Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
  • G03G5/14—Inert intermediate or cover layers for charge-receiving layers
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
  • G03G5/14—Inert intermediate or cover layers for charge-receiving layers
  • G03G5/142—Inert intermediate layers

Definitions

• Marjama ABSTRACT An electrophotographic plate comprising an electrically conductive substrate material overcoated with an interlayer material comprising a substituted silylisobutylethylenediamine, said interlayer, in turn, being coated with an overlayer comprising selenium and a method of preparing and process of using said plate are disclosed.
• This invention relates in general to electrophotography and, in particular, to electrophotographic plates, electrophoto graphic processes using such plates, and to processes for the production of said plates. More specifically, the invention relates to a novel electrophotographic plate comprising a relatively conductive backing having on at least one surface thereof an organic adhesive interface material overcoated with at least one layer comprising a photoconductive insulating material.
• suitable inorganic and organic materials may be used to form the photoconductive insulating layer on which the latent electrostatic image is formed. While many photoconductors have been used or attempted, selenium has been the most commercially accepted material for use in ,electrophotographic plates.
• 579,826 discloses employing certain epoxies, polyorganosiloxanes, polyurethanes, polyesters, phenoplasts, polyamides and polysulfides as interfacial layers of xerographic plates. While these materials aid in preventing a separation of the photoconductive layer from the substrate, some flaking, cracking, and spalling of the photoconductive layer during the fast belt operation is still evident. Further, the adhesive properties of these materials have been known to wane over a period of time with prolonged use of the plate or belt.
• an electrophotographic plate comprising a conductive substrate having coated thereover an interlayer comprising a silylisobutylethylenediarnine, said interlayer, in turn, being overcoated with a layer comprising selenium.
• novel electrophotographic plates of the present invention are preferably prepared by providing a precleaned conductive substrate, depositing an interfacial coating comprising a substituted silylisobutylethylenediamine adhesive on said substrate, drying the adhesive layer to remove excess solvent, and thereafter, depositing one or more layers of photoconductive insulating materials.
• the conductive substrate underlying the interfacial layer may comprise any suitable material having the capability of acting as a ground plane for the electrophotographic plate.
• Typical conductive materials include metals such as aluminum, brass, stainless steel, copper, nickel and zinc; conductively coated glass such as tin oxide, indium oxide, and aluminum coated glass; similar coatings on plastic substrates; or paper rendered conductive by the inclusion of a suitable chemical therein or conditioning in a humid atmosphere to assure the presence therein of a sufficient water content to render the material conductive. While materials having electrical resistivities of about ohm-centimeters are generally satisfactory for the supporting substrate of this invention, it is preferably to employ materials of less than 10" ohm-centimeters.
• the substrate Prior to coating of the conductive material with the interfacial adhesive layer, the substrate is cleaned of impurities which will adversely affect the mechanical or electrical properties of the electrophotographic plate. Primarily, the cleaning operation is conducted to remove grease, dirt, and any other contaminates which might prevent firm adherence of the interfacial layer to the conductive backing. Additionally, effective cleaning leaves the electrical properties of the backing uniform throughout its entire applicable surface area.
• brass substrates may be cleaned by degreasing the brass in boiling trichloroethylene, etching the degreased substrate in 30 percent hydrogen peroxide solution for a few minutes, rinsing in deionized water and subsequently, vacuum drying the conductive material.
• Brass substrates may also be cleaned by subjecting them to a vapor phase of trichloroethylene, soaking in an alkaline cleaner at an elevated temperature, and then soaking in an oxide-removing solution.
• a suitable alkaline material for cleaning nonferrous substrates is ALTREX made by Wyandotte Company which is used in a concentration of about 6 ounces of cleaner per gallon of distilled water.
• the brass substrate is soaked in this solution at about 80 C. for about one to two minutes.
• the use of the oxide-removing solution is an optional step in a complete cleaning process. It is believed that solvents, such as trichloroethylene or hydrocarbon solvents, become trapped in the outer oxide layer. To remove these impurities, it is necessary to etch away the oxide layer.
• the oxide-removing solution is primarily acidic, it will neutralize any alkali cleaner remaining on thepartially treated surface.
• a suitable oxide-removing solution comprises about 30 parts by weight of concentrated sulfuric acid, about 30 parts of concentrated nitric acid, and about 40 parts of distilled water. Soaking time is on the order of about 5 seconds.
• the adhesive interfacial material is coated thereon.
• This interlayer material may comprise any suitable substituted silylisobutylethylenediamine.
• Typical substituted silylisobutylethylenediamines include n-dimethoxymethylsilylisobutylethylenediamine, n-trimethoxysilylisobutylethylenediamine, n-diethoxymethylsilylisobutylethylenedi amine, n-diethoxyethylsilylisobutylethylenediamine, ntriethoxysilylisobutylethylenediamine, among many others.
• Best initial and long-lasting adhesion of the photoconductive layer to the underlying substrate occurs with the use of ndimethoxymethylsilylisobutylethylenediamine; n-trimethoxysilylisobutylethylenediamine; about 2 parts by weight, of ndimethoxymethylsilylisobutylethylenediamine and about 1 parts, by weight, of gamma-methacryloxypropyltrimethoxysilane; about 2 parts, by weight, of n-dimethoxymethylsilylisobutylethylenediamine and about 1 part, by weight, of vinyltriacetoxysilane and, accordingly, these materials are preferred.
• Optimum adhesion is present when about 2 parts, by weight, of n-dimethoxymethylsilylisobutylethylenediammine and about 1 parts, by weight, of gamma-methacryloxypropyltrimethoxysilane is employed as the interfacial material of the present invention.
• interlayer may be of any suitable thickness
• a film with a thickness in the range of about 0.1 micron to about 5.0 microns is preferred, since layers within this range exhibit excellent bonding ability between the conductive substrate and photoconductive insulating material while maintaining or improving the electrical properties of the electrophotographic plate.
• a thickness of less than about 0.1 micron may fail to provide necessary physical properties, such as sufficient bonding strength, whereas a thickness of over about 5.0 microns may fail to give optimum imaging properties, since a high residual potential may occur at such a thickness.
• the optimum thickness of the interfacial layer lies between the range of about 0.1 micron to about 2.0 microns, since at this range the best overall combination of electrical and physical properties is found to exist.
• any convenient method may be employed for depositing the adhesive interfacial material upon the conductive substrate.
• One method for applying this interlayer is by providing a solution of the desired adhesive material in a large tank, lowering the conductive substrate into the tank so that the area thereof to be coated lies below the surface of the adhesive solution, withdrawing the coated substrate at a constant rate, and allowing at least a portion of the solvent to be removed from the coating.
• the coating may be applied in several other ways as by spraying, through the use of a dip roll, an air knife, or a doctor blade, etc.
• a preferred method for depositing a uniform layer of adhesive interfacial material over the conductive substrate is a hydraulic coating method wherein the conductive substrate is placed in a unit which will accommodate sufficient adhesive solution to completely cover the entire surface of the conductive backing.
• a stopcock is provided at the bottom of the unit so that the adhesive solution can flow smoothly and easily from the unit when the stopcock is opened.
• the adhesive solution is added to the unit in amounts which are sufficient to completely cover the accommodated conductive backing, the stopcock is opened, and the excess solution drains out.
• This method is particularly suitable for depositing films on the order of about 0.1 micron and it has been found that this method of coating provides exceptionally even coatings having relatively few variations in thickness, thereby producing more uniform electrical properties in the final electrophotographic plate.
• any solution of appropriate adhesive material in a suitable solvent can be utilized in the coating of the conductive substrate.
• Any suitable solvent may be used to dilute the adhesive material of this invention to the desired concentration.
• Typical solvent materials include methyl alcohol, butyl acetate, toluene, etc. While any suitable solvent may be used, it is preferable to employ about 20 parts, by weight, of relatively pure methyl alcohol in about 1 part of deionized water.
• coating formulation of the instant invention may be applied to the underlying substrate at any suitable temperature, it is preferable, in order to provide a plate with improved mechanical and physical properties, to apply said formulation at about room temperature.
