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
  • G03G5/02—Charge-receiving layers
  • G03G5/04—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
  • G03G5/06—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being organic
  • G03G5/0601—Acyclic or carbocyclic compounds
  • G03G5/0609—Acyclic or carbocyclic compounds containing oxygen
  • G03G5/0611—Squaric acid
• • 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
  • G03G5/02—Charge-receiving layers
  • G03G5/04—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
  • G03G5/06—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being organic
  • G03G5/0664—Dyes
  • G03G5/0666—Dyes containing a methine or polymethine group

Definitions

• the present invention relates to electrophotographic photoconductors as claimed in Claim 1, and is based on the finding that there is a synergistic relationship which exists between only certain specific barrier layer ground plane members and a charge generation layer (CGL) which contains a squarylium compound.
• CGL charge generation layer
• ground planes which exhibit barrier layer characteristics and the use of a CGL which is based upon a squarylium molecule are individually known in the prior art.
• the use of the specific CGL and ground plane members defined herein, to form a xerographic photoconductor was not know.
• Such a combination would solve problems such as dark decay and dark fatigue associated with a CGL which is based upon a squarylium molecule.
• the prior art recognizes the advantages of using a barrier layer, i.e., an electrically insulating-like layer between the photoconductor's conductive metal ground plane and the CGL.
• U.S. Patent 4,485,161 is exemplary.
• the barrier layer serves to reduce dark decay, i.e., charge leakage to the ground plane which occurs in the absence of light.
• This patent also recognizes the need for a barrier layer material which is not soluble in the solvents which are used to coat the CGL onto the barrier layer.
• barrier layers of the present invention is a polyamide barrier layer. Use of such a layer under the photoconductor's ground plane is taught by U.S. Patent 4,307,166.
• U.S. Patent 4,495,263 is similar to the above- mentioned patent.
• this patent states that placing the polyamide barrier layer between the ground plane and the CGL is desirable since problems of haze, unstable sensitometry or unstable coatability result.
• the present invention also teaches the use of specific aluminum alloys as the barrier layer type ground plane onto which the squarylium-based CGL is coated.
• U.S. Patent 4,461,820 is related in that it describes a photoconductor in which amorphous silicon is placed onto an aluminum oxide substrate. The use of aluminum alloys as a substrate is also suggested.
• the present invention is useful in making eletro- photographic plates which have improved electrical response and improved useful electrical life.
• Electrophotographic photoconductors of the present invention comprise, in addition to an inert substrate, an electrically conductive ground plane of a critical construction and arrangement, and a CGL of a critical squarylium charge generating specie.
• a transport molecule may be used in a separate charge transport layer (CTL), or in conjunction with the CGL itself, to facilitate hole or electron mobility.
• CTL charge transport layer
• a particularly suitable field for their use is with solid state lasers emitting in the 7500 to 8500 A range.
• electrophotographic reproduction processes differ in the particular way in which they are carried out, particularly in the sequence in which electric charging (usually with a corona) and illumination are carried out. All electrophotographic reproduction processes, however, involve the process step of selectively rendering portions of a photoconductor electrically conductive by selective exposure to light.
• Photoconductivity involves at least two steps: 1) generation of charge; and 2) transportation of the charge.
• the present invention utilizes the ability of squarylium dye species to efficiently generate electron-hole pairs upon absorption of light, giving rise to a latent electrostatic image, after the appropriate carriers are injected into the conductive ground plane and the transport molecule.
• sensitometric responses that change as a result of cycling use are dark charge, residual potential, sensitivity and dark decay.
• a particular problem with prior art squarylium-based photoconductors is that an increase in dark decay occurs at relative humidities of 15 % or less. This condition occurs after cycling the photoconductor, with exposure to light, in this environmental condition. This increase in dark decay varies as a function of the properties of the conductive ground plane, and this dark decay property can be very inconsistent, and can ultimately give poor print quality from machines which must perform in this environmental condition.
• the coating must be insoluble in subsequent coating solvents which are used in fabricating the photoreceptor, particularly those which are used in coating the CGL onto the ground plane's coating. Since organic chemicals are usually used to fabricate photoconductors, it is very difficult to find barrier-like coating materials which are not affected to a great degree by these solvents. We have found that alcohol soluble polyamides, cross-linked epoxies and water-soluble polyvinyl alcohols (PVA) exhibit this impervious trait.
• PVA water-soluble polyvinyl alcohols
• silicon dioxide fabricated as an integral layer intermediate the CGL and aluminum ground plane, functions in a similar manner.
• Ground planes in accordance with our invention provide a relatively inexpensive and easy way to provide superior electrical properties to squarylium based photoconductors.
• a further advantage of the present invention is that electrical defects caused by electron injection into the conductive ground plane are significantly reduced. Such defects can be caused by high work function contaminants which are present in or on the conductive substrate prior to the coating step. Injection from the CGL's generating specie, or from the CTL's transporting specie, is then very facile under applied field, and a dark decay defect will be present in the subsequent copy or print. Such contamination can be present as common dust which contains iron, a high function metal.
• DuPont Poylester Type A, 300 gauge film was aluminized to an optical density of 1.7. This substrate was split into two sections, one for treatment in accordance with the present invention and the other to be processed as is.
• the substrate to be treated was coated with a 0.1 pm (micron) layer of Elvamide 8061 (DuPOnt), a lower alcohol soluble co-polyamide of caprolactam hexamethyl adipamide and hexamethylene sebacamide. Methanol solvent was used. Both substrates were then coated with the following layers to fabricate a photoconductor:
• the treated and untreated photoconductors were then tested in a sensitometer at less than 5% relative humidity.
• a charge corona was set to give an initial charge of negative 675 volts on the photoconductor. After 2000 cycles the dark voltage was measured, as was the dark decay rate. Dark fatigue is determined by subtracting the voltage on the photoconductor after 2000 cycles from the initial dark voltage as a function of time, and its units are volts per second.
• a quantity la- beled as the total dark excursion (TDx) is the sum of the dark fatigue plus the dark decay rate. Low values of this sum are a measure of goodness.
• the TDx for the two films referenced are listed below:
• a photoconductor was then prepared as in this Example, except that the Elvamide layer was 0.05 microns thick and contained 35% by weight Santolite MHP in order to provide an improvement in adhesion to the aluminized substrate.
• the TDx was then monitored as a function of relative humidity. Each reading was calculated as described after 2000 cycles.
• Aluminized Mylar (trademark) Type A was also used in these examples. Again one photoconductor was prepared from an untreated aluminized substrate and the aluminum surface of the other was treated in the following manner in accordance with the present invention: 0.5 grams of Epon 1001 (Shell) was dissolved in 25 Milliliters of tetrahydrofuran. To this was added 1.5 milliliters of Versamid V-150 polyamide resin (General Mills) at a 10% by weight loading in tetrahydrofuran. The resultant solution was coated onto the aluminum surface to a thickness of about 0.25 microns, and cured for two hours at 100°C. Epon is a brand name for a series of condensation products of epichlorohydrin and bisphenol A.
• the two substrates were then coated with the following generating and transport layers to fabricate the photoreceptor.
• the generating layer consisted of 1.5 grams of Epon 1009 (Shell) dissolved in 25 milliliters of tetrahydrofuran. To this solution was added a solution of 0.3 grams of hydroxy squarylium in 1 milliliter of ethylenediamine. This was then coated to a thickness of about one micron after the coating had cured for two hours at 100 ° C.
• the TDx of the untreated film was 339 while that of the treated film was 71 when tested on a sensitometer which simulates the IBM 3800 laser printer. Both photoconductors were tested at a relative humidity of less than 10% and were cycled for four hours in order to identify these sensitometric differences.
• a photoconductor was prepared as in Invention Example 1, except that the coating used to treat the aluminized substrate was a polyvinyl alcohol (PVA) solution in water (Aldrich Chemical Co.). When tested in the sensitometer as described in Example 1, the total dark excursion of this sample was 147. This represents an improvement of 33 over the control photoconductor whose aluminum substrate was untreated, and gave a TDx of 180.
• PVA polyvinyl alcohol
• Type A Mylar film was aluminized with pure aluminum, to form a comparative example, and then films were metallized with the following alloys to form three examples of the present invention (I, II, and 111), and a comparative example (IV): I-AICa (95:5); II-AISi (95:5); III-AIGa (95:5); IV-AISn (95:5).
• Photoconductors were prepared as in Example I, and the TDx was determined as in Example 2.
• Example 2 Aluminized Mylar Type A film was used as described in Example 1. Half of this substrate was treated by e-beam evaporating a 30 A thick layer of silicon dioxide on top of the aluminum. The photoconductor fabricated in Example 1 was then coated on the untreated and treated aluminized Mylar. When tested as described in Example 1, the TDx values were as follows:

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Health & Medical Sciences (AREA)
• Emergency Medicine (AREA)
• Photoreceptors In Electrophotography (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=25154981

Family Applications (1)

Country Status (3)

Families Citing this family (2)

Family Cites Families (9)

• 1986
  • 1986-09-08 JP JP20979686A patent/JPS62102250A/ja active Pending
  • 1986-09-23 EP EP19860113052 patent/EP0220489B1/en not_active Expired
  • 1986-09-23 DE DE8686113052T patent/DE3670383D1/de not_active Expired - Fee Related

Also Published As

Similar Documents

Legal Events