A coating material for eliminating ozone and an image processing apparatus incorporating same

Abstract: An apparatus for forming an image by electrostatic charge comprises an image forming section (10) including a photoconductive drum (20) and an electrostatic charger (21) for forming an image by electrostatic charge. An ozone eliminating filter (34,40) is located in the air flow generated by the rotation of the photoconductive drum (20) and comprises a coating layer made of a coating material to eliminate ozone in the ambient air. The coating material includes an ozone eliminating substance, an organic binder and a foaming agent. The ozone eliminating filter (34,40) may be made of adhesive double-coated tape (41) which includes an ozone eliminating substance (42) on one side (41a) thereof.

Description: The present invention relates to a coating material and an electronic image processing apparatus incorporating the coating material. More specifically, it relates to a coating material for eliminating ozone and an electronic image processing apparatus which forms an image by means of electrostatic charge. By way of clarity, in the specification and claims the word "eliminating" should be understood as encompassing both decomposing and absorbing. Electronic image processing apparatuses containing an electrostatically-charging image forming part generate ozone during the steps of charging a photoconductive member to a predetermined level of electric charge, transforming a toner image from the photoconductive member to a sheet of material paper, and removing the sheet having the received toner image from the photoconductive member. In these steps, activated particles of oxygen are. generated by the inelastic collision of oxygen molecules and charged particles generated by ionization of the air due to corona discharge. The activated particles and oxygen molecules react to generate ozone. The ozone can be absorbed by the surface of the photoconductive member to form an oxidized layer which lowers the resistance of the surface of the photoconductive member. If the photoconductive member is made of an organic photoconductive material, the photoconductive member can react with the ozone, lowering the sensitivity of the photoconductive member. These effects may cause improper developing by, for example, fading and spreading the image on the photoconductive member. Furthermore, the ozone generated in the electronic image processing apparatus is discharged to the outside of the apparatus by a fan or the like, increasing the ozone concentration in the ambient air. A high concentration of ozone in the ambient air can have an adverse affect on the human body. The publication Patent Abstracts of Japan, Vol. 9, No. 137 (P-363) [1860], June 12, 1985 discloses an image-forming device by which an ozone decomposing or an ozone absorbing agent is applied to a part in the device, so that discharge gas containing ozone generated in the device passes the applied part. The decomposing agent in the form of a paint is applied to the inside wall of the developing device and to the casing of the cleaning device. The publication Patent Abstracts of Japan, vol. 10, no. 185 (C-357) [2241], June 27, 1986 forms the basis for the first part of claim 1. It describes a paint for eliminating ozone in an electrophotographic device, said paint comprising an ozone decomposing substance dispersed in a binder resin. It is an object of the present invention to provide a coating material for eliminating ozone which can form an ozone eliminating filter to eliminate ozone efficiently. It is another object of the present invention to provide an electronic image processing apparatus wherein ozone is efficiently eliminated. It is yet another object of the present invention to provide an electronic image processing apparatus which decreases the ozone concentration in the exhaust air of the apparatus. According to the present invention there is provided a coating material for forming a coating layer to eliminate ozone from ambient air as defined in the claims. The coating material comprises an ozone eliminating substance, an organic binder, and a foaming agent. The coating material herein forms an ozone eliminating filter, consisting in a porous layer which incorporates the ozone eliminating substance foamed by means of the foaming agent. This ozone eliminating filter is of large area for contact with the ozone molecules, whereby ozone may be efficiently eliminated. Also according to the present invention there is provided an electronic image processing apparatus for forming an image by electrostatic charging as defined in the claims. The apparatus comprises an image forming section including a photoconductive drum and an electrostatic charger for forming an image by electrostatic charging, wherein a