JPH0696292B2 - Recording head unit of image forming apparatus - Google Patents

Description

The present invention relates to an improvement of a recording head device in an image forming apparatus such as an electrostatic printer.

[Prior art]

An electrostatic printer, which is one of image forming apparatuses, forms an electrostatic latent image on the surface of a dielectric and develops the latent image with toner to obtain an image. Various schemes have been proposed. As one of them, a method of generating ions by using discharge and extracting the ions to form a latent image on the surface of a dielectric is disclosed in, for example, Japanese Patent Publication No. S57-501348.

In this method, a high-frequency alternating current is applied between two electrodes separated by a dielectric member to generate a discharge, and the ions generated by the discharge are extracted according to an image signal to form a latent image on the dielectric drum. It is a thing.

The outline of such an ion head device and a method of forming a latent image on a dielectric drum using the same will be described below. FIG. 4 is a plan view of the ion head substrate of the ion head device as seen from the ion emission surface side, and FIG. 5 is a partially enlarged sectional view thereof. In the figure, 1 is an ion head supporting substrate, and the supporting substrate 1 has a central portion in the longitudinal direction,
Multiple (six in this example) line electrodes 2, 2, ...
Are embedded in the insulating layer 3, for example, so that only the surface is exposed. A large number of finger electrodes 15, 15, ... Which intersect the line electrodes 2, 2, ... At a predetermined angle via the transparent mica plate 4 on the line electrodes 2, 2 ,.
... is provided. And this line electrode 2, 2, ...
At the intersections of the finger electrodes 15,15, ..., With the line electrodes 2,2, ... Of the finger electrodes 15,15 ,. A diameter hole 15 'is provided.

An insulating layer 6 made of synthetic resin or the like in which a hole 6'having a larger diameter than the hole 15 'is formed on the finger electrodes 15, 15, ... A strip-shaped screen electrode 7 having a hole 7'corresponding to the hole 15 'of each finger electrode 15 is formed on the electrode 6, and all of the line electrodes 2, 2 ,. It is arranged so as to cover the part. The feed lines 2 ', 2' ... Of the line electrodes 2, 2, ... Are formed in three lines toward the both side surfaces of the support substrate 1 in this configuration example.
The 15 power supply lines 15 ″, 15 ″, ... Are alternately formed toward both side surfaces of the support substrate 1.

Then, the dielectric drum 8 is arranged so as to face the screen electrode 7 serving as the ion emitting surface of the thus configured ion head substrate and at a predetermined minute interval. The dielectric drum 8 is formed by providing a dielectric 10 on a cylindrical support 9 such as aluminum, and is configured to rotate at a constant speed.

Next, the electrostatic latent image forming operation will be described. First, as shown in FIG. 5, between the line electrodes 2, 2, ... And the finger electrodes 15, 15 ,. High-frequency high-voltage AC power supply 11 generates high-voltage AC voltage, for example, 1MHz
And apply a voltage of 2500 volts. Also finger electrodes
15 through the selector switch 12 to ground potential or negative voltage V _A
Is applied to the screen electrode 7, and the negative voltage V _{B having} a smaller absolute value than the negative voltage V _A applied to the finger electrode 15 is applied to the screen electrode 7.
Is applied.

By applying a high-voltage AC voltage between the line electrode 2 and the finger electrode 15, a discharge is generated in the hole 15 'of the finger electrode 15 and the air in the vicinity thereof is ionized. As shown in FIG. 5, when the changeover contact of the changeover switch 12 is on the a side, the negative voltage V _B is applied to the screen electrode 7 and the finger electrode 15 is at the ground potential,
The potential gradient is from the finger electrode 15 side to the screen electrode 7
Heading to the side. Therefore, among the ions generated in the vicinity of the finger electrode 15, negative ions are
It remains in the vicinity of.

