JPH0652442B2 - Image forming method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image forming method, and more specifically, an image capable of forming a positive image by using a photosensitive toner and a voltage application simultaneous exposure simultaneous transfer system. It relates to a forming method.

(Prior Art) Conventionally, a method of forming an image using a photosensitive toner and a voltage application simultaneous exposure simultaneous transfer system has been already known. For example, JP-A-60-98463 and 60-13856.
No. 6 discloses that a photosensitive toner layer is formed on a conductive substrate and the toner layer and the transparent electrode are opposed to each other so that the toner-adhering substrate side has the opposite polarity to the toner and the counter electrode side has the same polarity as the toner. It is described that a bias voltage is applied to the toner, the image is exposed, and the toner image irradiated with light is transferred to the counter electrode side to form an image.

(Problems to be solved by the invention) However, in the voltage application simultaneous exposure simultaneous transfer system,
An electric charge having a polarity opposite to that of the original toner is injected into the photosensitive toner of the exposed portion (bright portion), and the toner charged to the opposite polarity is electrostatically attracted to the counter electrode side to form an image. . Therefore, the image formed by the above method is a negative image, and in principle it was not possible to form a positive image on the counter electrode side by the above method.

Therefore, an object of the present invention is to provide an image forming method capable of forming a positive image using a photosensitive toner and a voltage application simultaneous exposure simultaneous transfer system.

Another object of the present invention is to provide a method by which sharp and high density images can be formed with a very simple system.

(Means for Solving the Problems) According to the present invention, a transparent electrode is arranged so as to face a conductive sleeve which is composed of an electrode having a curved surface and has a magnet inside, and a photosensitive toner and a magnetic carrier. A magnetic brush composed of a mixture of the above is formed on the conductive sleeve, a bias voltage is applied so that the conductive sleeve has the same polarity as the toner charge and the transparent electrode has the opposite polarity to the toner charge, and the magnetic brush is transparent. There is provided an image forming method, which comprises irradiating light from the transparent electrode side at a portion in contact with an electrode to transfer unexposed toner onto the transparent electrode surface to form an image.

(Operation) In FIG. 1 for explaining the principle of the present invention, a conductive sleeve 1 (hereinafter may be simply referred to as “toner supporting electrode”) composed of an electrode having a curved surface and a planar shape Transparent electrode (hereinafter, may be simply referred to as "counter electrode").

A layer of the photosensitive toner 3 is formed on the surface of the toner supporting electrode 1, and the toner supporting electrode 1 and the counter electrode 2 are in contact with each other via the layer of the photosensitive toner 3.

The toner supporting electrode 1 and the counter electrode 2 are connected to a bias electrode power source 4, and a bias voltage is applied so that the toner supporting electrode 1 has the same polarity as the toner charge, that is, the polarity, and the counter electrode 2 has the opposite polarity to the toner charge, that is, the polarity. Is applied. At the same time, the photosensitive toner layer 3 is imagewise exposed through the transparent counter electrode 2 at the contact portion. As a result, in the bright part L,
The photosensitive toner becomes conductive, and the charge is injected through the counter electrode 2 so that the charge disappears, or vice versa. Therefore, the toner in the bright portion L remains on the toner supporting electrode 1 as it is without being attracted to the counter electrode 2. On the other hand, in the dark portion D, since the photosensitive toner remains in the polarity, it moves to the opposite electrode 2 having the polarity along the bias electric field applied between the both electrodes, and the positive image is transferred.

Further, the toner is first transferred from the supporting electrode 1 to the counter electrode 2, and the photosensitive toner is exposed in this state, so that the toner in the bright portion L loses its charge or becomes polar, and is transferred to the supporting electrode 1. The toner of the dark portion D is pushed back and remains as it is on the counter electrode 2 side, so that a positive image may be transferred.

The toner transfer may be performed by the former method or the latter method, or both of them may be simultaneously performed.

In the present invention, it is important that the electrode surface forming the conductive sleeve 1 has a polar surface in order to smoothly form a positive image during voltage application simultaneous exposure and simultaneous transfer. Referring now to the position where the electrode surface of the toner supporting electrode 1 comes closest to the opposing electrode surface as a reference, the relationship between the angle θ from this reference position and the electric field strength E between the electrodes is plotted as shown in FIG. Become. The line N at the second time shows where the Coulomb repulsion force and the adhesion force of the toner / support electrode surface are in balance, and the toner transfer is performed when the electric field strength curve M exceeds the straight line N.

In the present invention, as shown in FIG.
, A conductive sleeve 5 is used, a magnet 6 is provided therein, a photosensitive toner is used in the form of a mixture with a magnetic carrier 7, a magnetic brush 8 is formed on the sleeve 5, and the magnetic brush 8 is used. While rubbing the counter electrode 2,
Simultaneous exposure with voltage application and simultaneous transfer are performed. That is, the photosensitive toner 3 is held on the surface of the magnetic carrier 7, the photosensitive toner 3 and the counter electrode 2 are smoothly contacted with each other, and the charge is injected into the photosensitive toner 3. Also,
The toner, which has adhered to the counter electrode surface 2 and has lost its charge, is also captured by the magnetic carrier 7 to enable the transfer image formation with high contrast. In this case, the area where the toner whose charge has disappeared is trapped by the magnetic carrier, that is, the cleaning area by the magnetic brush is limited to an extremely narrow range because the electrode forming the conductive sleeve 1 has a curved surface. ,
As a result, a transferred image with excellent image quality is formed.

(Preferred Embodiment of the Invention) In the present invention, the transfer to the counter electrode side may be performed by transferring the toner to the counter electrode itself, or to a conductive transfer material provided on the toner layer supporting electrode side of the counter electrode. You can go. This transfer material must of course be transparent.

Examples of the conductive substrate that constitutes the electrode include a metal such as aluminum, tin plate, copper, or a plastic film substrate such as a biaxially stretched polyester film to which an aluminum foil is attached or metal Al is vapor-deposited, or a conductive film. Any electrically conductive substrate such as transparent glass (NESA glass) is used.

In the curved surface of the toner supporting electrode, that is, the conductive sleeve, its radius of curvature (R) is preferably in the range of generally 10 to 100 mm, particularly preferably 20 to 50 mm. As described above, the toner supporting electrode is preferably a conductive sleeve (cylindrical member) having a radius of curvature within the above range, and the counter electrode is preferably a flat plate or a cylindrical transparent electrode.

Examples of the photoconductive toner include photoconductive pigments such as inorganic photoconductors such as zinc oxide and CdS in an electrically insulating resin fixing medium, perylene pigments, quinacridone pigments, pyranthrone pigments, phthalocyanine pigments, and disazo. Pigments,
Particles composed of a structure in which a photoconductive organic pigment such as a trisazo pigment is dispersed are used. The photoconductive pigment is preferably used in an amount of 3 to 600 parts by weight, particularly 5 to 500 parts by weight, per 100 parts by weight of the fixing medium. When the amount of the photoconductive pigment is less than the above range, the image density and toner sensitivity tend to be lowered, and when it is more than the above range, the charge retention property tends to be lowered.

As the fixing medium, an electrically insulating fixing resin known per se, for example, polystyrene, styrene-acrylic copolymer, acrylic resin, polycarbonate, polyarylate (polyester of bisphenol A and iso- or terephthalate acid), polyvinyl butyral. , Polysulfone can be used, and a photoconductive resin such as polyvinylcarbazole is also used for the purpose of the present invention alone or in combination with an electrically insulating resin.

In a suitable photosensitive toner, a charge transport medium is used as a fixing medium, the above-mentioned photoconductive pigment is dispersed as a charge generating pigment in the charge transport medium, and this dispersion system is used as a photoconductive toner. As the charge transport medium, the above-described electrically insulating resin and charge transport material, such as polyvinylcarbazole, phenanthrene, N-ethylcarbazole,
2,5-diphenyl-1,3,4-oxadiazole,
2,5-bis- (4-diethylaminophenyl) -1,
3,4-oxadiazole, bis-diethylaminophenyl-1,3-6-oxadiazole, 4,4'-bis (diethylamino) -2,2'-dimethyltriphenylmethane, 2,4,5- Triaminophenylimidazole, 2,5-bis (4-diethylaminophenyl)-
1,3,4-triazole, 1-phenyl-3- (4-
Diethylaminostyryl) -5- (4-diethylaminophenyl) -2-pyrazoline, hole transporting substances such as p-diethylaminobenzaldehyde- (diphenylhydrazone), 2-nitro-9-fluorenone, 2,7-dinitro- 9-fluorenone, 2,4,7-trinitro-9
-Fluorenone, 2,4,5,7-tetranitro-9-
Fluorenone, 2-nitrobenzothiophene, 2,4
8-trinitrooxanthone, dinitroanthracene,
A combination of at least one electron transport material such as dinitroacridine, dinitroanthraquinone is used. Generally, the charge transport material should be used in an amount of 10 to 200 parts by weight, particularly 30 to 120 parts by weight, per 100 parts by weight of the resin.

The photoconductive toner used in the present invention may contain, in addition to the above-mentioned essential components, auxiliary agents known per se in accordance with a known formulation. Examples of such auxiliaries include offset preventive agents such as waxes and pressure fixability imparting agents.

The toner can be molded by a dry method such as kneading, pulverizing and sieving, or a wet method of spray granulating in the form of a dispersion liquid, and the particle size of the toner particles is generally in the range of 5 to 30 μm. Is desirable.

Examples of suitable photoconductive toners include zinc oxide = styrene-acrylic resin type phthalocyanine = styrene-acrylic resin type and phthalocyanine = polyester resin type. These photoconductive toners have triboelectrification characteristics toward negative polarity. On the other hand, as the photoconductive toner having the triboelectrification property to the positive polarity, a toner containing a resin containing a nitrogen atom in its main chain or side chain such as polyamide resin may be used instead of the above-mentioned resin.

As described above, in order to hold the photoconductive toner on the toner supporting electrode (on the conductive sleeve), a magnet is provided inside the conductive sleeve, and a magnetic carrier such as iron powder or ferrite particles and a light carrier are provided. It is performed by forming a two-component magnetic brush composed of a mixture with a conductive toner on the sleeve. In this case, the magnetic carrier has a particle size of 30.
To 120 μm is preferable, and the mixing ratio of the carrier and the toner is preferably in the range of 97: 3 to 85:15 by weight. The length of the spikes of the magnetic brush is slightly different depending on other conditions, but a range of 0.3 to 1 mm is generally suitable.

The bias voltage applied between the toner support electrode and the counter electrode is generally in the range of 100 to 1000 volts, and preferably 300 to 800 volts, although it varies slightly depending on the radius of curvature of the curved surface of the electrode.

The image exposure is performed by transparent exposure through a transparent original or reflection exposure from an opaque original, but in any case, it is performed by slit exposure. In this case, the slit width for exposure is preferably narrower than the width of the contact area with the photosensitive toner, and generally 0.5 to 3 mm is suitable. Also,
Light irradiation is preferably performed at the tip of the contact portion in the counter electrode traveling direction.

The image formed on the counter electrode surface or on the transfer material thereon is electrostatically transferred onto a transfer paper or the like and fixed to form a copy.

(Effects of the Invention) According to the present invention, the surprising advantage that a positive image can be formed by a voltage application simultaneous exposure simultaneous transfer system with a very simple structure is achieved, and the formed image has a high density and sharpness ( It also has the advantage of being excellent in contrast.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the principle of the present invention, FIG. 2 is a diagram showing a relationship between an angle from a reference position and an electric field strength between both electrodes, and FIG. 3 is a diagram showing the present invention. It is a figure which shows an example. 1 ... Toner supporting electrode, 2 ... Counter electrode, 3 ... Photosensitive toner, 4 ... Bias voltage power supply, 5 ... Conductive sleeve, 6 ... Magnet, 7 ... Magnetic carrier, 8 ... Magnetic brush.

Claims (1)

[Claims] 1. A magnetic brush comprising a mixture of a photosensitive toner and a magnetic carrier, wherein a transparent electrode is arranged opposite to a conductive sleeve having an electrode having a curved surface and having a magnet therein. A bias voltage is applied so that the conductive sleeve has the same polarity as the toner charge and the transparent electrode has the opposite polarity to the toner charge, and the magnetic brush contacts the transparent electrode with light from the transparent electrode side. An image forming method, which comprises irradiating and transferring unexposed toner onto a transparent electrode surface to form an image.