Electrophotographic Properties Research Articles

Xerographic properties of metal/metal-free phthalocyanine composites in a double-layered photoconductor

The electrophotographic properties of a negatively charged double-layered photoconductor that con- sisted of y-type metal phthalocyanine (TiOPc) and x-type metal-free phthalocyanine (H2Pc) composites were studied. The undercoating layer (UCL) was fabricated by a dip-coating method with Al2O3 and polyamide, and the charge trans- port layer (CTL) was prepared from N,N'-Bis-(3-methylpenyl)-N,N''-bis-(phenyl)-benzidine (TPD), polycarbonate (PC), and polyester (PE). In the charge generation layer (CGL), the dispersion state becomes more homogeneous with in- creasing amounts of non-metal phthalocyanine (H2Pc). The electrophotographic properties of the photoconductor were obtained by using photo-induced discharge curves (PIDC) of charge acceptance, dark decay, photosensitivity, and pho- tofatigue. It was found that the initial charge potential was not dependent on the compositional ratio of the charge gener- ating material. However, the dark decaying rates and the photosensitivity were proportional to the content of TiOPc in the organic photoconductors.

Silica Sol/Gel Based Nano Structured Hard Coats for Organic Photoconductors

Objective of the present investigation was the development of a scratch resistant and anti-abrasion layer for organic photo-conductors which does not influence the electrophotographic properties like charge transporting properties and print quality A new class of hybrid polymers based on classical sol/gel materials has been developed. This two component material with covalently bonded functionalized silica nano particles in an epoxy matrix made of poly-functional epoxy components produces closed networks and exhibits excellent durability against liquid toner materials. By employing this material as a top coat on OPC drums, hardness and scratch resistance can be improved without having significant impact on printing properties such as the replication of single dots in high resolution digital printing.

Novel Sol-gel Materials with Charge Transporting Properties

A series of novel copolymers having components with hole transport and silane functionality have been synthesized. These copolymers were prepared by radical polymerization. Through a sol-gel process with methyltrimethoxysilane, solutions of the copolymers with were coated to form the hole transport layer of an organic photoreceptor. These hole transport active silsesquioxane layers were coated as either a charge transport layer (CTL) on a charge generation layer (CGL) or a protective overcoat on a CTL. The electrophotographic properties of photoreceptors prepared with these sol-gel layers were described.

Enhancement of the electrophotographic properties of DLC coated OPC drums by oxygen addition

Diamond-like carbon films with high transmittance over 90% and hardness substantially higher than that of a organic photoconductor (OPC) were deposited on OPC layers using a d.c.-remote plasma enhancement chemical vapor deposition (RPECVD) system with a magnetic field imposed around the cathode. All the electrophotographic properties except residual potential were enhanced by DLC coating. The hardness and resistivity of the DLC film were also improved by adding oxygen to CH 4 gas. However, the residual potential value can be reduced to 11.0 V which is acceptable even for high sensitivity laser printing, by using a CH 4–20at.% O 2 gas mixture in the RPECVD for DLC coating.

Electrophotographic properties of copolyimide Langmuir–Blodgett films having different chemical structures

A series of copolyimide Langmuir–Blodgett (LB) films with different chemical structure was fabricated into xerographic photoreceptors and its electrophotographic properties were measured by photoinduced discharge method. Comparison was made between the LB films and the corresponding 1 μm solvent-cast films. It was found that the copolyimide LB films have the advantage of high electrophotographic performance. The results could be ascribed to charge-transfer complexes formation, nanometer film thickness, compact molecular packing and chain alignment in the copolyimide LB films.

Effects of DC power on the properties of DLC coatings on the OPC drum

Diamond-like carbon (DLC) films were deposited on the organic photoconductor (OPC) drum of the laser printer using the dc-remote plasma enhancement chemical vapor deposition (RPECVD) method. Only methane (CH4) was used as a source gas for DLC coating. The transmittance of the DLC coatings is over 90% and the hardness of the DLC film (130 nm thick) coated OPC drum is higher than 1,000 Hv. Effects of dc-power on the physical properties of the DLC film and the electrophotographic properties of the DLC coated OPC drum were investigated. The hardness and the deposition rate of the DLC film deposited on the OPC drum increased but the transmittance and the surface roughness nearly did not change with increasing the dc power of the dc-RPECVD. The residual potential, the acceptance voltage, and the dark decay rate significantly increase but the photodischarge rate decreases with increasing the dc power of the RPECVD. The optimum dc power is 8.6 kW (950 V, 6A). The friction coefficient of the OPC drum is also lowered by DLC coating. In addition, it was found that the DLC deposition rate could be doubled by imposing magnetic fields around the cathode.

Influence of Methyl Substituents in Phenylenediamine Derivatives on the Properties of Electrophotographic Layers

Substituent effects on the electrophotographic properties of N,N,N′,N′-tetraarylphenylenediamines 1a—i derivatives have been investigated to obtain a molecular design guide to enhance photosensitivity of hole transporting materials for organic photoreceptors. The introduction of methyl groups into N-substituted phenyl moiety in all the cases increases considerably the photosensitivity and reduc—es the residual potential, moreover, the m- and p-substitution was found to be the most promising. On the other hand, the presence of alkyl substituents enhances the stability of glassy state of such low molecular weight organic compounds.

Cyclic Stability and Electrophotographic Properties of OPC doped Polycarbonate

Cyclic stability (to corona charging, to light or to the both of these factors), electrophotographic and spectral properties of charge transport layers (CTL) have been measured. The CTL used were the various OPC (triarylamines, hydrazones) doped polycarbonates of different types with and without cyclic stabilizers. The influence of OPC and stabilizer structures and possible mechanisms of cyclic durability of CTL have been investigated and discussed. It has been found that cyclic stability of the CTL can be essentially increased by addition of some stabilizers to the CTL.

Novel Crystals of Titanium Oxide Phthalocyanine with Submicron Diameter

Reported here are novel submicron diameter crystals of titanium oxide phthalocyanine (TiOPc) and the electrophotographic properties of photoreceptors that employ them. The use of triether solvents such as diethylene glycol dimethylether and dimethoxy tetrahydrofuran produces five times smaller TiOPc crystals than the phase 3 TiOPc crystals produced in tetrahydrofuran. The photosensitivity of these smaller TiOPcs is as high as that of the tetrahydrofuran produced phase 3 TiOPc crystals, which have been a source for one of the most photosensitive charge generation materials used in electrophotographic photoreceptors.

The effect of Sb alloying on the electrophotographic properties of amorphous selenium

The effect on the electronic density of gap states in amorphous selenium (a-Se) produced by the branching additive Sb has been studied by xerographic measurements. Xerographic experiments probe deep gap states which control injected carrier range. These measurements show that progressive addition of Sb to a-Se increases the integrated number of deep traps.

An Influence of Polycarbonate Molecular Weight and Structure on Hole Drift Mobility and Electrophotographic Properties of Photoconductors

Hole transport and electrophotographic properties of organic photoconductors (OPC) on the base of 4-(diethylamino) benzaldehyde-N,N′-diphenylhydrazone (DEH) and phenyl-4-tolyl-2-naphtylamine (PTNA) doped polymer binders such, as bisphenol-A-polycarbonates (PC-A), bisphenol-Z-polycarbonates (PC-Z) with different molecular weights, polymethyl methacrylate (PMMA) and others was investigated. Hole drift mobility was measured by the conventional time-of-flight (TOF) techniques and discussed in terms of Gill approach, disordered model and correlated dipole model. Influence of structure and molecular weight of polymer binder and concentration of OPC on the hole mobility and electrophotographic properties have been investigated.

