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 or to electrons; Manufacture thereof; Selection of materials therefor
  • G03G5/14—Inert intermediate or cover layers for charge-receiving layers
  • G03G5/147—Cover layers
  • G03G5/14704—Cover layers comprising inorganic material

Definitions

• An electrophotographic plate and method comprising a photoconductive layer including an inorganic glass material comprising an inorganic glass binder and finely divided inorganic photoconductive particles dispersed therein, said photoconductive layer having an overcoating comprising a composition selected from the group consisting of germanium dioxide, the oxides of vanadium, titanium dioxide, silicon dioxide, zirconium dioxide, aluminum'oxide; and mixtures thereof.
• This invention relates to electrophotography and more particularly to 7 a novel structure for an electrophotographic plate.
• photoconductive insulating coatings comprise anthracene, sulfur or various mixtures of these materials such as sulfur with selenium, etc., to thereby form uniform amorphous coatings on the base material.
• These materials have a sensitivity largely limited to the shorter wave lengths and have a further limitation of being only slightly light-sensitive. Consequently, there has been an urgent need for improved photoconductive insulating materials.
• vitreous selenium suffers from two serious defects: (1) its spectral response is very largely limited to the blue or near ultra-violet; and (2) the preparation of uniform films of vitreous selenium has required highly involved and critical processes, particularly processes involving the preparation of extremely clean and uniform substrates and vacuum evaporation techniques.
• a binder type plate having very desirable reusable properties comprises an inorganic pigment dispersed in a glass binder as disclosed in United States Patent 3,151,- 982.
• the use of a xerographic plate containing a glass binder material of various types of frits is disclosed in detail.
• a large number of suitable inorganic pigments were disclosed as being useful together with the above noted glass binder frits. The use of this xerographic plate (as described in US.
• Patent 3,151,982 has a number of significant advantages over the previously used selenium and other binder type plates. A more desirable spectral response and/ or speed has often been obtained by the use of such glass plates. In addition, a much more convenient commercially adaptable process has been provided than heretofore known in the manufacture of other xerographic plates.
• non-alkali-containing glasses have been shown to be humidity sensitive, particularly if they have been subjected to the action of conventional cascading xerographic developers or the action of a polishing abrasive.
• the Xerographic properties, especially the reusability of these glass binder plates has been seriously hampered by the tendency of these plates to absorb atmospherrc moisture and humidity. Since one of the desirable features of commercial acceptability of glass binder plates resides in their intended reusability, the commercial acceptance of such plates heretofore has been rather limited.
• Another object of this invention is to provide a novel overcoating for a glass binder xerographic plate.
• Another object of this invention is to provide a novel method of making an electrophotographic plate.
• Yet another object of this invention is to provide a xerographic plate having a novel photoconductor-overcoating layer combination.
• Yet still another object of this invention is to provide a method for increasing and improving the humidity limit of an electrophotographic plate.
• Still another object of this invention is to provide a novel method for improving the reusability of the glass binder-inorganic pigment xerographic plate.
• Still another further object of this invention is to provide a novel overcoating layer adapted for use with a xerographic plate having a photoconductive layer comprising an inorganic glass.
• an electrophotographic plate comprising a photoconductive layer including an inorganic glass material, said photoconductive layer having an overcoating comprising at least one composition selected from the group consisting of germanium dioxide, Geo the oxides of vanadium V V 0 V 0 titanium dioxide, TiO silicon dioxide SiO zirconium dioxide ZrO aluminum oxide, Al 'O and mixtures thereof.
• the photoconductive layer upon which the overcoating of this invention is deposited may comprise an inorganic glass material which acts as a binder or as the photoconductive material per se.
• any of the glass-pigment materials defined in US. 3,151,982 may be used as the photoconductive layer in the present invention.
• the humidity limit of glass electrophotographic plates has been increased from about 45% to about 65% for alkali glass containing plates and from about 40% to about 65% for abraded non-alkali glass plates.
• humidity limit is meant, for the purposes of this invention, that amount of humidity that a plate can tolerate and yet be imageable.
• the glass containing photoconductive layers and the corresponding electrophotographic plates can be made less humidity sensitive by treatment with vapors of zirconium tetrachloride, vanadium tetrachloride, aluminum trichloride, silicone tetrachloride, germanium tetrachloride and mixtures thereof. At least one surface of the photoconductive layer of a glass containing xerographic plate is exposed in a heated atmosphere to the vapors of these chlorides until the formation of the desired overcoating is completed. It is believed that the reaction of these materials on the surface of the plate involves hydrolysis of the chlorides with atmospheric water, thereby depositing the corresponding oxides on the plate surface and giving off hydrogen chloride.