coating material described above is provided disposed in the path of air flow generated by rotation of said photoconductive drum. In the electronic image processing apparatus, the image forming part forms an image on the photoconductive drum by means of electrostatic charge. The electrostatic charging device generates ozone as a side effect. The ozone is circulated in the air flow generated around the photoconductive drum by the rotation of the drum. However, the circulating ozone is eliminated by the ozone eliminating filter located in the air flow. Accordingly, the concentration of ozone in the electronic image processing apparatus is decreased so that deterioration of the photoconductive drum due to contact with ozone is minimized, and the concentration of ozone in the exhaust air is decreased. The present invention will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a sectional schematic view of an electronic image processing apparatus representing an embodiment of the present invention; Fig. 2 is a sectional schematic view showing an image forming part of the apparatus; and Fig. 1 is a sectional schematic view of a copying machine representing an embodiment of the present invention. In the machine body 11, an optical exposure system 19 for obtaining information from an original image is located in the upper portion. The exposure system 19 consists of a light source, mirrors, etc. Disposed in the central portion of the machine body 11 is an image forming part 10. A paper transportation path 27 is provided between the paper cassette cases 14 and 15 and the image forming part 10, and a paper discharging path 28 is provided to the left of the image forming part 10. Between the paper discharging path 28 and the copy tray 18 is a fixing unit 30 for fixing a transferred image on to the transported sheet. Fig. 2 shows the structure of the image forming part 10. A photoconductive drum 20 on which an electrostatic latent image is formed is located in the central part of the image forming part 10. Surrounding the drum 20, are a main charger 21 for charging the photoconductive drum 20 to a predetermined level of electric charge; a blank lamp unit 32 for trimming and masking an electrostatic latent image on the photoconductive drum 20; a developing unit 22 for developing the electrostatic latent image; a transferring device 23 for transferring a toner image to a sheet of material paper; a detaching device 24 for detaching the sheet from the photoconductive drum 20; a cleaning unit 25 for removing toner from the photoconductive drum 20; and an erasing lamp unit 31 for erasing electric charge remaining on the photoconductive drum 20. The photoconductive drum 20 is driven by a driving motor (not shown) to rotate in the direction shown by the arrow causing an air flow, as shown by the double arrows, to be generated around the drum 20. In the image forming part 10, the main charger 21 and the other components surrounding the photoconductive drum 20 each has a coating layer 34 on its outer surface contacting the air flow. The layer 34 comprises a coating material for eliminating ozone. The coating material for eliminating ozone used in the coating layers 34 includes a substance for decomposing ozone or a substance for absorbing ozone. The ozone decomposing substance may be a powder of palladium-carbon, a metal oxide such as manganese dioxide or lead peroxide, a metal such as nickel or rhodium, or a binary composite oxide consisting of titanium and silicon. A powder of the binary composite oxide consisting of titanium and silicon increases ozone decomposing efficiency when it is used with manganese dioxide. The ozone absorbing substance may be activated carbon, silica gel or alumina. The coating layers 34 of the ozone eliminating material are formed of a coating material consisting of an organic binder with an ozone eliminating substance dispersed in the binder and a foaming agent The organic binder used in the coating material may be an emulsion including a polymer of polyacrylicester type (for example, polycyanoacrylate), polymeatcrylicester type, polyvinyl acetate type or polyethylene type; a copolymer of vinylacetate/acrylicester type or styrene/butadiene type; acetal resin; butylal resin; polyimide resin; or polyamide resin. These kinds of organic binder usually consist of a solid component which ranges from 2 to 100 percent by weight -- preferably from 5 to 50 percent by weight. The mixing ratio of the ozone eliminating substance to an organic binder of 100 parts by weight may range from 3 to 100 parts by weight and is preferably from 5 to 50 parts by weight. If the quantity of ozone eliminating substance were less than 3 parts by weight, then a sufficient ozone eliminating effect would not be obtained. In addition, if the quantity of ozone eliminating substance were more than 100 parts by weight, the manufacturing cost would be increased without further benefits being obtained. Furthermore, the coating layers 34 of the ozone eliminating substance could easily become detached in such cases. The coating material for making the coating layers 34 for the elimination of ozone is foamable. A foamable coating material consists of a foaming agent added to a coating material consisting of an ozone eliminating substance, an organic binder as described above, and a solvent. The foaming agent can be, for example, sodium bicarbonate, ammonium carbonate, dinitrosopentamethylenetetramine, azobisformamide, azobisisobutyronitryl, bariumazodicarboxylate, or trihydrazinotriazine. More specifically, the coating material can comprise one of the following examples. (1) A mixture of manganese dioxide of 80 parts by weight, butylal resin of 10 parts by weight, and ammonium carbonate of 0.05 parts by weight, which are dissolved in ethanol of 100 parts by weight. (2) A mixture of palladium-carbon powder of 95 parts by weight, butylal resin of 10 parts by weight, and dinitrosopentamethylenetetramine of 0.03 parts by weight, which are dissolved in ethanol of 100 parts by weight. (3) A mixture of a mixed powder of manganese dioxide and binary composite oxide consisting of titanium and silicon of 100 parts by weight, acrylic resin of 10 parts by weight, and azobisformamide of 0.08 parts by weight, which are dissolved in toluene of 80 parts by weight. The coating material including an ozone eliminating substance described above may be conveniently applied by spraying or brush painting. The solvent is then removed from the applied coating substance by, for example, a heating process at 100°C for one minute so that the ozone eliminating substance is baked on to form a coating layer 34 for eliminating ozone. With the foaming agent included in the coating material, porous coating layers 34 for eliminating ozone are formed by means of the foaming agent. The operation of the copying machine shown in Fig. 1 will now be described. In the copying machine, negative corona discharging occurs at the main charger 21, the transferring device 23, and the detaching device 24 of the image forming part 10 while image processing is taking place. Ozone is generated as a side effect at the main charger 21, the transferring device 23, and the detaching device 24. The ozone circulates around the photoconductive drum 20 owing to the air flow surrounding the drum 20. However, the air flow encounters the coating layers 34 so that the ozone in the air flow is decomposed or absorbed by the ozone eliminating substance of the coating layers 34. Thus, the ozone generated at the main charger 21, etc., is effectively eliminated. Therefore, the concentration of ozone in the copying machine is decreased so that the photoconductive material of the photoconductive drum 20 is maintained at a high quality and the concentration of ozone in the exhaust air is decreased. With the foaming agent, the applied layers 34 for the elimination of ozone are made porous. Hence, the coating layers 34 have a maximal surface for contact with ozone molecules so that ozone is more effectively eliminated. EXPERIMENTS Experiment 1 A coating material was made by adding vanadium oxide of 50 parts by weight to a solid binder of 100 parts by weight which consisted of a polymer emulsion of poly vinyl acetate containing solid of 5 percent by weight. The material contain no foaming agent. This coating material was used to coat parts in a copying machine in a similar manner to the parts as shown in Fig. 2, and then it was dried to form the coating layers. A copying process was carried out in the copying machine incorporating the coating material. Ozone concentration in the exhaust air from the copying machine was measured with an ozone monitor (EG-2001; Ebara-jitsugyosha) immediately after 100 copies had been made. The ozone concentration was 0.2 ppm. Experiment 2 A coating material was made by dissolving a mixed powder of 100 parts by weight of manganese dioxide and a binary composite oxide of titanium and silicon, acrylic resin of 10 parts by weight, and azobisformamide of 0.08 parts by weight into toluene of 80 parts by weight. This coating material was used to coat the parts in a copying machine in a similar manner to the parts as shown in Fig. 2, and then the material was dried to form the coating layers. The coating layers had a porous surface. The ozone concentration of the copying machine was measured in a like manner to Experiment 1. The ozone concentration was 0.1 ppm. Comparative Example The ozone concentration of an ordinary copying machine, which has no coating layers in accordance with the present invention, was measured in a like manner to Experiment 1. The ozone concentration was 1.5 ppm.