When the changeover switch electrode 12 is switched to the b side, the negative voltage V _A is applied to the finger electrode 15. Since the absolute values of the negative voltages V _A and V _B are | V _A |> | V _B |, the potential gradient goes from the screen electrode 7 side to the finger electrode 15 side. Therefore, the negative ions remaining in the vicinity of the finger electrode 15 are accelerated toward the screen electrode 7 by this potential gradient and are discharged from the hole 7'to the dielectric drum 8 side. The released negative ions are held on the dielectric drum 8 and form a 1-dot latent image of the image. That is,
A latent image of a 1-dot unit pixel for image formation is formed by switching-controlling whether or not ions are emitted from the holes 7'of the screen electrode 7.

Next, a method of forming a latent image corresponding to a predetermined image from such dot-shaped unit pixel latent images will be described with reference to FIG. FIG. 6 is an enlarged view showing a part of the screen electrode of FIG. 4 with the screen electrode removed. In FIG. 6, a plurality of line electrodes are shown as 2 _-0 , 2 _-1 , ..... 2 _-5 in order to distinguish them, and finger electrodes 15a, 15b, 15c are also shown. In addition, the ion generating part formed at the intersection of the finger electrode and the line electrode is also displayed.
13 _a0 , 13 _b0 , 13 _c0 ... 13 _a5 , 13 with subscripts
It is displayed like _b5 , 13 _c5 . In order to briefly explain the image forming method, the ion head substrate has three finger electrodes 5a, 5b, 5c and six line electrodes 2 _-0 , as shown in the figure.
‥‥‥ be described as being composed of 2 _-5.

In the ion head substrate is configured as shown in FIG. 6, for example in order to generate ions only from the ion generating unit 13 _b4 drives the line electrodes 2 _-4, the finger electrodes 15b, by adding the signal The negative voltage (-V _A ) is applied to the ON state, and the other finger electrodes 15a and 15c are left in the OFF state to which the ground potential is applied without applying a signal. When the line electrode 2 _-4 is driven, as described above, ions are generated inside the ion generators 13 _a4 , 13 _b4 , 13 _c4 . However, since the finger electrodes 15a and 15c are in the OFF state, the ions generated in the ion generating parts _13a4 and _13c4 remain inside, while the finger electrode 15b is turned on by the signal.
As a result, the ions generated in the ion generator 13 _b4 are released from the inside, and the ion generator 13 _b4 on the dielectric drum 8 is released.
_A 1-dot latent image is formed at a position corresponding to _b4 .

Since the ion generating parts 13 _a0 , 13 _b0 , ..., 13 _c5 are arranged in a matrix, the line electrodes 2 _-0 , 2 _-1 ,
‥‥‥ 2 _-5 and finger electrodes 15a, 15b, the power supply to 15c,
By switching and applying each based on the signal,
Ions are selectively emitted from the ion generator to form a 1-dot latent image of a unit pixel on the dielectric drum, and by repeating such an operation, dots corresponding to a predetermined image are formed on the dielectric drum. Electrostatic latent image is formed.

The process of forming the electrostatic latent image on the dielectric drum will be further described. In the ion head device having the ion head substrate having the structure shown in FIG. 6, a linear latent image is formed in the lateral direction. In this case, first drive the line electrodes _2-0 and turn on the finger electrodes 15a, 15b, 15c,
As shown in FIG. 7 (A), ions are ejected on the recording line on the surface of the dielectric drum, that is, at positions corresponding to the ion generating portions 13 _a0 , 13 _b0 , 13 _c0 on a straight line parallel to the line electrode. _Dotted electrostatic latent images _14a0 , _14b0 , _14c0 are formed. Then, with the rotation of the dielectric drum to Figure 6 X direction, electrostatic latent image 14 _a0, 14 _b0, 14 _c0 reaches the position where the position of the formed recording line corresponding to the line electrodes 2 _-1 Then, the line electrode 2 _-1 is driven and the finger electrode 1 is similarly driven.
5a, 15b, when 15c to be in ON state, as shown in FIG. 7 (B), the ion generator 13 previously _a0, 13 _b0, 13 _c0 electrostatic latent image 14 _a0 formed by emitted ions from, Latent images 14 _a1 , 14 _b1 , and 14 _c1 are formed by the ions emitted from the ion generating portions 13 _a1 , 13 _b1 , and 13 _{c1 in} a state where they partially overlap with 14 _b0 and 14 _c0 .

Similarly, the line electrodes 2 _-2 , 2 _-3 , ... 2 _-5 are sequentially driven in synchronism with the rotation of the dielectric drum to sequentially form latent images by ion emission. As shown in C), a linear electrostatic latent image is formed. Further, by selectively driving the line electrodes and the finger electrodes, for example, FIG. 7 (D)
The character A can also be formed as a dot-shaped latent image, as shown in FIG.

The electrostatic latent image thus formed on the dielectric drum is subjected to predetermined developing, transferring, and fixing processes to form an image on recording paper.

[Problems to be solved by the invention]

By the way, when an electrostatic latent image is formed by an ion head device having an ion head substrate having such a configuration, some finger electrodes, for example, the finger electrode 15b in FIG. Is not turned on, no ions are emitted from the ion generating parts 13 _b0 , 13 _b1 , ..., 13 _b5 formed by the finger electrodes 15b, and the ion is generated on the dielectric drum corresponding to those ion generating parts. No electrostatic latent image is formed.

If an electrostatic latent image is formed in a line in the lateral direction in such a state of finger electrode failure or contact failure, ions will be emitted from the ion generators 13 _b0 , 13 _b1 , ... 13 _b5. The electrostatic latent image is line electrode 2 _-0 ,
As 2 _-1 , ... 2 _-5 are driven in sequence, they are formed as shown in Fig. 8 (B), (C), (D), and finally a straight line is cut in the middle. Is formed. Also, when an attempt is made to form a latent image of the letter A, FIG. 8 (E)
A latent image is formed in the state as shown in (1), and even if it is developed and transferred to recording paper, it becomes an unreadable image.

This is because, as shown in FIG. 9, the range in which a latent image in the horizontal axis direction can be formed on such an ion head substrate is 15 _aw , 1 independently by each finger electrode 15a, 15b, 15c.
This is because it is defined as shown by 5 _bw and 15 _cw , and there is only one finger electrode that forms a dot-shaped latent image at any position in the horizontal axis direction. Therefore, when a signal is not applied to the finger electrode 15b due to a failure as described above, a latent image is not formed in the latent image forming area _15bw of the finger electrode 15b. Thus, in the conventional ion head device,
If a recording signal input failure occurs even in the finger electrodes of the book, there is a problem that it greatly impairs image formation.

The present invention has been made to solve the above problems in the ion head device of the conventional image forming apparatus, and does not affect the image quality even if a recording signal input defect partially occurs. An object is to provide a recording head device of an image forming apparatus.

In order to solve such a problem, the present invention provides a recording head device of an image forming apparatus that selectively irradiates an image receiving member with ions to form an electrostatic latent image. Line electrodes, a plurality of finger electrodes that intersect the line electrodes at a predetermined angle to form a matrix together with the line electrodes, and a large number of pixel formation portions formed at the intersections of the line electrodes and the finger electrodes. And the plurality of finger electrodes are arranged such that the latent image forming areas of the pixel forming portions belonging to the individual finger electrodes overlap in the horizontal axis direction.

That is, as shown in FIG. 1, each finger electrode 5a, 5a
Each latent image forming area in which a latent image is formed by b, 5c overlaps with the latent image forming area of each adjacent finger electrode, so that each finger electrode 5a, 5b, 5c,
Adjacent electrodes are arranged so as to overlap each other in the lateral direction. In FIG. 1, the latent image forming area 5 _bw carried by the finger electrode 5b is overlapped with the latent image forming areas 5 _aw and 5 _cw carried by the adjacent finger electrodes 5a and 5c, respectively. The two finger electrodes are overlapped with each other in the forming range, and are formed so as to be shared by the two finger electrodes.

With such a configuration, FIG. 2 (B) to (D)
First, a primary pixel is formed every other pixel, and then a secondary pixel is formed between the already formed pixel and the pixel as shown in FIG. 2 (E). .

Further, by configuring in this way, even if the recording signal is not input to some finger electrodes, for example, the finger electrode 5b, the latent image forming range of this finger electrode 5b, adjacent finger electrodes 5a and 5c A latent image is formed by the ion generating portion arranged above, and it is possible to prevent the remarkable deterioration of image quality.

〔Example〕

Examples of the present invention will be described below. Figure 2 (A)
Shows an ion head substrate portion of an embodiment in which the present invention is applied to an ion head device. In the figure, 2 _-0 , 2 _-1 , ...
_2-5 are line electrodes for applying high frequency high voltage, 5a, 5b, 5c, 5d
..... is a finger electrode that controls the ion flow, 13 _a0 , 13
_{b0, ‥ ... ‥ 13 a1,} 13 b1, ‥ ... ‥ 13 a5, 13 b5, ‥ ... ‥ is,
The ion generation part formed in the intersection of a line electrode and a finger electrode is shown. In this ion head substrate, the area in which each finger electrode forms a dot-shaped latent image is configured so as to partially overlap the latent image forming areas in the other finger electrodes adjacent to both sides of the finger electrode. Therefore, even if ions are not generated in a specific ion generation part, the ion generation part that can form a latent image is arranged at a position sufficiently close to the position where the ion generation part forms a latent image. It seems to be.

In the ion head substrate thus configured,
Now, for example, when the line electrode _2-0 is driven when the recording signal for turning on the ion generating portion to the finger electrode 5b is not applied due to a failure or the like, as shown in FIG. 2 (B). In addition, the electrostatic latent image is formed on the dielectric drum, and the latent image is not formed at the position indicated by the dotted line corresponding to the ion generating portion _13b0 .

In the case of forming a linear latent image in the lateral direction, by sequentially driving the next line electrodes 2 _-1 , 2 _-2 , ... 2 _-5 ,
As shown in FIGS. 2 (C), (D), and (E), latent images are formed, and as can be seen from FIG. 2 (E), finger electrodes are formed.
Despite the fact that the ion generators 13 _b0 , 13 _b1 , ... 13 _b5 on 5b do not operate, the electrostatic latent image is formed linearly without interruption in the middle, and significant deterioration in image quality is recognized. There is no state.

At this time, even if there are many overlapping portions of the dot-shaped electrostatic latent images, the potential of the electrostatic latent image formed by only one dot and
When there is no significant difference in the density after development due to the potential of the electrostatic latent image formed by overlapping dots or more dots, that is, the potential of one dot of the electrostatic latent image is in the potential-density characteristic curve. If it is equal to or higher than the saturation potential, almost no deterioration in image quality is recognized.

As described above, the recording signal is not transmitted to a part of the finger electrode, and therefore the ion generating portion on the finger electrode does not generate ions, and a dot-shaped electrostatic latent image is not formed on the dielectric drum. However, it is possible to prevent the deterioration of the image quality by being covered by the ion generating portions of the adjacent finger electrodes.

Further, in the conventional ion head device shown in FIG. 6, when a straight line is drawn in the horizontal axis direction, for example, as shown in FIG. Since the electrostatic latent image pixels are formed as described above, the newly formed pixels are not always circular uniform pixels due to the influence of the potential of the left pixel, and the left and right pixels of only the last pixel group. There is a problem in that the pixel shape is locally changed largely due to the influence of the potential.

However, according to the ion head device of this embodiment, as shown in FIG. 1, the latent image forming areas of the ion generating portions, which are the pixel forming portions belonging to the individual finger electrodes, are overlapped in the horizontal axis direction. As shown in FIG. 2 (E), even when pixels are formed with the same density as the ion head device shown in FIGS.
Since the next pixel is formed and then the secondary pixel is formed between the already formed pixel and the pixel, the influence of the potential from the already formed primary pixel is always equal to the left and right when the secondary pixel is formed. Therefore, only the last pixel is not locally largely deformed, and a high-definition image is formed.

FIG. 3 is a schematic diagram showing a second embodiment of the present invention. In _{FIG, 2 -0, 2 -1, ‥} ... ‥ 2 -5 the line frequency voltage electrode, 5a ', 5b' ‥‥‥ 5f ' are finger electrodes for controlling the ion flow, 13 _a0', 13 _b0 ', ... 13 _f0 ',
... 13 _a5 ', 13 _b5 ', ... 13 _f5 'indicate the ion generating portions existing on the intersections of the line electrodes and the finger electrodes.
In the ion head substrate of this embodiment, the area in which one finger electrode forms a dot-shaped latent image is two finger electrodes adjacent to both sides thereof, that is, a total of four finger electrodes.
Each finger electrode is arranged so as to partially overlap with each latent image forming area of each finger electrode. Then, even if ions are not generated in an arbitrary ion generating part, two other ion generating parts that can form a latent image at the same position where the ion generating part forms a latent image are arranged. It is configured to be.

With this configuration, assuming that a recording signal is not applied to the finger electrode 5c 'due to an obstacle or the like, when the line electrode _2-0 is driven, the ion generating portion _13c0 ' is formed on the dielectric drum. No electrostatic latent image is formed. However, the position where the ion generator 13 _c0 ′ should form a latent image is determined by the rotation of the dielectric drum.
When it reaches directly under 3 _b2 ', the line electrode _2-2 and the finger electrode 5b' are driven so that ions are generated from the ion generating part _13b2 'and an electrostatic latent image is formed at the above position. Even when the position on the dielectric drum reaches directly below the ion generating part 13 _a4 ′, the ion generating part is
Ions are generated from 13 _a4 ′ and overlapped to form an electrostatic latent image. That is, in the ion head substrate thus configured, three ion generating portions capable of forming a one-dot electrostatic latent image are arranged at the same position, and there is an ion generating portion that does not generate ions for some reason. Even so, the image quality is not further affected.

〔The invention's effect〕

As described above based on the embodiments, according to the present invention, it is possible to suppress a local pixel shape change and form a high-definition electrostatic latent image. Further, even if a recording signal input defect partially occurs, the image quality is not affected.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view for explaining a basic configuration of the present invention, FIG. 2 (A) is a schematic diagram showing a first embodiment of the present invention, and FIGS. 2 (B), (C), (D) and (E) are views showing a latent image forming state according to the embodiment shown in FIG. 2 (A), FIG. 3 is a schematic view showing the second embodiment, and FIG.
A plan view of an ion head substrate of a conventional ion head device,
FIG. 5 is a partially enlarged sectional view thereof, FIG. 6 is a partially enlarged plan view of the ion head substrate shown in FIG. 4, and FIGS. 7 (A), (B), (C) and (D ) Are views showing a latent image forming mode by the ion head substrate shown in FIG. 6, respectively.
FIG. 8 (A) is a partially enlarged plan view of an ion head substrate similar to that shown in FIG. 6, FIG. 8 (B), (C),
(D) and (E) are views showing a latent image forming mode when the operation of some finger electrodes in the ion head substrate shown in FIG. 8 (A) is stopped, and FIG. 9 is shown in FIG. It is a figure which shows the latent-image formation range of each finger electrode in the ion head substrate. In the figure, 2 _-0 , 2 _-1 , ... 2 _-5 are line electrodes, 5a, 5b, 5
c and 5d are finger electrodes, 13 _a0 , 13 _b0 , ... 13 _a5 , 13 _b5 ,
...... indicates an ion generating part, and 5 _aw , 5 _bw , 5 _cw , and 5 _dw indicate latent image forming areas.

Claims (3)

[Claims] 1. A recording head device of an image forming apparatus for selectively irradiating an image receiving member with ions to form an electrostatic latent image, comprising: a plurality of line electrodes arranged in a horizontal axis direction; A plurality of finger electrodes that intersect at a predetermined angle and form a matrix together with the line electrodes, and a large number of pixel formation portions formed at the intersections of the line electrodes and the finger electrodes, The recording head device of the image forming apparatus, wherein the electrodes are arranged such that the latent image forming areas of the pixel forming portions belonging to the individual finger electrodes overlap in the horizontal axis direction. 2. A pixel forming section belonging to different finger electrodes from each other so that adjacent pixels are formed over the entire image roughness on the recording line.
A recording head device of the image forming apparatus according to the above item. 3. The finger electrode according to claim 1, wherein the pixel forming portions belonging to the plurality of finger electrodes are arranged so as to correspond to substantially the same pixel positions on the recording line. Head device of the image forming apparatus of.