JPH0412469B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention includes a laser source, a polygon mirror that scans light from the laser source in the width direction of a photoreceptor, and a charging, developing, and
The present invention relates to a laser printer having transfer and cleaning mechanisms, and particularly relates to an improvement in a pre-exposure device provided for the purpose of keeping the sensitivity of a photoreceptor constant in such a laser printer.

Pre-exposure is carried out immediately before the first exposure after the photoconductor has been in the dark without being exposed for a long time. If this is not done, fogging may occur, or density changes may occur when printing a large number of sheets. Furthermore, a memory effect occurs in which the previous image is stored on the photoreceptor for a while. For this reason, current laser printers are equipped with a pre-exposure device to prevent the above problems from occurring, but current laser printers are equipped with tungsten lamps, neon lamps, or Since the configuration includes an LED array, etc., contamination with toner is likely to occur, which causes the hassle of frequent maintenance work.Also, since the entire length of the photoreceptor in the width direction must be pre-exposed, a tungsten lamp is not used. It is necessary to provide a pre-exposure light source such as the like over the entire width of the photoreceptor, which has disadvantages such as high equipment costs, increased power consumption, and an increase in the size of the printer as a whole.

SUMMARY OF THE INVENTION Therefore, the present invention provides an extremely useful pre-exposure device that can pre-expose the entire width of a photoreceptor using a single point light source as a pre-exposure light source without causing toner contamination.

Embodiments of the present invention will be described below based on the drawings. In FIG. 1, 1 is a laser source, for example
He-Ne that generates laser light with a wavelength of 632.8 nm
It consists of a gas laser 2, optical lenses 3, 3' and a modulator 4. The modulator 4 controls the direction of diffraction of the laser beam based on the printed code sent from the character generator 5, and outputs only the diffracted light in a predetermined direction to a polygon mirror 6, which will be described later. However, a semiconductor laser can be used instead of a gas laser, in which case the modulator is not required.

A polygon mirror 6 scans the laser beam in the width direction of the photoreceptor 7 by rotating it. Reference numeral 8 denotes an f/theta lens, and 9 a reflection mirror for reflecting the laser beam that has passed through the f/theta lens 8 and irradiating it onto the photoreceptor 7 at a predetermined angle. The photoreceptor 7 has a drum shape with a photoconductor layer made of a selenium-based material, and a charging mechanism 10, a developing mechanism 11, a transfer mechanism 12, and a cleaning mechanism 13 are provided around the drum along the rotation direction of the photoreceptor. It is being However,
The photoreceptor is not limited to a drum shape, but may also be an endless strip having a structure wound around a plurality of rolls.

Therefore, in the laser printer having this configuration, the present invention uses a long wavelength LED that emits light for pre-exposure.
(Light Emitting Diode) 14
is provided at a location optically farther from the photoreceptor 7 than the polygon mirror 6, so that pre-exposure light is irradiated onto the photoreceptor via the polygon mirror 6. The reason why an LED with a particularly long wavelength is used here is that the photoreceptor is susceptible to optical fatigue due to long wavelengths. Generally long wavelength LED1
The emission wavelength of 4 is preferably longer than the wavelength of the laser beam emitted by the laser source 1, and is preferably set in the range of 700 to 900 nm. Further, as for the installation position of the long wavelength LED 14, it is desirable to set it immediately near the optical path of the laser beam, as shown in FIG. This is because if the installation position is too far away from the optical path of the laser beam, the scanning range of the pre-exposure light will shift, resulting in a portion of the photoreceptor that is not irradiated with the pre-exposure light. Further, the range where the laser beam is scanned by the polygon mirror 6 is the photoreceptor 7.
perfectly matches the width of the LED, so the long wavelength LED15
If the installation position of the photoconductor 7 is even slightly away from the optical path of the laser beam, there will be a portion of the photoreceptor 7 that is not exposed beforehand, as shown in FIG. 15 long wavelength
An LED 14 may be provided, and during pre-exposure, the cylinder 15 may be rotated to position the long wavelength LED 14 on the optical path of the laser beam. Alternatively, as shown in FIG. 3, a mirror 16 that can be moved in and out by rotation is provided in the optical path of the laser beam, and during pre-exposure, this mirror 16 is inserted into the optical path of the laser beam to absorb the light emitted by the long wavelength LED 14. The light may be reflected by the mirror 16 and sent to the polygon mirror 6. Note that the long wavelength LED 14 may be turned on after the photoreceptor has been in the dark without being exposed for a long time and before it is exposed for the first time, similar to the conventional pre-exposure device. The lighting time and power can be appropriately determined depending on the size, type, etc. of the photoreceptor. In the figure, 17 is a lens that guides pre-exposure light to the polygon mirror 6.

As explained above, the present invention includes a laser source,
In a laser printer that includes a polygon mirror that scans light from a laser source in the width direction of a photoreceptor, and charging, developing, transfer, and cleaning mechanisms provided around the photoreceptor, the pre-exposure light is A long-wavelength LED that emits light is placed optically farther from the photoreceptor than the polygon mirror, and the light emitted by it is irradiated onto the photoreceptor via the polygon mirror, resulting in the following effects: be.

The light emitted by the long wavelength LED is irradiated onto the photoreceptor through the polygon mirror, so the long wavelength LED
It is no longer necessary to provide an array around the photoreceptor as in the past, and there is no fear that the long wavelength LED will be contaminated by toner. Therefore, it can be used stably for a long period of time without maintenance or the like.

Since the light emitted by the long-wavelength LED is scanned onto the photoreceptor by a polygon mirror, the long-wavelength LED can uniformly pre-expose the entire width of the photoreceptor even if it is a single point light source. For this reason, the manufacturing cost is only required to install a single long wavelength LED, which is a point light source, making it extremely inexpensive and consumes little electricity.Furthermore, the overall configuration is effective in making effective use of existing components such as polygon mirrors. The effect is that it can be summarized in an extremely compact manner.

[Brief explanation of drawings]

FIG. 1 is a perspective view of essential parts showing one embodiment of the present invention;
FIGS. 2 and 3 are diagrams showing other embodiments of the present invention, respectively. 1... Laser source, 6... Polygon mirror, 7
...Photoreceptor, 10...Charging mechanism, 11...Developing mechanism, 12...Transfer mechanism, 13...Cleaning mechanism, 14...Long wavelength LED.

Claims (1)

[Claims] 1 a laser source, a polygon mirror that scans the light from the laser source in the width direction of the photoreceptor,
A long-wavelength LED that emits light for pre-exposure in a laser printer that has charging, developing, transfer, and cleaning mechanisms installed around a photoreceptor.
A pre-exposure device for a laser printer, characterized in that the light emitted from a long wavelength LED is provided at a location optically farther from a photoreceptor than a polygon mirror, and the photoreceptor is irradiated with light via the polygon mirror.