Photoreceptors substrates

Fig. 2. Schematics of (a) single-layer photoreceptor, where the + signs represent the corona-deposited charge, D the photoconductor, and 1 the conductive substrate and (b), the CdS Sej (Katsuragawa) photoreceptor, where D represents the insulating layer, the CdS Sej, and I the...

Amorphous (vitreous) selenium, vacuum-deposited on an aluminum substrate such as a dmm or a plate, was the first photoconductor commercially used in xerography (6). It is highly photosensitive, but only to blue light (2). Its light absorption falls off rather rapidly above 550 nm. Because of the lack of photoresponse in the red or near infrared regions, selenium photoreceptors caimot be used in laser printers having He—Ne lasers (632.8 nm), or soHd-state lasers (680—830 nm). 

Sensilizdiioii of the phomrcceptor. The photoreceptor consists of a vacuum-deposited film of amorphous Se, 50 pm thick, on an Al substrate this is sensitized by electrostatic charging from a corona discharge using a field of lO Vcm . ... 

Beharry, S, Zhong, M, and Molday, RS, 2004. N-retinylidene-phosphatidylethanolamine is the preferred retinoid substrate for the photoreceptor-specific ABC transporter ABCA4 (ABCR). J Biol Chem 279, 53972-53979. 

The electrophotographic process involves the production of an electrostatic latent image on a photocondnctor (also called a photoreceptor) and the conversion of this into a visible image with a charged toner, which is then transferred to the substrate, (usually paper) where it is fixed. The six individual steps in the process are ... 

There are a large number of reasons to revert to an alternate baseline. The most important is the fact that the chromophores of vision are not formed within the photoreceptor cell. There is an extensive database on how they are formed and stored within the RPE cells and subsequently transported to the Outer Segments for coating of the protein substrate known as opsin. 

Figure 5.1.1-1 Predicted secondaiy structure of salamander red rod rhodopsin as reported by Crouch Ma. Based on their identification of the source of this material as a red rod, it is likely that this material forms the substrate of the disks of a M-channel photoreceptor. See Crouch Ma, 2000 for details.

Typical The coating of the protein substrate, Opsin, by the chromophore Rhodonine as it is released from the fluid filling the cavity between the RPE and the layer of photoreceptor Inner Segments. 

Where visible absorption peaks have been found in natural photoreceptor material, no NMR or X-ray crystallographic data has been put forward to demonstrate the presence of a retinene in the material (See Chapter 7). It is proposed here that any such tests will demonstrate the presence of a Rhodonine instead. Rhodonine contains two polar groups separated by a conjugated carbon chain. It is further proposed that opsin is only present as a completely passive substrate. Its association with the liquid crystalline Rhodonine is via a weak hydrogen bond that does not change the electronic configuration of the Rhodonines. 

The work of Papermaster and others have clearly shown that the protein used in the substrates (disks) of the outer segment of photoreceptor cells is formed within those cells. The material (opsin + retinal) is secreted by those cells and formed into disks within a cavity associated with the inner segment of the photoreceptor cells. The work of Bridges, et. al. shows clearly that the retinoids used in the functional part of the visual process, the Rhodonines, do not pass through the photoreceptor cells. They are delivered to the outer segments via the RPE. 

Fig. 2. Structure of a-Si H photoreceptor and its energy diagram indicating the blocking behaviors. (1) Photoconductive layer, (2) blocking layer, (3) conducting substrate.

Now we discuss the PID performances of photoreceptors made of high-resistivity films. In Fig. 6, typical PID curves are illustrated for the a-Si H drum made of a film 44 fim thick containing oxygen. A sufficient amount of chaige with either polarity can be maintained on the surface of the film freshly deposited onto an A1 substrate. Nakayama et al. (1982) had put their a-Si H drum to a practical test inside a copying machine and presented their conclusions from laboratory-level measurements of copying life and image quality. Further critical evaluation should be undertaken for the a-Si H photoreceptor from an industrial viewpoint. The performances are summed up in Table II for the two types of photoreceptor. 

Jubran [2] and Tokarski [3] prepared photoreceptors comprising an electrically conductive substrate and a photoconductive element consisting of phenothia-zines, (III) and (IV), and carbazole, (V), derivatives, respectively. 

Fig. 10.26. Typical structure of a xerographic photoreceptor showing the blocking layer at the substrate, the surface layer and the photoconductor (Pai 1988).

The absorption of an image exposure by the photoreceptor creates electron-hole pairs. Under the influence of a field, a fraction of the pairs separate and are displaced to the free surface and the substrate electrode. The surface charge is thus dissipated in the exposed regions and an electrostatic charge pattern is created. 

When ions produced by a corona discharge are deposited on a photoreceptor surface, charges of the opposite polarity are created in the substrate electrode. When equal charge distributions reside at the surfaces, the potential V is related to the surface charge density Os as... 

---