JPH04195070A - Electrostatic recorder - Google Patents

Abstract

PURPOSE:To improve the density of a transferred image without increasing the amount of developer carried on a developer carrier by transferring a developer thin layer on the developer carrier to a recording medium which moves at a speed lower than the moving speed of the surface of the developer carrier. CONSTITUTION:The carrying speed B of the recording medium 18 is set at a specified value by a recording medium carrying speed control means 23. Then, an image signal speed control means 20 supplies an image signal to an ion current modulation means 8 at an image signal speed synchronizing with the carrying speed B of the medium 18. Meanwhile, a developer carrier control means 21 sets the carrying speed A of the developer thin layer on the carrier 4 alpha times (alpha>1) as high as the carrying speed B of the medium 18. Namely, an electrostatic latent image formed on the developer thin layer is varied in terms of power to be alpha times in a developer thin layer carrying direction. Furthermore, the electrostatic latent image is compressed to be 1/alpha when it is transferred to the medium 18 and a developed image is formed on the medium 18. Thus, the density of the developer on the recording medium is made alpha times as high as the density on the developer carrier, and the image density is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrostatic recording device, and in particular to an electrostatic recording device in which image signals are formed on a thin layer of charged developer on a developer carrier by means of ion flow modulation means. The present invention relates to an electrostatic recording device that forms a corresponding latent image and selectively transfers this latent image onto a recording medium to make it visible.

[Conventional technology]

As a type of electrostatic recording device that uses electrophotography,
As disclosed in U.S. Pat. No. 3,689,935, developer is supplied from a developer (toner) supply source and from an array of opening electrode pairs facing each other in the main scanning direction with an insulating layer in between. 2. Description of the Related Art Electrostatic recording apparatuses are known that control the amount of charged developer that passes through using a control means to form an image of the developer on a recording medium in accordance with an image signal.

In this type of electrostatic recording device, developer adheres to the opening of the control means, contaminating the area around the opening, and in severe cases, clogging may occur, resulting in no recording or low recording speed. , it has not been put into practical use.

Further, the electrostatic recording device disclosed in Japanese Patent Publication No. 5B-33550 modulates the ion flow according to the image signal by means of ion modulation means, and between the ion modulation means and the recording medium,
An image is formed by charging solid or aerosol developer particles in accordance with an image signal and depositing the charged developer on a recording medium.

However, with this method, it is difficult to supply the developer uniformly, and the inside of the apparatus is contaminated by scattering of the developer.

In order to solve this problem, as disclosed in Japanese Patent Application Laid-Open No. 61-25166, an ion generator is used to apply an image to a thin layer of a developer having a -like charge formed on a developer carrier. A method of writing a latent image by irradiating an ion flow modulated according to a signal has been proposed.

As the above-mentioned ion generator, for example, Japanese Patent Application Laid-Open No. 59-164
The air flow assisted ion flow control head (hereinafter simply referred to as an ion head) disclosed in Japanese Patent Application Laid-open No. 154 and Japanese Patent Application Laid-Open No. 190854/1987 is suitable.

These ion heads are fixed so as to form a main scanning line with respect to the developer carrier, and have an ion generation source connected to a high-voltage power supply inside, and generate ion flow using compressed air flow and an electric field. It is something that generates.

A control electrode for ion flow modulation is provided in the ion flow path from the ion generation source to the ion head exit opening, and controls the ion flow by passing or blocking the ion flow in response to image signals. The electrostatic latent image can be modulated to write an electrostatic latent image on a thin layer of developer formed on the developer carrier facing the ion outlet opening.

A developed image is obtained by inserting a recording medium between the developer carrier and the transfer electrode, and transferring this electrostatic latent image onto the recording medium using a transfer electric field applied between the developer carrier and the transfer electrode. It is something.

The advantages of using the above-mentioned ion head are that a large amount of ions can be extracted from the ion source compared to when there is no air flow, and that the voltage applied to the control electrode for ion flow modulation can be reduced ( Furthermore, since the airflow is used, the outlet opening is less likely to be clogged with toner.

[Problem to be solved by the invention]

In an electrostatic recording device in which a developed image is obtained by transferring an electrostatic latent image formed by a modulated ion flow onto a thin layer of developer on a developer carrier onto a recording medium using a transfer electric field, the developer carrier is The thin layer of developer carried on the body is a single layer of the developer, or an extremely thin layer close to a single layer.

Therefore, there is a problem in that the absolute amount of developer for forming a transferred image (developed image) is limited, making it impossible to obtain a sufficient density of the recorded image.

An object of the present invention is to provide electrostatic recording that can improve the density of a developed image transferred onto a recording medium, that is, a transferred image, without increasing the absolute amount of developer carried on a developer carrier. The goal is to provide equipment.

[Means to solve the problem]

The present invention provides a thin layer of developer that is formed on the surface of a developer carrier that moves at a certain speed relative to a fixed ion head, and is transported while being irradiated with an ion stream and forming a latent image.
By transferring the image onto a recording medium that moves at a speed lower than the moving speed of the surface of the developer carrier, the image is compressed on the recording medium and the density of the image is improved.

That is, in order to achieve the above object, the present invention comprises: a developer carrier (4) carrying a thin layer of charged developer on its surface; an ion generating means (7); and an ion flow modulating means (8). ), a modulated ion flow supply means (6) for supplying an ion flow modulated by an image signal toward a thin layer of developer on the developer carrier; In an electrostatic recording device, the electrostatic latent image formed on a thin layer of developer on a developer carrier by the modulated ion flow supply means is transferred to a recording medium by a developer In the transport direction,
α times the developed image obtained on the recording medium by the transfer means (α〉
1), comprising an electrostatic latent image biasing means for biasing the magnification, and as the electrostatic latent image biasing means, an image signal speed control means (20) for controlling the speed of the image signal supplied to the ion flow modulation means. a developer carrier control means (21) for controlling the conveyance speed of the thin layer of developer on the developer carrier; and a recording medium conveyance speed control means (23) for controlling the conveyance speed of the recording medium. It is characterized by having the following.

[Function] By sliding the layer forming member (5), a thin layer of a developer uniformly charged, for example, negatively, is formed on the surface of the developer carrier (4).

The modulated ion flow supply means (6) consists of an ion generation means (ion source 7) and an ion flow modulation means (control electrode 8).
The positively charged ion flow is modulated according to the image signal,
The thin developer layer is irradiated with this to reverse the charging polarity of the thin developer layer, thereby forming an electrostatic latent image.

At this time, the conveyance speed of the recording medium is set to a certain value by the recording medium conveyance speed control means (23), and the image signal speed control means (20) adjusts the image signal speed synchronized with the recording medium conveyance speed. An image signal is supplied to the ion flow modulation means.

The developer carrier control means (21) increases the conveyance speed of the thin developer layer on the developer carrier by α times the recording medium conveyance speed (α>1).
).

In other words, since the conveying speed of the thin developer layer is α times (α>1) the image signal speed which is synchronized with the recording medium conveying speed, the electrostatic potential formed on the thin developer layer is The image is magnified by α times (α>1) in the developer thin layer transport direction.

The electrostatic latent image formed on the thin developer layer is transferred to the transfer means (17
), when only the developer carrying the latent image is selected based on its charging polarity and transferred to the recording medium (18), the difference in conveyance speed between the developer thin layer and the recording medium increases by 1/2. α is compressed to form a visible image on the recording medium.

As a result, the developer density on the recording medium is increased to α times the density on the developer carrier, so that the image density is improved.

In this way, by enlarging the electrostatic latent image in the sub-scanning direction on the thin developer layer, the resolution of the formed image is improved in the sub-scanning direction, and halftone expression by area gradation is improved. It will be advantageous.

Furthermore, by providing a recording medium speed detection means that feeds back the detection output to the developer carrier control means and the image signal speed control means, it is possible to prevent synchronization between the recording medium conveyance speed and the developer carrier due to fluctuations in the recording medium conveyance speed. It is possible to eliminate density unevenness caused by this, image length unevenness in the sub-scanning direction caused by a synchronization difference between the recording medium conveyance speed and the image signal speed, and the like.

〔Example〕

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

FIG. 1 is a schematic configuration diagram illustrating an embodiment of an electrostatic recording apparatus according to the present invention, in which 1 is a hopper, 2 is a developer, and 3 is a hopper.
4 is an auxiliary roll, 4 is a developer carrier, 5 is a layer forming member, and 6 is an auxiliary roll.
1 is an ion head as a modulated ion flow supply means, 7 is an ion source, 8 is a control electrode as an ion flow modulation means, 9 is an insulating substrate, 10 is an insulating spacer, 11 is a compressed air supply device, 12 is an image signal source, 13 is a DC high-voltage power supply for the ion source, 14 is a DC high-voltage power supply for ion extraction, 16 is a DC high-voltage power supply for transfer, 17 is a transfer electrode, 18 is a recording medium such as transfer paper, 19 is a fixing means, and 20 is an image signal speed. control means, 21
2 is a developer carrier control means; 22 is a recording medium conveyance means;
3 is a recording medium conveyance speed control means. The image signal speed control means, 21 is a developer carrier control means, 22 is a recording medium transport means, and 23 is a recording medium transport speed/control means, which constitutes an electrostatic latent image magnification changing means.

The developer carrier 4 is made of a conductive cylinder or cylinder made of a metal material such as aluminum or stainless steel, or a roll-shaped member in which a dielectric layer made of an insulating material such as phenol resin is formed on the surface of the cylinder.

The developer 2 stored in the hopper 1 is transferred to the auxiliary roll 3
The developer is deposited on the surface of the developer carrier 4 by the rotation of the developer.

When the developer carrier 4 rotates in the direction of the arrow a, the developer 2 deposited on the surface of the developer carrier 4 is moved by the layer forming member 5 that slides in elastic contact with the surface of the developer carrier 4. In addition to being made into a uniform thin layer, the electrostatic charge (here, the negative pole)
is charged.

The ion head 6 includes an ion source 7 made of a discharge wire to which voltage is applied from a DC high voltage power source 13 and a casing 71.
By corona discharge, ions having a polarity opposite to the polarity of the charge on the thin developer layer on the developer carrier 4 (in this case, positive polarity) are generated and supplied to the air chamber from the compressed air supply means 11. An ion stream is output from the slit 61 (ion head output opening) using compressed air kept at a constant pressure.

Further, this slit 61 extends in the axial direction of the developer carrier 4 (hereinafter referred to as the main scanning direction), and this slit 61 is connected to a part of the casing 71 and the control electrode 8 divided into pixel units. are formed by opposing insulating substrates 9 on which are formed.

Note that since the air flow discharged from the slit 61 is directed in the direction of arrow C and the ions are directed in the direction of arrow d, the developer will not be scattered by the air flow.

The insulating substrate 9 is connected to the casing 71 via the insulating spacer 10.
This insulating spacer 10 also has the function of changing the slit size by changing its thickness.

The ion flow is modulated by passing or blocking the ion flow in the slit 61 according to the image signal from the image signal speed control means 20.

An ion extraction high-voltage power supply 14 that forms an ion extraction electric field is connected between the developer carrier 4 and the ground.

Further, a DC high voltage power supply 16 is connected between the transfer electrode 17 and the developer carrier 4 to form a transfer electric field.

The fixing means 19 includes a heating heat loaf 19a and a pressure roll 19b, and heats and presses the recording medium 18 onto which the developer has been transferred to fix the developed image.

At this time, the developer 2 may be either one-component or two-component, and may be magnetic or non-magnetic, as long as it is supported on the surface of the developer carrier 4.

However, when a magnetic developer is used, the developer carrier 4 needs to be a cylindrical roll equipped with a magnet that magnetically attracts the developer.

When the developer is a one-component type developer, as shown in the figure, the developer is thinned by a layer forming means 5 that applies a triboelectric charge by contacting the developer directly supplied onto the developer carrier 4. form a layer.

In addition, when using a two-component developer, a bias voltage is applied between the developing roll and the developer carrier of a known two-component developer for electrophotography to transfer the developer onto the developer carrier. A thin developer film is formed by a method such as uniform deposition.

An ion flow modulated according to an image signal applied to the control electrode 8 is irradiated from the slit 61 of the ion head 6 toward the developer carrier 4 on which a thin layer of developer has been formed. The charging polarity (in this case, negative polarity) of the upper developer thin layer is reversed to positive polarity to form an electrostatic latent image.

The developer carrier 4 on which the electrostatic latent image has been formed continues to rotate and reaches the transfer section 170 where the transfer electrode 17 is arranged.

In the transfer section 170, the recording medium 18 is conveyed and reflected in the direction indicated by the arrow in contact with the transfer electrode 17 between the transfer electrode 17 and the developer carrier 4.

A transfer power source 1 is provided between the transfer electrode 17 and the developer carrier 4.
A transfer electric field is formed by 6 and the ion extraction power source 14,
Due to the transfer electric field, only the developer whose polarity is reversed is selectively transferred to the recording medium 18 .

The developer is fixed to the recording medium 18 onto which the developer has been transferred by being heated and pressurized by a fixing means 19.

The conveyance speed of the recording medium 18 is determined by the recording medium conveyance speed control means 2.
3.

Since the image signal speed synchronized with the transport speed of the recording medium 1B is self-evident, the image signal speed control means 20 sets the image signal speed according to the set transport speed of the recording medium for one day.

At this time, the rotational speed of the developer carrier 4 is such that the circumferential velocity of the surface of the developer carrier 4 (arrow A) is equal to the transport speed of the recording medium 18 (
It is controlled by the developer carrier control means 21 so that it is α times the arrow B) (α>1).

FIG. 2 is a block diagram of main parts for explaining the recording operation of the electrostatic recording apparatus according to the present invention, and the same reference numerals as in FIG. 1 correspond to the same parts.

In the figure, the rotation radius of the developer carrier 4 is R (mm).
, when the angle of rotation is ω (rad/5ec), the circumferential velocity V1 of the surface of the developer carrier 4 relative to the fixed ion head 6 is expressed as V1=R·ω(mm/5ec).

Furthermore, if the conveyance speed of the recording medium 18 is 2, then in this conventional apparatus, V1=V2, and the length of the electrostatic latent image to be written and the image transferred to the recording medium 18 in the recording medium conveyance direction (sub-scanning direction). While the ratio of the height is 1:1, the ratio of the smell of the present invention is as follows: V1=α·V2 (mm/sec).

Note that α>1, and it is preferable to set α to approximately 1.2 to 1.5. However, the present invention is not limited to this.

Furthermore, when the circumferential speed Vl of the surface of the developer carrier 4 is set preferentially, the recording medium conveyance speed ■2 is V2=V1/α(
mm/5ec), and in synchronization with this, the image signal speed is controlled by the image signal speed control means 20.

The control of the image signal line by the image signal speed control means 20 at this time will be explained below.

FIG. 3 is an explanatory diagram of electrostatic latent images on the developer carrier of the image signal line of the prior art and the image signal line of the present invention.

(a) shows the conventional technique, that is, the case where the speeds in the transfer area of the developer carrier and the recording medium are the same, and (b) shows the case of the present invention, that is, the case where the speeds in the transfer area of the developer carrier and the recording medium are α:1. are shown respectively.

In the figure, tL is the length of the latent image in the main scanning direction (line length), jFsLF' is the length of the latent image in the sub-scanning direction (frame length), 1. .about.fn, l, and .about.1n' respectively indicate image signal lines.

In a conventional electrostatic recording device, since the velocity of the developer carrier and the recording medium in the transfer area are equal, the recorded image signal has the same frame length as the transferred image, as shown in (a). 1. A latent image is formed on the developer carrier.

On the other hand, in the present invention, the latent image formed on the developer carrier 4 is multiplied by α by the image signal speed control means 20 shown in FIG. It is formed by being stretched in the sub-scanning direction.

That is, the length tl in the line direction (main scanning direction) is (a
), but each line 21 ′~! n′
The interval is line (a)! It is biased so that it becomes α times the interval of 1 to 2n.

FIG. 4 is an explanatory diagram of the effect of improving the latent image of a recorded image according to the present invention, in which FPo and LPo are the frame pulse (write start pulse) and line pulse (write start pulse) of the image signal input to be recorded.
line writing pulse), FPw and LPw are the frame pulse and line pulse polarized by α times, In is the latent image formed on the developer carrier 4, ! p indicates the developed image transferred onto the recording medium.

In the figure, it is assumed that a line pulse LPo exists between frame pulses FPo, and, for example, image writing starts at the falling edge of the first frame pulse and ends at the rising edge of the next frame pulse.

As a result, the latent image on the developer carrier 4 becomes as shown in In.

As described above, in this type of electrostatic recording device, since the absolute amount of developer in the thin developer layer formed on the developer carrier 4 is small, if the latent image is transferred as it is to the recording medium 18, The image density becomes low.

In the present invention, the conveyance speed of the recording medium 18 is
The line formed by the transfer is compressed in the sub-scanning direction as shown by Ip.

As a result, the density of the developed or transferred image is compressed and a substantial improvement in density is achieved.

FIG. 5 is a schematic configuration diagram of another embodiment of the electrostatic recording apparatus according to the present invention, in which a recording medium conveyance speed detection means 24 is provided in the configuration shown in FIG. 1, and this recording medium conveyance speed detection means The detection output of 24 is sent to the developer carrier control means 21.
This is fed back to the image signal speed control means 20 in real time to avoid density unevenness and transferred image length unevenness caused by subtle fluctuations in the conveyance speed of the recording medium due to gear precision, etc.

That is, in the configuration shown in the figure, the recording medium conveyance speed v2
If the relationship V1=α・V2 (mm/5ec) with the developer thin layer transport speed Vl collapses due to fluctuations in It appears.

Therefore, the developer carrier control means 21 controls the angular velocity ω of the developer carrier 4 based on the signal from the recording medium speed detection means 24 so as to maintain the relationship V1=α·■2 with high precision.

Furthermore, if synchronization with the image signal is lost due to fluctuations in the recording medium conveyance speed (2), In==α·Ip, that is, FPw-cr-FP.

The relationship between the two is disrupted, and this appears in the length and shortness of the transferred image.

Therefore, the image signal speed control means 20 controls the magnification rate of the frame pulse FPw based on the output signal from the recording medium speed detection means 24 so as to maintain the relationship In=α·IP with high precision.

As a result, good image quality without density unevenness, image length unevenness, etc. can be obtained.

Since the recording medium speed detection means 24 can be a known means, its explanation will be omitted here.

Note that the present invention is not limited to the configurations shown in each of the above embodiments, but may be applied to any configuration of the ion head.

The configuration of the developer carrier, the charging polarity of the developer, the shape of the transfer electrode, etc. can be changed arbitrarily within the scope of the idea of the present invention, and the charging characteristics of the developer and the shape of the developer layer can be changed as desired. The thickness, dimensions of each member, discharge amount of compressed air, electric field strength at each part, value of α, etc. are set to optimal values according to other design conditions.

For example, it is possible to use a roll-shaped transfer electrode, and it goes without saying that the present invention can be applied to an electrostatic recording apparatus of a type in which a recording medium is disposed above a horizontal portion where an image is formed.

[Effect of the Invention J As described in detail above, according to the present invention, when the latent image formed on the developer carrier is transferred to the recording medium by the transfer means, the latent image is transferred to the developer carrier and the recording medium. Due to the difference in medium conveyance speed, the image is compressed to 1/α and a visible image is formed on the recording medium.

As a result, the developer adhered to the developer carrier is concentrated on the recording medium, and the developed density, that is, the density of the image formed by transfer, is improved, and the developer adhered to the developer carrier is concentrated on the recording medium. Even if the amount of developer for the formed latent image is small, the finally obtained transferred image will have sufficient density and clear image quality.

That is, by enlarging the electrostatic latent image in the sub-scanning direction on the thin layer of developer deposited on the developer carrier, the resolution of the formed image is improved by α times in the sub-scanning direction. ,
This is advantageous for expressing halftones using area gradation.

Furthermore, by providing a recording medium speed detection means that feeds back a detection signal to the developer carrier control means and the image signal speed control means, it is possible to completely synchronize the recording medium conveyance speed, developer carrier surface circumferential velocity, and image signal velocity. It is possible to reproduce images of good quality without density unevenness, image length unevenness, etc.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram illustrating an embodiment of the electrostatic recording device according to the present invention, FIG. 2 is a diagram illustrating the main part of the electrostatic recording operation according to the present invention, and FIG. 3 is an image of the prior art. FIG. 4 is an explanatory diagram of the electrostatic latent image on the developer carrier of the signal line and the image signal line of the present invention. FIG. 4 is an explanatory diagram of the density improvement effect of the recorded image according to the present invention. FIG. It is a schematic structure explaining another example of a recording device. L: hopper, 2: developer, 3: auxiliary roll, 4: developer carrier, 5: layer forming member, 6: ion head, 7...Ion source,
8... Control electrode as ion flow modulation means, 9...
...Insulating substrate, 10...Insulating spacer, 11...
- Compressed air supply device, 12... Image signal source, 13.
... DC high voltage power supply for ion source, 14... Power supply for ion extraction, 16... DC high voltage power supply for transfer, 17...
...Transfer electrode, 18...Recording medium, 19...Fixing means, 20...Image signal speed control means, 21...
. . . Developer carrier control means, 22. . . Recording medium conveyance means, 23. . . Recording medium conveyance speed control means, 24.
...Recording medium conveyance speed detection means.

Claims (1)

[Scope of Claims] Consisting of a developer carrier carrying a charged developer thin layer on its surface, an ion flow generating means and an ion flow modulating means, the developer carrier is configured to direct the developer toward the developer thin layer on the developer carrier. An electrostatic recording device comprising: a modulated ion flow supply means for supplying an ion flow modulated by an image signal; and a transfer means for selectively transferring the developer on the developer carrier to a recording medium. An electrostatic latent image formed on a thin layer of developer on a developer carrier by a flow supply means is biased in the developer conveyance direction to α times the conveyance speed of the recording medium (α>1). An electrostatic recording device characterized by being provided with an image deflection magnification means.