Claims: A coating material suitable for use in an electronic image processing apparatus for forming a coating layer to eliminate ozone from ambient air, comprising an ozone eliminating substance, an organic binder, and being characterised by a foaming agent. A material as claimed in Claim 1, characterised in that said organic binder includes solid of between 2 and 100 percent by weight. A material as claimed in Claim 2, characterised in that said solid ranges between 5 and 50 percent by weight. A material as claimed in one of Claims 1 to 3, characterised in that, said ozone eliminating substance ranges from between 3 and 100 parts by weight. A material as claimed in Claim 4, characterised in that said ozone eliminating substance ranges from between 5 and 50 parts by weight. A material as claimed in any one of Claims 1 to 5, characterised in that said ozone eliminating substance comprises an ozone decomposing substance. A material as claimed in any one of Claims 1 to 6, characterised in that said ozone eliminating substance comprises manganese dioxide, said organic binder comprises butylal resin and said foaming agent comprises ammonium carbonate. A material as claimed in Claim 7, characterised in that it comprises ethanol as a solvent and in that it consists of manganese dioxide at 80 parts by weight, butylal resin at 10 parts by weight and of ammonium carbonate at 0.05 parts by weight all dissolved in said ethanol at 100 parts by weight. A material as claimed in any one of Claims 1 to 6, characterised in that said ozone eliminating substance comprises palladium-carbon powder, said organic binder comprises butylal resin and said foaming agent comprises dinitrosopentamethylenetetramine. A material as claimed in Claim 9, characterised in that it comprises ethanol as solvent and in that it consists of palladium-carbon powder at 95 parts by weight, butylal resin at 10 parts by weight, and dinitrosopentamethylenetetramine at 0.03 parts by weight all dissolved in said ethanol at 100 parts by weight. A material as claimed in any one of Claims 1 to 6, characterised in that said ozone eliminating substance is powder comprising a binary composite oxide of titanium and silicon, said organic binder is acrylic resin, and said foaming agent is azobisformamide. A material as claimed in Claim 11, characterised in that said ozone eliminating substance further comprises manganese dioxide. A material as claimed in Claim 12, characterised in that it comprises toluene as a solvent and in that it consists of a mixed powder of 100 parts by weight of said manganese dioxide and said binary composite oxide of titanium and silicon, of said acrylic resin at 10 parts by weight, and of said azobisformamide at 0.08 parts by weight all dissolved in said toluene at 80 parts by weight. A material as claimed in any one of Claims 1 to 6, characterised in that said ozone eliminating substance comprises an ozone absorbing substance. An electronic image processing apparatus for forming an image by electrostatic charging comprising an image forming section (10) including a photoconductive drum (20) and an electrostatic charger (21) for forming an image by electrostatic charging, wherein a coating material for eliminating ozone (34) is provided disposed in the path of air flow generated by rotation of said photoconductive drum (20), characterised in that said coating material is the material of one of the preceding claims. An apparatus as claimed in Claim 15, characterised in that said electrostatic charger (21) includes a charging device (21) for charging said photoconductive drum (20) with a predetermined level of electric charge, a transferring device (23) for transferring a toner image from said photoconductive drum (20) to a sheet of paper, and a detaching device (24) for detaching said paper from said photoconductive drum (20), wherein said devices (21, 23, 24) have a coating layer (34) of said coating material on an outer surface contacting said air flow. An apparatus as claimed in one of Claims 15 or 16, characterised in that said image forming section (10) comprises a developing device (22) for developing an electrostatic latent image on said photoconductive drum (20), a cleaning unit (25) for removing toner from said photoconductive drum (20), and an erasing lamp unit (31) for erasing the charge remaining on said photoconductive drum (20), wherein said device and said units (22, 25, 31) have a coating layer (34) of said coating material on an outer surface contacting said air flow.

Inventors: YOSHIDA TAKESHI, YOSHIDA, TAKESHI
Applicants: MITA INDUSTRIAL CO LTD, MITA INDUSTRIAL CO., LTD.
Application year: 1990
Main classification: G03G21
IPC codes: G03G21, B01D53