JPH0117867B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electrostatic printing devices, so-called electrostatic printers, blocks. (Hereinafter, electrostatic printing devices will be referred to as electrostatic printers.) Conventional electrostatic printers have a dot configuration, as shown in Figures 1 and 2, and are used for low-speed facsimiles, etc. The electrostatic pin 1 is brought into direct contact with the electrostatic recording medium 2 to create an electrostatic latent image using a pulse signal.
Alternatively, a static fixing method is used, in which several hundred to several thousand electrostatic pins 1, called a multi-stylus 5, which are used in high-speed line printers, are embedded in resin in one to several rows. Alternatively, an electrostatic latent image is created on the electrostatic recording medium 2 by applying voltage to a dynamic circuit in several blocks.

By the way, the method shown in Figure 1 has a slow writing speed of about 1 to 5 minutes for one sheet of _A4 paper due to the mechanical scanning speed of the needle electrode, and is not intended to be faster. For example, the only way to make scanning easier was to increase the number of needle electrodes to the level of resolution, as shown in FIG.

This means that the multi-stylus 5 is required, and in order to cover the _A4 size horizontally at 10 dots/mm, it is necessary to arrange more than 2000 needle electrodes in an orderly manner. Naturally, a dynamic drive system in which control electrodes 6 are provided for each block as shown in FIG. 3, or a dynamic drive system using a matrix 33 as shown in FIG. 4 had to be adopted. 31 is a block signal generating section, and 32 is a print signal generating section. However, the relationship between the needle electrodes 1 is very close (for example,
(approximately 50μ), crosstalk occurs due to capacitive coupling caused by floating capacitance.
It is essential to control the width of the applied voltage and the potential of the needle electrodes adjacent to each other.

Furthermore, as a conventional image forming method, there is a method in which matrix electrodes are used above and below an electrostatic recording medium, and controlled driving is performed so that printing is performed only when voltage is applied to both electrodes. If there is a gap between them, the image will be distorted due to the charge, so it is necessary to bring the recording medium into contact with the electrode, and at that time, a fairly large pushing force is required to achieve reliable contact, so it is difficult to quickly In addition to problems such as missing prints, when an electrode is brought into contact with an electrostatic recording medium and a voltage is applied, the current flows over a fairly wide range, resulting in poor resolution and difficulty in improving print quality. Ta. For details, please refer to "Electronic Photography, Volume 7, No. 3, Pages 102 and 103."

From the above, conventional electrostatic printers can only be made at low speed if the main focus is on simplifying the mechanism, cost, and lowering the price.If a writing electrode with a multi-stylus is adopted to increase speed, it is possible to make a multi-stylus printer. Both the stylus and driver are very complex and large.
It was expensive and could only be applied to very limited applications, such as output terminals (line printers) for large computers.

Now, in recent years, the prices of CPUs, memory, etc. have been lowered due to the advancement of semiconductor technology, and the prices of microcomputers, office computers, etc. have also become lower. As EDPS has expanded from only special experts to the general public, there has been a strong resistance to output in Roman characters and katakana, and there has been a strong desire for output in kanji and kana letters.

Furthermore, Japanese word processors and the like, which did not previously exist, are approaching the point where they can be widely used in terms of cost.

However, as mentioned above, the prices of circuits and memory for such systems have been steadily decreasing, and this is expected to continue in the future, but when it comes to printers, which are one of the output terminals, Because we use kanji, etc., the resolution of 5 x 7 dots or 9 x 11 dots, which was sufficient for conventional alphanumeric characters, is not sufficient to express the kanji-like character, and if you want a certain degree of print-like character. A resolution of about 32 x 32 dots was required, and of course high resolution and high speed needed to cope with the drop in printing speed caused by high resolution, making the printer extremely expensive. It is closed. Currently, there are only optical printers that use lasers, OFT (optical fiber tubes), and multi-stylus electrostatic printers that can satisfy this requirement, and both are extremely expensive, resulting in the cost of the entire system. This is a major factor that is hindering the system's penetration into the market (despite the market need for it). The above situation is basically the same for high-speed facsimile machines and CRT hard copying machines.

In view of this situation, the prior art of the present invention attempted to provide an epoch-making printer using the principle of electrostatic recording, and its purpose was to provide high resolution, high quality,
The purpose of the present invention is to provide a printing principle and configuration that allows a high-speed electrostatic printer to be manufactured with a simple configuration, high reliability, small size, and low cost.

Next, the basic structure and printing principle of a prior example of the present invention will be described.

FIG. 5 shows an example of the structure of the write signal generating section, in which one or more linear electrodes 9 are wound around a cylindrical drum 8, which is a substrate.

The substrate 8 may be a conductor, but in that case, the linear electrode 9 must be raised above the substrate 8 as shown in FIG. When the substrate 8 is an insulator, the surface of the linear electrode 9 is on the substrate 8, as shown in FIGS. 7 and 8.
The heights of the surfaces of the two surfaces may be the same, or they may be drawn in on the contrary.

The configuration of the linear electrode 9 is one example, and the configuration is not limited thereto.

Next, the signal forming section is composed of a thin film layer 11 having an end surface 10 as shown in FIG. The shape of the end face may be a straight line as shown in FIG. 9, or may be non-straight as shown in FIG. 10 depending on the usage. Moreover, the cross section of the end face part is the first
1, Fig. 12, Fig. 13, etc. are various. Therefore, the end surface may be a band-shaped surface or a linear surface with a pointed tip.

Next, an example of the structure according to the present invention is shown in FIGS. 14a and 14b and FIG. 15, and the printing principle thereof will be explained.

A wire electrode 9 is spirally wound on a rotating cylindrical drum 8, and adjacent thereto in a plane parallel to the axis of the cylindrical drum 8, a thin film layer 11 having an end surface 10, which is a signal forming part, is placed. ing. The distance between the linear electrode 9 and the thin film layer 11 is 50~
Approximately 150 μm is appropriate, but in order to reduce the size of generated dots, the shorter the distance, the better. However, if they come into contact, wear becomes a problem.

Furthermore, an electrostatic recording medium 2 is placed in front of the electrostatic printing signal generating section configured in this manner in proximity to or in contact with the electrostatic printing signal generating section, and a back electrode 12 is provided on the opposite side from the electrostatic printing signal generating section, and the shaped electrode 9 and the back electrode 1
The structure is such that a voltage is applied between the two. Furthermore, a developing section 30 and a fixing section 31 are connected.

The principle function of the signal forming section will be explained with reference to FIG. A thin plate of a signal forming section consisting of a two-layer structure of a thin ferromagnetic layer 13 and a resistor layer 14 covering its upper surface and end surface is placed on the electrostatic recording material 2 that is sent over the back electrode 12 on the back electrode 12 side. It is attracted by the magnet 15. When a voltage pulse is applied to the line electrode 9, a discharge occurs between the line electrode 9 and the nearest point on the resistor layer 14, and the generated space charge 16 is transferred to the electrostatic recording material along the end surface 10 of the signal forming section. 2 and creates an electrostatic latent image. Originally, the discharge image formed by the line electrode 9 would be a line, but by adjusting the position of the signal forming section, it can be formed into dots. However, since the space charge 16 diffuses while descending along the end face 10 of the signal forming part, the signal forming part must be thin and is brought into close contact with the electrostatic recording medium by magnetic force. Since the ferromagnetic thin layer 13 is a conductor, if this end face is exposed, the charges generated by the discharge will be absorbed by the ferromagnetic thin layer 13 before reaching the electrostatic recording body 2. Among the charges generated by the discharge, those that arrive on the resistor push up the potential of this portion and reduce the potential difference in the discharge gap 17, so that the discharge is stopped. If the resistor layer 14 is a conductor, the charge generated by the discharge will not be retained on the resistor layer 14, and the potential difference in the discharge gap 17 will not decrease, so the discharge will not stop. In order to print a page with this printing device, discharge must be repeated at the same location in the signal forming section at certain time intervals depending on the printing speed. For this, the charge held on the resistor layer 14 must escape to ground during this time interval. This time is determined by the time constant of the escape route. As described above, the resistance value of the resistor layer 14 is determined during the sufficient time (about 100 ms) to stop the discharge.
must be large enough to hold a charge,
Sufficient time (1ms) to repeat discharge at high speed
It must be small enough to allow the charge to escape. The specific resistance of a resistor that satisfies this requirement is 10 ³ to 10 ⁸ Ωcm for a 10 μm resistor layer, but there are not many materials that have such a specific resistance and a high electrical breakdown voltage. In the two-layered signal forming section, if the resistance layer 14 is destroyed, the resistance value decreases and the amount of discharge increases, resulting in an increase in the size of the dots formed.

The present invention uses a three-layer structure forming part in order to overcome such drawbacks and stabilize a small amount of discharge even when using a material with a low electrical breakdown voltage, and will be described below.

The signal forming section with the three-layer structure is as shown in Fig. 17.
It has a structure in which an insulating layer 18 is sandwiched between a ferromagnetic thin layer 13 and a resistive layer 14 covering its upper surface and end surfaces. FIG. 18 shows an equivalent circuit of a discharge system when a three-layered signal forming section is used. When a high voltage is applied to the discharge gap 17 between the wire electrode and the resistor layer by the high-voltage pulse generator 19, the generated discharge charge is transferred to the capacitance 20 in the thickness direction of the resistor layer that has moved through the discharge gap 17, and is placed in series therewith. The capacitor 21 formed by the insulating layer is charged to reduce the potential difference in the discharge gap 17, and the discharge ends. The double structure lacks this capacitor 21, but in the triple structure, the presence of this capacitor 21 reduces the combined capacitance of the entire system. Since the amount decreases greatly, the discharge stops with a small amount of discharge. In addition, since the voltage is divided between the resistor layer and the insulating layer, the resistor layer is difficult to break down, and even if it breaks down, the discharge charge will be directly connected to the ground 2.
4, so the amount of discharge does not become excessive. 2
2 and 23 are the resistances in the thickness direction of the resistor layer, respectively;
This is the resistance in the plane direction. The charge held on the resistor layer and stopping the discharge escapes to the ground 24 through the resistor 23 and enables the next discharge. The present invention will be explained in detail below using examples.