• the coated substrate is allowed to drain for a reasonable period of time, preferably from about 30 to about 60 seconds. After draining, said coated substrate is placed in a drying oven and dried for about 2 to about 15 minutes at about 1 10 C. to about 160 C. While any suitable time and temperature may be employed in this drying step, it is found that for drying about a l to 2 micron coating about 4 minutes at about C. produces the best results. Lower temperatures or less time is preferred for the drying of coatings of less than about 1 micron.
• the interlayer material is dry, it is coated with at least one layer of a photoconductive insulating material.
• a photoconductive insulating material any suitable photoconductive material may be used in this invention, it is preferable that a selenium-containing layer be employed since selenium is the photoconductive material used most extensively today in commercial electrophotography.
• the selenium-containing layer may comprise selenium or any suitable selenium alloy or mixture of other materials with selenium.
• Typical selenium alloys or selenium-containing mixtures include cadmium selenide, cadmium sulfo-selenide, mixtures of sulfur and selenium such as are described by Carlson in U.S. Pat. No. 2,297,691; mixtures of arsenic and selenium such as are described by Mayer et al. in U.S. Pat. No. 2,822,300; mixtures of selenium and tellurium as described by Paris in U.S. Pat. No. 2,803,541; arsenic selenide; tellurium selenide; and mixtures thereof.
• the selenium-containing layer may include various sensitizing additives, such as the halogen dopants disclosed in copending application Ser. No. 516,529, filed Dec. 27, 1965.
• the selenium employed in the preparation of electrophotographic plates should be free of impurities which adversely affect its ability to hold electrostatic charges. If impurities are present, conducting paths may be formed in the film or said impurities may promote formation of conducting hexagonal selenium, with the result that electrostatic charges leak off rapidly, even in the dark, and electrostatic deposition of powder or other finely divided material cannot be obtained.
• relatively pure vitreous selenium should be employed. Vitreous selenium is available in pellet form oneseventeenth inch to one-eighth inch in size under the ARQ (ammonia reduced in quartz from selenium oxide) as manufactured. This grade of selenium is essentially pure, containing less than about 20 parts per million of impurities. If purified, other grades of selenium such as DDQ (double distilled in quartz) and CCR (commercial grade) as manufactured, may likewise be employed in the process disclosed herein. Procedures used to purify these grades of selenium are well known in the art.
• the selenium layer has been described as vitreous, the exact molecular structure is not known, the term being used as descriptive of its physical appearance. It is believed that the selenium is present substantially in amorphous form containing minor proportions, if any, of a crystalline form of selenium, although it is not desired to restrict this invention to the presence of such a mixture of forms. It is, therefore, to be understood that the various crystalline or amorphous structures included in the vitreousappearing formof selenium are likewise to be included in the term vitreous as used herein and in the claims.
• selenium includes not only pure selenium but also selenium that may be modified by a controlled amount of an additive, such as noted above (i.e., arsenic, tellurium, etc.) that is consistent with retention of useful photoconducting properties.
• an additive such as noted above (i.e., arsenic, tellurium, etc.) that is consistent with retention of useful photoconducting properties.
• the teachings of the present invention may be used to improve the bond of any of the photoconductive insulator layers to the supporting conductive substrate of any of the elcc trophotographic plates known to those skilled in the art.
• such plates are described as to preparation, composition, thickness and other parameters, in U.S. Pat. No. 2,745,327 to Mengali; U.S. Pat. No. 2,803,541 to Paris U.S. Pat. No. 2,803,542 to Ullrich, Jr.; U.S. Pat. No. 2,863,768 to Schafiert; U.S. Pat. No. 2,901,348 to Dessauer et al., U.S. Pat. No. 2,901,349 to Schaffert et al., U.S.
• any suitable method can be used for depositing the vitreous selenium upon the substituted silylisobutylethylenediamine interfacial layer.
• Many suitable processes are described in the aforementioned patents as well as in the patents to Mengali et al. U.S. Pat. No. 2,657,l52; to Bixby et al. U.S. Pat. No. 2,753,278; to Bixby, 2,970,906, etc.
• the photoconductive layer is deposited through vacuum evaporation of selenium onto a backing plate held at a temperature of at least about 20? C., and generally in the range between about 40 and about C. and preferably, on the order of about 50 C.
