JPS63271364A - Recorder - Google Patents

Abstract

PURPOSE:To increase image density without thickening the layer thickness of developer carried by a developer carrier, to prevent the generation of fogging and to obtain an excellent multiple color image by setting up the moving speed of the developer carrier faster than that of an image carrier. CONSTITUTION:The image carrier 12 to be moved in a prescribed direction is provided with latent image forming means 16, 22 for forming electrostatic latent images, the 1st and 2nd developing means 18, 24 for supplying the developer to the electrostatic latent images and forming developed images, a bias voltage impressing means, and a transfer means 26 for collectively transferring the developed images to a recording body. The 1st and 2nd developing means 18, 24 forms the developed images contactlessly with the image carrier 12. The 1st developing means 18 has the developer carrier to be moved while carrying the developer on its surface and the moving speed of the developer carrier is set up faster than that of the image carrier 12. Consequently, the image density can be increased without thickening the layer thickness of the developer, the generation of fogging can be prevented and an excellent multiple color image can be obtained.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Field of Application) The present invention is directed to the production of one set of one copy per revolution or one set of two revolutions.
The present invention relates to a recording device such as a multicolor electrophotographic device for copying.

(Prior Art) In the field of color recording technology, conventional techniques include first charging, first image exposure, first development, second charging (recharging), and second charging.
A method is known in which a color image is obtained by repeating the process of image exposure and second development a necessary number of times and then transferring the images all at once to recording paper (U.S. Pat. No. 4,61,90).
1).

However, if a non-contact type developing device is used and the layer thickness of the developer is increased in order to obtain sufficient image density by the first development, fogging will increase significantly as well as image density. The problem is that there isn't one. Moreover, 1. This fog hardly occurs in normal monochromatic recording, and is unique to this method.

The reason for this is that, as shown in FIG. 5(a), in the color process, among the developer images formed by the first development, the developer 2a of normal polarity (in this case, positive polarity) is
Although it adheres to the image area A, the defective developer 2b of opposite polarity (negative polarity in this case) mixed in the developer adheres to the non-image area B.

In conventional monochromatic recording, since the transfer is then performed by a negatively charged corona device (not shown) in the transfer process, the transferred developer on the photoreceptor drum 6 is of positive polarity (i.e. Only the regular developer 2a) is transferred, and the developer 2b in the non-image area B is hardly transferred. For this reason,
It's not a big problem.

However, in this method, as shown in FIG. 5(b), as a result of receiving the second charge of positive polarity by the charging corona device 4, all of the developer up to the opposite polarity developer 2b on the photoreceptor drum 6 is charged. It becomes positive polarity. After that, as shown in FIG. 5(C), when the transfer is performed on the transfer paper 8 by negative corona after the second development, the developer 2b in the non-image area B is
Since all of the images are transferred, the fog becomes extremely large.

Furthermore, as shown in Figure 6, when trying to increase the image density by increasing the thickness of the toner on the developing roller (unit: a+g/cff12), the fogging in non-image areas also increases rapidly. There is a problem.

Such problems can be solved by - component toner being pressed with an elastic pressing blade (
The toner is formed into a thin layer on the developing roller (toner forming blade) and at the same time tribo-electrified, placed opposite the electrostatic latent image surface of 400 to 1000 volts without contact, and developed by applying an alternating current or direct current bias voltage to the gap. In addition to non-contact developing devices, this problem also occurs in non-contact developing devices that separate only toner from a two-component developer onto a developing roller to form a single layer of toner, and other known non-contact developing devices. This is a difficult problem in that fogging cannot be prevented unless all toner is completely removed.

(Problems to be Solved by the Invention) As described above, when a non-contact developing device is used and the toner layer is made thicker in order to increase the image density, there is a problem in that fog increases significantly as the image density increases.

The present invention has been made based on the above-mentioned circumstances, and an object of the present invention is to provide a recording device that prevents fogging and allows good multicolor images to be obtained. a latent image forming means for forming an electrostatic latent image on an image bearing member moving in a predetermined direction; and a latent image forming means provided along the moving direction of the image bearing member for developing the electrostatic latent image formed by the latent image forming means. a first and a second for supplying a developer to form a developer image;
a developing means, a bias voltage applying means for applying an alternating current electric field during development between the first and second developing means and the image carrier, and a developer formed by the first and second developing means. and a transfer means for transferring the image onto the recording medium at once,
The first and second developing means form a developer image without contacting the image carrier, and the first developing means has a developer carrier that moves while carrying developer on its surface. However, the moving speed of this developer carrier is faster than the moving speed of the image carrier.

(Function) The moving speed of the developer carrier is made faster than the moving speed of the image carrier, thereby increasing the image density without increasing the layer thickness of the developer carried on the developer carrier.