Example Using a board made of permalloy rolled to a thickness of 30 μm as a substrate, a 25 μm thick polyimide layer was used as an insulator layer, and a polyimide layer was coated with carbon particles uniformly diffused onto the polyimide layer as a resistor to a thickness of 15 μm to reduce the overall thickness.
70μm, -1000V, 10ms width pulse applied,
We succeeded in forming dots with a diameter of 100 μm. When this pulse was applied at a period of 1 ms and discharge was caused at the same location on the end face of the signal forming part, the discharge did not fail due to delayed escape of the charge. The sheet resistance of the resistance layer is
10 ⁹ Ω/□.

As a material for the resistor, a material obtained by diffusing a conductor such as carbon particles or semiconducting particles such as iron oxide in an organic material such as polyimide, polyethylene, or polyester, or a thick film resistor paste can be used. The insulator layer may be made of polyimide or any material that can form a thin layer with high dielectric strength.

As described above, the present invention provides an inexpensive printing device that can stably form high-resolution images (10 dots/mm) at high speed.

[Brief explanation of drawings]

Figure 1: Outline of a conventional low-speed electrostatic printer.
Figure 2: Outline of a conventional high-speed electrostatic printer. Fig. 3: An example of the dynamic drive system of a conventional high-speed electrostatic printer; Fig. 4: Another example of the dynamic drive system of a conventional high-speed electrostatic printer; Fig. 5: an example of the dynamic drive system of a conventional high-speed electrostatic printer; Another example of the configuration of the write signal generating section according to the prior example, FIG. 6...An example of a cross section of the write signal generating section according to the prior example of the present invention, FIG. 7...
...Another example of the cross section of the write signal generating section according to the prior example of the present invention, FIG. 8...Another example of the cross section of the write signal generating section according to the prior example of the present invention, FIG. An example of a signal forming section according to a prior example, FIG. 10...
Another example of the signal forming section according to the preceding example of the present invention, FIG. 11...An example of a cross section of the signal forming section according to the preceding example of the present invention, FIG. 12...Other example of the signal forming section according to the preceding example of the present invention An example of a cross section, FIG. 13: An example of another cross section of a signal forming section according to a prior example of the present invention, FIG. 14: An example of the configuration of an electrostatic printing apparatus according to a prior example of the present invention (electrostatic printing signal generation section only), No. 15
Figure: An example (overall) of the configuration of an electrostatic printing device according to a prior example of the present invention, Figure 16: A ferromagnetic layer and a resistor layer are used in the signal forming section of an electrostatic printing device according to a prior example of the present invention. FIG. 17 is an example of a configuration using a two-layer structure consisting of a ferromagnetic layer, a resistor layer, and a three-layer structure consisting of a resistor layer in the signal forming section of the electrostatic printing device according to the present invention. An example, FIG. 18: Equivalent circuit of a three-layer structure consisting of a ferromagnetic layer, an insulating layer, and a resistor layer in the signal forming part of the electrostatic printing device according to the present invention, 2... Electrorecording body, 8... Substrate, 9... Linear electrode, 10... End surface,
11... thin film layer, 12... back electrode, 13... ferromagnetic thin layer, 14... resistor layer, 15... magnet,
16...Space charge, 17...Discharge gap, 18
...Insulator layer, 19...High voltage pulse generation section, 20
...Capacitance due to the resistor layer, 21...Capacitance due to the insulator layer, 22...Resistance in the thickness direction of the resistance layer, 23
...Resistance in the plane direction of the resistance layer, 24... Ground.

Claims (1)

[Scope of Claims] 1. A linear electrode 9 disposed on the surface of the cylindrical drum 8 to be rotated at an angle with respect to the rotation axis; A back electrode 12 on which the electrostatic recording body 2 is placed, a magnet 15 disposed on the back surface of the back electrode, and a surface and end surface of the ferromagnetic thin layer 13 disposed on the surface in contact with the electrostatic recording body. A sheet member that is integrally formed by sequentially laminating an insulating layer 18 and a high-resistance layer 14, is arranged with a gap from the cylindrical drum, and has an end surface parallel to the rotation axis of the cylindrical drum. The sheet member is configured to reduce the effective applied voltage between the linear electrode and the sheet member to stop the discharge due to the discharge charge stored in the sheet member, and to reduce the effective voltage applied between the linear electrode and the sheet member to stop the discharge, and to reduce the discharge charge stored in the sheet member after the discharge is stopped. An electrostatic printing device characterized in that the electrostatic printing device is formed of a high-resistance layer having a specific resistance that allows discharged charges to escape through the high-resistance layer.