JPS6382754A - Image forming method - Google Patents

Abstract

PURPOSE:To obtain a stable transfer image with little unevenness in density, by a method wherein an ink layer of which the electric resistance and viscosity coefficient are specified is formed on a carrier, and charged in an image state by projecting an ion stream modulated in an image state and an ink image is transferred on a transfer material by applying an electric field. CONSTITUTION:An ink layer of a given thickness is formed on the surface of an ink roller 1 and changed by projecting an ion stream modulated in an image state according to a recording signal sent from a recording power source 7 with an ion stream recording head 6. Therefore, transfer paper 8 is superimposed on this ink layer which is charged in an image state, and the ink picture is transferred to be formed on the transfer paper by applying transfer electric- field from the back side by a transfer roller 9. Ink is not less than 10<9>OMEGAcm in the electric resistance from the standpoint of the keeping capacity of electrified change, and 10<-2>-10<3> centipoise in viscosity coefficient from the standpoint of the ink feed property and transfer efficiency to the depressed part of the ink roller to be used. A good image without unevenness in density can be formed on a transfer material thereby.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming method used in printers, facsimile machines, copying machines, printing machines, etc., and particularly relates to an image forming method using ink.

[Prior art] Powder toner is formed in a layer on a carrier, and an imagewise modulated corona ion stream is projected onto this toner layer to imagewise charge it, and then an electric field is applied to this toner layer. An image forming method in which a toner image is transferred onto a transfer paper is disclosed in Japanese Patent Laid-Open No. 57-167
It is described in Publication No. 050. This image forming method is
This method is implemented because the toner layer is image-wise charged and transferred electrostatically, so development and transfer are performed at the same time, and there is no need for a cleaning process.
This has the advantage that the installation can be simplified and the size can be reduced.

[Problems to be solved by the invention] This image forming method has difficulty in making the powder toner layer formed on the carrier to have a uniform thickness, which tends to cause density unevenness in the transferred image; In addition, the powder toner tends to scatter and contaminate the inside of the device, and in order to stabilize the charging characteristics and fluidity of the powder toner, it is necessary to narrow the tolerance range of the toner particle size distribution. The process is kneading,
There are problems such as the need for multiple steps such as crushing and classification.

This invention has been made in view of the above-mentioned problems, and provides an image forming method that requires fewer manufacturing steps and therefore uses extremely low-cost ink to obtain stable transferred images with less density unevenness and with less peripheral contamination. The purpose is to provide.

Means and operation for solving problem E] The image forming method according to the present invention includes forming an ink layer having an electrical resistance of 100-01 or more and a viscosity of 10" to 103 centivoise on a carrier, Next, an imagewise modulated ion stream is projected onto this ink layer to imagewise charge it, and an electric field is applied to the imagewise charged ink layer to transfer the ink image onto the transfer body. It is characterized by being carried out by

That is, the electrical resistance formed on the carrier is 109Ω·cu
A layer of ink with a viscosity greater than e and a viscosity of 10-' to io' centipoise forms a uniform layer on the carrier and can be image-wise charged by the projected ion stream, and thus can be deposited by an electric field on the transfer member. The transferred image forms a stable ink image with little density unevenness.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

(First example) FIG. 1 shows a first embodiment of the invention.

An ink roller 1 serving as a carrier is rotatably supported and coupled to a drive source (not shown) to be rotationally driven. An ink tank 2 is provided below the ink roller 1, and the bottom surface of the ink roller 1 is immersed in ink 3 in the ink tank 2. On the downstream side of the ink roller 1 in the rotational direction with respect to the ink tank 2, there is a doctor blade 4 for scraping off ink adhering to the surface of the ink roller 1 and forming an ink layer of a constant thickness on the surface of the ink roller 1. is provided. Further, on the downstream side of this doctor blade 4, an ion flow recording head 6 is arranged close to the cylindrical surface of the ink roller 1. A recording power source 7 is coupled to this ion flow recording head 6 . Further downstream from the position of the ion flow recording head 6, a transfer roller 9 is provided as a transfer means for transferring an ink image onto a recording paper 8 as a transfer body. A transfer power source 9 for applying a transfer electric field between the transfer row 59 and the ink roller 1 is coupled to the transfer row 59 .

In this image forming method, the ink roller 1 is rotated at a constant speed in the direction of the arrow by a drive source (not shown), and the ink adhering to the surface of the ink roller that has passed through the ink 3 in the ink tank 2 is scraped off by a doctor blade 4. 1
An ink layer of a certain thickness is formed on the surface of the recording cylinder ll1t7 from the ion flow recording head 6.
An ion flow modulated into an image is projected according to the recording signal sent from the ink layer, and the ink layer is charged in an image. Next, the transfer paper 8 is superimposed on the image-shaped charged ink layer and transferred. A transfer electric field is applied by a transfer roller 9 from the back side of the paper 8 to transfer and form an ink image onto the transfer paper.

The configuration of each part will be explained in detail below.

Regarding the ink roller, if the cylindrical surface of the ink roller 1 is smooth, the ink may flow on the roller surface and distort the charge image. It is desirable that the ink layer be formed independently in minute units by using the doctor blade 4 so that the ink remains only in the recesses 5. If the line density of the lines is too small, the image will become rough, and if the line density is too large, the amount of ink per point will be extremely small and the contrast will decrease, so the line density forming the edges of the recesses should be 10 to 1.
000 lines/cg+, preferably 50 to
Used at 500 lines/C■. Furthermore, if the depth of the recess 5 is too shallow, the image density will decrease, and if it is too deep, the thin lines of the line drawing will be crushed, so the depth of the recess is used in the range of 50 to 150 μm, preferably 20 to 100 μm. used. These ranges are selected depending on the characteristics of the ink and transfer material. To form fine mesh-like recesses on the surface of the ink roller, processing methods such as etching, mechanical engraving, and laser light are used, similar to plate making in gravure printing.

The main body of the ink roller is made of metal such as chrome-plated copper. Further, when the electrical resistance value of the ink is low, in order to prevent charge leakage, the metal surface may be coated with a resin, or an aluminum material may be anodized to form an insulating thin layer.

Although an ink roller was used as an ink carrier,
An endless belt such as a metal seat belt with minute recesses formed in a mesh pattern on the surface thereof can be used.

In addition, the ink used should have an electrical resistance value of 1090 C1 or more, preferably in the range of 10 to 10 ΩC, from the viewpoint of its ability to retain electrical charge, and the viscosity of the ink should be adjusted to the extent that the ink is supplied to the recesses of the ink roller. From the viewpoint of performance and transfer efficiency, 104 to 103 centipoise is used, preferably 10'4 to 102 centipoise.

As the ink material, a non-aqueous ink in which a colorant such as a pigment or dye and a resin binder are dispersed in a non-aqueous dispersant is used from the viewpoint of charge retention ability. As the dispersant, a petroleum aliphatic hydrocarbon, a halogenated aliphatic hydrocarbon, or an aromatic liquid solvent is used. The coloring agent is not particularly limited, and conventionally known pigments and dyes can be used. For example, carbon black, iron oxide, oil blue, alkali blue,
Benzine yellow, fast red, phthalocyanine green, titanium white, etc. are used. As the resin binder, resins such as acrylic resin, phenol-modified resin, and synthetic rubber are used. A liquid ink is created by mixing and dispersing the above coloring material and resin binder in a dispersant.

Alternatively, the colorant is dispersed using a wax such as low molecular weight polyolefin or natural wax as a dispersant and binder and solidifies at room temperature.

It is also possible to create an ink in the form of a liquid and use it as an ink by heating and melting it in a liquid state.

Regarding the transfer paper used as the transfer body, in order to prevent ink from being transferred in non-image areas due to the adhesive force of the ink, the transfer paper is impregnated with a material that is non-adhesive to the ink, such as silicone. It is desirable to use it.

The ion flow recording head 6 has control electrodes for the passage of ions in one or more rows of openings, and controls the passage of ions for each opening in response to a control signal from a control power source. A charged image is formed by projecting an image-like pattern of ion dots onto a charging member. As such an ion flow recording head, the Japanese Patent Publication No. 56-358
As shown in Japanese Patent No. 74, an ion current changing device having control electrodes on both sides of an insulating member having a row of openings is placed in the projected electric field formed between the corona generation source and the object to be charged. There are those that control the ion flow passing through each hole, and those that control the ion flow passing through each hole, and
As shown in Japanese Patent No. 4-78134, an excitation electrode is integrally provided with the ion flow modulation II device via an insulating layer, and corona ions are generated from one end of the control electrode and passed through the opening of the ion flow modulation device. Something that modulates the ion flow is used.

