JPH0574178B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a fluorescent tube for optical writing in an optical printer using an electrophotographic method.

Prior Art Conventionally, a fluorescent display tube used for a display has a cathode, usually a directly heated filament, placed in a vacuum container 3 which is made up of a substrate 1 and a face glass 2, at least one of which is transparent in the field of view. 4, an anode 7 made of a conductor having a grid 5 and a phosphor 6 formed on its surface (see FIG. 1). 8 is an insulator. When the anodes 7 having such a structure are used as minute dots, for example, 10 dots/mm, the pitch of each anode 7 is 100 μm, and the dot size of the phosphor 6 is 50 to 60 μm on each side, as shown in FIG. The structure is such that the dots are arranged in a line to form a dot array 9. The length of this dot array 9 is the same as the print width. For example, if you are printing on A4 size 210 mm wide, the length of the dot array 9 is 210 mm and the width is 2100 mm.
The phosphors 6 are arranged in a row.

The dot array-shaped fluorescent tube 10 is selectively controlled to emit light from each dot (fluorescent body 6) in accordance with a printing signal, and a 1-magnification imaging element 11 (for example, a focusing optical fiber array) is used to focus the light on the photoreceptor. An optical printer as shown in FIG. 3 is a device that forms an image on the image 12 and prints using an electrophotographic method. 13 is an electrostatic charger, 1
4 is a developing device, 15 is a transfer charger, 16 is a transfer paper, 17 is a static elimination lamp, and 18 is a cleaner.

In such an apparatus, in order to obtain a printing speed of 10 sheets per minute, for example,
If an exposure energy of 10 erg/cm ² is required, the luminance of the phosphor 6 is required to be 7,000 to 10,000 fL (however, the phosphor 6 is made of ZnO:Zn, and the light utilization efficiency of the 1-magnification imaging element 11 is (is assumed to be 5%). According to this,
Normally the brightness required for display is 200 ~
Since it is about 1000fL, a fairly high luminance power is required. Now, if the size of the phosphor 6 is 50 x 50 μm ² , a current of about 10 μA will flow at 10000 fL, and the current density at the anode 7 is quite high. As a result, if the phosphor 6 is used under such conditions, a decrease in luminance (deterioration) over time becomes a problem.

Purpose The present invention was made in view of the above points, and an object of the present invention is to obtain a fluorescent tube for optical writing that can substantially extend the service life even if high-intensity light emission is required. .

Configuration An embodiment of the present invention will be described based on FIGS. 4 and 5. Components that are the same as those shown in FIGS. 1 to 3 are designated by the same reference numerals, and description thereof will be omitted. In this embodiment, a plurality of anodes, two in this embodiment, are arranged on the same anode 7.
phosphors 6a and 6b are provided, and these phosphors 6
a, 6b form two rows of dot arrays 9a, 9b, and these dot arrays 9a,
Grid 5a, which can be independently controlled in correspondence with 9b;
5b is provided. Here, grid 5
usually has a mesh structure made of a metal thin film and is formed by covering the anode 7 (in the case of a display), but in the case of a dot array tube, the light emitting path of the phosphors 6a and 6b is a grid mesh. The dot arrays 9a and 9b have a slit-like structure so that they are not blocked by the dot arrays 9a and 9b.

Here, when the grid 5 turns on the dot array 9, a positive voltage is applied to the anode 7, and the grid 5 is set to a lower positive potential than the anode 7. At this time, the filament 4 is set to 0 potential. If the grid 5 is at a negative potential or zero potential, even if the anode 7 is at a positive potential, electrons from the filament 4 will not enter the phosphor 6 and the phosphor 6 will not emit light.

Therefore, in the structure of this embodiment, when only the dot array 9 is used, only the grid 5a may be set to a positive potential and the grid 5b may be set to a negative potential or 0 potential. Then, due to changes over time, the dot array 9
When the dot a has deteriorated, by setting only the grid 5b to a positive potential, the phosphor 6b of the dot array 9b will emit light, and the deterioration on the dot array 9a side can be substantially compensated for. For this purpose, since the anode 7 is common to each of the phosphors 6a and 6b, there is no need to replace the drive IC or other external parts, and it is only necessary to change the voltage to be applied to the grids 5a and 5b. , all you need is one switch.

Effects As described above, the present invention comprises disposing a cathode, a grid, and an anode made of a conductor with a phosphor on its surface in a vacuum container, at least one of which is transparent. In a fluorescent tube for optical writing, in which the dots are arrayed in a row in a minute dot-like pattern, and a voltage is independently applied to each anode by an electric signal, a plurality of dot-like phosphors are arranged on the same anode. These phosphors form a plurality of parallel rows of dot arrays, and each dot array has a grid that can be independently controlled to select which row to use. Even if the phosphor deteriorates, the phosphor of that dot array can be used by applying a control potential to the grid corresponding to the other dot array, so that the deterioration of the phosphor can be avoided simply by selectively controlling the grid. It is possible to substantially compensate for this and extend the lifespan.

[Brief explanation of drawings]

Fig. 1 is a longitudinal side view showing a conventional example, Fig. 2 is a plan view thereof, Fig. 3 is a schematic side view of an optical printer, Fig. 4 is a plan view showing an embodiment of the present invention, and Fig. 5 is a plan view thereof. It is a longitudinal side view. 3... Vacuum container, 4... Filament (cathode),
5a-5b... Grid, 6a-6b... Fluorescent material, 7... Anode, 9a-9b... Dot array.

Claims (1)

[Claims] 1 In a vacuum container where at least one side is transparent,
A cathode, a grid, and an anode made of a conductor with a phosphor formed on its surface are arranged, and the phosphor of these anodes is arrayed in a row as a minute dot-like pattern, and each anode is independently activated by an electric signal. In a fluorescent tube for optical writing, a plurality of dot-shaped phosphors are formed on the same anode, and these phosphors form a plurality of parallel rows of dot arrays. 1. A fluorescent tube for optical writing, characterized in that a grid is provided which can be independently controlled to select a column to be used for each dot array.