JPH03246563A - Electrostatic recording device - Google Patents

Abstract

PURPOSE:To stabilize high resolution on plain paper, to simplify structure and to improve durability by making the paper travel to an electrode opposing part where a control electrode is provided between a pair of electrodes and controlling the driving of the voltage impressed on the control electrode in accordance with recording information in a state where a bias pulse voltage is impressed on a pair of electrodes. CONSTITUTION:The bias pulse voltage having the same polarity as the electrostatically charged polarity of toner is impressed on a spiral electrode body 4. The control electrode 8 is disposed between a specified path where the toner is carried and the spiral electrode body 4 and the bias voltage having the opposite polarity to the electrostatically charged polarity of the toner is impressed on the electrode 8. A cylindrical electrode 6 is rotatably disposed on the toner carrying surface side of a toner carrying body 5 so as to be opposed to the spiral electrode body 4, and the pulse voltage having the reverse polarity to the electrostatically charged polarity of the toner is impressed on the electrode 6. Then, the bias voltage is made low in accordance with input recording information and the toner on the toner carrying body 5 is selectively transferred to the paper fed between the toner carrying body 5 and the electrode 6, so that a toner recorded image is formed. Thus, the durability is improved, the high-resolution image on the pain paper is stabilized and the structure is simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an electrostatic recording device that can directly form a toner image on plain paper without using an intermediate transfer medium.

[Prior art and its problems]

Conventionally, multi-stylus printers are well known as electrostatic recording devices. This multi-stylus printer constructs a recording head by arranging a large number of needle-like electrodes (styli) at minute intervals, and selectively applies high voltage to each needle-like electrode according to the image signal, producing electrical discharge directly onto the paper. This process forms an electrostatic latent image. In such multi-stylus printers, if the distance between the tip of the needle electrode and the paper surface is wide, the discharge electric field will spread and the dots formed will become larger.
It is difficult to obtain high-resolution recorded images. For this reason, a gap layer is provided on the surface of the paper, and the gap layer and the needle-like electrode are brought into sliding contact to ensure a minute gap. However, this multi-stylus printer has a drawback in terms of durability, such as wear of the needle electrodes because the paper is constantly in sliding contact with the tips of the needle electrodes.

Further, the above-mentioned multi-stylus printer usually uses special paper coated with a high electrical resistance agent so that electric charge can be easily and stably retained on the paper. However, since the surface of such special paper is coated with an electrical resistance agent, it is difficult to write on it with a pencil, pen, etc., and it is not suitable for use as office paper. In addition, it changes in quality depending on environmental conditions such as humidity and temperature,
There is also a problem with storage stability.

Therefore, as an electrostatic recording method that can use plain paper, a method is often used in which a toner image is first formed on an intermediate medium and then the toner image is transferred onto plain paper. In this method, the transfer process via the intermediate medium complicates the structure of the electrostatic recording device, which is disadvantageous for downsizing the electrostatic recording device.

[Purpose of the invention]

The present invention has been made in view of the problems of the prior art described above, and provides an electrostatic recording device with a simple structure that has excellent durability and can stably record high-resolution images on plain paper. The purpose is to

C. Summary of the Invention The above object is to provide a toner conveying body that carries toner on its surface and conveys the toner along a predetermined path, and a toner conveying body rotatably disposed on the opposite side to the toner carrying surface of the toner conveying body. , a helical electrode body in which a linear electrode is laid in a helical manner on the circumferential surface and a bias pulse voltage of the same polarity as the charging polarity of the toner is applied, and the spiral electrode body is disposed between the predetermined path for conveying the toner and the helical electrode body. , a control electrode to which a bias voltage having a polarity opposite to the charging polarity of the toner is applied, and a control electrode rotatably disposed on the toner carrying surface side of the toner transporting body facing the helical electrode body, The toner on the toner transport body is transported between the toner transport body and the cylindrical electrode by applying a polar pulse voltage to the cylindrical electrode and reducing the magnitude of the bias voltage according to input recording information. By providing an electrostatic recording device characterized by selectively transferring toner to form a recorded image on paper,
achieved.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to FIGS. 1 to 8.