An example of the latter will be explained with reference to FIG. This ion flow recording head 6 includes a field electrode 11, an insulating aperture plate, a control electrode 13, an insulating plate 14, an excitation electrode 15, and an insulating shield 1.
6 are laminated and fixed in this order. The field electrode 11 is a rectangular metal plate with a plurality of holes 17 arranged in a row in the longitudinal direction, and the insulating hole plate 12 has a hole diameter larger than the hole diameter at a position relative to each hole 17 of the field electrode 11. A large diameter aperture is provided. Further, the control electrode 13 has each aperture 18 at a position corresponding to each aperture 17 of the field electrode 11, and the control electrode 13 has a plurality of apertures 18 surrounded by the aperture 18 and each aperture separated into one unit and separated from each other and insulated from each other. The insulating plate 14 consists of this electrode plate.
It has a rectangular shape so as to cover the entire surface of one side of the control electrode 13. Furthermore, the excitation electrode 15 has a long and narrow plate shape, and the insulating plate 14
It is provided on the other side so as to extend at a position facing each opening of the control electrode 13. This excitation electrode 15 is covered with an insulating material 6 and isolated from the outside air. The ion flow recording head 6 is arranged close to the ink roller 1 with its opening 17 facing the ink roller 1 .

Excitation electrode 15 and control l! An AC high voltage is applied between the excitation electrode 13 and each section of the excitation electrode 13, and a control voltage (for example, a positive pulse voltage) is applied between the field electrode 11 and the ink roller 1. A rotating speed voltage (for example, a positive voltage) is applied.

Assuming that a positive pulse voltage is applied to each section of the control electrode 13 as a control signal synchronized with the rotation of the ink roller 1, the control electrode 13 is connected to the field electrode 11.
Among the positive and negative ions generated in each aperture 18 of the control electrode 13 by the AC high voltage applied between the excitation electrode 15 and the control electrode 113, Since a promoting electric field is formed for positive ions, the positive ions reach the apertures 17 of the field electrode 11. This positive ion flow is further applied between the field electrode 11 and the ink roller 1. The accelerating electric field formed by the positive voltage is projected onto the surface of the ink roller 1, forming a dot-shaped charging pattern on the surface. In this case, the negative ions will not reach the surface of the ink roller 1 because they are blocked by the positive potential applied to the field electrode 11, so the Ill @ signal applied to each section of the control electrode 13 Correspondingly, the surface of the ink roller 1 is image-wise charged by a positive dot pattern. Of course, a negatively charged image can be formed on the surface of the ink roller 1 by making the voltage applied to each electrode negative.

Note that in FIG. 2, the apertures of the ion flow recording head 6 are arranged in one row to simplify the explanation, but a plurality of apertures can be arranged in a matrix by intersecting a plurality of excitation electrodes and a plurality of control electrodes in a matrix. It is possible to form heads arranged in a shape. Furthermore, by making the pulse voltage of the control signal multi-valued instead of binary, it is possible to increase or decrease the amount of charge of each dot, thereby obtaining an image with gradation.

(Second Embodiment) FIG. 3 shows a second embodiment of the invention. In the explanation of this example, parts that overlap with the explanation of the first embodiment are omitted. In this example, ink 3 in an ink tank 2 is applied to an ink roller 1, an ink layer of a certain thickness is formed by a doctor 4, and a charged image is formed on this ink layer by an ion flow recording head 6. is the same as in the first embodiment, but an intermediate transfer row 520 serving as an intermediate transfer member is pressed against this image-charged ink layer, and a transfer charge l! ! 1
This method is characterized in that an ink image is first electrostatically transferred onto the surface of the intermediate transfer roller 20 using a transfer electric field of zero. The ink image on the intermediate transfer roller 20 is transferred onto the transfer paper 22 by pressing the transfer paper 22 supplied from the paper feed section 21 against the surface of the intermediate transfer roller 20 by the nip roller 23, and this transfer paper 22 is discharged. It is discharged onto the tray 24. The surface of the intermediate transfer roller 20 is coated with a material that is non-adhesive to ink (silicon resin, fluororesin, etc.), which prevents highly adhesive ink from adhering to non-image areas of the intermediate transfer roller. At the same time, the transfer of the ink image to the transfer paper 22 is facilitated.

According to this example, since the ink image is transferred to the transfer paper using an intermediate transfer roller that is non-adhesive to the ink, the non-image ink is transferred to the transfer paper regardless of the material of the transfer paper. Adhesion is prevented and a fog-free image can be formed on the transfer body.

(Third Embodiment) FIG. 4 shows a third embodiment of the present invention. Also in the explanation of this example, the explanation of parts that overlap with those of the first and second embodiments is omitted. This example is the same as the first and second examples up to the point where a layer of ink 3 is formed on the surface of the ink roller 1 and a charged image is formed on this ink layer by the ion flow recording head 6. An intermediate transfer belt 40 serving as an intermediate transfer body is placed slightly apart from the charged ion layer, and a transfer electric field is formed between the ink layer and the intermediate transfer belt by a transfer power source 41 to generate a transfer electric field on the ink claw 51. This method is characterized in that an ink layer charged with an image is caused to fly toward the intermediate transfer belt 40 to form an ink image on the intermediate transfer belt 40. Further, in this example, a composite color image is formed by arranging a plurality of similar devices for each ink color.

That is, the device shown in FIG. 4 has an ink roller 1-1.1-
The device that forms a charged image on the ink layer of 2.1-3.1-4 by the ion flow recording head 6-1.6-2.6-3.6-4 is yellow (Y) and cyan (C). , magenta (
They are provided for each ink color of M) and black (B), and are arranged along the travel path of the intermediate transfer belt 40. Ink rollers for each color 1-1.1-2.1-3.1-
Backup rollers 42-1.42-2.42-3.42-4 of the intermediate transfer belt 40 are arranged opposite to 4,
A transfer electric field is formed between the two by a transfer power source 41, and ink images of each color are sequentially ejected from each ink roller onto the intermediate transfer belt and overlapped to form a composite color image. This flying of the ink image is based on the same principle as so-called jumping development, and the ink in the non-image area does not adhere to the intermediate transfer belt 40, which is not in contact with the ink roller. Since the transferred ink image does not adhere to the next ink roller, a good color image without fogging is formed on the intermediate transfer belt. Next, the transfer paper 22 is fed onto the intermediate transfer belt 40 by the paper feeder 21 and transferred to the nip roller 23.
The color image on the intermediate transfer belt 40 is transferred onto the transfer paper 22 by being pressed between the transfer paper 22 and the backup roller 43 of the intermediate transfer belt 40, and is heated and fixed by the heater 44 to form an agricultural image.

It goes without saying that the present invention is not limited to the above-described embodiments, but may include many changes and modifications. For example, after the ink layer on the carrier is uniformly negatively charged by a corona charger, it is image-wise charged by a positive charge by an ion flow recording head to form a charged image in which only the image area is neutralized, and the previously negatively charged transfer is performed. There is also an image forming method in which the body is brought into contact with this ion layer to prevent the negatively charged ink layer from adhering to the non-image area, and only the image area is transferred by adhering to the transfer body using the adhesion force of the ink. It is included in this invention.

[Effects of the Invention] According to the present invention, an ion flow recording head is used to print a band 1! Since an image is formed and an electric field is applied to the ink image to be transferred onto the transfer member, a good image without density unevenness or fogging can be formed on the transfer member.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining a first embodiment of the present invention, and FIG. 2 is an illustration of an ion flow recording head used in the present invention.
FIG. 3 is a diagram for explaining a second embodiment of the present invention, and FIG. 4 is a diagram for explaining a third embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Ink roller, 3... Ink, 6... Ion flow recording head, 8... Transfer paper, 9... Transfer roller, 10... Transfer power source, 20... Intermediate transfer roller , 4
0...Intermediate transfer belt, 41...Transfer power supply.

Claims (3)

[Claims] (1) Forming an ink layer on a carrier with an electrical resistance of 10^9 Ωcm or more and a viscosity of 10^-^2 to 10^3 centipoise, and forming an image on this ink layer. An image characterized by comprising a step of image-wise charging by projecting an ion flow modulated by ion, and a step of applying an electric field to the image-wise charged ink layer to transfer an ink image onto a transfer body. Formation method. (2) The image forming method according to claim 1, characterized in that in the step of transferring the ink image onto the transfer body, a transfer body coated with a material that is non-adhesive to ink is used. (3) The step of transferring the ink image onto the transfer member is a step of holding the transfer member in a non-contact manner with respect to the imagewise charged ink layer and transferring the ink by flying the ink onto the transfer member by applying an electric field. An image forming method according to claim 1, characterized in that: