JPS6270891A - Recording device - Google Patents

Abstract

PURPOSE:To prevent a non-image forming area of a photosensitive body from adhesion of toner or carrier by setting up the electrostatic charge potential of the non-image forming area of the photosensitive body lower than that of an image forming area. CONSTITUTION:A liquid crystal head 3, a developing unit 4, a transfer unit 6, a cleaner 7, a destaticizing lamp 8 are arranged on 45 deg., 90 deg., 180 deg., 270 deg., and 315 deg. positions respectively from an electrostatic charger 2. When a print start switch (SW) is turned ON, the charger 2 and a destaticizing lamp 8 are turned ON, a switch relay 2f of the charger 2 is turned ON and the non-image forming area on the leading end of the image forming area of the photosensitive drum 1 is charged with -450V. When the drum 1 is rotated by 45 deg., the relay 2f is turned OFF and the image forming area of the drum 1 is charged with -800V. At the 90 deg. rotation of the drum 1, a halogen lamp 3a, a liquid crystal driver and a developing bias are turned on, and at the 225 deg. rotation of the drum 1, the image forming area reaches the transfer unit 6 and the transfer unit 6 is turned ON. At the end of one rotation of the drum 1, the halogen lamp 3a is turned OFF and the liquid crystal driver is also closed.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a recording device using a liquid crystal head.

[Traditional technique]

Conventionally, this type of device uses a liquid crystal head in which a large number of microshutters are arranged in the main scanning direction of a photoreceptor, and the individual microshutters of this head are controlled to open and close according to recording signals to detect light from the light source. It is configured to form an electrostatic latent image of a document on a photoreceptor by modulating light. As a means of visualizing this electrostatic latent image, there is a reversal development method in which toner is attached to the low potential portion of the electrostatic latent image (in this specification, the level of potential indicates a comparison of absolute values). used.

However, in such a recording device, the entire surface of the photoreceptor is charged and exposed to light by a light source.
Toner also adheres to non-image forming areas where there is no transfer paper before and after the image forming area, resulting in a problem that toner is wasted.

Therefore, as a means to solve this problem, the light source of the liquid crystal head is turned off when it leaves the non-image forming area of the photoreceptor.
A method that maintains the charged potential on the photoreceptor surface at a high level, or a method that maintains the charged potential on the photoreceptor surface at a high level by keeping the light source of the liquid crystal head on and closing the liquid crystal shutter in the non-image forming area. is proposed.

By the way, when optical writing is performed on a photoreceptor using a liquid crystal head, light leaks even when the liquid crystal head is closed, making it difficult to completely block light from a light source. In other words, as shown in FIG. 4, when the photoreceptor is charged to an initial potential of -vs, when optical writing is performed by opening and closing the liquid crystal shutter using a control signal according to the recorded information, when the liquid crystal shutter opens, it is fully charged. Optical attenuation is performed on V2 (approximately OV
).

On the other hand, when the liquid crystal shutter is closed, the light is attenuated to 1 due to leakage light. Therefore, when reversing an electrostatic latent image, use a developing bias VB equal to or slightly lower than ■1.
A method is adopted in which toner is applied to the 72 portion by applying +aS to form a visible image.

[Problems with conventional technology]

However, in the former method described above, when the light source is turned off, no light hits the photoreceptor, so the surface potential of the photoreceptor is maintained at the initial potential (8) and the developing bias vB+
The potential is much higher than as.

Therefore, when the potential difference between the initial potential (■5) and the developing bias VBIαS increases, for example, if a single-component developer is used, toner will adhere to the initial potential (■3) area, and if a two-component developer is used, a large amount of carrier will adhere to the area. There is a drawback that it does.

In addition, in the latter method, it is possible to prevent toner from adhering to the image forming area by keeping the light source turned on to set the potential before and after the image forming area to vl, but if a halogen lamp with a large amount of heat is used as the light source, for example, However, there were drawbacks such as an increase in temperature within the device and a shortened lamp life.

[Purpose of the invention]

In view of the above-mentioned conventional drawbacks, the present invention prevents toner or carrier from adhering to the non-image forming area of the photoreceptor, and increases the temperature inside the device even when a lamp with a large amount of heat, such as a halogen lamp, is used as a light source. An object of the present invention is to provide a recording device that can prevent shortening of lamp life.

[Summary of the invention]

In order to achieve the above object, the present invention includes a photoreceptor, a charging means for charging the photoreceptor, and an electrostatic latent image formed by irradiating the photoreceptor with light from a light source in a modified manner using a liquid crystal shutter. In a recording apparatus comprising an optical recording means for forming an electrostatic latent image, and a developing means for attaching toner to a low potential area of the electrostatic latent image and developing it, the charging means charges a charging potential of a non-image forming area of the photoreceptor. The charge potential is lower than that of the image forming area, and the light source is turned off when the image is not formed.