FIG. 1 is a schematic sectional view showing the overall structure of an electrostatic recording device as an embodiment of the present invention, and FIGS. 2 and 3 are a schematic sectional view and a perspective view showing the image recording process, respectively. It is.

In FIG. 1, the cassette is a paper feed cassette which stores untreated plain paper P and is removably attached to the side of the machine. A paper feed roll 1a is disposed above the tip of the inserted paper feed cassette 1 so as to be rotatable in the direction of the arrow. A pair of standby rolls 2 is disposed in front of the paper feed roll 1a in the paper feed direction A, and after temporarily stopping the advance of the paper P fed out by the paper feed roll 1a and adjusting the conveyance posture, The re-feeding is performed in synchronization with the recording timing by the recording head unit W. The standby roll pair 2 of this example has a heater 2c built into the upper roll 2a, and heats and dries the paper when it is conveyed while being held between both rolls 2at2b that roll into contact with each other. This improves the toner transfer efficiency in the image recording process described later. Furthermore, heater 2
c may be built into the lower roll 2b, or may be built into both rolls. Further, a drying roll or a drying heater may be provided separately from the standby roll pair 2.

A static elimination brush 3 is disposed downstream of the pair of standby rolls 2 in the paper conveyance direction. The static eliminating brush 3 extends over substantially the entire area in the width direction of the paper transport path, and removes the charged charges by bringing its tip close to or in sliding contact with the entire area of the paper. Thereby, it is possible to prevent an adverse effect on image recording due to the charged charges. In this example, the static elimination brush 3 is arranged on the front side of the paper (the side on which the recorded image is formed), but the brush 3 is not limited to this, and may be arranged on the back side of the paper or the ii4 side. .

A recording head section W is installed downstream of the static eliminating brush 3 to form a toner recorded image directly on the paper.

The recording head section W includes a toner conveying body 5 containing a developing roll 4 and a cylindrical electrode 6 disposed facing each other. The toner conveying body 5 is constructed by cutting out a part of the circumferential surface of a toner conveying sleeve 5a made of a non-magnetic rigid body such as metal or hard resin, and stretching a film 5b made of a visible insulating material over the notched portion. . In this example, polyethylene terephthalate (PET) with a thickness of several tens of micrometers is used as the film 5b. Such a toner conveying body 5 is arranged in the developing container 7 so that the part on which the film 5b is stretched projects from the opening lower a. In this example, a one-component high-resistance magnetic toner t whose frictional charging polarity is negative is stored in the developer container 7 . The opening edge 7b of the developer container 7 is formed so as to function as a blade that regulates the layer thickness of the toner conveyed on the circumferential surface of the toner conveyor 5.

As shown in FIG. 3, a control electrode 8 is formed on the surface of the film 5b. The control electrode 8 of this example is made up of a pair of control electrodes 8a and 8b extending parallel to the axial direction of the toner conveying body 5 with a predetermined gap 8c in between. In this case, a suitable method for depositing the electrodes is to perform etching treatment after depositing copper on the film 5b. A bias power supply 9 is connected to the control electrode 8 for applying a bias voltage of positive polarity in this example, which is opposite in polarity to the charged polarity of the magnetic toner t. This bias power supply 9 is signal-connected to the recording control section C. The recording control section C transforms the bias voltage applied to the control electrode 8 according to recording information.

Returning to FIG. 1, a developing roll 4 is rotatably disposed in the upper part of the toner conveying body 5 so that its upper peripheral surface and the inner surface of the film 5b are in sliding contact. The developing roll 4 is made up of a magnet roll 4b fixed to the inner surface of a cylindrical screw pole 4a having linear electrodes arranged spirally on its circumferential surface, and is driven and rotated in the counterclockwise direction shown by arrow a. As shown in FIG. 3, the screw pole 4a is made up of linear electrodes 4al arranged spirally at predetermined intervals on the circumferential surface. A bias pulse power source 10 for applying a bias pulse voltage having the same polarity as the friction charging polarity of the magnetic toner t is connected to this linear electrode 4al. In this example, since the frictional charging polarity of the magnetic toner t is negative, a bias pulse voltage of negative polarity is applied to the linear electrode 4al. The circumferential surface of the magnet roll 4b is magnetized with N and S poles alternately along its circumferential direction. Therefore, when the developing roll 4 is rotated in the direction of arrow a by a drive motor (not shown), The magnetic toner t in the developer container 7 is attracted to the circumferential surface of the toner conveying member 5 and conveyed in the opposite direction indicated by the arrow mark (clockwise direction). At this time, the layer thickness of the transported magnetic toner is regulated to a predetermined layer thickness (approximately 40 μm in this example) by the opening edge 7b of the developer container 7.

A cylindrical electrode 6 is rotatably disposed above the developing roll 4 with the film 5b in between. The cylindrical electrode 6 is made of a metal sleeve made of aluminum or the like, and is connected to a bias pulse power source 6a.

The bias pulse power source 6a applies a bias pulse voltage having a polarity opposite to the charging polarity of the magnetic toner, that is, a bias pulse voltage having a positive polarity in this example, to the cylindrical electrode 6. Cylindrical electrode 6
As shown in FIG. 2, is arranged opposite to the developing roll 4 with a predetermined distance G maintained therebetween via the toner conveying body 5, and is driven and rotated in the counterclockwise direction shown by the arrow C. . The distance G between the cylindrical electrode 6 and the surface of the developing roll 4 needs to be set to such an extent that an electric field-free state in which an electric field for transferring magnetic toner (described later) is substantially absent can be formed. In this example, the gap G is set to 250 am, and the thickness LF of the film 5b is 40 μm. The thickness Lt of each is similarly set to 40 μm1.

Therefore, the distance G between the surface of the toner layer 11 and the surface of the cylindrical electrode 6
l is 170 μm. During this interval G1, the recording paper P
is transported with the back surface supported by the circumferential surface of the cylindrical electrode 6. In this case, if the thickness Lp of paper P is 90 μm, paper 2
The spatial distance G2 between the surface and the surface of the toner layer tL is 80 μm
becomes. This spatial distance G2 is a distance over which the toner t is transferred, and must be strictly maintained in order to obtain a clear recorded image. In the present invention, the cylindrical electrode 6 functions as a backup roller, and is configured to smoothly transport the paper P while always supporting it in a fixed position, and to ensure the above-mentioned spatial distance G2 stably and with high precision.

In the electrode facing portion F where the circumferential surface of the cylindrical electrode 6 is closest to the circumferential surface of the developing roll 4 with a gap G, image recording and development are performed simultaneously, and a toner recorded image is formed on the paper P. That is, as will be described later, the cylindrical electrode 6 passes from the screw pole 4a through the electrode gap 8C depending on the potential of the control electrode 8.
An electric field extending to is selectively formed, and the magnetic toner t conveyed along the surface of the toner conveying body 5 is selectively transferred to the cylindrical electrode 6 side by the force of the electric field. This transferred toner adheres to the paper P that is fed during the interval G between the electrode facing portions F with timing determined by the pair of standby rolls 2, and a recorded image is formed as a toner image.

Returning to FIG. 1, on the downstream side of the recording head unit W, an air succinct conveyor belt 11 is stretched horizontally, and while sucking the back side of the paper on which an image has been recorded, it moves forward. The image is transported toward a fixing device 12 provided therein. The fixing device 12 consists of a heating roll 12a and a pressure roll 12b, and thermally fixes the toner image when the paper is held between the two rolls and conveyed. After the fixing, the sheets are discharged from the discharge port 13 and stacked on the paper discharge tray 14 in a face-down state with the image side facing down.

As described above, in the electrostatic recording device of this example, the entire paper transport path from paper feeding to paper ejection is formed in a substantially straight shape, so the paper feeding operation is generally smooth, and printing is possible. Paper feeding defects such as defects and jams are less likely to occur. It also has the advantage that the above-mentioned straight sheet passing path can achieve a face-down sheet discharge state that does not require page alignment, which is preferable for the recording apparatus.

Here, the recording operation by the above-mentioned electrostatic recording device will be explained.

FIGS. 4(a) to 4(C) are explanatory diagrams schematically showing the electric field state at each stage in the electrode facing part F, and FIG. 5 is a schematic plan view showing the electrode facing part F.

In FIG. 5, an electric field E corresponding to one dot of the recorded image is formed at the intersection of the gap 8C between the pair of control electrodes 8a+8b and the linear electrode 4al on the circumferential surface of the screw pole 4a. In this case, the formation state of the electric field E is determined by the bias voltage (hereinafter referred to as control voltage) Vl applied to the control electrode 8 and each bias pulse voltage V2 applied to the cylindrical electrode 6 and the linear electrode 4al. V3 changes into the following three states depending on the combination of high and low voltages at three locations. In this example,
Control voltage Vl is +200V and +30V1 Bias pulse voltage (hereinafter referred to as electrode pulse voltage) applied to cylindrical electrode 6 V2 is +170V and 0 (ground)■1 Linear electrode 4al
The bias pulse voltage (hereinafter referred to as wire rod pulse voltage) V3 applied to O (ground) V,! =-800V.

Switch between each.

FIG. 4(a) shows the electric field state during recording.

In this case, the electrode pulse voltage v2 is lowered to ground potential, the control voltage Vl is lowered to +30V, and the linear pulse voltage v3 is also lowered to +30V.
It is lowered to 00V (increased in absolute value). Therefore, the potential difference between the cylindrical electrode 6 and the linear electrode Ja1 becomes 800 V, and an electric field of several mega V/m is formed as indicated by the lines of electric force (■).

This electric field acts on the magnetic toner t (see Figure 2) on the control electrode 8 (film 3b), and moves the negatively charged magnetic toner t in a direction opposite to the direction of the electric force lines A (arrow direction). is transferred to the surface side of the cylindrical electrode 6 and attached to a paper (not shown). Note that an anti-transfer electric field is formed between the control electrode 8 and the cylindrical electrode 6 in the direction of pulling the magnetic toner back toward the control electrode 8, but since the potential difference is as small as 30 V, it is canceled by the above-mentioned transfer electric field and the magnetic toner is The transfer of the toner t onto the paper is hardly hindered.

FIG. 4(b) shows the electric field state during non-recording. In this case, only the control voltage Vl is increased to +200V, and the other pulse voltages V2. V3 is held at the same level as during the above-mentioned recording. Therefore, the potential difference between the linear electrode 4al and the cylindrical electrode 6 remains at 800V, which is the same as during recording, but the linear electrode 4al
The potential difference between al and the control electrode 8 becomes as large as 100OV. As a result, the transfer electric field that transfers the magnetic toner t onto the paper is blocked by the electric field between the control electrode 8 and the linear electrode 4a1 and does not extend to the cylindrical electrode 6, and the toner is held on the control electrode 8. It will remain as it is. In addition, the control electrode 8 and the cylindrical electrode 6
Since the potential difference therebetween is also as large as 200 V, the force for holding the toner on the control electrode 8 is further strengthened. However, in this case, the yen f111! There is a possibility that the magnetic toner t' (see FIG. 2), which has been transferred onto the pole 6, may be pulled back onto the control electrode 8.

FIG. 4(C) shows a no-electric field state. in this case,
The control voltage Vl remains +200V, the same as when not recording, but the cylinder rod pulse voltage V2 and the wire rod pulse voltage V3 are respectively +
Increase to 170v and 0 (ground) ■. As a result, the potential difference between the cylindrical electrode 6 and the linear electrode Aa1 is reduced to 170V, and the potential difference between the control electrode 8 and the cylindrical electrode 6 is reduced to 30V.

As described above, since the distance G between the cylindrical electrode 6 and the linear electrode 4a1 is sufficiently secured, the strength of the electric field between the two electrodes becomes extremely small, and almost no electric field exists. Therefore, under this state of no electric field, not only the toner on the control electrode 8 but also the toner transferred onto the cylindrical electrode 6 is held at their respective positions without being pulled back.

The developing roll 4 is in the direction of arrow a (counterclockwise direction) in FIG.
When rotated, the linear electrode 4al moves in parallel in the direction of arrow d (main scanning direction) in FIG.

As a result, the dot forming electric field E also moves in the main scanning direction d as the developing roll 6 rotates. Therefore, by driving and rotating the cylindrical electrode 6 and the developing roll 4 in the counterclockwise direction at a predetermined speed, and controlling the control voltage according to the recording information by the recording control section C, the state of the dot-forming electric field E can be changed as will be described later. As a result, a toner recorded image is formed with high resolution on the circumferential surface of the cylindrical electrode 6 according to the recorded information. In this case, by controlling the control voltage within a small fluctuation range of about 170V, it is possible to freely form the strong electric field necessary to transfer the toner. In other words, the electric field shutter effect, which can freely control the transfer of toner, can be freely exerted by low-voltage drive control under the application of high-voltage pulses at regular intervals, making it possible to form recorded images efficiently. Become.

FIG. 6 is a timing chart showing the relationship over time between each voltage and the state of the dot-forming electric field E when forming a recorded image in this example. In this example, the cylinder rod pulse voltage V2
and the wire rod pulse voltage V3 are both set to have a DUTY ratio of 50%, and are applied at timings in which they are in the same phase. Under this condition, when forming black dots (recording), the control voltage V
Switch l from the high level of +200V to the low level of +30V (let it fall). In this case, each bias pulse voltage V2. The control voltage Vt is caused to fall when V3 falls. As a result, one black dot can be formed in the first half of the write period Tw in which one dot writing is performed, and a no-electric field state SDs of the electric field E can be ensured in the second half. That is, the recording state S of the electric field E. After N, a no-electric field state SO8 is always ensured.

Electric field E is recording state S. Immediately from N to non-recording state S. F2
If the switching is made, there is a possibility that the toner that was previously transferred to the cylindrical electrode 6 side will be pulled back to the control electrode 8 side.

In this example, the electric field E is in the recording state S. After becoming N and forming one black dot, it always switches to the no-electric field state SOS, so
The above-mentioned disadvantage of pulling back the transferred toner is prevented. As a result, one black dot is clearly formed, and the resolution of the recorded image is significantly improved. Furthermore, in the no-electric field state Sos, as shown in FIG. 4(C), a slight electric field is formed that pulls the toner back toward the control electrode 8, and this electric field causes the transfer of the toner onto the paper due to the so-called mirror image force. , and further improves image resolution.

Incidentally, the electric field state before forming the first black dot at the start of recording must be set to a no-electric field state SOS in which no transfer electric field acts on the toner. Therefore, the voltage application start time T1 to the control electrode 8 is made to precede the voltage application start time T2 to the cylindrical electrode 6, and the voltage application start time T3 to the linear electrode 4al is delayed from T2. Furthermore, since it is necessary to end the recording in the no-field state SO8, the time point T4 at which the voltage application to the linear electrode 4al ends is preceded by the time point T5 at which the voltage application to the cylindrical electrode 6 ends, and the time point T4 at which the voltage application to the control electrode 8 ends. The voltage application end point T6 is delayed from T5. Also, in the figure,
Pw is the time for applying a low-level bias voltage to the control electrode 8 to form one black dot, and P'W is the time for applying a low-level bias voltage to the control electrode 8.
This is the time for applying one falling pulse to the linear electrode 4al. By varying the above-mentioned Pv with respect to P'w according to the image gradation frequency, it is also possible to form a recorded image with gradation control.

Next, another embodiment of the present invention will be described based on FIG. 7.

FIG. 7 is an explanatory diagram showing the relationship between the control electrode body 15 consisting of a plurality of control electrodes (not shown) and the linear electrode lea of the screw pole 16 when the screw pole 16 is expanded. In this example, the control electrode body 15 is formed by arranging a large number of control electrodes in parallel, and each control electrode is provided with a slit portion 15a.

These slit portions 15a are arranged in a houndstooth pattern on two sides along the axial direction of the screw pole 16. In this example, the screw pole 16 rotates in the a' direction, and the linear electrode 18a moves in parallel in the arrow d' direction (main scanning direction). In this case, each slit portion 15a is moved in the main scanning direction d'
In contrast, the rear end side is tilted slightly toward the upstream side in the sub-scanning direction e, thereby correcting the deviation of the recorded image in the sub-scanning direction. Each control electrode is driven by a two-column time-division control method. Providing a large number of control electrodes (slit portions 22a) as in this example complicates the drive control circuit for applying the aforementioned control voltages to them according to the recorded information, but the recording speed is greatly increased. This is an advantage.

It should be noted that the present invention is not limited to the specific embodiments described above, and it goes without saying that various modifications can be made within the technical scope of the present invention.

For example, the polarity and magnitude of the voltages applied to the cylindrical electrode, the control electrode, and the spiral electrode body are not limited to the combinations of the above embodiments, but are based on the conditions that satisfy the correlation that allows the toner transfer electric field to be formed according to the recorded information. Various combinations are possible below. As an example, FIG. 8 shows a method of applying each voltage when toner having a positive friction charging polarity is used.

It can be seen that in this case, the polarity of each voltage is opposite to that in the case where the negative polarity toner described above is used. Therefore, when the pi and as voltage Vl of the control electrode is in the rising state, the electric field S in the recording state. N is formed and one black dot is formed.

Furthermore, in the embodiment shown in FIG.
b may be fixedly installed separately from the screw pole 4a, and only the screw pole 4a may be rotated. in this case,
The control electrode may be fixedly installed between the toner conveying body 5 and the screw pole 4a.

Furthermore, the developer is not limited to magnetic toner, and various developers such as non-magnetic component developer and two-component developer can be used.

〔Effect of the invention〕

As described above in detail, according to the present invention, a sheet of paper is run through an electrode facing part in which a control electrode is provided between a pair of electrodes,
By driving and controlling the voltage applied to the control electrode according to recording information while applying a bias pulse voltage to each of the pair of electrodes, a recorded image can be stably and efficiently formed on paper at a low voltage. . In this case, since the electric field is switched from the recording state to the non-recording state via the no-electric field state, the inconvenience of pulling back the transferred toner that forms the image is prevented, and the resolution of the recorded image is significantly improved. In addition, since a sheet of paper is run in the area facing the electrodes and a recorded toner image is directly formed thereon, it is possible to use plain paper, and a transfer process section is not required, which facilitates the miniaturization and weight reduction of electrostatic recording devices. can do. Furthermore, since it is a non-contact recording method, recording members such as electrodes are not worn out, and the durability of the electrostatic recording device is improved.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the overall configuration of an electrostatic recording device as an embodiment of the present invention, FIG. 2 is a schematic cross-sectional view showing the image recording section of the electrostatic recording device, and FIG. 3 is a schematic diagram showing the image recording unit of the electrostatic recording device. FIG. 4(a) to FIG. 4(C) are explanatory diagrams showing each stage of changes in the electric field state, FIG. 5 is a schematic plan view showing the image recording section, and FIG. 6 is a perspective view showing the recording section. 7 is a timing chart showing a voltage control method in an image recording operation, FIG. 7 is a plan view showing an expanded image recording section as another embodiment of the present invention, and FIG. 8 is a voltage control method according to the present invention. FIG. 4 is a timing chart diagram showing another embodiment of the present invention. 4...Developing roll 4 a + I El... Screw pole 4a1
．． 16a... Linear electrode 5... Toner transport body 5b... Film 6... Cylindrical electrode 6a, 10... Via... Developing container 8+ ga, sb... Control electrode 8c... Electrode gap 9...Bias power supply 15...Control electrode body C...Recording control section E...Dot forming electric field F...Electrode opposing portion t+ t'...Magnetic toner P...Paper ( Plain paper) W...Recording head Asbarus power supply

Claims (1)

[Claims] a toner conveying body that carries toner on its surface and conveys the toner along a predetermined path; and a toner conveying body rotatably disposed on the opposite side to the toner carrying surface of the toner conveying body, and a linear electrode spirally arranged on the peripheral surface. a helical electrode body to which a bias pulse voltage having the same polarity as the charged polarity of the toner is applied; a control electrode to which a bias voltage of is applied; and a cylindrical electrode rotatably disposed on the toner carrying surface side of the toner transporting body facing the helical electrode body and to which a pulse voltage having a polarity opposite to the charging polarity of the toner is applied. and selectively transferring the toner on the toner conveying body onto the paper conveyed between the toner conveying body and the cylindrical electrode by reducing the magnitude of the bias voltage according to input recording information. An electrostatic recording device characterized in that it forms a toner recorded image.