JPS626382B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrostatic recording method used, for example, in facsimiles and printers. Conventionally, in recorded images obtained by multi-stylus type electrostatic recording devices, density unevenness occurs more or less periodically along the screen. Proposals to solve this problem have been made in the past, but nothing definitive has yet been made. Examples of what has been proposed so far are as follows. FIG. 1 is a diagram for explaining an example of a conventional electrostatic recording method proposed for eliminating density unevenness in recording. In Fig. 1, 1 is a multi-stylus divided into blocks (also called recording electrode group);
2 is an electrostatic recording paper, 3 is an auxiliary electrode (also called a counter electrode), S ₁ , S ₂ ......S〓...Sn is an input terminal of the multi-stylus 1, B ₁ , B ₂ , B ₃ are auxiliary electrodes The input terminal of electrode 3 is shown. In the electrostatic recording method shown in FIG. 1, three auxiliary electrodes 3 are arranged symmetrically with respect to the multi-stylus 1 of the first block, and the electrostatic recording paper 2 is located between the multi-stylus and the auxiliary electrode. . During scanning recording, first, when recording with the stylus in the first half of the first block, the input terminals _S1 to S〓 (however, n
is an even number), and the auxiliary electrode B ₁
A voltage of opposite polarity to the voltage applied to S ₁ to S is applied to and B ₂ . As a result, discharge occurs in the stylus in the first half of the first block, and the electrostatic recording paper 2 is charged with electric charge to form an electrostatic latent image. In the second half of the first block, voltages are applied to the terminals S ₊₁ to Sn and the auxiliary electrodes B ₂ and B ₃ to form an electrostatic latent image. Similarly, the second
After forming one line of electrostatic latent image by sequentially scanning the block and third block, it is developed and fixed by an appropriate method to record. However, with this method, due to the potential distribution generated in the conductive layer (not shown) of the electrostatic recording paper 2, a portion of low recording density occurs every 1/2 block of the multi-stylus 1, and such electrostatic recording Unique recording unevenness occurs. Therefore, in order to prevent this uneven recording, the conventional method is to scan the stylus of the first half or the second half of the block to be recorded from both ends toward the center, instead of sequentially scanning the multi-stylus 1. This is an example of a proposal. However, in the conventional method for eliminating recording unevenness as described above, voltage is sequentially applied to each stylus in a divided multi-stylus group one by one or several styli in series. The scanning time for one line is limited because of the 10 μs to 100 μs, which has the disadvantage that it cannot be used particularly in high-speed electrostatic recording devices. For example, if the total number of recording electrodes (also referred to as a stylus) for one line is N and the recording electrode energization period is T, then the one line scanning time t _L in the conventional example described above is expressed by the following equation. t _L = T x N/2 As a representative value in the above formula, N = 2000 pieces T =
Substituting 100 μs gives t _L =100 ms. In other words, it takes 100ms to scan one line, and for example, one A4 sheet of recording paper has a linear density of 8 lines/mm.
If we consider the case where recording is performed, the recording time t _P is as follows. t _P = 100ms x 300mm x 8 lines/mm = 240 seconds = 4 minutes In other words, the conventional technology can only be used in low-speed recording devices where the recording speed for one sheet of A4 paper is about 4 minutes. , it cannot be used in recording devices that take advantage of the high speed, which is the greatest feature of electrostatic recording. Therefore, the recording speed that has been developed in recent years
In a high-speed recording device of about 10 seconds, it is inevitably necessary to drive a large number of recording electrodes simultaneously. For example, in order to record one A4 sheet of recording paper in 10 seconds with the above specifications, it is sufficient to drive 24 recording electrodes simultaneously. This invention was made based on the above-mentioned technical background, and therefore, the purpose of this invention is to apply it to a high-speed type that aims to eliminate recording unevenness peculiar to electrostatic recording. The purpose is to provide an electrostatic recording method. The gist of the configuration of this invention is that recording unevenness occurs in the electrostatic recording method because the potential distribution during recording on the recording medium is not uniform, and that the cause is that voltage is applied twice to the same auxiliary electrode in succession. Recognizing that this is the point of performing the following steps, we have avoided applying voltage multiple times in a row. Hereinafter, first, the mechanism of periodic density unevenness occurring in the electrostatic recording method will be clarified, and then embodiments of the present invention will be explained. FIG. 2 is a diagram for explaining the mechanism of occurrence of density unevenness, and shows the arrangement relationship between the recording paper and the electrodes, the voltage drive waveform at the electrodes, the potential distribution at the electrodes, etc. FIG. 3 is a diagram showing the mode of density unevenness that occurs on the recording paper in the arrangement relationship between the recording paper and the electrodes as shown in FIG. In these figures, 1 is a recording electrode group (the S symbol is used to identify the recording electrode groups), and 2 is a recording paper, which includes a base layer 2-1, a conductive layer 2-2, and a dielectric layer 2-3. It consists of. 3 is an auxiliary electrode (a B code is used to identify the auxiliary electrodes). The mechanism of density unevenness will be explained using a double-sided recording method, which is a typical example of electrostatic recording, as an example. As is well known, the double-sided recording method means that two sheets of recording paper
Voltages of opposite polarity are applied to a series of auxiliary electrode group B and recording electrode group S, which are arranged opposite to each other, and the sum of the absolute values of both voltages causes a discharge on the dielectric layer surface 2-3, and the static This is a method to obtain a charge image. In this explanation, an example will be taken in which a positive voltage is applied to the auxiliary electrode 3 and a negative voltage is applied to the recording electrode group 1 to obtain a negative electrostatic latent image, which is visualized with an appropriate toner and then fixed. Density unevenness for each recording electrode group S (see FIG. 3) does not occur in the process after visualization, but is caused when a latent image is created, so this will be explained. The latent image forming process consists of sequentially driving the auxiliary electrode group B and the recording electrode group S.
That is, the manner in which both electrode groups are driven is as follows.

[Table] As shown in Figure 2, for example, when auxiliary electrodes Bi-1 and Bi are driven by voltage, a, recording electrode Si-1 is driven, and then Bi and Bi+1 are driven b. while driving Si, then driving Bi+1 and Bi+2 c
while driving Si+1, scanning to the right in FIGS. 2 and 3. Moreover, it will be clear from the above description that each of the auxiliary electrodes 3 is continuously driven twice during one line of scanning. In fact, this two-time continuous drive is the cause of uneven density. The reason is as follows. The voltage applied to the auxiliary electrode 3 charges the capacitance of the base layer 2-1 of the recording paper 2 and then reaches the conductive layer 2-2 of the recording paper. On the other hand, when a voltage is applied to the recording electrode group 1 at the same time as the auxiliary electrode 3, the voltage applied to the auxiliary electrode 3 charges the capacitance of the base layer 2-1 and charges the conductive layer 2-2.
At the point in time, a discharge occurs due to the voltage applied to the recording electrode group 1. i.e. for example auxiliary electrodes
When a voltage is applied to Bi and Bi+1 (Fig. 2 b) and a voltage is applied to the recording electrode Si (Fig. 2 h), the recording electrode
An electrostatic latent image is obtained on the recording paper directly under the Si. However, since the voltage has been applied to the auxiliary electrode Bi once before (i.e., when the recording electrode Si-1 was energized) (Fig. 2a), the potential rise rate of the conductive layer directly under the auxiliary electrode Bi is not the same. The rate of potential increase in the conductive layer portion directly below the auxiliary electrode Bi+1 is different. In other words, since the auxiliary electrode Bi has been energized once before, the capacitance of the base layer 2-1 directly below it is in a charged state to some extent. In other words, it is not completely discharged. Therefore, the time required for the voltage applied to the auxiliary electrode Bi to be transmitted to the conductive layer 2-2 is short. On the other hand, since the auxiliary electrode Bi+1 is energized for the first time, the potential of the conductive layer increases after first charging the capacitance of the base layer directly below it. The time for charging the base layer 2-1 described here does not pose much of a problem if the voltage application time to the auxiliary electrode 3 is long enough, but in cases where the voltage application time cannot be too long, for example for high-speed recording. If this is done, it becomes impossible to ignore, and density unevenness occurs due to the difference in potential rise speed. This situation is explained in FIGS. 2e to 2g. Auxiliary electrodes Bi and Bi+
When a voltage is applied to the auxiliary electrode Bi+, the potential rise in the conductive layer directly under the auxiliary electrode Bi is fast, as shown in Fig. 2e, for the reason mentioned above.
The potential rise in the portion of the conductive layer immediately below 1 is slow, as shown in FIG. 2f. In reality, the potential distribution is a combination of both (Fig. 2g). In this state, the recording electrode Si
When a voltage is applied to (Fig. 2h), the potential distribution g
A discharge occurs based on the composite waveform i of and h. This composite waveform i becomes flat over the width of the recording electrode as time passes, but as mentioned earlier, in a high-speed recording device where the voltage application time of the recording electrode is not long enough, Image recording will be performed under the potential distribution state of waveform i. For this reason, as shown in FIG. 2J, within one recording electrode group Si, the recording density decreases along the scanning direction, causing density unevenness. In other words, the first half of the recording electrode group (for example, Si) has a relatively high concentration, and the concentration decreases toward the second half. Since this is periodically repeated for each recording electrode group, an image with periodic density unevenness as shown in FIG. 3 is created. As explained in detail above, periodic density unevenness in electrostatic recording is caused by the non-uniform potential distribution directly under the recording electrode group, and the reason for the non-uniform potential distribution is that The idea is to drive the electrodes twice in succession. Therefore, if this point is solved, periodic density unevenness can be eliminated. FIG. 4 is a diagram showing an embodiment of the present invention. In FIG. 4, 4 is a shift register, 5 and 5a are buffer registers, 6 is an inverter, D is a drive circuit for auxiliary electrode B, V is a drive circuit for recording electrode group S, and R is each stage of shift register 4. ,A
indicates an and gate, and OR indicates an or gate. Please refer to FIG. A recording medium (not shown) is placed in contact with the auxiliary electrode B and the recording electrode group S, and a voltage is applied to both types of electrodes to perform electrostatic recording on the recording medium. The manner of voltage driving the auxiliary electrode B and the recording electrode S will be described below. First, when the switching signal to the AND gate is on, the AND gate A1 opens and the data input is held in the buffer register 5. Now, it is assumed that clock pulses CP sequentially enter the shift register 4 and drive each stage of the shift register 4. When stage R1 is first driven, drive circuits D1 and D2 operate to voltage drive auxiliary electrodes B1 and B2. At this time, the recording electrode group S11 is driven via the drive circuit V11 according to the data content held in the buffer register 5. Next, when stage R2 is driven in shift register 4, drive circuits D3 and D4 operate to drive auxiliary electrode B.
3 and B4. At this time, the recording electrode group S12 is driven by the drive circuit V12. Similarly, when stage R3 in shift register 4 is driven, drive circuit D5
and D6 operate to drive auxiliary electrodes B5 and B6. At this time, the recording electrode group S13 is driven by the drive circuit V13. When the switching signal is turned off, the AND gate A2 is opened by the action of the inverter 6, and the data input is entered into the buffer register 5a and held there. In this state, when stage R4 is driven in shift register 4, drive circuits D2 and D3 operate and auxiliary electrodes B2 and B3 receive voltage drive. At this time, the recording electrode group S21 is driven by the drive circuit V21 according to the data content held in the buffer register 5a. Thereafter, in the same manner, stage R5 of shift register 4 is driven, drive circuits D4 and D5 operate, and auxiliary electrodes B4 and B5 are driven. At this time, recording electrode group S2
2 is driven by a drive circuit V22. Depending on the drive of stage 6 in shift register 4, drive circuits D6 and D7 operate to drive auxiliary electrodes B6 and B7. At this time, the recording electrode group S23 is driven by the drive circuit V23. In addition, the clock pulse
It goes without saying that CP, switching signal on/off control, data input control, etc. are performed based on control commands with appropriate timing from a system control circuit (not shown). The manner of driving the auxiliary electrode B and the recording electrode group S described above is summarized in the following table.