[Embodiments of the invention]

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a time chart when the recording apparatus of the present invention prints two sheets, and FIG. 2 is a schematic diagram of the configuration of the recording apparatus of the present invention. First, explanation will be given according to FIG.

In FIG. 2, reference numeral 1 denotes a photosensitive drum having a photoconductive thin film formed on its circumferential surface, and is adapted to rotate in the direction shown. Around the photosensitive drum 1, there is a charger 2 that charges the surface of the photosensitive drum 1, a liquid crystal head 3 that forms an electrostatic latent image corresponding to an image to be recorded on the photosensitive drum 1, and this electrostatic latent image. A developing device 4 is provided for developing the image using a reversal development method. Note that as the charger 2, a Scorotron type charger is used. Further, 6 is a transfer device that transfers the developed toner image onto the transfer paper 5, 7 is a cleaner that removes untransferred toner remaining on the photosensitive drum 1 after the transfer, and 8 is also on the photosensitive drum 1 after the transfer. A charge eliminating lamp 9 optically eliminates the residual charge of the paper 5, and a fixing device 9 fixes the toner image transferred to the paper 5.

The photosensitive drum 1 is first charged by the charger 2,
This scorotron type charger will be explained with reference to FIG. 3.

In the figure, 2a is a charging shield, and a stainless steel mesh 2c is disposed between the shield 2a and a photosensitive drum (not shown) on the lower surface thereof. Constant voltage elements 2d and 2e are connected in series between the stainless steel mesh 2c and the ground of the main body, and a voltage switching relay 2f is connected in parallel to one low voltage element 2d. When discharging from the charging wire 2b to the photosensitive drum, the photosensitive drum 1 is uniformly charged by applying a voltage to the stainless mesh 2c, and the charging potential is switched by switching the applied voltage with the switching relay 2f. It is now possible to In this embodiment, the constant voltage element 2d is a 390V constant voltage element, and the constant voltage element 2e is a 470V constant voltage element. When charging the image forming area of the photosensitive drum 1, the switching relay 2f is turned off and the voltages of the constant voltage elements 2d and 2e are applied to the stainless mesh 2C, thereby charging the surface of the photosensitive drum 1 by 1800 m. ■ Charges. on the other hand,
When charging a non-image forming area between the previous image forming area and the next image forming area in continuous printing, the switching relay 2f is turned on and only the voltage of the constant voltage element 2e is applied to the stainless steel mesh 2c. As a result, the surface of the photosensitive drum 1 is charged to -450V. In this embodiment, varistors are used as the constant voltage elements 2d and 2e.

After charging, negative exposure corresponding to the image to be recorded is performed by the liquid crystal head 3 to form an electrostatic latent image on the photosensitive drum. Here, negative exposure refers to irradiating light to a portion to which black is ultimately desired to lower the potential to (2). In other words,
When printing a character image, irradiate light only on the character part,
This means that light is not irradiated onto the bank ground.

The charger 2 and the liquid crystal head 3 are located 45 degrees out of phase with respect to the rotation axis of the photosensitive drum 1, and the developing device 4 is further shifted 45 degrees clockwise from the liquid crystal head 3.

The liquid crystal head 3 uses a high-intensity halogen lamp 3 as a light source.
a, a liquid crystal shutter 3b consisting of a large number of micro-shutters using guest-host type liquid crystal, and an imaging lens (SELFOC Lens Array (product name)) 3 that performs 1-magnification imaging.
c and a light guide 3d made of transparent acrylic that transmits only light without transmitting the heat generated from the halogen lamp 3a to the liquid crystal shank 3b, etc., and opens and closes the liquid crystal shutter 3b in response to an external recording signal. . In this case, the halogen lamp 3a as the light source is turned on when the image forming area of the photosensitive drum 1 passes, and is turned off when the non-image forming area between the preceding and succeeding image forming areas in continuous printing passes. It is supposed to be done. That is, charger 2
Accordingly, the light is turned on for the image forming area charged to -800V, and the light is turned off for the non-image forming area charged to -450V.

Note that the liquid crystal shutter 3b in this embodiment is
Since a host-type liquid crystal is used, even if the shutter is closed, some light will still pass through the shutter.

Therefore, the surface potential of the photosensitive drum 1, which was the initial potential Vs of the image forming area = 800■, is the same as that of the liquid crystal shutter 3 in the open state.
When the light passing through the liquid crystal shutter 3b is irradiated, V2=approximately -20V, and when the light passing through the closed liquid crystal shutter 3b is irradiated, the voltage becomes V+-450. Further, in the non-image forming area charged to -450V, the voltage of -450V is maintained because the light source is turned off. In other words, in the image forming area, each of the aforementioned micro shutters opens and closes individually according to the recording signal, so that -450V and -20V are applied to the surface of the photosensitive drum 1.
An electrostatic latent image with a contrast of V is formed, and a potential of -450 V is maintained in the non-image forming area.

Next, when reversal development is performed by the developing device 4, in the image forming area, toner adheres to the low voltage area (-20V'') and does not adhere to the high voltage area (closed area of the micro shutter). Development is performed. Also, the non-image forming area is charged to -450 cm as described above, and this potential and bias V
Since the voltage is close to s+α5-400V, there is no adhesion of toner or carrier.

Thereafter, the toner image formed on the photosensitive drum 1 is transferred onto the transfer paper 5 by a positive charge applied by a transfer device 6 located 90 degrees from the developing device 4, and then heated and fixed by a fixing device 9. Ru. On the other hand, the residual toner on the photoreceptor drum 1 is removed by a cleaner 7, and the residual charge is further removed by photostatic discharge by a static elimination lamp 8.

Next, a timing chart for two-sheet printing according to the present invention will be explained with reference to FIG. In this embodiment, the liquid crystal head 3, developing device 4, transfer device 6, cleaner 7, and static elimination lamp 8 are arranged at 45°, 90°, and 1° from the charger, respectively.
They are located at 80°, 270°, and 315°.

Now, when the print start SW (switch) is turned on, °
, the main motor starts rotating. At the same time, the SWs of the charger 2 and the static elimination lamp 8 are also turned on. At the same time, the switching relay 2f of the charger 2 is turned on, and the non-image forming area at the tip of the image forming area of the photosensitive drum is changed to 1450 as described above.
■ Charges. In the figure, a large scale with numerical values indicates one rotation of the photosensitive drum 1. Therefore, a small scale indicates a state in which the photosensitive drum 1 is rotated by 90 degrees. When the photosensitive drum 1 further rotates by 45 degrees from the starting point, the switching relay 2f is turned off and the image forming area of the photosensitive drum is charged to -800V. In this state, the photosensitive drum is
It is held until it rotates by 15 degrees (until the imaging area passes). Further, when the photosensitive drum rotates 90 degrees from the starting point, the halogen lamp 3a, the liquid crystal drive, and the developing bias are turned on. Note that the reason why the switching relay 2f is turned on and the halogen lamp and liquid crystal drive are deviated by 45 degrees is because the charger and the liquid crystal head are installed with a 45 degree deviation.

On the other hand, when the photosensitive drum 1 has rotated 225 times since it started rotating (when the image forming area reaches the transfer device), the transfer device 6 is turned on. Then, the halogen lamp 3a is turned on while the photosensitive drum 1 rotates by 270 degrees, and the liquid crystal is also driven in accordance with the recording signal during that period. When the photosensitive drum 1 completes one rotation, the halogen lamp 3a is turned off, the liquid crystal drive is also closed, and the non-image forming area between the previous image forming area and the next image forming area in continuous printing is used as a light source and liquid crystal drive. operation stops. Thereafter, the electrostatic latent image formed on the photosensitive drum is developed by a developing device, further transferred to transfer paper, and fixed, thereby completing the recording process for the first sheet.

As explained above, in the recording apparatus of the present invention, the image forming area and the non-image forming area of the photosensitive drum 1 are charged to different potentials, so even if reversal development is performed, the toner remains in the non-image area where there is no light attenuation. or carriers will not stick to it.

In addition, in the embodiment, an example was shown in which varistors were used as the constant voltage elements 2d and 2e, but the present invention is not limited to this, and similar effects can be obtained by using other constant voltage elements or resistance elements. .

Also, if you change the arrangement of each process means of the recording device,
It is obvious that the timing chart will be different.

〔Effect of the invention〕

According to the recording apparatus of the present invention configured as described above, carrier adhesion to the non-image area of the photoreceptor can be prevented, and carrier consumption within the developing device can be significantly reduced. Furthermore, even when a one-component developer is used, it is possible to prevent toner from adhering to non-image areas, so toner is not wasted. Furthermore, since it is not necessary to keep the light source lit, there is an effect that an increase in the temperature inside the device can be prevented and the life of the light source can be extended.

[Brief explanation of drawings]

FIG. 1 is a timing chart of the recording device of the present invention, FIG. 2 is a schematic diagram showing the recording device of the present invention, FIG. 3 is a diagram of the configuration of the charger, and FIG. 4 is the surface of the photosensitive drum. It is an electric potential diagram. 1... Photosensitive drum, 2a... Charging shield, 2b... Charging wire, 2c... Stainless steel mesh, 2d... Constant voltage element, 2e... Constant voltage element, 2f... Switching Relay, 2... Charger, 3... Liquid crystal head, 4... Developer, 6... Transfer device, 7... Cleaner, 8... Static elimination lamp.

Claims (1)

[Claims] a photoreceptor, a charging means for charging the photoreceptor, an optical recording means for forming an electrostatic latent image by modulating and irradiating the photoreceptor with light from a light source using a liquid crystal shutter, and the electrostatic latent image. In the recording apparatus, the charging means charges a non-image forming area of the photoreceptor to a charging potential lower than that of the image forming area; A recording device characterized in that the light source is turned off for the non-image forming area.