JPS63159870A - Printing device - Google Patents

Abstract

PURPOSE:To raise transfer property, to execute a transfer, especially, at the time of a high temperature, to decrease the number of processes, and to miniaturize a device, by using a mixture of a conductive toner and an insulating toner, as a toner, in a printing device using a simultaneous method. CONSTITUTION:A recording medium 17 is superposed on the surface of an image forming body on which a toner image has been formed, and the reverse side of the medium 17 is electrified to the opposite polarity to the charge which has been injected at the time of forming an image of a toner by a corona transfer device 20. By this simultaneous method, the toner is transferred onto the medium 17 from on the photoconductive body layer by an electrostatic force generated between the toner and the charge of the reverse side of the medium 17. In this case, the charge of a conductive toner 24 which has been brought into contact electrically with the medium 17 is neutralized by a short relaxation time, and also, a charge injection from the medium 17 to the toner 24 is generated by a transfer electric field, and scattering of the toner 24 is generated. In this state, the probability that the toner 24 comes into contact with the medium 17 by an insulating toner 25 drops remarkably, and a ratio of the toner to which the charge is injected from the medium drops. In such a way, the scatter is decreased, and the transfer property is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a printing device using a photoconductor, so-called xerography technology, and more specifically, to a printing device that uses a photoconductor and uses a so-called xerography technology. The present invention relates to a printing device that utilizes xerography technology.

[Prior Art] In recent years, various printing devices using xerography technology have been put into practical use and used. To outline the toners used in this technology, in the case of printing devices using the "Carlson process", insulating non-magnetic toner and jumping toner are used in two-component magnetic brush development method and float electrode effect development method (FEED method). In the development method, an insulating magnetic toner is used, and in the case of electrofax, a conductive magnetic toner is used.

Recently, a method using new xerography technology that forms images by simultaneously performing exposure and development (hereinafter referred to as the "simultaneous method"), which has the potential to greatly simplify the process, has been studied in various places. For example, JP-A-58-15395
7 has been proposed.

This simultaneous method eliminates the need for chargers, static eliminators, and cleaner processes that are required in printing devices using conventional xerography technology, and also does not generate waste toner.
This simplifies the process and saves toner, making it possible to downsize the device and reduce costs. An overview of this simultaneous method is as follows:
The most suitable developing method is considered to be a method in which the surface of an image forming body containing a photoconductor layer is rubbed with a brush of conductive magnetic toner to which a bias voltage is applied during exposure. There is a difference in the amount of charge injected into the toner in contact with the surface of the image forming body due to the insulator pressure, depending on when it acts as a conductor (unexposed area) and when it acts as a conductor (exposed area). The difference in charge amount becomes a difference in electrostatic adhesion force to the surface of the image forming body, and it becomes possible to form a toner image.

[Problems to be solved by the invention] However, due to the conductivity of the toner used in the simultaneous method, charge injection occurs from the paper to the toner during transfer, and the transferred material to the leather strap is scattered. , there are problems such as a decrease in density and a disturbed image.

In particular, at high temperatures, the conductivity of paper increases.
Further, the transferability deteriorates, which is the biggest drawback when configured as a printing device.

The object of the present invention is to provide a printing device using the simultaneous method, which does not have the above-mentioned drawbacks. Specifically, the object is to provide a toner printing device that can be developed by a simultaneous method and transferred to plain paper by an electrostatic transfer method.

[Means for Solving the Problems] The printing apparatus of the present invention exposes the photoconductor layer to light on the image forming body including the photoconductor layer, and simultaneously or immediately after the exposure, the printing device A toner layer is brought into contact with the image forming body from the opposite side, and a developing bias voltage is applied to the photoconductor layer and the toner layer to selectively adhere the toner to form an image, and the toner image is formed by applying a developing bias voltage to the photoconductor layer and the toner layer. In a printing device that creates a printed matter by transferring from an image forming body onto a recording medium, the toner is a conductive toner having a resistivity of 106ΩCm or less and an insulating toner having a resistivity of 1o13ΩcI11 or more in a weight mixing ratio. A means of using a mixture of 1 to 5 parts of the conductive toner to 0.1 to 5 parts of the electrically conductive toner; By applying an electric field between a means for moving the image forming body onto the image forming body and the image forming body and the recording medium in a direction that attracts the charge injected into the conductive toner during the image formation toward the recording medium side. means for transferring both the conductive toner and the insulating toner attached to the conductive toner onto the recording medium; and means for fixing both the conductive toner and the insulating toner onto the recording medium. A printing device characterized by having:

[Function] When the toner used in the printing apparatus of the present invention has the above configuration, the toner is stirred by a toner conveying means such as a so-called magnetic brush or a fur brush during development.
Even if a large amount of insulating toner is included, a large number of conductive paths will be formed within the toner layer. Therefore, charges are injected into the conductive toner in contact with the surface of the image forming body by the developing bias applied between the toner conveying means and the image forming body, and the conductive toner adheres to the exposed area due to electrostatic force. arise. At this time, the insulating toner adheres to the conductive toner due to forces acting between powders, such as surface tension due to water, electrostatic force, and intermolecular force, so it moves onto the image forming body together with the conductive toner. . As a result, the toner adhering to the surface of the image forming body contains a large amount of insulating toner as well as conductive toner, and during transfer, this insulating toner becomes an insulator that prevents charge injection from the paper to the conductive toner. As a result, the proportion of conductive toner into which charge is injected from the paper is reduced, and therefore, scattering of conductive toner is reduced and transferability is improved.

[Embodiment] FIGS. 1(a) and 1(b) show an embodiment of a printing apparatus according to the present invention. Figure (5) is an overall view, and figure (b) is an enlarged view of the main parts. An image forming body 4 formed by laminating a transparent conductor layer 2 and a photoconductor layer 3 on a belt-shaped transparent support 1 is a roller 1.
0 rotates in the direction of arrow 5. Reference numeral 6 denotes a toner supply device, in which a toner 7 mixed with a conductive toner 24 and an insulating toner 25 is conveyed to the surface of the image forming body 4 by a well-known magnetic brush composed of a magnet roller 8 and a sleeve 9.

The toner layer supplied in this manner is arranged to contact the image forming body 4 from the side opposite to the exposure side at the same time or immediately after the exposure 12 by the exposure device 11, and the toner layer is placed in contact with the image forming body 4 from the side opposite to the exposure side. Due to the effect of the bias voltage 13 applied between the exposed and non-exposed areas, there is a difference in the adhesion force to the surface of the image forming body 4, and as a result, selective toner adhesion occurs depending on the exposure, and the image is is formed.The exposure device 11 includes a self-focusing rod lens array 14 and an LCS head substrate 1.
5. This LCS head, which has a line light source 16 made of a halogen lamp or a fluorescent tube as a main component, is disclosed in, for example, Japanese Patent Laid-Open No. 193521/1983. The image forming body 4 on which the toner image has been formed moves in the direction of the arrow 5, and the recording medium 17 is fed from the direction of the arrow 19 by the conveyance roller 18, and is placed under a well-known corotron 20 facing the image forming body 4. While moving at the same speed as the image forming body 4, the toner image is electrostatically transferred from the image forming body 4 to the recording medium 17. The toner image thus formed on the recording medium 17 passes through a well-known heat fixing roller 21, is fixed, becomes a printed matter, and is discharged in the direction of an arrow 22. After the transfer, the image forming body 4 reaches the image forming unit consisting of the toner supply device 6 and the exposure device 11 again, and enters the next printing process, but the residual material remaining on the image forming body without being transferred is removed. By this time, the charge of the toner and the image forming body has been neutralized in accordance with the relaxation time, and the electrostatic adhesion force has weakened, so the toner is collected by the magnetic brush of the toner supply device 6, leaving no previous history. It turns out that there isn't.

FIG. 2 shows details of how an image is formed in the printing apparatus according to the present invention. In the figure, the same elements as in FIG. 1 are given the same numbers. An image forming body 4 formed by laminating a transparent support layer 1, a transparent conductor layer 2, and a photoconductor layer 3 in this order receives image exposure 12 as it moves in the direction of an arrow 5.

A well-known magnetic brush formed using a magnet roller 8 and a sleeve 9 causes the toner layer 23 to be in contact with the image forming body 4 at the exposure portion. A bias voltage 13 is applied to the sleeve 9, and it is agitated by the rotation of the magnetic roller 8 or sleeve 9, so that the toner in contact with the image forming body 4 is charged by the sleeve 9 in accordance with the polarity of the bias voltage. Injected into toner. At this time, the amount of charge injected is different between the exposed area and the unexposed area, resulting in a difference in the electrostatic adhesion force of the toner to the surface of the photoconductor layer 3, and image formation is performed. Further, at this time, the insulating toner 25 in the toner 7 is attached to the conductive toner due to forces acting between powders, such as surface tension due to moisture, electrostatic force, and intermolecular force. Therefore, the insulating toner 25 adhering to the conductive toner 24 moves onto the image forming body together with the conductive toner 24.

Note that it is also possible to increase the adhesion force by controlling the chargeability of the toner or by adding a magnetic substance to the toner. For example, the resin constituting the insulating toner is placed above or below the charging series of the resin constituting the conductive toner, and an electrostatic force is generated by frictional charging between the conductive toner and the members in the developing device. Further, by setting the charge polarity to be opposite to the charge injected into the conductive toner during image formation, the electrostatic adhesion force can be increased.

Further, it is conceivable that both the conductive toner and the insulating toner contain a magnetic substance so that the toner can be attached by magnetic force.

Further, the resistance value of the conductive toner is determined from the charge injection time. The charge injection time is given as a rough approximation by the circuit shown in FIG. Here, Cpc is the capacitance per unit area of the photoconductor, Rpc is the resistance per unit area of the photoconductor, and Rt is the resistance per unit area of the toner layer. From this, the time constant τ of charge injection into the capacitor Cpc is obtained as follows: τ=CpcX (Rpc/Rt'). Here, 夛 represents parallel resistance. Now, if we use general values for a photoconductor, such as a relative dielectric constant of 3, a resistivity during light irradiation of 1010 Ωcm, and a thickness of 20 μm, then Cpc@1, 3 X 10-”F/cmR
PC? 2.0XIO' Ωc4. When the exposure time is 2 m5ec, since the implantation is performed within this time, τ≦2 m5ec, and from this, Rt≦108 ΩC is obtained. Estimating the effective thickness of the toner layer to be 200 um and converting it into volume resistivity, 2 x 106 Ωam is obtained. Therefore, in order for charge injection to occur within the exposure time, the resistivity of the toner must be at least 106 Ωcm or less, and the increase in resistivity due to mixing with insulating toner can be offset by stirring in the toner transport means. Then, this one cycle is considered to be the resistivity required for the conductive toner.

FIG. 3 shows details of how the image is transferred by the electrostatic transfer method in the printing apparatus of the present invention.

In the figure, the same elements as in FIG. 1 are given the same numbers.

A recording medium 17 is placed on the surface of the image forming body 4 on which a toner image is formed, and a corona transfer device 2 is placed on the back side of the recording medium 17.
0, the toner 7 is charged to the opposite polarity to the charge injected during image formation. As a result, the toner is transferred from the photoconductor layer onto the recording medium due to the electrostatic force generated between the toner and the charge on the back surface of the recording medium. At this time, the charge of the conductive toner 24 that is in electrical contact with the recording medium 17 is neutralized in a short relaxation time, and furthermore, charge injection from the recording medium 17 to the conductive toner 24 occurs due to the transfer electric field, and the conductive toner 24 scatterings occur. In the present invention, the probability that the conductive toner 24 comes into contact with the recording medium 17 is significantly reduced due to the large number of insulating toners 25 present in the toner, and the proportion of the conductive toner into which charge is injected from the recording medium 17 is reduced. Therefore, toner scattering is reduced and transferability is improved.

Furthermore, from the experimental results of the transfer efficiency of one-component magnetic toner in the Carlson method (Nakajima et al., Proceedings of the 44th Research Conference of the Society of Electrophotography, P, 25-(1979) J), as a mixed toner, at least 1013 Ωcm or more. It is thought that a resistance value of It can be said that it is a value.

Regarding the mixing ratio of conductive toner and insulating toner, increasing the mixing ratio of insulating toner to conductive toner lowers the charge injection rate during development, so it is desirable that the ratio is 5 or less; If the mixing ratio of the insulating toner to the conductive toner is reduced, the reverse charge injection rate during transfer increases, so the ratio is preferably 0.1 or more.

Next, an example of the structure of the mixed toner used in the printing apparatus according to the present invention will be shown.

[Configuration example a] Conductive toner: Resistivity 103ΩCm Average particle size 10
μm Maximum magnetization 40 emu/g Insulating toner: Resistivity 10゛4Ωcm Average particle size 1
0 μm Maximum magnetization 20 emu/g Weight mixing ratio: 1 conductive toner to 2 insulating toner [Configuration example b] Conductive toner: Resistivity 104Ωcm Average particle size 10
μm Maximum magnetization 40 emu/g (Negative charge injected during image formation) Insulating toner: Resistivity 1o14Ωcm Average particle size
3 μm Charging polarity Positive weight mixing ratio: 1 part conductive toner to 1 part insulating toner In either configuration, good toner image formation and transferability can be obtained.

Further, in the present invention, a coloring agent such as a dye or a pigment for visualizing an image may be contained in at least one of the conductive toner and the insulating toner.

For example, it is also possible to use fine particles of silicon dioxide as the insulating toner. Fine particles of silicon dioxide are also often used as a toner fluidity improver.

In this case, it is necessary to mix silicon dioxide fine particles to an extent that does not reduce the density of the image formed by the conductive toner.

[Effects of the Invention] As described above, the printing device according to the present invention uses a mixture of a conductive toner and an insulating toner as a toner in a printing device using a simultaneous method, which solves the problems caused by the simultaneous method. This improves transferability, which was previously impossible, and makes it possible to perform transfers that were previously impossible, especially at high temperatures. Furthermore, this makes it possible to provide a compact, low-cost printing device that has significantly fewer steps included in a printing cycle than a printing device that uses conventional xerography technology.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are diagrams showing an embodiment of the printing device according to the present invention, FIG. 2 is a diagram showing details of how image formation is performed in the printing device according to the present invention, and FIG. FIG. 4 is a diagram showing how images are transferred by the electrostatic transfer method in the printing apparatus according to the invention, and FIG. 4 is an equivalent circuit diagram during image formation according to the invention. 1 Transparent support 13 Bias voltage 2 Transparent conductor layer 16 Ramo 3 Photoconductor layer 17 Recording medium 4 Image forming body 18 Conveyance roller 6 Toner supply device 20 Corotron 7 Toner 21 Heat fixing roller 8 Magnet roller 23 Toner layer 9 Sleeve 24 Conductive toner 11 exposure device
25 Insulating toner 12 Exposure or more Fig. 1 4 Box-shaped book 4 Fig. 2 Fig. 4

Claims (3)

[Claims] (1) On an image forming body comprising a photoconductor layer, the photoconductor layer is exposed to light, and at the same time or immediately after the exposure, a toner layer is brought into contact with the image forming body from the side opposite to the exposed side. and applying a developing bias voltage to the photoconductor layer and the toner layer to selectively adhere toner to form an image, and transfer the toner image from the image forming body onto a recording medium to produce a printed matter. In a printing device for producing a toner, a conductive toner having a resistivity of 10^6 Ωcm or less and an insulating toner having a resistivity of 10^1^3 Ωcm or more are mixed in a weight mixing ratio to the conductive toner 1. A means of using a toner mixed at a ratio of 0.1 to 5 with insulating toner, and a method of applying both the conductive toner and the insulating toner attached to the conductive toner onto the image forming body during image formation. The conductive toner is moved by applying an electric field between the image forming body and the recording medium in a direction that attracts the charge injected into the conductive toner toward the recording medium during image formation. It is characterized by comprising means for transferring both the insulating toner attached to the conductive toner onto the recording medium, and means for fixing both the conductive toner and the insulating toner onto the recording medium. printing device. (2) The printing apparatus according to claim 1, wherein at least one of the conductive toner and the insulating toner contains a magnetic material. (3) The printing apparatus according to claim 1, wherein the insulating toner is charged with a polarity opposite to that injected into the conductive toner during image formation.