JPS5837075Y2 - OFT printer device - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an electrophotographic printer (hereinafter referred to as an OFT printer) using an OFT (optical fiber tube) in a printing section.

Fig. 1 is a schematic diagram of a conventional OFT printer, in which 1 is an OFT, an example of which is shown in Fig. 2, 2 is a charging corotron, 3 is a developing device, 4 is a photosensitive drum, and 5 is a transfer corotron. .

Figure 2 is a plan view and a side view of a conventional OFT.
1 is a (glass) neck part, 22 is a (ceramic) cone part, 23 is an anode electrode provided on the cone part, 24 is fixed to the tip of the cone part 22, and a number of optical fibers 25 are embedded in the center part. The image plane 26 is a conductive film formed on the outer surface of the cone part 22 except for the peripheral part of the anode electrode 23.

In such a conventional OFT printer device, after the photosensitive drum 4 is uniformly charged by the charging corotron 2,
When an optical image is projected onto the photosensitive drum 4 by 0FT1, a portion corresponding to a bright portion of the image signal is discharged, causing a potential change, and an electrostatic image as shown by curve A1 in FIG. 3 is formed.

Incidentally, in the OFT printer, a method is adopted in which an optical signal output from the tip of the optical fiber 25 embedded in the image plane 24 of the 0FT1 is projected onto the photosensitive drum 4 for direct exposure, so the size of the exposure spot can be adjusted. In order to maintain a predetermined value, the distance between 0FT1 and drum 4 must be set extremely narrow (usually 100 to 350 μm).

For this reason, the charge leaked from the corotron 2 and accumulated in the 0FT1, or from the high voltage part to the cone part 22.
The electric charge leaked through the joint between the image plane 24 and the glass constituting the image plane 22 and the fiber 25 embedded therein is recharged toward the electrostatic latent image on the surface of the drum 4. Sometimes.

In this type of development, if there is eccentricity of the drum 4 or irregularities on the drum surface, the surface of the drum 4 may come into contact with or abnormally approach 0FT1 when the drum 4 rotates.
It becomes especially noticeable.

FIG. 4 schematically shows this state.

In other words, the positive charges on the image plane 24 at 0FT1 move along the lines of electric force to the surface of the drum 4, recharging the bright part of the electrostatic latent image, and causing the bright part of this part to become brighter as shown by curve A2 in the figure. Increase potential.

As a result, a part of the electrostatic latent image becomes faint or disappears, or an undesired image (nozzle) appears in a place other than the image.

In the conventional device, for example, the anode potential of 0FT1 is +
12 KV, the surface potential of the drum 4 is +500■, the distance between the drum and the OFT is 200 μm, the thickness of the image plane 24 (the length of the optical fiber 25) is 5 mm, and the thickness of the selenium coating on the surface of the drum 4 is 60 μm. The potential difference between the drum and the drum surface is approximately 1500 V, which is a field strength sufficient to cause dielectric breakdown.

Although the case where the positively charged drum is recharged by the positive charge of the OFT has been described above, it is easily understood that the same development occurs even if the charging polarity is reversed.

The present invention extends the conductive film of the cone portion until it covers the entire image surface of the OFT, the peripheral portion of the image surface excluding the light output portion, or the joint surface between the cone portion and the image surface. By grounding the membrane, the aforementioned drawbacks are eliminated.

FIG. 5 is a plan view and a side view of an OFT suitable for the present invention, and the same reference numerals as in FIG. 2 represent the same parts.

In this example, the entire image plane 24 including the exposed surface of the optical fiber 25 is covered with a conductive film 26.

When the OFT having such a structure is arranged as shown in Fig. 1 and the conductive film 26 is grounded, the potential difference between the OFT1 and the surface of the drum 4 is reduced to a sufficiently low value and stabilized, so that eccentricity of the drum 4 and Because of the unevenness of the surface, even if the distance between the OFT and the drum surface becomes small or they come into contact, there is no charge transfer between them, and the electrostatic charge on the drum 4 formed by the image output light of 0FT1 is eliminated. The latent image is no longer recharged.

Therefore, the reproduced image is prevented from becoming faint or missing.

In FIG. 5, a conductive coating is formed on the entire exposed surface of the optical fiber 25, so it is clear that at least the portion of the image plane 24 where the optical fiber 25 is present needs to be covered with a transparent conductive coating. 24 said optical fibers 2
Even if the conductive film is not formed on the exposed portion of 5, it is possible to obtain substantially the same effect as that of 5.

Further, as shown in FIG. 6, the cone portion 22 and the image plane 24
Simply extending the conductive film 26 to the extent that it covers the bonding surface with the bonding surface eliminates recharging due to leakage of charge from the bonding surface, and is thus far more effective in preventing loss of reproduced images.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram of the OFT printer device, Figure 2a,
1) is a plan view and a side view of a conventional OFT, FIG. 3 is a diagram showing the state of an electrostatic latent image on the surface of a photosensitive drum, FIG. 4 is a diagram showing a state of a recharged electrostatic latent image, and FIG. Figure 5 a, l) is a plan view and side view of an OFT suitable for the present invention, and Figure 6 is an OFT suitable for the present invention.
FIG. 3 is a side view showing another example of FT. 1...OFT, 2...Charging corotron, 3...Developer, 4...Photosensitive drum,
5... Transfer corotron, 24... Image surface, 25... Optical fiber, 26... Conductive film.

Claims (1)

[Scope of utility model registration request] The surface of the photosensitive drum is uniformly charged and exposed to light output from the OFT image plane to form an electrostatic latent image on the drum surface, which is developed according to a conventional method and transferred to a recording medium. In the OFT printer device that
A conductive coating provided on the cone of the T is extended to cover at least the joint surface between the cone and the image plane, and the coating is grounded, thereby preventing the drum surface from being recharged after exposure. An OFT printer device featuring: