JPH021885A - electrostatic recording device - Google Patents

Abstract

PURPOSE:To obtain a satisfactory image on a regular paper stably by means of a simple structure by opposing a segment electrode as a signal electrode to a spiral electrode as a counter electrode, through a toner carrying body made of dielectrics. CONSTITUTION:A corona discharger 7 discharges a corona ion having a positive polarity to the rear surface of a direction drum 6, and toner (t) uniformly adheres to the periphery of the drum 6 by virtue of electrostatic attraction force. The adhered toner t is carried under an counter electrode part and is selectively transferred onto a paper by means of a printing head 4 according to image information; thereby an image is printed. The printing head 4 consists of a segment pole 4a and screw pole 4b, and between them, the periphery 6a of the dielectric drum runs in the direction shown by an arrow B. Printing is performed by applying a high voltage 4f through a switch 4e to the segment electrodes 4d disposed with an insulating plate 4b in-between and by forming an electric field between the spiral electrode 4g on the pole 4b and segment electrode.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to an electrostatic recording device, and more particularly, the present invention relates to an electrostatic recording device, and more particularly to an electrostatic recording device that can print on plain paper without forming an electrostatic latent image and using a simple image forming process. This invention relates to electronic recording devices.

[Prior art]

A multi-stylus printer is known as one of the recording methods that do not use a photoreceptor. A multi-stylus printer forms an electrostatic latent image by arranging needle-like electrodes at minute intervals and directly discharging them onto a sheet of paper according to an image signal.

After the electrostatic latent image is developed with toner, it is fixed by a fixing device.

Also, as shown in Equity No. 513-54631,
There is also a device in which an electrode provided spirally on the surface of a rotating cylindrical body and a segment electrode are disposed facing each other, a sheet is conveyed between them, and a high voltage is applied between these two electrodes to form an electrostatic latent image. In this case as well, similarly to the multi-stylus printer, an electrostatic latent image is first formed on a sheet of paper, the latent image is developed with toner, and then fixed by a fixing device.

[Problems with conventional technology]

However, in the case of the above-mentioned multi-stylus printer, the needle-shaped electrode is made to correspond to the dot density (DPI) of 0.
0846 (3000PI) ~ 0.1058 City (240
The needle electrodes must be arranged in the main scanning direction at intervals of 0 PI), and the structure becomes extremely fine, making the needle electrode alone expensive. In addition, since the needle-like electrode has a fine and precise structure,
Even the slightest amount of dirt has a significant negative impact on image quality.

All of the above-mentioned electrostatic recording devices have a major problem in that they cannot use plain paper. In other words, in order to form an electrostatic latent image directly on the paper, the paper must have high electrical resistance characteristics even in a high humidity environment, and for this reason, it is necessary to use special paper with a high electrical resistance agent coated on the paper surface. There is.

Such special paper is difficult to write on with pencil, ink, etc. due to its surface nature, and is therefore undesirable as paper for office use.

Therefore, as an electrostatic recording device that can use plain paper, a dielectric belt is movably stretched around the dielectric belt, and an electrostatic latent image is formed on the dielectric belt by the above-mentioned multi-stylus recording head, and then developed with toner. A method is known in which the toner image is transferred onto plain paper. This method has the disadvantage that the multi-stylus head has a fine structure and requires a process equivalent to a normal electrophotographic process, making the structure of the entire device extremely complicated.

[Purpose of the invention]

The present invention has been made in view of the problems of the prior art described above, and is an electrostatic recording method that uses an electrostatic recording method, can use plain paper, has a simple structure, and can stably obtain good images. The purpose is to provide equipment.

[Key points of the invention]

According to the present invention, the present invention provides an endless dielectric body provided to be movable in a predetermined direction, a toner attachment means for uniformly attaching toner to the surface of the dielectric body, and a toner attachment means for uniformly attaching toner to the surface of the dielectric body; A plurality of segment electrodes are disposed on one side of a sheet facing section in which the sheet is opposed to the dielectric surface with a minute interval therebetween, and a plurality of segment electrodes are arranged rotatably on the other side of the sheet facing section and have a spiral shape on the circumferential surface. a screw pole on which an electrode is laid, and selectively transfers the toner on the dielectric material to the paper by applying a high voltage according to print information between the segment electrode and the screw pole. This is achieved by providing an electrostatic recording device having the following characteristics.

[Embodiments of the invention]

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic cross-sectional view showing the overall configuration of an electrostatic recording device as an embodiment of the present invention. In the same figure, ``■'' is a paper feed cassette, which stores untreated plain paper P, and is installed on the side of the upper part of the machine so that it can be inserted and removed. A paper feed roll 1a is disposed above the leading end of the paper feed cassette 1 in the insertion direction 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, a pair of standby rolls 2 Synchronize and refeed. 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 2a and 2b that are in contact with each other. This improves the toner transfer efficiency in the printing process described later. Furthermore, heater 2
c may be built in the lower roll 2b, or may be built in 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 elimination brush 3 extends over substantially the entire width of the paper conveyance path, and brings its tip close to or in sliding contact with the entire area of the paper to remove the electrical charges.

Thereby, it is possible to prevent an adverse effect during printing due to the charged charges. In this example, the static elimination brush 3 is brought into sliding contact with the back surface of the paper (where no image is printed), but the brush 3 is not limited to this and may be brought into sliding contact with the front surface or both sides of the paper.

A printing section consisting of a print head 4 and a toner supply device 5 is formed downstream of the static elimination brush 3. The print head 4 is composed of a segment ball 4a and a screw pole 4b, and the print head 4 passes through the circumferential surface of a dielectric drum 6, which has toner uniformly adhered to its surface, to an electrode facing part F in which these balls 4a and 4b face each other. At the same time, toner is selectively transferred onto the paper being conveyed to form an image. The configuration of the print head 4 will be explained in detail later.

In the toner supply device 5, a dielectric drum 6 as a toner conveying member is rotatably supported in a housing 5a in which toner t is stored, and is driven and rotated in the direction of the arrow. Note that in this example, a one-component toner containing no carrier is used. The dielectric drum 6 is arranged so that its circumferential surface passes through the above-mentioned electrode facing portion F, and a corona discharger 7 as a toner adhering means is disposed inside the drum 6 on the upstream side in the rotational direction. A scraper 8 serving as a cleaner is disposed on the downstream side of the electrode facing portion F on the outer circumferential surface of the dielectric drum 6 with its tip in sliding contact to remove toner that is not used for printing and remains on the circumferential surface of the dielectric drum 6. scrape off. In this example, two stirring rolls 9 are installed at the bottom of the toner supply device 5.
．． 9 is disposed to frictionally charge the stored toner t to a predetermined, for example, negative polarity while stirring it.

In the toner supply device 5 configured as described above, first, corona ions having a polarity opposite to the frictionally charged polarity of the toner t are discharged toward the back surface of the dielectric drum 6 by the corona discharger 7, and the electrostatic charge is The toner t is uniformly applied to the circumferential surface of the dielectric drum 6 by the suction force. As the dielectric drum 6 rotates, the toner t is adhered and carried on the circumferential surface of the dielectric drum 6.

is conveyed to the electrode facing section F, where it is selectively transferred onto the paper by the print head 4 according to the image information, and the image is printed. This printing operation will also be explained in detail later.

The toner to' remaining on the circumferential surface of the dielectric drum 6 after the printing process is removed by a scraper 8 that is in sliding contact with the downstream side of the dielectric drum 6.
The toner is scraped off and the stored toner is returned inside. The scraped toner t' is sufficiently stirred and mixed with the stored toner t by a stirring roll 9.9, and then used for printing again. Further, the circumferential surface of the dielectric drum 6 from which the toner to' has been removed is immersed in toner, and then reaches the position where the corona discharger 7 is disposed, where toner is again applied. In this case, the circumferential surface of the dielectric drum 6 has been restored to its substantially initial state by once removing all the attached toner to' by the scraper 8.
The toner always adheres uniformly, and there is no risk of generating an afterimage. Note that a brush-like cleaner may be provided in place of the scraper 8.

On the downstream side of the print head 4, an air spool type conveyor belt 10 is stretched horizontally, and while sucking the back side of the paper after printing, it directs it to the fixing device 11 provided in front of it. and transport it.

The fixing device 11 is composed of a heating roll lla and a pressure roll 11b, and thermally fixes the paper when the paper is held between the two rolls and conveyed. After the paper has been fixed, it is discharged from the discharge port 12 onto a paper discharge tray 13 in a face-down state with the image side facing down, and is stacked thereon.

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. Further, it has the advantage that page alignment is unnecessary and a face-down paper discharge state, which is preferable for the recording apparatus, can be obtained with the above-mentioned straight paper passage path.

Here, the configuration of the print head 4 will be explained using FIG. 2.

The print head 4 is composed of a segment ball 4a and a screw pole 4b, and a dielectric drum peripheral surface 6a is connected between the two.
travels in the direction of arrow B (sub-scanning direction). The segment ball 4a has a large number of segment electrodes 4d sandwiching an insulating plate 4c, and these segment electrodes 4d are arranged in two directions (main scanning direction) perpendicular to the paper conveyance direction (sub-scanning direction) as indicated by the arrow opening. They are arranged in a houndstooth pattern of columns. Each segment electrode 4d is connected to a high voltage power source 4 via a switch 4e.
f is connected, and when the switch 4e is closed, the segment electrode 4
An electric field is formed between d and a linear electrode 4g provided on the screw pole 4b, and printing is performed by the force of the electric field as described later.

On the other hand, the screw pole 4b has a plurality of linear electrodes 4g laid spirally on the surface of a cylindrical base 4h, each linear electrode 4g does not touch each other, and all the linear electrodes 4g Grounded. Figure 3 (a), (b)
) are two types of screw poles 4b with different methods of laying the linear electrodes.

4b' is a sectional view showing the screw pole 4b of the same figure (a), in which a linear electrode 4g is wound around the surface of the base 4h. In this case, the electric field can be formed more stably if the tip of the linear electrode 4g is as sharp as possible. Also, the same figure (b)
The screw pole 4b' has a linear electrode 4g' embedded in the surface of the base 4h', and has the advantage of little wear even after long-term use. Similar to the screw pole 4b described above, the narrower the width of the linear electrode 4g' is, the more stable the electric field formation state will be.

Next, the structure of the electrode facing portion F will be explained in detail based on FIGS. 4 to 7. 4 and 5 show the segment ball 4a with the linear electrode 4g expanded.
FIG. 4 is a perspective view of a segment electrode 4d and a linear electrode 4g viewed from above. Moreover, FIG. 6 is a longitudinal cross-sectional view of the electrode facing part F.
FIG. 7 is an enlarged vertical sectional view of section Q in FIG. 6.

As shown in FIG. 6, the paper P and the circumferential surface of the dielectric drum 6 are both caused to run along the sub-scanning direction B between the tip of the segment electrode 4d formed into a tapered shape and the linear electrode 4g. . In this case, the paper surface P and the dielectric drum peripheral surface 8
The traveling routes of the two vehicles are set so that the two vehicles can travel while maintaining a predetermined minute gap G between them. The minute gap G is the toner layer t supported on the dielectric drum circumferential surface 6a. is the paper surface P
, it is preferable to set it as small as possible within the limit of not touching .

Now, when the screw pole 4b is rotated in the direction corresponding to the sub-scanning direction, the linear electrode 4g is translated from the left to the right in FIG. During this movement, the segment electrode 4
When a magnetic high voltage is applied to d, as shown in FIG. 7, an electric field is formed at the intersection of the segment electrode 4d and the linear electrode 4g, and along the lines of electric force (indicated by broken lines) The monopolarly charged toner io is transferred onto the paper surface Pt, and one dot is printed. In this case, since the voltage is applied via the dielectric drum 6, the strength of the electric field is less affected by the electrical resistance value of the paper P unlike in conventional multi-stylus printers, and even in a high humidity environment Good print quality can be stably obtained. Further, since unnecessary charges on the paper P are also removed by the static eliminating brush 3, the print quality is further stabilized.

