JPH02217270A - Image forming head - Google Patents

Abstract

PURPOSE:To make uniform a potential on the surface of an image forming member across the entire surface of said member and minimize the deterioration in print quality by allowing electrodes separated from each other for the formation of a latent electric charge image to come in contact with a common electrode before the passage of the image forming member through the electrodes. CONSTITUTION:An image forming member first touches a common electrode 2 when coming in contact with an image forming head, and controls a potential on the entire surface of the member to a specified value. After this, the member comes in contact with an electrode for image formation 3. After its passage through the electrode, the image forming member has an electric charge image formed on the surface. Then an image development process takes place, for the visualization of the electric charge image. If the case occurs that the surface of the member comes in contact with an insulating or a conductive member during the above-mentioned process, the electric charge image is disturbed. Therefore, the thickness of each electrode needs to be controlled, that is, the electrode for image formation 3 must protrude from the surface of an insulating substrate 1 more outstandingly than the common electrode 2. This allows the image forming head to tilt against the image forming member. Consequently, the image forming member passing through the electrode for image formation 3 is displaced away from the substrate, so that the electric charge image can be prevented from being disturbed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention particularly relates to the structure of an image forming head that forms an image by injecting charge from an electrode, which is used in an image forming apparatus disclosed in Japanese Patent Application No. 111923/1982.

[Prior Art] A conventional image forming head that injects charges from electrodes is one in which needle-like conductors are separated by an insulating resin, as shown in Japanese Patent Publication No. 43746/1983. However, they were lined up to form an electrode group, and this electrode group was held in place by an insulating material.

[Problems to be Solved by the Invention] However, as shown in Japanese Patent Publication No. 63-43746, in the prior art, the disturbance of the latent charge image due to the occurrence of frictional electrification with the image forming member at the end surface portion other than the electrode is difficult to solve. This tends to cause deterioration in print quality. Regarding this point, Japanese Patent Publication No. 63-43746 discloses a method for improving disturbances caused by frictional charging at the rear end of the electrode.

Another major factor that degrades print quality is image non-uniformity.The main cause of image non-uniformity is non-uniformity of the surface potential on the image forming member before writing to the image forming head of the image forming member. can be mentioned. Regarding this point, Japanese Patent Application No. 63-111923 proposes the use of a conductive roller. However, after the image forming member passes through the conductive roller and before it comes into contact with the electrode of the image forming head, it comes into contact with a part other than the electrode, for example, an insulating member that holds the head electrode, and new potential non-uniformity occurs. However, deterioration in print quality due to this is unavoidable.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems, and more specifically, to provide a head with an improved structure at the tip end of the image forming apparatus, thereby providing a new head structure.

[Means for Solving the Problems] In order to develop the above problems, the image forming head of the present invention has the following features:
an insulating substrate, a plurality of mutually separated electrode groups 1 formed on the insulating substrate, and at least a circuit that independently applies a voltage to each electrode of the electrode group 1 as a component, and is in contact with an image forming member; The image forming head moves while moving and forms a charge image on the image forming member by the electrode group 1, and after the iron surface and the image forming member come into contact with a common electrode, the electrode group 1
A common electrode is arranged on the insulating substrate so as to be in contact with the insulating substrate.

As the insulating substrate, ceramic, glass, resin, ceramic particle dispersed resin, or a substrate in which an insulating resin (eg, polyimide resin) is coated on a conductive substrate (eg, metal) can be used. Specific materials include forsterite, borosilicate glass, glass-filled epoxy resin, and polyimide coated stainless steel substrate.

The electrode material is not particularly limited as long as it is a conductive material with good sliding wear resistance and electric field wear resistance.

For example, titanium metal, titanium alloy, molybdenum metal, molybdenum alloy, tungsten metal, tungsten alloy, chromium metal, chromium alloy, tantalum metal, tantalum alloy,
Nickel metal, nickel alloy, etc. are recommended.