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 3.

Reference numeral 12 in FIG. 1 denotes a photosensitive drum (image carrier) rotatably provided in the direction of arrow a. Around this photosensitive drum 12, a first charger 14, a first image exposure device 16, a first developing device (first developing means) 18, a second
, a charging charger 20, a second image exposure device 22, a second developing device (second developing means) 24, a transfer charger (transfer means) 26, a peeling charger 28, a cleaning device 30. and a static eliminator 32 are arranged in this order along the rotational direction of the photoreceptor drum 12.

Further, 34 indicates the photosensitive drum 12 and the transfer charger 26.
This is a transport path for the transfer paper (recording material) p that passes between the film and the peeling charger 28, and this transport path 34 includes a fixing device 36.
is provided.

The first and second chargers 14.20 charge the surface of the photoreceptor drum 12 by corona discharge, and the first and second image exposure devices 16.22 emit laser light in accordance with the image information to be recorded. An electrostatic latent image is formed on the charged portion of the photosensitive drum 12 by irradiating the beams 16a and 22a.

The first and second developing devices 18 and 24 perform so-called -component non-magnetic non-contact development, and the first developing device 18 uses black toner (-component developer) T as the first color. The second developing device 24 uses blue toner T as a second color to develop each electrostatic latent image to form a toner image.

The transfer charger 26 transfers the toner image on the photosensitive drum 12 onto the transfer paper p by applying an electric charge to the back surface of the transfer paper p on the transfer path 34, and the peeling charger 28 transfers the toner image on the transfer paper p after transfer. is electrostatically peeled off from the photoreceptor drum 12.

The fixing device 36 fixes the toner image transferred onto the transfer paper p. The cleaning device 30 removes the toner T remaining on the photoreceptor drum 12 without being transferred, and the static elimination lamp 32 removes the residual potential on the photoreceptor drum 12.

Next, the operation of the device configured as described above will be explained.

The photosensitive drum 12 is rotated in the direction of arrow a, and its surface is first uniformly charged to about 600V by the first charger 14.

゛Next, the first laser beam 16a is irradiated from the first image exposure device 16 to the charged portion of the photoreceptor drum 12 corresponding to the black portion of the information to be recorded, thereby forming an electrostatic latent image. Ru.

In this case, the exposed portion has a potential of, for example, approximately 10
It is formed to a potential of 0■. That is, a so-called potential well is dug by the first laser beam 16a.

Next, black toner T is supplied from the first developing device 18 and electrostatically adheres to the electrostatic latent image.

As a result, a toner image (developer image) is formed.

In this case, positively charged black toner T is attached to the potential well, and so-called reversal development is performed.

Next, the second charger 2 is directed toward this toner image.
The surface potential of the photoreceptor drum 12 is uniformized to approximately 1000V by applying corona discharge. In this case, the background potential, that is, the potential of the portion not exposed by the first image exposure device 16 is charged to about 1000V, and the potential of the exposed portion where a potential well is formed is charged to about 950V.

Next, a second laser beam 22a is irradiated from the second image exposure device 22 to form an electrostatic latent image to form a blue image. In this case, only the image area is exposed and a potential well of 100V is formed.

Next, a second developing device 24 is installed in this potential well.
The toner T is attached thereto, and reversal development is performed in the same manner as the development by the first developing device 18.

Next, the black toner image and the blue toner image formed on the photosensitive drum 12 are transferred all at once onto the transfer paper p on the transfer path 34 by the transfer charger 26. in this case,
In the transfer charger 26, corona ions having a polarity opposite to that of the photoconductor drum 12, that is, negative corona ions, are applied to the back surface of the transfer paper p that has been conveyed to the transfer charger 26 portion in synchronization with the photoconductor drum 12. is applied to charge the transfer paper p. As a result, an electric field is formed between the photosensitive drum 12 and the transfer paper p, so that the toner image is transferred to the transfer paper p by Coulomb force.

The transfer paper p on which the toner image has been transferred is transferred to a peeling charger 28
It is peeled off from the photoreceptor drum 12 by the fixed tube device 36.
The toner image is transported to the transfer paper p, where the toner image is fixed on the transfer paper p.

On the other hand, the toner T remaining on the surface of the photosensitive drum 12 without being transferred to the transfer paper p is removed by the cleaning device 30. Then, the surface of the photoreceptor drum 12 is neutralized by the static eliminating device 32 .

Next, the first and second developing devices 18.24 will be explained.

As shown in FIG. 2, the developing device 18.24 includes a storage section 38 that stores the toner T, and a developing roller (developer-carrying member) that supplies the toner T in the storage section 28 toward the photoreceptor drum 12. body) 40 are provided. Developing roller 40
is provided so as to be rotatable in the direction of the arrow. The peripheral surface of the developing roller 40 is roughened to facilitate triboelectric charging and conveyance of the toner. The tip of an elastic blade 42 extending toward the storage section 38 is pressed around the developing roller 40 . Since the tip of the elastic blade 42 extends in the direction opposite to the rotation of the developing roller 40, the wedge-shaped space formed by the surfaces of the elastic blade 42 and the developing roller 40 is reduced. It is possible to prevent the toner T from being embedded in the toner. In addition, the first
In the developing device 18, the layer thickness of the toner T on the developing roller 40 is kept below a thickness at which the toner T does not have a component of opposite polarity.

Inside the storage portion 38, there is further a stirrer 4 for stirring the toner T.
A supply roller 46 is provided for supplying toner T to the developer roller 4 and the developing roller 40 . The supply roller 46 is provided in contact with the developing roller 40 and is configured to rotate in a direction opposite to the rotational direction of the developing roller 40 (direction C). Below the developing roller 40 is a collecting blade 4.
8 is pressed against the developing roller 40, and the toner T remaining on the developing roller 40 is collected into the storage section 38.

The developing roller 40 and the photosensitive drum 12 are opposed to each other with a predetermined gap therebetween. An alternating current bias voltage is applied between the developing roller 40 and the photosensitive drum 12 by a bias power source (bias voltage applying means) 50. In the second developing device 24, only a unidirectional electric field is generated by the bias power supply 50.

In the first developing device 18, the peripheral surface of the developing roller 40 is configured to move at a faster speed than the moving speed of the surface of the photoreceptor drum 12 and in the same direction at mutually opposing portions.

On the other hand, in the second developing device 24, the circumferential surface of the developing roller 40 moves at approximately the same speed as the moving speed of the surface of the photoreceptor drum 12 and in the same direction at mutually opposing portions.

According to the above configuration, since the moving speed of the developing roller 40 of the first developing device 18 is made faster than the moving speed of the photoreceptor drum 12, the layer thickness of the toner T carried on the developing roller 40 can be increased. The image density can be increased without any problems. That is, when the speed ratio of the developing roller 40 to the photosensitive drum 12 is increased from the conventional 1:1 speed ratio, the image density increases significantly, as shown in FIG. 3. Moreover, if the layer thickness of the toner T is set to 1 mg/crA2 or less (for example, m-0,7 mg/cm2 in FIG. 6), fogging can be sufficiently tolerated even at a relative speed of 3.
A sufficient image density of around 1.5 can be obtained. In this way, the layer thickness of the toner T on the developing roller 40 is set to be sufficiently thin so that uncharged toner T does not occur, and the resulting decrease in image density can be improved by changing the speed of the developing roller 40.

In addition, in the second developing device 24, even if toner T of the opposite polarity were to adhere to the non-image area, the polarity would not be reversed.
It is difficult to appear as a fog on the transfer paper p. Moreover, only a unidirectional electric field is formed between the developing roller 40 and the photosensitive drum 12, that is, for example, a DC electric field or a bias voltage with a superimposed alternating current that does not generate this field is applied. The toner image formed by the first developing device 18 is not peeled off by the second developing device 24. Note that when using the DC bias voltage, the developing roller 40
If the photosensitive drum 12 does not have a substantially constant velocity, blurring of thin lines or ghost images will occur, so it is necessary that the photosensitive drum 12 have no relative velocity. Moreover, since the second developing device 24 is of a non-contact type, the toner image formed by the first developing device 18 is not peeled off due to mechanical contact.

In the above embodiment, the - component toner T is applied with an elastic pressing blade (
The toner is formed into a thin layer on the developing roller 40 by the toner forming blade (toner forming blade) 42, and at the same time is frictionally charged. A non-contact developing device 18.24 was used for the development, and as shown in FIG. It is also possible to use a non-contact developing device 64 that forms a single layer of toner by separating it on top. In FIG. 4, 66 is a toner hopper, 68 is a bias power source for toner separation, and 70 is an AC bias power source.

Further, in the above embodiment, a so-called one-rotation, one-copy set of multicolor recording apparatus has been described, but the present invention may be applied to a so-called two-rotation, one-copy set of recording apparatus.

That is, for example, a charger, an image exposure device, a first developing device, a second developing device,
and a transfer charger are arranged in this order, and during the first rotation of the photosensitive drum, first charging is performed by the charger, first latent image formation is performed by the image exposure device, and first latent image is formed by the image exposure device.
During the second rotation of the photosensitive drum, second charging is performed by the charger, second latent image formation is performed by the image exposure device, development is performed by the second developing means, and the above is performed by the developing device. The transfer may be performed using a transfer charger.

