JP2000267405A - Method and device for latent image formation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suitably control gradation and to form a sharp multivalued latent image having high resolution, by selectively applying voltage of different voltage values to an image carrier provided with a ferroelectric layer, causing polarizations of different intensities in the ferromagnetic layer, thereby forming a multivalued, polarized latent image. SOLUTION: By means of a heater 2 the entire ferroelectric layer 1b of an image carrier 1 is heated to a temperature that is lower than a Curie point, and polarization is removed. Then, a voltage is applied to the image carrier 1 by the conductive roller 3b of a voltage application device 3. Consequently, the ferroelectric layer 1b is polarized in one direction by the specific electric fluid. Further, according to an image to be formed, a voltage is applied to each area of the image carrier 1 from the electrode of a latent-image writing device 4. By applying the voltage of different values to the once uniformly polarized image carrier 1 by the latent-image writing device 4 in such a manner, different remanent polarizations of different intensities occur in the ferromagnetic layer 1b, so that a multivalued, polarized latent image is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a latent image forming method and a latent image forming apparatus used for an image forming apparatus such as a copying machine, a printer, a facsimile, and the like.

[0002]

2. Description of the Related Art An electrophotographic latent image forming method of forming a latent image by uniformly charging the surface of an image carrier made of a photoreceptor by discharging and then selectively attenuating the potential by exposure is known. Have been. However, this electrophotography method
Ozone is generated at the time of discharge, the surface of the photoreceptor is deteriorated by NOx, so it is necessary to use the photoreceptor while shaving it, resulting in poor durability, and the latent image is unstable with changes in temperature and humidity environment. There is. In electrophotography,
So-called repetition printing is impossible and productivity is low.

On the other hand, a latent image forming method using an image carrier having a ferroelectric substance or a pyroelectric substance has been proposed. Since a latent image forming method of this type generally forms a binary latent image, a density gradation technique using a multi-valued latent image essential for obtaining a high-definition image has been demanded. . On the other hand, Japanese Patent Application Laid-Open No. 9-281781 has an image carrier having a pyroelectric layer and a thermal head, and realizes a density gradation by forming a multi-valued latent image by adjusting a heating amount. A latent image forming method has been proposed.

[0004]

However, Japanese Patent Application Laid-Open No.
In the latent image forming method described in Japanese Patent No. 281781, the amount of heat stored in the thermal head and the pyroelectric element changes, so that high-precision gradation control is difficult, and a desired gradation cannot be obtained. Further, in this latent image forming method, since the heat applied by the thermal head is diffused in the pyroelectric body, the potential difference between the latent image portion and the other portions is reduced, so that the edge of the visualized image is not affected. Clarity is not enough resolution.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a latent image forming method capable of suitably controlling gradation and forming a high-resolution clear multi-valued latent image.

[0006]

In order to solve the above-mentioned problems, a first invention is to apply a voltage to an image carrier having a ferroelectric layer selectively and with different voltage values, and It is an object of the present invention to provide a latent image forming method for forming a multi-level polarization latent image by causing polarization of different strengths in a dielectric layer.

In the latent image forming method of the present invention, a multi-valued polarized latent image is formed on an image carrier. Therefore, when this polarized latent image is visualized with toner or liquid ink and transferred to a transfer material, an image having a density gradation is obtained. Further, the latent image forming method of the present invention forms a polarization latent image by a voltage,
The blurring of the latent image as in the case of using the pyroelectric effect is reduced, and a latent image having a large potential difference between the latent image portion and other portions can be formed with high resolution. Further, in the latent image forming method of the present invention, gradation control can be easily performed only by adjusting the voltage value.

It is preferable that the ferroelectric layer is preliminarily polarized in one direction before the voltage is applied to the image carrier selectively and at different voltage values. If a multi-value voltage is applied while the polarization of the ferroelectric layer is made uniform once,
The gradation control by making the voltage values different is further facilitated.

It is preferable to apply heat to the ferroelectric layer to eliminate polarization by applying a voltage to the image carrier selectively and with different voltage values. As described above, once the polarization of the ferroelectric layer is erased, gradation control by changing the voltage value becomes easier.

According to a second aspect of the present invention, there is provided an image carrier having a ferroelectric layer, and a voltage selectively applied to the image carrier with different voltage values, and polarization having different intensities is applied to the ferroelectric layer. And a multi-level voltage applying means for forming a multi-level polarization latent image.

Before applying a voltage by the multi-value voltage applying means, it is preferable to provide a voltage applying means for polarizing the ferroelectric layer in one direction.

It is preferable to provide a heat applying means for applying heat to the ferroelectric layer to eliminate polarization before applying a voltage by the multi-value voltage applying means.

The latent image forming apparatus includes: developing means for electrostatically supplying a developer to the polarized latent image of the image carrier to visualize the latent image; and transfer means for transferring the developer image to a transfer medium. Further, it may be provided.

[0014]

Next, an embodiment of the present invention shown in the drawings will be described. (First Embodiment) A heating device (heat applying means) 2 and a voltage applying device (voltage applying means) are arranged around an image carrier 1 which is rotationally driven by a driving device (not shown) along a rotation direction indicated by an arrow A. 3.) Latent image writing device (multi-value voltage applying means)
4, a developing device 5, a transfer device 6, and a cleaning device 7 are provided. The image forming apparatus includes a fixing device 8.

The image carrier 1 is provided on a drum 1a made of aluminum by PVDF / TeFE (a copolymer of vinylidene fluoride and tetrafluoroethylene, and a VDF fraction of 80%).
mol%) of the ferroelectric material by the dipping method to a film thickness of about 3 μm.
The ferroelectric layer 1b applied so as to be m is provided.
The drum 1a is grounded. The material forming the ferroelectric layer 1b is not limited to PVDF / TeFE, and any material having polarization orientation may be used, and a known ferroelectric material can be used. For example, the ferroelectric layer 1b is made of lead titanate, lithium tantalate, barium titanate, P
LZT, polyvinylidene cyanide, a copolymer of vinylidene cyanide and vinyl acetate, vinylidene cyanide, a copolymer of vinylidene fluoride and trifluoroethylene, and the like may be used.

The heating device 2 has a heat roller 2a which is heated by a heater (not shown), and has a function of heating the ferroelectric layer 1b of the image carrier 1 to about 120 ° C. to erase the polarization as described later. Have. The heat roller 2a may be in contact with or close to the surface of the image carrier 1. The structure of the heating device 2 is not particularly limited, and may include a plate-shaped or belt-shaped heat conducting member,
The image carrier 1 may be heated by a method such as radiation heating or induction heating.

The voltage applying device 3 is connected to a power source 3a, includes a conductive roller 3b that rotates in contact with the surface of the image carrier 1, and a ferroelectric material of the image carrier 1 as described later. It has a function of polarizing the layer 1b in one direction. The voltage application device 3 may be a device that superimposes and applies an AC voltage. In this case, the ferroelectric layer 1b can be more stably and uniformly polarized. The structure of the voltage applying device 3 is not particularly limited, and may be a conductive brush, a conductive blade, a conductive film, an injection charger via a conductive liquid, or a charging corona charger.

The latent image writing device 4 includes a multi-stylus array 10, a voltage adjusting device 11, and a power supply 12.

As shown in FIG. 2, the multi-stylus array 10 includes a resin base 10a.
Many fine electrodes 10b are arranged in series at a constant pitch. The power supply 12 is connected to each electrode 10b via the voltage adjusting device 11. The voltage adjusting device 11 controls whether or not a voltage is applied to each electrode 10b and a voltage value to be applied based on image information read by an image reader or the like or a print supplied from an external device such as a personal computer.

The latent image writing device 4 is not limited to the one having the multi-stylus array as described above.
It may be an ion flow charger or the like.

The developing device 5 includes a thin layer roller 5b and a stirring / transporting roller 5c in a housing 5a containing the toner 13. The negatively charged toner 13 for forming a thin layer on the thin layer roller 5b is used for the developing device 5. Then, the latent image formed on the surface of the image carrier 1 is electrostatically supplied, and the latent image is visualized as a toner image.

The developing method of the developing device 5 is not particularly limited. In addition to the dry or wet developing method generally used in the electrophotographic method, a liquid ink is deposited by utilizing a change in wettability due to charging and polarization. It may be.

The transfer device 6 includes a transfer roller 6a to which a voltage having a polarity opposite to that of the toner image on the surface of the image carrier 1 is applied from a power supply (not shown). The toner image is transferred to the transfer medium 14.

The transfer method of the transfer device 6 is not particularly limited.
In addition to electrostatic corona transfer, roller or brush transfer, thermal transfer for melting and transferring toner, adhesive transfer, pressure transfer, and the like may be used.

The fixing device 8 includes a pair of fixing rollers 8a and 8b, at least one of which is heated to a predetermined temperature, and melts and fixes the toner image on the transfer medium 14 supplied from the transfer device 6. Thereafter, the sheet is conveyed to a sheet discharge unit (not shown).

The tip of the cleaning device 7 is the image carrier 1
The cleaning blade 7a is in contact with the surface of the image carrier 1, and the cleaning blade 7a scrapes and collects the toner (residual toner) remaining on the surface of the image carrier 1 even after the transfer process. Note that the cleaning device 7 may include a cleaning brush or a cleaning roller.

Next, a method for forming a latent image and development of the latent image in the latent image forming apparatus will be described with reference to FIGS.

First, as shown in FIG. 4, the entire ferroelectric layer 1b of the image carrier 1 is heated to 120 ° C. below the Curie point by the heating device 2 to eliminate polarization. The state of the ferroelectric layer 1b at this time is represented by a point P0 in FIG.

Next, as shown in FIG.
A voltage is applied to the image carrier 1 by the conductive roller 3b. The voltage of the voltage applying device 3 is set so that the electric field acting on the ferroelectric layer 1b of the image carrier 1 is 100 V / μm. This electric field causes the ferroelectric layer 1b to be uniformly polarized in one direction. The state of the ferroelectric value layer 1b at this time is
In FIG. 3, it is represented by a point P1 (polarization: 65 mC / m ² ). After passing through the conductive roller 3b, the external electric field disappears, and the state of the ferroelectric layer 1b changes to a point P11 (polarization 60 mC /
m ² ). Note that the arrow B in the figure indicates the direction of polarization, indicating that the proximal end is negative and the distal end is positive.
The size of the arrow B indicates the size of polarization (polarization intensity).

Further, as shown in FIGS. 6A to 6C, the electrode 1 of the latent image writing device 4 is changed according to the image to be formed.
From 0b, a voltage is applied to each position of the image carrier 1.
For example, in FIG. 6A, the ferroelectric layer 1b has -55 V / .mu.
m, and as a result, the polarization at this part is shown in FIG.
At 30 mC / m ² as indicated by point P2. Also, in FIG. 6B, an electric field of -70 V / μm acts on the ferroelectric layer 1b, and as a result, the polarization at this portion becomes 0 mC / m ² as shown by a point P3 in FIG. further,
Field of -70V / [mu] m is applied to FIG. 6 (C) in the ferroelectric layer 1b, as a result, the polarization at this portion becomes -30mC / m ² as shown in Figure 3 smell points Te P4. After passing through the latent image writing device 4, the point P
2, point P3 and point P4 are respectively connected to point P21 (polarization 35
mC / m ² ), point P31 (polarization 5 mC / m ² ) and point P4
1 (polarization: -25 mC / m ² ).

By applying different voltage values to the image carrier 1 once uniformly polarized by the latent image writing device 4 as described above, different residual polarizations having different strengths are applied to the ferroelectric layer 1b. As a result, a multi-level polarization latent image is formed.

Next, the polarized latent image is developed by the negatively charged toner supplied from the developing device 5. At this time,
As shown in FIGS. 7A to 7C, as the change in polarization is larger than before the latent image writing by the latent image writing device 4, the amount of the toner 13 attached increases, and the density gradation is realized. You.

This toner image is transferred to the transfer roller 6 of the transfer device 6.
The medium 14 to be transferred is supplied to the transfer position in synchronism with the arrival at the position (transfer position) that comes into contact with a. A positive voltage is applied to the transfer roller 6a, and FIG.
As shown in (C), the negatively charged toner 13 on the surface of the image carrier 1 is electrostatically attracted to the transfer medium 14, and the toner image is transferred to the transfer medium 14. After that, the transfer medium 14 is conveyed to the paper discharge unit after the toner image is fused and fixed by the fixing device 8. Toner image is transferred to medium 1
After the transfer to the surface 4, the surface of the image carrier 1 is cleaned of the residual toner by the cleaning device 7, and returns to the position facing the voltage application device 2.

As described above, in this embodiment, the image carrier 1
, A multi-valued polarization latent image is formed. Therefore, when this polarized latent image is visualized with the toner 13 and transferred to a transfer material, an image having a density gradation is obtained. In addition, since the polarization latent image is formed by the voltage, blurring of the latent image as in the case of using the pyroelectric effect is reduced, and the potential difference between the latent image portion and other portions is large, thereby forming a high resolution latent image. be able to. Further, gradation control can be easily performed only by adjusting the voltage value applied to each electrode 10a of the latent image writing device 4.

When a new image is formed, the image shown in FIG.
5, the ferroelectric layer 1b is heated by the heating device 2 to erase the polarization latent image, and the ferroelectric layer 1b is turned on by the voltage application device 3 as shown in FIG. After being uniformly charged in one direction, FIG. 6A to FIG.
The multi-level polarization latent image is formed by the latent image writing device 4 shown in FIG.

On the other hand, when developing the same image again,
The processes in FIGS. 7 and 8 may be repeated without performing the polarization elimination in FIG. 4, the uniform polarization in FIG. 5, and the formation of the multi-level polarization latent image in FIG. Note that the image density may decrease while the same image is repeatedly developed. In this case, heating to a low temperature below the Curie point (for example, about 80 ° C. in the case of the first embodiment) and short-circuiting the surface of the image carrier 1 at the same time as or immediately after this heating will produce a good image again. Is obtained. This step may be performed as needed,
This step can be executed by switching the setting of the heating temperature of the heating device 2 and the voltage of the voltage application device 3.

(Second Embodiment) A second embodiment of the present invention shown in FIG.
In the embodiment, the latent image forming apparatus has the same configuration as that of the first embodiment except that the heating apparatus 2 is not provided.

In the second embodiment, the voltage is applied to the image carrier 1 by the conductive roller 3b of the voltage application device 3 as shown in FIG. As a result, the ferroelectric layer 1b is uniformly polarized in one direction (point P11 in FIG. 3). Next, FIG.
As shown in FIG. 3C, electric fields of different magnitudes are applied by the multi-stylus array 10b of the latent image writing device 4 according to the image to be formed.
As shown by points P31 and P41, a multi-valued polarization latent image having a plurality of polarizations is formed. This polarized latent image is the toner 1
7, as shown in FIGS. 7A to 7C, the larger the change in polarization, the larger the amount of toner 13 attached to the latent image writing device 4 as compared to before the latent image writing. That is, density gradation is realized. The toner image is transferred to the transfer material 1 as shown in FIGS.
4 is transferred.

Other functions and effects of the second embodiment are the same as those of the first embodiment.

(Third Embodiment) In a third embodiment of the present invention shown in FIG. 10, the latent image forming apparatus has the same configuration as that of the first embodiment except that it does not include the voltage applying device 3. .

With reference to FIGS. 11 to 15, a method of forming a latent image and development of the latent image in the latent image forming apparatus will be described.

First, as shown in FIG. 12, the entire ferroelectric layer 1b is heated to 120 ° C. below the Curie point by the heating device 2.
Until the polarization is erased, and the ferroelectric layer 1b is brought into a state shown by a point P0 'in FIG.

Next, as shown in FIGS. 13A to 13C, the electric field acting on the ferroelectric layer 1b is 150 V
/ Μm, 100 V / μm, and 60 V / μm, voltages are applied from the electrodes 10 b of the latent image writing device 4 to individual positions of the image carrier 1. As a result, the electrodes in these portions are respectively indicated by points P1 ′, P2 ′ and P2 in FIG.
As shown by 3 ′, 80 mC / m ² , 65 mC / m ² , 5
0 mC / m ² . After passing through the latent image writing device 4, the external electric field disappears, so that points P1 ', P2' and P3 '
Are the points P11 ′ (polarization 70 mC / m ² ), P2
1 ′ (polarization 60 mC / m ² ) and P31 ′ (polarization 45 mC / m ² )
C / m ² ). By changing the voltage applied from the latent image writing device 4 to the ferroelectric layer 1b from which the polarization has been once erased, a multi-valued polarization latent image is formed.

Then, as shown in FIGS. 14A to 14C, when the negatively charged toner 13 is supplied from the developing device 5, an amount of the toner 13 corresponding to the polarization at that location is supplied to the image carrier. 1 adheres to the surface. Then, FIGS. 15 (A) to 15 (C)
As shown in (1), when the toner image is transferred to the transfer material 14, an image having a density gradation is formed on the transfer material 14.

Other functions and effects of the third embodiment are the same as those of the above-described first embodiment.

The present invention is not limited to the above embodiment, and various modifications are possible.

For example, as shown in FIG. 16, a flat plate-shaped image composed of a conductive substrate 21a and a ferroelectric layer 21b reciprocating in the left and right directions in the figure as shown by arrows C1 and C2 by a driving device (not shown). A carrier 21 is provided, and a heating device 2, a voltage application device 3, a latent image writing device 4, a developing device 5, a transfer device 6, and a cleaning device 6 including a cleaning brush 7b are arranged above the image carrier 21 in this order. Is also good.

In this latent image forming apparatus, an arrow C
When the image carrier 1 moves in the direction indicated by 1, the polarization erasure by the heating device 2, the unidirectional polarization by the voltage application device 3, and the multi-value polarization by the latent image writing device 4 as in the first embodiment. Formation of latent image, visualization of latent image by developing device 5, transfer to transfer medium 14 by transfer device 6, and cleaning device 7
, The remaining toner is sequentially collected. Thereafter, the image carrier 1 moves in the direction indicated by the arrow C2 and returns to the initial position. Other operations of the latent image forming apparatus are the same as those of the first embodiment. Note that the processes of the second and third embodiments may be performed on a flat image carrier.

[0049]

According to the latent image forming method of the present invention, a multivalued polarized latent image is formed by adjusting the voltage value applied to the ferroelectric layer of the image carrier from the multivalued voltage applying means. Therefore, when this polarized latent image is visualized with toner or liquid ink and transferred to a transfer material, an image having a density gradation is obtained. Further, in the latent image forming method of the present invention, since a polarized latent image is formed by a voltage, blurring of a latent image as in the case of utilizing a pyroelectric effect is reduced, and a potential difference between a latent image portion and another portion is reduced. A large, high-resolution latent image can be formed. Further, in the latent image forming method of the present invention, gradation control can be easily performed only by adjusting the voltage value.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a latent image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic perspective view showing a latent image writing device.

FIG. 3 is a diagram showing a relationship between an electric field and polarization in a ferroelectric layer.

FIG. 4 is an enlarged view of a main part showing polarization elimination by a heating device.

FIG. 5 is an enlarged view of a main part showing uniform polarization in one direction by a voltage application device.

FIGS. 6A, 6B, and 6C are enlarged views of a main part showing formation of a multi-valued polarized latent image by the latent image writing device.

FIGS. 7A, 7B, and 7C are enlarged views of a main part showing development. FIG.

FIGS. 8A, 8B and 8C are enlarged views of a main part showing transfer.

FIG. 9 is a schematic configuration diagram illustrating a latent image forming apparatus according to a second embodiment of the present invention.

FIG. 10 is a schematic configuration diagram illustrating a latent image forming apparatus according to a third embodiment of the present invention.

FIG. 11 is a diagram showing a relationship between an electric field and polarization in a ferroelectric layer.

FIG. 12 is an enlarged view of a main part showing polarization elimination by a heating device.

FIGS. 13A, 13B and 13C are enlarged views of a main part showing the formation of a multi-valued polarized latent image by the latent image writing device.

FIGS. 14A, 14B and 14C are enlarged views of a main part showing development.

FIGS. 15A, 15B, and 15C are enlarged views of a main part showing transfer. FIG.

FIG. 16 is a schematic configuration diagram illustrating a latent image forming apparatus according to a modified example of the invention.

[Explanation of symbols]

 1, 21 Image carrier 1a Drum 1b Ferroelectric layer 2 Heating device (heat applying device) 3 Voltage applying device (voltage applying device) 4 Latent image writing device (multi-value voltage applying device) 5 Developing device (developing device) 6 Transfer device (transfer means) 7 Cleaning device 8 Fixing device 10 Multi-stylus array 11 Voltage adjusting device

Continued on the front page (72) Inventor Katsuhiko Takeda 2-3-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Co., Ltd. (72) Inventor Masahiko Matsuura 2-chome Azuchicho, Chuo-ku, Osaka-shi, Osaka No. 13 Osaka International Building Minolta Co., Ltd. (72) Keiko Momotani 2-13-13 Azuchicho, Chuo-ku, Osaka City, Osaka Prefecture Osaka International Building Minolta Co., Ltd. (72) Inventor Yukiko Mizuguchi, Osaka City Osaka Central 2-13, Azuchi-cho, Ward, Osaka International Building Minolta Co., Ltd. F-term (reference) 2C162 AE21 AE29 AE31 AE44 AE64 AE74 2H029 AB16 AB18 AD06 DA00 DB01

Claims (7)

[Claims] A voltage is selectively applied to an image carrier having a ferroelectric layer with different voltage values, and polarizations having different intensities are generated in the ferroelectric layer to provide a multi-level polarization latent. A latent image forming method for forming an image. 2. The latent image forming apparatus according to claim 1, wherein the ferroelectric layer is polarized in one direction in advance before applying a voltage to the image carrier selectively and at different voltage values. Image forming method. 3. The method according to claim 1, wherein, prior to applying a voltage to the image carrier selectively and with different voltage values, heat is applied to the ferroelectric layer to eliminate polarization. Item 3. The latent image forming method according to Item 2. 4. An image carrier having a ferroelectric layer, and applying a voltage to the image carrier selectively and at different voltage values to generate polarizations having different intensities in the ferroelectric layer. A multi-level voltage applying means for forming a multi-level polarization latent image. 5. The latent image forming apparatus according to claim 4, further comprising voltage applying means for polarizing the ferroelectric layer in one direction before applying a voltage by said multi-value voltage applying means. 6. The latent image according to claim 4, further comprising a heat application unit for applying heat to the ferroelectric layer to eliminate polarization before applying a voltage by the multi-value voltage application unit. Forming equipment. 7. A developing means for electrostatically supplying a developer to a polarization latent image of an image carrier to visualize the developer, and a transfer means for transferring the developer image to a transfer medium. Apparatus according to any one of claims 1 to 6.