• the deposition of the selenium layer is halted when the layer has reached the desired thickness such as, for example, in the order of about 10 to about 200 microns, preferably about 20 to about 50 microns.
• Deposition is conducted under pressure conditions on the order of less than about I micron of mercu- Specifically, the plate temperature is maintained at a level whereby vitreous selenium is deposited during the deposition process. Thus, temperatures on the order of about C. may be used, provided the time of deposition is relatively short; whereas lower temperatures are more commonly used with longer periods of deposition.
• the selenium is held in a temperature controlled container which is maintained at a temperature above the melting point of selenium and at a point where its vapor pressure is sufficient to provide substantial deposition on the conductive backing. Deposition rates of about 5-20 microns per hour are easily obtainable but it is contemplated that under appropriate conditions higher rates of deposition can also be obtained.
• the first test performed is a qualitative tape test which rapidly eliminates unsatisfactory specimens.
• a pressure-sensitive adhesive tape such as Scotch” brand cellophane tape, is applied to the bonded photoconductive insulator to the underlying conductive substrate.
• the strip of tape is napped off the photoconductor insulator surface by a quick movement of the hand; an insufficiently bonded material will be pulled off, either in part or in toto.
• a second test entails scribing the photoconductor surface with a pointed steel tool and noting the amount of photoconductor removed from the substrate.
• a scale known as a CSN scale of l to 10, denotes the amount of photoconductor removed.
• a CSN of l is very poor while a CSN of 10 is excellent.
• a third test namely a qualitative flex test, is performed by bending the specimen once over cylindrical steel mandrels of varying diameters and carefully observing any cracking or cracking noises. Afier the test specimen is flexed, it is then observed in a darkened room under a Bausch & Lomb stereo microscope using cross-lighting techniques. Basically, the method involves impinging a beam of light at a small angle to the surface being tested. The microscopic examination will show very fine surface-crack lines which would not be distinguishable by the naked eye.
• the electrical characteristics of the electrophotographic plate are measured with an electrostatic contrast scanner which simulates normal electrophotographic operation but does not utilize toner. Characteristics measured include initial voltage, equilibrium voltage, background potential, dark discharge, and residual voltage.
• electrophotographic prints are made by taping the test specimens on a rigid xerographic drum and performing the sequential operations disclosed by Carlson U.S. Pat. No. 2,297,691 and elsewhere throughout the patent literature.
• EXAMPLE I A 4 mil brass substrate, about 7 inches long and about inches wide, is vapor degreased in trichloroethylene, soaked for approximately 1 minute in about a 5 percent solution of ALTREX alkaline cleaner, manufactured by Wyandotte Corporation, rinsed with deionized water, and dipped in an etching solution containing about 30 parts by weight of concentrated sulfuric acid, about 30 parts by weight of concentrated nitric acid, abut 39.9 parts by weight of distilled water, and about 0.01 parts by weight of sodium choride.
• the cleaned substrate is coated to a thickness of about 1 micron with an adhesive mixture comprising about 2 parts by weight of n-dimethoxymethylsilylisobutylethylenediamine and about 1 part by weight of gamma-methacryloxypropyltrimethoxysilane in about 20 parts by weight of methyl alcohol and about 1 part by weight of deionized water.
• the coated substrate is then dried for about 4 minutes at about 140 C., placed in a vacuum deposition vessel, and coated with about 40 microns of selenium.
• the plate has electrical properties substantially identical to standard selenium plates, clear xerographic copies are obtained, and the unit flexes without peeling, cracking, or flaking (microcracks are not visible in the photoconductor surface when viewed at 7-10X magnification with incident light). Further, no material is pulled off from the substrate under the Scotch tape test. Finally, the CSN is approximately 9.5.
• EXAMPLE ll As a control for the plate of example I, the method of preparation is repeated. A similar brass substrate is cleaned as in example I and 40 microns of selenium are vacuum deposited thereon. No adhesive layer is placed between the substrate and selenium layer. When flexed, the selenium does not adhere to the brass substrate.
• Example I is repeated with a polyorganosiloxane adhesive mixture comprising about 4 parts by weight of vinyl triethoxysiloxane and about 8 parts by weight of aminopropyltriethoxysiloxane in about 78 parts methanol solvent containing about 9.25 parts acidified (0.75 mil conc. HCl) water (pH 8.2).
• This polyorganosiloxane adhesive is HCO proprietary formulation known as Chemlok, a product of the Lord Manufacturing Co.
• the coated substrate is dried for about 4 hours at room temperature, placed in a vacuum deposition vessel, and coated with about 40 microns of selenium.
• the plate has electrical properties substantially identical to standard selenium plates, clear xerographic copies are obtained, and no material is pulled off from the substrate under the Scotch tape test. However, said plate demonstrated only a maximum CSN of 6.5 as compared to 9.5 in example I and shows evidence of microcracking when the photoreceptor is passed over a 1 inch or 2 inch mandrel.
• cEXAMPLE IV A 4 mil brass substrate, about 7 inches long and about 5 inches wide is vapor degreased in trichloroethylene, soaked in chromating solution (Kenvert 30-C), rinsed with deionized water and air dried.
• the cleaned substrate is coated to a thickness of about 3 microns with an adhesive mixture comprising about 2 parts by weight of dimethoxymethylsilylisobutylethylenediamine, 1 part by weight of vinylbutacetoxysilane, in about 40 parts by weight of toluene and about 5 parts by weight of deionized water.
• the coated substrate is then air cried at room temperature for about 1 hour and then oven dried for about one-half hour at about 70? C. This is followed by placing said substrate in a vacuum deposition vessel and coating it with about 50 microns of a selenium alloy containing about 17.5 percent by weight of arsenic and 1,000 parts per million by weight of iodine.
• the unit After deposition of the selenium alloy, the unit is heat treated for about hours at about 50 C.
• the selenium alloy adheres well to the substrate; no signs of flaking are present; the unit has excellent electrical properties and very good xerographic copies are produced with the plate.
• the plate exhibits a CSN of about 9 and flexes without cracking when passed over I inch and 2 inch steel mandrels.
• Example IV is repeated using Chemlok (see example Ill) in place of dimethoxymethylsilylisobutylethylenediamine and vinyltriacetoxysilane. While electrical properties are excellent and, further, while no peeling can be seen by the naked eye, there are several signs of microcracking in the prepared plate. Moreover, as compared with a CSN of about 9 in example IV, the present plate exhibits a CSN of only about 6.
• EXAMPLE Vl Example IV is repeated using dimethoxymethylsilylisobutylethylenediamine without vinyltriacetoxysilane. Electrical properties are very good; only very few microcracks occur when the resulting plate is flexed over a 1 inch and a 2 inch mandrel; the plate passes the Scotch tape test I00 percent, and the CSN is found to be about 8.
• EXAMPLE VII The process of example I is repeated using clean 3.5 mil stainless steel in place of brass as the underlying substrate. The results obtained are similar to those obtained in example l.
• EXAMPLE Vlll The process of example I is repeated employing about a 0.] micron layer of adhesive mixture in place of 1.0 microns of same. The results obtained are similar to those obtained in example l.
• EXAMPLE lX The process of example I is repeated employing about a 5.0 micron layer of adhesive mixture in place of 1.0 microns of same. The results obtained are similar to those obtained in example l.
• Three aluminum drums commonly utilized in the 8l3" xerographic copier manufactured by Xerox Corporation of Rochester, New York are coated in solutions of the adhesive formulation of example I by the known hydraulic coating technique and dried in an oven for about 4 minutes at about 140 C.
• the coated drums are placed in a vacuum deposition vessel and coated with about 20, 40 and 60 microns of vitreous selenium and then heat treated for about 40 hours at about C.
• the drums are placed in a standard 8 13" xerographic copier and good xerographic prints are obtained with each unit. After 500 copies are produced no microcracking is observed.
• An electrophotographic plate comprising an electrically conductive substrate material, said substrate being overcoated with an interlayer material selected from the group consisting of n-dimethoxymethylsilylisobutylethylenediamine; ntrimethoxysilylisobutylethylenediamine; about 2 parts, by weight of n-dimethoxymethylsilylisobutylethylenediamine and about 1 parts, by weight of gamma-methacryloxypropyltrimethoxysilane; and about 2 parts, by weight, of n-dimethoxymethylsilylisobutylethylenediamine and about 1 part, by weight, of vinyltriacetoxysilane and mixtures thereof, said interlayer, in turn, being coated with an overlayer comprising selenium.
• an interlayer material selected from the group consisting of n-dimethoxymethylsilylisobutylethylenediamine; ntrimethoxysilylisobutylethylenediamine; about 2 parts
• the plate of claim 1 wherein the thickness of said interlayer ranges from about 0.1 micron to about 5.0 microns 3.
• the plate of claim 1 wherein the thickness of said interlayer ranges from about 0.1 micron to about 2.0 microns.
• said overlayer is selected from the group consisting of selenium, selenium alloys, selenium-containing mixtures, and mixtures thereof.
• said overlayer is selected from the group consisting of selenium, mixtures of arsenic and selenium, mixtures of tellurium and selenium, mixtures of sulfur and selenium, mixtures of cadmium, sulfur, and selenium, mixtures of cadmium and selenium, arsenic selenide, tellurium selenide, sulfur selenide, cadmium selenide, cadmium sulfoselenide, and mixtures thereof.
• An electrophotographic imaging process comprising the steps of a. providing an electrophotographic plate comprising an electrically conductive substrate material, said substrate being overcoated with an interlayer material selected from the group consisting of n-dimethoxymethylsilylisobutylethylenediamine; n-trimethoxysilylisobutylethylenediamine; about 2 parts, by weight, of ndimethoxymethylsilylisobutylethylenediamine and about 1 part, by weight, of gamma-methacryloxypropyltrimethoxysilane; about 2 parts, by weight, of ndimethoxymethylsilylisobutylethylenediamine and about 1 part, by weight, of vinyltn'acetoxysilane and mixtures thereof, said interlayer, in turn, being coated with an overlayer comprising selenium;
• electrophotographic imaging process of claim 9 wherein said electrostatic image is formed by uniformly electrostatically charging the surface of said plate and exposing said plate to an image of activating electromagnetic radiation.
• said overlayer is selected from the group consisting of selenium, mixtures of arsenic and selenium, mixtures of tellurium and selenium, mixtures of sulfur and selenium, mixtures of cadmium, sulfur, and selenium, mixtures of cadmium and selenium, arsenic selenide, tellurium selenide, sulfur selenide, cadmium selenide, cadmium sulfo-selenide, and mixtures thereof.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Photoreceptors In Electrophotography (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Laminated Bodies (AREA)

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Cited By (3)

Citations (4)

• 1968
  • 1968-05-24 US US731743A patent/US3619153A/en not_active Expired - Lifetime
• 1969
  • 1969-04-30 BR BR208479/69A patent/BR6908479D0/pt unknown
  • 1969-05-19 PL PL1969133693A patent/PL80007B1/pl unknown
  • 1969-05-20 AT AT478569A patent/AT305764B/de not_active IP Right Cessation
  • 1969-05-20 SE SE7076/69A patent/SE341926B/xx unknown
  • 1969-05-20 IL IL32250A patent/IL32250A/en unknown
  • 1969-05-20 LU LU58678D patent/LU58678A1/xx unknown
  • 1969-05-21 GB GB1229559D patent/GB1229559A/en not_active Expired
  • 1969-05-21 NO NO2065/69A patent/NO125557B/no unknown
  • 1969-05-21 IE IE698/69A patent/IE33281B1/xx unknown
  • 1969-05-21 BE BE733402D patent/BE733402A/xx unknown
  • 1969-05-22 DE DE19691926056 patent/DE1926056A1/de active Pending
  • 1969-05-22 CS CS3655A patent/CS165333B2/cs unknown
  • 1969-05-22 DK DK279169A patent/DK131833C/da active
  • 1969-05-23 NL NL6907912A patent/NL6907912A/xx unknown
  • 1969-05-23 BG BG012309A patent/BG17353A3/xx unknown
  • 1969-05-23 FR FR6917079A patent/FR2009297A1/fr not_active Withdrawn
  • 1969-05-23 CH CH794369A patent/CH511461A/de not_active IP Right Cessation
  • 1969-05-23 ES ES367618A patent/ES367618A1/es not_active Expired

Patent Citations (4)

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