In the above print head 4, the moving speed of the linear electrode 4g (rotation speed of the screw pole 4b), the segment electrode 4
By appropriately setting the period of high voltage application to d, the relative position of the linear electrode 4g and the segment electrode 4d, etc., it is possible to print separated into dots of a desired size. These numerical relationships will be explained below using FIG.

First, the running speed V of the dielectric drum circumferential surface 6a and the paper P
ppc is (PPM: number of sheets printed per minute) Effective length L8g of segment electrode 4d is LSE=DS
@N (-) ・・・・・・・・・・・・・・・
... (2) (Ds: Size of 1 dot) (Number of dots supported by N21 segment electrode) Total length LLsI of segment electrode 4d! is LL, ya=Lsa+2α1
+2α2 [stop]... (3) (α,: segment electrode 4
(position and accuracy of d) (α2: minimum required length of the tip and end of the segment electrode 4d) The main scanning direction interval Lsp of the linear electrode 4g is Lsp” D
sX (1/ DUTY) (+11m) ---(
4) (DUTY: Printing duty) The sub-scanning direction interval Hsp of the linear electrode 4g is HsP:Ls
P・tanθsp (mm) ---...-(5)(
Osp: angle formed by the linear electrode 4g with the main scanning direction) The pitch PSP of the linear electrode 4g is: P sp” L sp 11sinθsp (-m)
""""'--(8) Printing time T for one line in the main scanning direction
W is the energization time Two of the high voltage power supply 4f to form one dot is T wo” T W・DUTY (S)...
・・・・・・・・・・・・・・・(8) The rotational speed ゛T6P of the screw pole 4b is (CYCLE: the number of linear electrodes 4g), where the circumferential speed Hsp/T of the screw pole 4b is The relationship between w and traveling speed v ppc must be Hsp/T w >> V ppc.

Now, if we try to realize a printer with the following specifications, the numerical values of equations (1) to (9) above will be as follows.

a) Arrangement of segment electrodes 4d Staggered arrangement in 22 rows b) Number of linear electrodes 4g: CYOLE = 10C) Printing duty: DUTY = 1 / 128d) θsp”45
Degree e) Number of pages printed per minute: PPM = 4 (A4 vertical feed) f)
Paper spacing = 50-m g) Ds = 0. 084e1. (300DPI) Applying these values to formulas (1) to (9) above, travel speed: V ppc= 23.13 (m+I/
s'] Effective length of upper segment pole 4d: L S, =:
8. (137C dragon) (However, when N=95 is set) Total length L of segment electrode 4d Lsu=9.56C*
s] (However, set 2α1 + 2α2 to 18・D8)
Main scanning direction interval: L gp: 1G, 8288 C] Sub-scanning direction interval: HlIP: 10.8288
(m+*) Pitch of line electrode 4g: P sp” 7.
857 (m+*] Printing time: T w” 3. [i
fi (w) 1 dot 1 dot time: T wo” 28
．． 59 Cμs] Rotation speed: T sp: lEi
:l! l[:rpm).

With these numerical values, a printer having the specifications a) to g) above can be realized.

Next, print timing in the sub-scanning direction will be explained with reference to FIG. The time required for the linear electrode 4g to move from position A to position B in FIG. 5 by a distance LBP is Tw, during which time 128 dots are printed. At this time, the first printing position and the final printing position of the 128th dot are as follows:
This results in a shift in the sub-scanning direction by Ds, which is the size of one dot.

Also, before the first segment electrode 4d+ finishes printing 95 dots, the second segment electrode 4d2 prints 96 dots.
Printing starts after the dot. Second segment electrode 4d
Printing starts at Q when the linear electrode 4g moves to position C. Here, the distance from the left end of the first segment electrode 4dl to the intersection with the first segment electrode 4d when the linear electrode 4g comes to the C position is defined as Y, and
is defined as x=t, 5R−y. Further, the amount of deviation in the sub-scanning direction at the intersection with the trajectory E followed by the printed dot is defined as a. The first dot τ printed by the second segment electrode 4d2 is the first dot τ as f' on the final paper.
must be adjacent on the locus E to the final dot g printed by the segment electrode 4d. For this purpose, \FAHsFl between the first segment electrode 4d and the second segment electrode 4d2 in the a11 scanning direction must not be an integral multiple of Ds, but must be the interval shown below. That is, when printing starts using the second segment electrode 4d2, the first
The printing position by the segment electrode 4d is already shifted by a from the first segment electrode 4d+.

Therefore, the interval Hall must be set in consideration of this amount of deviation. In order to make f' adjacent to g on the locus E as described above, the interval Hst must be larger than an integral multiple of Ds (
It must be set wider by L12·tan θ1-a). Here, θ is the angle between the main scanning direction and the trajectory E, and in this example, tanθ=1/128. Therefore, the interval Ha11 is HSE= M IID s +
It can be expressed as L ss ・tanθw−a −(10).

Here, M is an integer, and the first segment electrode 4d+
This is the number of delay stages between the print data by the second segment electrode 4d2 and the print data by the second segment electrode 4d2.

As can be seen from Figure 5, a+ Y+ X are respectively a=Y
*tar1w Y=L! ! E−X X=HsH*cotθsp. Therefore, a = (Lsi-HsI!Φcotθsp)・tanθ
W, and by substituting this into equation (10), nXr spacing H
8I! becomes. Now, if we set M=35, then H
8[! = 2, 984 C--).

Next, the printing timing of each segment electrode 4d will be explained. As can be seen from FIG. 5, printing by the second segment electrode 4d may be started when the linear electrode 4g moves from position A to position C, that is, when it moves by distance Y. . Here, the distance Y is calculated from the above formula as follows: Y'' L s!-Hsvr ・coto, p=5.0
The time required to move the oLsp IO, 8288 mm to become 53 C, , ) is 3.66111 s, so 5.0
53 ■■ The time required to move is 1.71 m5.

FIG. 8 is a time chart showing the timing of printing, and the period from the start of printing by the first segment electrode 4dl to the start of printing by the second segment electrode 4d2 is determined by the movement of the above-mentioned distance Y indicated by NTD2. This means that it is only necessary to delay the time required by 1.71m5. In addition, T
The period indicated by woX 95 is the actual printing period. or,
Considering the printing start timing of the third segment electrode 4dq, the distance between the left end of the first segment electrode 4d and the left end of the third segment electrode 4d3 is 2-L.
s,: 18.074II11, and when the linear electrode 4g reaches the left end of the third segment electrode 4d3, the previous linear electrode 4g is on the left by L sp = 10.8288 dragons. Therefore, when its position is calculated as the distance from the left end of the first segment electrode 4d+, 2IILsl! -, 3P=5.24521Im. Calculating in the same way as above, 5.2452+n is 1.77
m5 and T shown in FIG. 3 is this delay time.

The delay time T. When N is expressed in a general formula, it is as follows.

First, odd-numbered segment electrodes 4d+, 4d3°4d
Regarding IS..., it can be expressed as follows. However, n=L L 5..., and the value in 11 of equation (12) is defined as the value obtained by truncating the calculated value below the decimal point.

Next, even numbered segment electrodes 4d2, 4d4°4d
Regarding e..., it can be expressed as follows. However, n=2+416..., and the value in 11 in equation (13) is defined as the value obtained by truncating the calculated value below the decimal point.

Next, when considering the synchronization difference between the drive clocks of the odd-numbered segment electrodes and the drive clocks of the even-numbered segment electrodes, as can be seen from FIG. The printing timing differs from the pole by a time corresponding to the distance ff1Y. Converting this into time, it becomes t'' (Y/Lsp)・Tw.Here, if we define Y=1・D3+β (however, l is a natural number and β is the distance shown in Figure 5). ,
t is t: (1-D s/L 5p)T w”(β/L
5pLT w"' (14) Here, since both the numerator and denominator of the first term on the right side of the above equation are integral multiples of Ds, it has no relation to the synchronization difference. Therefore, the time of the second term on the right side of the above equation is This is the synchronization difference time.If the synchronization difference time is t, then t
,=(β/Lsp)・Tw・・・・・・・・・・・・・
(15), and since Y in the above example is 5.05:l++, 1=59. β:0.0
[ilGmm. Therefore, the synchronization shift time t, is t,=20.82 μS. FIG. 9 is a clock time chart showing the period shift relationship when the drive clock for the odd segment electrodes is ckl and the drive clock for the even segment electrodes is ck2.

In the above printing operation of the print head 4, the printed dots are shifted from the main scanning direction by an angle OW. In the case of A4 size, this amount is 210Xtanθw:1.
114mm. In order to correct this amount of deviation, the printing timing of each dot can be delayed in the sub-scanning direction by a delay means, or the print head 4 can be arranged in advance so as to be shifted by an angle of 90+01 with respect to the sub-scanning direction. good. Further, the direction of rotation of the screw pole 4b may be opposite to that in the above embodiment.

It should be noted that the present invention is not limited to the preferred embodiments described above, and it goes without saying that various modifications can be made within the technical scope of the present invention. For example, as shown in FIG. 10, a plate-shaped toner adhesion plate 14 may be provided as the toner adhesion means of the toner supply device 5, and its abdomen may be brought into pressure contact with the circumferential surface of the dielectric drum 6. As a result, the toner t is pinched between the toner adhering plate 14 and the circumferential surface of the dielectric drum 6, is charged by friction, and is forced to adhere to the circumferential surface of the dielectric drum 6. According to this method, toner can be uniformly adhered to the circumferential surface of the dielectric drum 6 by simple mechanical means. Further, the segment balls 4a and the screw poles 4b may be arranged oppositely to the dielectric drum 6.

〔Effect of the invention〕

As described in detail above, according to the present invention, by arranging the segment electrode as a signal electrode and the spiral electrode as a counter electrode to face each other via a toner transport body made of a dielectric material, no special surface treatment is required. Silence on plain paper? I! An electrostatic recording device capable of recording information can be easily realized by a simple image forming process that does not form a latent image. In this case, an electrostatic recording device can be provided at low cost because a print head with a complicated structure such as a multi-stylus is not required, and individual image forming process members such as a developer and a cleaner are not required. Furthermore, since printing is performed directly on plain paper via a dielectric material, good printing quality can be stably obtained regardless of environmental conditions such as humidity. Furthermore, since only the minimum amount of toner required is transferred to the paper, toner consumption efficiency is improved and running costs are reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing the overall structure of an electrostatic recording device as an embodiment of the present invention, FIG. 2 is a perspective view showing the printing section of the electrostatic recording device, and FIG. ) and Figure 3(b)
) are longitudinal cross-sectional views showing different configurations of the screw poles, FIG. 4 is a plan view showing the arrangement relationship between segment electrodes and linear electrodes, FIG. 5 is an explanatory diagram showing printing timing in the sub-scanning direction, and FIG. 7 and 7 are schematic cross-sectional views and enlarged cross-sectional views respectively showing the electrode facing part F and its main parts, FIG. 8 is a printing time chart of each segment electrode, and FIG. 9 is a timing diagram of the drive clock. The chart diagram and FIG. 10 are explanatory diagrams showing a modified embodiment of the present invention. 1... Paper feed cassette 2... Standby roll pair 3.
... Static elimination brush 4 ... Print head 4a ...
Segment ball 4b...Screw pole 4d...Segment electrode 4f...High voltage power supply 4g...
... Linear electrode 5 ... Toner supply device 6 ... Dielectric drum 8 ... Scraper 7 ... Corona discharger 9 ... Stirring roll 14 ... Toner adhesion plate

Claims (1)

[Claims] an endless dielectric body provided to be movable in a predetermined direction; toner attachment means for uniformly attaching toner to the surface of the dielectric body; It has a plurality of segment electrodes disposed on one side of a paper facing part in which paper faces are made to face each other, and a screw pole rotatably disposed on the other side of the paper facing part and having a spiral electrode laid on its circumferential surface. . An electrostatic recording device, wherein toner on the dielectric material is selectively transferred to the paper by applying a high voltage according to print information between the segment electrode and the screw pole.