[Effects of the Invention] As explained above, according to the present invention, the moving speed of the developer carrier is made faster than the moving speed of the image carrier, thereby increasing the layer thickness of the developer carried on the developer carrier. Since the image density can be increased without increasing the thickness, fogging can be prevented and excellent effects such as good multicolor images can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing an embodiment of a multicolor recording device according to the present invention, FIG. 2 is a sectional view showing a developing device of the same device, and FIG. 3 is a diagram showing image density, photoreceptor drum, and developing roller. FIG. 4 is a sectional view showing another embodiment of the developing device used in FIG. 1, and FIGS. 5(a) to (c)
) is a diagram for explaining the problems of the conventional apparatus, and FIG. 6 is a diagram showing the relationship between image density and toner layer thickness. 12... Image carrier (photosensitive drum), 14... First
electrification charger, 16...first image exposure device, 18
...First developing means (first developing device), 2°...
Second electrification charger, 22... second image exposure device,
T... Developer (toner), 24... Second developing means (second developing device), 26... Transfer means (transfer charger), 40... Developer carrier (developing roller) , 50
...bias voltage application means (bias power supply), p...
・Recording material (transfer paper). Applicant's representative Patent attorney Takehiko Suzue 113 Figure 6 Procedural amendments Director General of the Patent Office Kunio Ogawa 1, Case indication patent application No. 106836/1983 2, Invention title recording device 3, Relationship with the case of the person making the amendment Patent applicant (307) Toshiba Corporation 4, agent 3-7-2 Kasumigaseki, Chiyoda-ku, Tokyo UBE Building The scope of the patent claims is amended as shown in the attached document. 2. Claims (1) A latent image forming means for forming an electrostatic latent image on an image bearing member moving in a predetermined direction; and a latent image forming means provided along the moving direction of the image bearing member; First and second developing means supply developer to the formed electrostatic latent image to form a developer image, and a developing device is provided between the first and second developing means and the image carrier. a bias voltage applying means for applying an alternating current electric field; and a transfer means for collectively transferring developer images formed by the first and second developing means onto a recording medium; The developing means forms a developer image without contacting the image carrier pair, and the first developing means has a developer carrier that moves while carrying developer on its surface. A recording apparatus characterized in that the moving speed of the developer carrier is faster than the moving speed of the image carrier. (2) The second developing means has a developer carrier that moves while carrying a developer on its surface, and the developer carrier moves at a speed approximately equal to the moving speed of the image carrier and has mutually opposing portions. and a unidirectional electric field is formed between the image carrier and the second developing means. Recording device. (3) Claims characterized in that the layer thickness of the developer supported on the developer carrier of the first developing means is kept below a thickness at which the developer does not contain components of opposite polarity. The recording device according to item 1. (4) The image carrier is a drum-shaped member that rotates in a predetermined direction, and during the first rotation of the image carrier, the latent image forming means forms a first latent image, and the first developing means development is performed, and during the second rotation of the image carrier, a second latent image is formed by the latent image forming means, development is performed by the second developing means, and transfer is performed by the transfer means. A recording device according to claim 1, characterized in that:

Claims (4)

[Claims] (1) A latent image forming means for forming an electrostatic latent image on an image bearing member moving in a predetermined direction; and a latent image forming means provided along the moving direction of the image bearing member, and an electrostatic latent image formed by the latent image forming means. first and second developing means supplying developer to the image to form a developer image; applying an alternating current electric field between the first and second developing means and the image carrier during development; A bias voltage applying means and a transfer means for collectively transferring the developer images formed by the first and second developing means onto the recording medium, the first and second developing means The first developing means forms a developer image without contacting the carrier, and the first developing means has a developer carrier that moves while carrying the developer on its surface, and the movement of the developer carrier A recording device characterized in that the speed is faster than the moving speed of the image carrier. (2) The second developing means has a developer carrier that moves while carrying a developer on its surface, and the developer carrier moves at a speed approximately equal to the moving speed of the image carrier and has mutually opposing portions. and a unidirectional electric field is formed between the image carrier and the second developing means. Recording device. (3) Claims characterized in that the layer pressure of the developer supported on the developer carrier of the first developing means is kept below a thickness at which the developer does not have a component of opposite polarity. The recording device according to item 1. (4) The image carrier is a drum-shaped member that rotates in a predetermined direction, and during the first rotation of the image carrier, the latent image forming means forms a first latent image, and the first developing means development is performed, and during the second rotation of the image carrier, a second latent image is formed by the latent image forming means, development is performed by the second developing means, and transfer is performed by the transfer means. A recording device according to claim 1, characterized in that: