 1945-01-09 Bell Telephone Labor Inc Electrographic recording medium
US3152903A (en) * 1959-04-30 1964-10-13 Minnesota Mining & Mfg Reproduction system

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3493481A (en) * 1966-10-27 1970-02-03 Photocircuits Corp Method of testing printed circuit boards
US3494837A (en) * 1966-10-27 1970-02-10 Photocircuits Corp Method of testing printed circuits

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GB1063771A (en) 1967-03-30
DE1201853B (en) 1965-09-30

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