JPS6031169A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain an image forming device which is capable of coping with both requests of a distinct reproduction of a line and a good reproduction of half tone by adding a means for changing a relative position of a developing sleeve and a scanning optical beam irradiating position. CONSTITUTION:A mirror 10' is supported so as to be rotatable by a center axis 20, the rear side is a magnetic material, and an angle of the mirror 10' is varied centering around the axis 20 by an operation of two solenoids 18, 19 placed so as to be opposed to said mirror. In this way, a scanning optical beam 7' of a semiconductor laser 7 can change a relative position of an exposed position of the rear side of a photosensitive body 1 and a developing sleeve 4, and when it is desired to show clearly a line, the exposure is executed at the most adjacent point, and when it is desired to shown clearly tone, the exposure is executed at the downstream side of the most adjacent point.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus that forms an image as a toner image on a photoreceptor, for example, electrical image information that is calculated or read out from an electronic computer or an image reading device, or An image display device that reproduces and displays image information stored on magnetic tape or microfilm as a visible image, or an image display device that is attached to image forming equipment such as a copying machine or office automation device as an image monitor. The present invention relates to an image forming apparatus including an image forming apparatus.

FIG. 1 is a longitudinal sectional side view showing a schematic structure of an example of this type of image display device. In FIG. 1, an endless belt-shaped photoreceptor 1 consisting of a transparent and conductive substrate provided with a photoconductive layer is placed on rows 22 and 2 with the transparent substrate on the back side.
' to rotate in the direction of the arrow.

On the other hand, a toner carrier (non-magnetic sleeve) surrounds the conductive and magnetic toner 5 30 times.
4 and brought into contact with the photoreceptor while being held by the magnetic force of the magnet 3. The base and toner carrier are arranged so that the base side is negative when the photoconductive layer is an N-type semiconductor, and the base side is positive when the photoconductive layer is a P-type semiconductor. passing through the substrate with a laser beam 7' while applying an electric field due to a DC voltage between the substrate 4 and
When the photoconductive layer in the area in contact with the toner 5 is irradiated with optical information, toner adheres to the surface of the photoconductive layer in the area irradiated with this light. The above process is disclosed in Japanese Unexamined Patent Publication No. 58-98746, and detailed explanation thereof will be omitted here.

To be more specific, the output light beam (optical information corresponding to the above signal) of the semiconductor laser 7 modulated using an electric signal corresponding to a display image (image to be displayed) γ is a scanner such as a galvanometer mirror or a rotating polygon mirror. 8 is scanned in one direction (perpendicular to the plane of the drawing), and exposed to the back surface of the belt-shaped photoreceptor 1 through an f/theta lens 9 and a mirror 10. (Elements 7, 8, 9, 10 are belt 1
is placed inside. ) This photoreceptor 1 moves in the direction of the arrow, and it is better to provide a thin film of indium tin oxide on the surface of a transparent polyethylene terephthalate film (this is the base material) which is made conductive. It is coated with a special photoconductive layer. CdS doped with copper and indium and sensitive to near-infrared light emitted by the semiconductor laser 7 is used. A developing device 12 is provided on the outside of the photoreceptor belt 1, facing the exposure position of the photoreceptor belt 1 where the radar light beam 7' hits. The developing device is provided with a stationary non-magnetic sleeve 4 having a magnet 3 inside thereof, said magnet 3 rotating in the direction of the arrow.

The conductive and magnetic toner 5 attached to the surface of the sleeve 4 moves on the surface of the sleeve 4 in a direction opposite to the direction of rotation of the magnet 30, is uniformly regulated by grade 6, and comes into contact with the surface of the photoreceptor 1. Since the above-mentioned DC voltage is applied between the base of the photoconductor 10 and the sleeve 4, the photoconductor surface induced by the voltage differs between the areas hit by the laser beam 7' and the areas not hit by the laser beam 7'. There is a large difference in static electricity between the charge of the toner particles in contact with the photoconductor and the charge of the opposite polarity on the photoconductor side. The presence or absence of adhesion occurs, and development is thus performed. Since the width of the area where the toner 5 is in contact with the surface of the photoreceptor in the photoreceptor movement direction is much larger than the incident spot of the laser beam 7' on the photoreceptor, the development is completed after exposure with the laser beam 7'. It continues to be carried out even after that. Rollers 11 and 11' are provided near the positions where exposure and development are performed, which keep the photoreceptor 11 smooth and keep the distance between the surface of the photoreceptor 1 and the sleeve 4 of the developer device accurately constant. It is kept in

The toner image formed on the surface of the photoreceptor at a position facing the developing device is sent to the display section 13 by the movement of the photoreceptor, and the movement of the photoreceptor 1 is temporarily stopped at this position. In the display section, the toner image on the surface of the photoreceptor can be visually observed through the glass 13'.