• oxides is meant the oxygen containing composition resulting from the vapor treatment of the plate and is intended to include mono, di, tri and tetra oxides formed by whatever method they are deposited.
• the thickness of the resulting oxide overcoating layer may vary but generally satisfactory coatings range from about monomolecular to about 2.5 microns depending on the material. However, it was found that preferred results including good reusability with the retention of high sensitivity of the plates was obtained when an overcoating of from 0.2 to 0.5 micron was used with titanium dioxide.
• any of the listed chlorides function within the present invention, optimum xerographic properties of the plate were obtained when exposing the plate to a composition comprising titanium tetrachloride or aluminum trichloride.
• the preferred embodiments of the present invention therefore, comprise a glass binderinorganic pigment xerographic photoconductive layer having an overcoating comprising titanium dioxide or aluminum oxide.
• the overcoating layers of this invention are applied by merely holding the photoconductive glass layer over a source of the particular chloride vapor in a warm air atmosphere.
• a particularly preferred form of the invention which produces markedly improved results, as illustrated in the following examples, involves applying the chloride vapor in a humidity-free atmosphere such as one which is filled with the chloride vapor. It is believed that this further improvement is achieved because when the chloride vapors are applied in air, they are hydrolyzed to 3,397,982 i g V the corresponding oxide by atmospheric water and de posited on the glass surface whereas when a moisture-free atmosphere is employed, the chlorides are forced to abstract absorbed moisture from the glass surface itself in order to form the oxide.
• the chloride vapors serve the dual function of removing harmful absorbed moisture from the plate and at the same time, sealing and protecting its surface from moisture abrasion, etc. with the oxidewhich forms simultaneously with moisture abstraction.
• TiCl titanium chloride
• CCl CCl
• the tray of TiCl -CCl solution is placed near a hood opening and warmed slightly to produce a turbulent stream of white fumes in which is placed the pre-heated glass plate.
• the plate is kept in motion in the fumes until the first signs of deposition are visible.
• the deposition is continued until the first color fringes due to light interference are visible.
• the plate is then cooled, washed with deionized water to remove any possible residual chlorides and rubbed dry with a clean towel.
• a comparison of the glass plate produced in this example without the overcoating is made to that plate resulting by adding the overcoating of this example.
• the thickness of the layer is measured and found to be about 0.4 micron.
• the plates coated with the oxides of titanium, germanium, silicon, aluminum, vanadium, and zirconium are numbered plate numbers I-VI.
• the plate In testing the various plates for humidity tolerance, the plate is mounted in an apparatus very similar to the xerographic oflice copier described in US. Patent 2,945,434 to Eichler. This apparatus is positioned in a controlled humidity chamber which enables the operator to control the relative humidity therein and a range of from about 25% to about 95% relative humidity is made in the test. Copies aremade using the plate at several intervals over the humidity range. By observing and comparing copies made at the various degrees of humidity, an approximate measure of the humidity limit for a particular sample plate is observed. This type of test may be conducted either before and after the oxide overcoating is applied or with only one-half of the plate bearing an oxide overcoating to attain a valid comparison of the results of the overcoating.
• the plate is print tested in controlled humidity with the same type of apparatus used for general humidity limit determination before and after an accelerated abrasion test in which the plate is subjected to the abrasive action of xerographic developer cascading over its surface.
• this test is carried out by masking a portion of the plate with tape to expose only part of its surface to the abrasion test and then the abraded and unabraded portions of the same plate are tested for print quality, with the abrasion time necessary to cause unacceptable copy properties in the plate being a measure of the resistance of the plate to the abrasion which it would be expected to undergo in an ordinary oflice copier.
• Example I An unovercoated glass plate made according to the formula above for alkali containing glass plates is print tested and found to operate satisfactorily up to about 40% relative humidity. As the relative humidity is increased above this point, print resolution begins to decrease markedly apparently because of lateral conductivity and unsatisfactory prints are produced.
• Example II An unovercoated glass plate containing the non-alkali glass formula described above is print tested at various humidities and found to make acceptable copy up to about 73% relative humidity after which print quality decreases rapidly.
• Example III The glass plate of Example II is exposed to the accelerated abrasion test described above, and after three minutes of accelerated abrasion the humidity limit at which the plate will produce acceptable print copy is found to be reduced down to about 55% RH. and after five minutes of abrasion it is found that the plate will not even operate satisfactorily at 40% relative humidity.
• Example IV The alkali containing plate of Example I is subjected to the accelerated abrasion testing procedure of Example III and it is found that after five minutes of abrasion, the plate will not even produce satisfactory prints above 30% relative humidity.
• Example V A non-alkali glass plate made according to the same formulation as the Example III plate is coated with titanium dioxide by subjecting it to the chloride vapors according to the procedure described above on half of its surface.
• the humidity limit in coated areas is about 75% relative humidity versus about 73% relative humidity in uncoated areas for the production of acceptable prints.
• Abrasion of the whole plate in the accelerated abrasion test for three minutes is found to cause a decrease in the humidity limit to about 50% relative humidity in the uncoated areas while the coated areas can still produce high quality prints up to about 65% relative humidity.
• Example VI An alkali containing glass plate made according to the formulation used to prepare the plate of Example I is overcoated with titanium dioxide-according to the procedure described above and found to raise the humidity limit from about 40% relative humidity to about 75 relative humidity. This higher humidity limit of the coated plate is found to remain essentially unchanged by two minutes in the accelerated abrasion test.
• Example VII A non-alkali glass plate made according to the same formulation used for the Example II plate is treated with aluminum trichloride vapors according to the procedure described above to produce an aluminum oxide coating on one-half of the area of this plate with the other half being masked to prevent coating thereon.
• the humidity limit to produce acceptable print quality is about 82% relative humidity for both the coated and uncoated portions of the plate.
• the uncoated portion of the plate After one minute of abrasion, the uncoated portion of the plate has a humidity limit of about 60% RH. whereas the coated portion is essentially unchanged. Two minutes of abrasion reduces the humidity limit of the coated and uncoated portions to about and 60% relative humidity, respectively.
• Example VIH An alkali containing plate made according to the glass plate formula used for Example I is treated with aluminum chloride vapors to produce an aluminum oxide coating thereon. When print tested, it is found to produce good quality prints up to about 85% relative humidity.
• Example IX an alkali containing plate made according to the glass formulation used in the Example I plate is also coated with aluminum trichloride to produce an aluminum oxide coating thereon except that instead of using the procedure described above, the glass plate is placed on an alumina, heat resistant thimble containing the aluminum trichloride.
• This assembly is placed inside a pair of closed silica trays with only a few small openings to allow for the escape of vapor. Heat is then applied with a hot plate from below the trays under an exhaust hood causing the aluminum chloride to sublime and essentially filling the whole closed tray assembly with aluminum trichloride vapors to the exclusion of air.
• This plate is print tested and found to produce good quality prints up to relative humidity. After 12 minutes of abrasion in the accelerated abrasion test, the humidity limit at which the plates would still produce acceptable quality prints is only reduced to about 80% relative humidity.
• Example X Another plate is made exactly according to the technique of the coated plate of Example IX and found to have produced acceptable quality prints up to a relative humidity in excess of 85% and after 60 minutes of abrasion in the accelerated abrasion testing it is still capable of producing acceptable quality prints at relative humidities in excess of 80%.
• any of the above oxide overcoatings may be prepared via materials other than the disclosed chlorides. Also, if suitable, other materials may be used with the disclosed chlorides to form the overcoatings used in the present invention. Other materials and conditions can be substituted in the foregoing examples for the specific materials and conditions set forth therein with similar results.
• An electrophotographic plate having a humidity limit of at least about 65%, said plate consisting essentially of a photoconductive layer including an inoragnic glass binder and finely divided inorganic photoconductive particles dispersed throughout said binder, and an overcoating consisting essentially of aluminum oxide contained on said photoconductive layer,
• a method of imaging an electrophotographic plate having a humidity limit of at least about 65 which comprises providing a plate having a photoconductive layer including an inorganic glass binder having finely divided inorganic photoconductive particles dispersed throughout said binder, said photoconductive layer having an overcoating consisting essentially of aluminum oxide, imaging said plate by forming a latent electrostatic image on the surface of said plate, and developing said electrostatic image whereby a visible image is formed on the surface of said plate.

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• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Photoreceptors In Electrophotography (AREA)
• Glass Compositions (AREA)

Priority Applications (7)

Applications Claiming Priority (1)

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Cited By (7)

Citations (4)

• 1964
  • 1964-12-21 US US420170A patent/US3397982A/en not_active Expired - Lifetime
• 1965
  • 1965-12-02 GB GB51207/65A patent/GB1129674A/en not_active Expired
  • 1965-12-14 FR FR42199A patent/FR1460232A/fr not_active Expired
  • 1965-12-15 SE SE16232/65A patent/SE319976B/xx unknown
  • 1965-12-21 BE BE674140A patent/BE674140A/xx unknown
  • 1965-12-21 DE DE1497230A patent/DE1497230C3/de not_active Expired
  • 1965-12-21 NL NL6516672A patent/NL6516672A/xx unknown

Patent Citations (4)

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