[Table] As is clear from this table, auxiliary electrode B is
No electrode is driven twice in succession.
For example, the auxiliary electrode B2 is driven in the drive order, but it is driven next in the order,
The auxiliary electrode B3 is not driven to the rank after being driven in the rank. In this way, no auxiliary electrode is driven twice or more consecutively, and this point is different from the conventional electrostatic recording method. FIG. 5 is a diagram showing another embodiment of the invention. Note that the numbers in circles indicate the order of voltage drive of the electrodes. In the embodiment shown in FIG. 4, the recording electrodes were divided into two groups and driven, but this embodiment differs in that they are divided into three groups G1, G2, and G3 and driven. First, the auxiliary electrodes B1 and B2 and the recording electrode group S1 opposite thereto, then B4 and B5.
and S2 opposite it, then B7 and B8 and S3 opposite it, then B2 and B3 and S4 opposite it, etc., and so on, every auxiliary electrode is repeated twice or twice in succession. The above is the same as the embodiment shown in FIG. 4 in that it is not driven. FIG. 6 is a diagram showing a third embodiment of the present invention. The recording electrode group is divided into three groups, which is the same as the embodiment shown in FIG. 5, but the driving order is different. First, auxiliary electrodes B1 and B2 and the recording electrodes facing them, then B3 and B4 and the recording electrodes facing them, then B5 and B6 and the recording electrodes facing them, and so on, the recording electrode group G1 The voltage is applied in the repeating order of →G2 →G3. As is clear from the above detailed explanation, according to the present invention, a major cause of density unevenness in electrostatic recording has been eliminated, so even in high-speed electrostatic recording methods, density unevenness can be reduced. This has the advantage that a good record of no occurrences can be obtained. It goes without saying that the present invention is applicable to both cases where a single-sided control method or a double-sided control method is adopted as electrode voltage distribution in electrostatic recording.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a conventional example proposed for eliminating density unevenness in electrostatic recording, Fig. 2 is a diagram for explaining the mechanism of density unevenness occurring in a conventional electrostatic recording method, and Fig. 3 FIG. 4 is a diagram showing an embodiment of the present invention, FIG.
The figure similarly shows the second embodiment, and FIG. 6 similarly shows the third embodiment. In the figure, 1 is a multi-stylus (also called a recording electrode group), 2 is an electrostatic recording paper, 3 is an auxiliary electrode (also called a counter electrode), 4 is a shift register, 5 and 5a are buffer registers, and 6 is an inverter. , D is a drive circuit for the auxiliary electrode, V is a drive circuit for the recording electrode group, S is the recording electrode group or its input terminal,
B is an auxiliary electrode or its input terminal, R is a shift register stage, A is an AND gate, OR is an OR gate, CP is a clock pulse, and G is a group.

Claims (1)

[Claims] 1. It has a plurality of recording electrode groups divided into groups, and a plurality of auxiliary electrodes for one recording electrode group and arranged astride adjacent recording electrode groups of the recording electrode group. In an electrostatic recording method in which an electrostatic latent image is formed on a recording medium by sequentially switching and driving the auxiliary electrodes with voltage, the same auxiliary electrode is not continuously driven with voltage. Electrostatic recording method.