Amorphous chalcogenide Se1−x−y TexPy semiconducting alloys: thermal and mechanical properties

Thermal and mechanical properties of ternary Se rich Se1−x−yTexPy semiconducting glasses (Te < 20 at % and P < 10 at %) in vitreous bulk and film form have been studied by differential scanning calorimetry (DSC) and microhardness measurements. Bulk vitreous samples were prepared by conventional melt quenching techniques and the amorphous photoreceptor films were prepared by vacuum deposition onto oxidized aluminum substrates whose electrophotographic properties were reported previously. We measured the glass transition temperature Tg starting from a well defined thermal history and using both heating and cooling scans as a function of composition. Tg increases monotonically with both Te and P content. Both bulk and film samples evince similar compositional Tg dependence. The increase in Tg with the P content in the glasses follows the Tanaka rule, that is, P addition has a networking effect due to the trivalent nature of the P atom and increases the mean coordination number. Both Te and P additions initially inhibit crystallization but at high Te contents (∼20 at %) the crystallization behavior is comparable to the pure a-Se case. Glasses with ∼10 at % Te seem to have the greatest resistance to crystallization. The crystallization behavior does not correlate with the Tg behavior over the whole composition range. The Vickers microhardness HV increases with both Te and P content. HV vs. Te and P behavior is similar to that of Tg vs. Te and P content . The compositional dependence of both HV and Tg can be explained by the same factors that reduce Se chain mobility.

Amorphous Silicon Photoreceptors: Homogeneity of Electrophotographic Properties

Small pixel size or high resolution necessary for gray scale and color reproduction requires a high uniformity of the electrophotographic properties of the photoreceptor. The uniformity of the properties depends mainly on the thickness of thin layers and interfaces in the multilayer photoreceptor structure and doping uniformity. Structure and properties of a-Si:H photoreceptors meet these essential requirements. We investigated the preparation of a-Si:H photoreceptors and the electrophotographic properties: charge acceptance, dark decay, exposure-voltage-(E-V-) characteristic, residual potential and sensitivity. We have shown that an non-uniformity below &#xB1; 3 % in respect of the full photoreceptor surface can be achieved.

Light Stability and Electrophotographic Properties of Polycarbonate Layers Doped by Organic Photoconductors

Possible reasons of a fatigue of organic photoreceptors such, as the photochemical processes in charge transfer layers (CTL) are investigated and discussed. The results concern a study of influence of corona discharge, exposure and joint action of both the factors on cyclic stability of organic photoreceptors. The charge generation layers (CGL) use titanyl phthalocyanine (TiOPc), bisazo dye and effective stabilizers. The organic photoconductor (OPC) in CTL are p-diethylaminobenzaldehyde diphenylhydrazone (DEH), N-phenyl-4-tolyl-&#x3B2;-naphtylamine (PTNA) or N,N&#x2032;-diphenyl-N,N&#x2032;-bis(3-methylphenyl)-(1,1&#x2032;-biphenyl)-4,4&#x2032;-diamine (TPD) without stabilizers. It was established, that the values of a residual potential and dark decay of potential greatly depend on the exposure conditions such as light wavelength in cycle &#x201C;charging-exposition&#x201D;. It can be conditioned by reactions of bication radicals or photoexited monocation radicals of OPC molecules, for example with impurities involved in CTL.

Synthesis and electrophotographic properties of copolyimides containing tetraphenylporphyrin

A series of polyimide copolymers based on pyromellitic dianhydride, oxydianiline (ODA) and terta(4-aminophenyl)porphyrin were synthesized. The ‘precursors’, copolyamic acids and the copolyimides, were characterised by UV–visible spectra, IR spectra and thermogravimetry. The mole ratios of tetraphenylporphyrin (TPP) to diphenylether in the polymers calculated from the UV–visible spectra indicate that TPP and ODA were incorporated into the polymer backbones as expected. To investigate the photoconductivity of the copolyimides (CPIs), three and four-layered photoreceptors containing the CPI films as charge-generating layers were fabricated. It was found that the photosensitivity of the CPIs increased with the incorporation of TPP into the polymer chains. These results were compared with those of tetraphenyl-porphyrin doped pyromellitic/oxydianiline (PMDA/ODA) polyimide and explained on the basis of the formation of charge-transfer complexes.

Absorption Spectra and Electrophotographic Properties of Squarylium Dyes Containing a Nitro group

Squarylium dye containing a nitro group, absorbs at 676 nm in chloroform and showed a bathochromic shift of 22 nm in comparision to the unsubstituted analogue. The reaction between squaric acid and 2,3,3-trimethyl-5-nitroindolenine proceeded readily giving a product in 97% yield. Electrophotographic characteristic of negatively charged dual-layered photoreceptors with squarylium dyes for charge generation materials and five charge transport materials have been investigated. Photoreceptors that used squarylium dyes containing a nitro group, exhibited high sensitivity under light exposure.

Effect of negative rf bias on electrophotographic properties of hard diamond-like carbon films deposited on organic photoconductors

Hard diamond-like carbon (DLC) films were prepared on organic photoconductor (OPC) and PMMA (polymethyl methacrylate) samples by electron cyclotron resonance (ECR) plasma deposition with low substrate bias. The films exhibited a specific electrical resistivity above and very high transmittance for the visible spectrum of 370-800 nm. The hardness of the OPC samples was increased at least fourfold after deposition of DLC films. The acceptance voltage, photodischarge rate and dark decay rate of the DLC-coated OPC samples were all improved, and reached optimal values for rf biases around . The results indicated that the deposition of hard DLC films on OPC is a very promising technique to lengthen the working lifetimes of the OPC materials.

Syntheses, characteristics and electrophotographic properties of new dithiosquarylium dyes

A new class of dithiosquarylium dyes (DTSQ) has been synthesized by the reaction of squarylium dye (SQ) with Lawesson's reagent or P 4S 10. The λ max , of DTSQ dyes undergoes a bathochromic shift of about 25 nm compared with corresponding SQ dyes. The visible absorption spectra of DTSQ dyes are well accounted for by Pariser-Parr-Pople Molecular Orbital (PPP-MO) calculations. Electrophotographic characteristics of negatively charged dual layered photoreceptors with DTSQ for charge generation materials (CGM) and 1-phenyl-1,2,3,4-tetrahydroquinoline-6-carboxyaldehyde-1′,1′-diphenylhydrazone as a charge transport material (CTM) have been investigated. The photoreceptor that used DTSQs exhibited high photosensitivity at white light.

Protective AlZrN film for organic photoconductors

AlZrN protective film with high transmissivity was deposited onto the organic photoconductor (OPC) surface, and the surface hardness was greatly increased by a factor of 1.5–3. The OPC surface protected by (Al100−xZrx)N (x ≤ 58.5%) film was significantly harder than that protected by AlN film. The electrophotographic properties of the OPC coated with (Al100−xZrx)N (x ≤ 37.7%) film were also better than those without coating or protected with AlN film, thus demonstrating the suitability of AlZrN film as a protective coating for enhancing the operating life of OPC.

Protective AlCrN film for organic photoconductors

(Al 100− x Cr x )N ( x≤36%) protective film with high transmissivity was deposited onto organic photoconductor (OPC) surface by RF reactive magnetron sputtering. The surface hardness was increased by a factor of 1.5–3.2. The OPC surface protected by (Al 100− x Cr x )N ( x≤71%) film was harder than that by AlN film, and the maximum surface hardness was achieved using ∼47% Cr content. The electrophotographic properties of (Al 100− x Cr x )N ( x≤36%) coated OPC are better than those of either uncoated or AlN-coated OPC. These results confirm the suitability of (Al 100− x Cr x )N ( x≤36%) film to prolong the operating life of OPC.