The lamps 14 and 15 have the function of illuminating the surface of the photoreceptor to make the toner image easier to see, and also to erase from the photoreceptor the history caused by the electric field received during the image forming process. The lamp '16 is for erasing the history of the photoreceptor, and is turned on only while the belt-shaped photoreceptor is moving, and is turned off when the belt-shaped photoreceptor is stopped.

When changing the displayed content, the photoreceptor 1 is moved again, and the surface retains the previously formed toner image (5). At the same time as the previously formed toner image on the body surface is erased, the next toner image is formed.

By using the above-mentioned device, it is possible to display any image by adjusting the semiconductor laser 7 using the image electric signal. If it is an electrical signal, it is easy to guide the signal inside the belt.

Image forming apparatuses that display an image by forming the image to be displayed as a toner image on the surface of an image carrier using a photoconductor as described above have a higher resolution than, for example, a CRT display apparatus or a display apparatus using liquid crystal. The image quality is good, the images are easy to see and there is little fatigue, and if necessary, it is possible to easily obtain hard copies by adding a mechanism to transfer the toner image formed on the belt surface to the copy paper surface. It has the following advantages.

However, in such an image forming apparatus, there is a problem (6) in that when trying to make lines clearly, it becomes difficult to express halftones, and vice versa. In other words, if you want the line to appear clearly, it is better to narrow the area where the density change with respect to the exposure change is linear.
In this case, it is difficult to express halftones due to changes in exposure, and even when dithering is used, a coarse mesh image is created, making it difficult to apply multilevel dithering.

On the other hand, in order to express gradation well, it is better to widen the region where the density change with respect to the exposure amount change is linear, so in this case, it becomes difficult to make lines clearly.

Therefore, in the past, it was only possible to choose between producing good lines and producing good gradation.

The present invention is an image forming apparatus of this type that can overcome the above-mentioned drawbacks and meet the requirements of producing images with clear lines and producing images with good gradation. The purpose is to provide

The present invention is characterized in that, in the above type of image forming apparatus,
The present invention is provided with means for varying the relative positional relationship between the toner carrier (sleeve 4) and the position where the information light corresponding to the image signal is irradiated on the photoreceptor.

The phenomenon observed in the image forming apparatus shown in FIG. 1, in which gradation deteriorates when trying to produce clear lines, and lines do not appear clearly when trying to produce good gradation, is caused by the image exposure position. The inventor's experiments have revealed that it depends on the relationship between and the position of the developing device sleeve. This will be explained below.

FIG. 2 is a diagram schematically showing the image exposure position (the position where the laser beam hits the photoreceptor 1) and the position of the developing sleeve 4. As shown in FIG. 1 is a photoreceptor belt, which moves in the direction of the arrow. Photoreceptor 1 consists of three layers 1-1.1-2.1-1. The layer 1-1 is given conductivity by having an indium tin oxide thin film on the surface in contact with the layer 1-2.
It is a transparent substrate made of polyethylene terectrate, and layer 1-
2 is a photoconductive layer made of copper- and indium-doped CdS hardened with a resin binder, and layers 1-3 are white surface layers made of titanium oxide fixed with a resin binder to improve the user's usability. A sleeve 4 made of non-magnetic stainless steel and having a diameter of 32 is fixed in the developer container 12. 3 is an 8-pole magnet roll whose N and S poles are alternately magnetized to generate a magnetic field of 800 Gauss each on the surface of the sleeve 4, and rotates within the sleeve 4 in the direction of the arrow A at 150 Orpm.

Reference numeral 17 denotes a regulating member for uniformly applying the conductive magnetic toner 5 onto the sleeve 4.

The conductive magnetic toner 5 is spread over the surface of the sleeve 4 by the magnet roll 3.
Upon zero rotation, the magnet 3 moves in a direction opposite to the rotational direction of the magnet 3 and comes into contact with the photoreceptor 1 . Here, while the toner is in contact with the photoconductor, it spreads from the closest position A between the sleeve 4 and the photoconductor to point B on the upstream side in the direction of photoconductor movement, and to point 0 on the downstream side.
have. According to actual measurements, this width between B and C is approximately 10. and B
-A was about 7 Wn1 person - 0 was about 3m+.

In such an image forming apparatus, when the laser beam 7' is irradiated to the nearest point (7'-0 in the figure), (9), and when it is irradiated to the upstream and downstream sides (7' in the figure).
-1, 7'-2), experiments were conducted on the relationship between exposure amount-image density characteristics and exposure position-sleeve position. The photoreceptor was made of a CdS binder system with a thickness of 65 microns, was exposed to a semiconductor radar beam with a wavelength of 780 TR, and developed by magnetic brush development as described above using a sleeve 4 with a diameter of 24 mm and conductive magnetic toner 5. went. The experimental results are shown in Figs. 3 and 4.

Figure 3 shows the exposure amount-image density characteristic curve when the closest point is irradiated (7'-'O), and Figure 4 shows the characteristic curve when the IWI is irradiated from the closest point to the downstream side of the IWI (7'-1 )
This is an exposure amount vs. image density characteristic curve.

From Figures 3 and 4, it can be seen that when you want to make a line clearly, it is better to expose at the closest point, and when you want to get better gradation, it is better to expose at the downstream side of the closest point.

The present invention takes advantage of this fact by changing the relative positional relationship between the exposure position and the developing sleeve (1'o) to meet both the requirements for reproducing clear lines and reproducing good gradation. That is.

FIG. 5 shows an embodiment of the present invention in which the exposure position is relatively changed in this manner. The same parts as in FIGS. 1 and 2 are indicated by the same reference numerals, and the principle of forming an image is the same as described above. The output light beam 7' of the semiconductor laser 7, which has been modulated using an electrical signal corresponding to the image to be displayed, is scanned in one direction by a rotating polyhedral scanner 8, and transmitted through an f/θ lens 9 and a mirror 1σ into a belt-shaped beam. The back surface of the photoreceptor 1 is exposed.

The i-two 10' is rotatably supported on a central shaft 20, and has a magnetic back surface, and the angle of the mirror 10' is controlled around the shaft 20 by the operation of nine and two solenoids 18 and 19 arranged opposite to this. change.

That is, when the solenoid 18 is excited, the mirror 10' is attracted and comes into contact with it, and the laser beam 7' takes the optical path A. Furthermore, when the solenoid 19 is excited, the mirror 10' comes into contact with it and the laser beam 7' takes the optical path B. This allows the exposure position to be selectively changed relative to the position of the sleeve 4.

In order to change the optical path in order to change the exposure position of the photoreceptor with the laser beam γ, other means such as moving the laser 7 or moving the scanner 8 can also be used.

FIG. 6 shows an embodiment in which the relative position of the developing sleeve with respect to the exposure position of the scanning light beam 7' is changed by moving the developing device in the traveling direction of the photoreceptor belt.

However, when moving the developing device, care must be taken to ensure that the closest distance between the sleeve and the photosensitive plate does not change. In FIG. 6, the entire developing device is equipped with a foot so that it can slide on a guide rail 21 in a direction parallel to the photosensitive plate, and a crank mechanism 23 whose one end is fixed to a part of the developing device.

With the above device configuration, the position of the developing device can be changed by rotating the crankshaft in the direction of arrow 24 using an external motor (not shown) or manually.

By adding a means for changing the relative position between the developing sleeve and the scanning light beam irradiation position as described above, the required exposure amount-density characteristic curves shown in FIGS. 3 and 4, respectively, can be changed. You can choose. The relative positional relationship between the developing sleeve and the scanning light beam that shows the exposure amount-density characteristic curve as shown in FIG. If the relative positional relationship of the light beams is set to the position for halftone originals, it is possible to deal with both line originals and intermediate m-originals by switching and selecting them using the above-mentioned means.

In the above embodiment, a light beam modulated as information light was used as an example, but other methods such as slit exposure of an original image,
An information light generating means using an LED element array or a combination of a light source and a liquid crystal shutter can be used. For example, when using an IJD element array or a liquid crystal screen, the same effect as above can be obtained by changing the position of these elements with respect to the photoreceptor instead of changing the reflection angle of the top and front 1 et la. It becomes possible to obtain.

Further, the transparent substrate 1-1 of the photoreceptor does not necessarily have to be transparent (13), but may be anything that can guide the information light to be used to the photoconductive layer 1-2.

As described above, according to the present invention, a simple mechanism that selectively changes the relative positional relationship between the toner carrier and the irradiation position of the scanning optical information beam enables clear reproduction of lines and good halftones. It becomes possible to provide an image forming apparatus that can meet all of the requirements for reproduction.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of a conventional example of an image display device to which the present invention relates, Fig. 2 is a side sectional view showing the light beam exposure position and the developing sleeve position, and Fig. 3 is a side sectional view of a conventional example of an image display device related to the present invention. , and FIG. 4 is an experimental graph showing the exposure amount-image density characteristic curve when exposed downstream of the closest point, and FIGS. 5 and 6 are side sectional views showing fogging embodiments of the present invention, respectively. It is. DESCRIPTION OF SYMBOLS 1... Photoreceptor belt, 3... Rotating magnet, 4... Developing sleeve, 7... Laser, 7'... Laser light beam, 8... Scanner, 9... f/θ lens, 1
0...Fixed mirror 9-1io'...Movable mirror, 18.
19... Solenoid (14) Do, 21... Roll, 22... Rack and pinion gear (
15) 1st grade, 4th grade, 6th grade

Claims (1)

[Claims] a photoreceptor comprising a photoconductive layer provided on a conductive substrate; a toner carrier disposed close to the photoconductive layer and bringing conductive magnetic toner into contact therewith; and between the substrate and the toner carrier. In an image forming apparatus comprising means for applying a DC voltage and means for irradiating information light corresponding to an image signal onto the photoreceptor from the substrate side, the position where the information light is irradiated on the photoreceptor and the toner carrier are arranged. An image forming apparatus characterized by being provided with means for changing relative positional relationship.