[Operation] The image forming head configured as described above contacts a common electrode before the image forming member passes through electrodes separated from each other that form a charge latent image, and changes the potential on the surface of the image forming member to the image forming member. Can be made uniform over the entire surface. Since this common electrode and the electrodes separated from each other are formed on the same insulating substrate, it is easy to control the arrangement interval and thickness of the image electrodes, and the surface potential of the image forming member whose surface potential is adjusted by the common electrode is The chance of contact with a material that changes the surface potential, such as an insulating substrate, before contacting the separated electrode for image formation can be minimized, and surface potential fluctuations of the image forming member can be practically ignored. . Therefore, it is possible to minimize deterioration in print quality.

Hereinafter, the details of the present invention will be shown by examples.

[Example] Example 1 FIG. 1 shows an example of the image forming head of the present invention. Reference numeral 1111 is a view of the tip of the head viewed from the top surface of the substrate. A common electrode 2 is formed at the tip of an insulating substrate 1. An image forming electrode 3 is arranged at the rear of the common electrode 2. The arrangement pitch of the electrodes 3 defines the resolution of the image to be written. The common electrode 2 starts from the edge of the substrate 1, and an image forming electrode is arranged at a small distance from the end of the common electrode.

The common electrode 2 and the electrode 3 are connected to an IC driver 6 through a connection 4. Image signals, power for driving the driver, and voltage for applying the electrodes are connected to the IC from the outside through a connector 7.
Sent to driver 6.

The circuit board 5 on which the IC driver 6 is mounted differs from the board on which electrodes are formed, and the head consists of two boards, and these boards are connected by wires.

This is a measure to reduce the area of the substrate 1 that requires photoetching, increase manufacturing efficiency, and realize cost reduction. There is no problem even if the electrode section and the IC driver are arranged on the same substrate, and the driver section and the electrode section may be formed on the same substrate by utilizing thin film transistor manufacturing technology.

In order to explain the arrangement of the common electrode and the image forming electrode, FIG. The structure is such that the image forming electrode is thicker than the common electrode and protrudes from the substrate. Further, the common electrode 2 completely covers the edge portion of the substrate 1, or as shown in FIG. 2, the common electrode 2 constitutes the edge portion at the tip of the head.

As shown in FIG. 2, the present invention has a sufficient effect even if the common electrode does not extend to the edge portion of the substrate, but it is easier to increase the pressure on the image forming member when the common electrode extends to the edge portion. This results in better rad touch and a greater effect of the common electrode.

The gap between the common electrode 2 and the image forming electrode 3 may be made small enough to prevent the image forming member from coming into contact with the insulating substrate 1 due to deformation of the image forming member. It is determined by the thickness of the electrode, the thickness of the image forming electrode, the elasticity of the image forming member, the pressure applied by the image forming head to the image forming member, etc.

The effect of the head of the electrode with such a configuration on the image forming member will be explained below.The image forming member forms a charge image on the surface of the image forming member while moving in contact with the image forming head. When it comes into contact with the common electrode 2, the potential of the entire surface of the image forming member is controlled to a predetermined value. Thereafter, the image forming member contacts the image forming electrode 3 without contacting the insulating portion of the substrate portion.

After passing through the electrode 3, a charge image is formed on the surface of the image forming member. Thereafter, a development process is started to visualize the charge image, but if the surface of the image forming member comes into contact with an insulating or conductive member before the development process, the charge image may be disturbed. In order to avoid this problem, in this embodiment, the thickness of each electrode is controlled so that the image forming electrode 3 protrudes from the surface of the insulating substrate 1 more than the common electrode 2. The image forming head can be arranged at an angle with respect to the image forming member.

As a result, the image forming member that has passed through the image forming electrode 3 moves away from the substrate, thereby preventing disturbance of the charge image. The appropriate thickness difference between the common electrode 2 and the image forming electrode 3 varies depending on the distance between the common electrode 2 and the image forming electrode 3.
As mentioned above, if it is preferably arranged at an angle of 20° or more, sufficient pressure can be secured with the picture electrode, and a better head touch can be achieved. In this case, it is desirable that the angle of inclination is larger because it allows for greater pressure.

Embodiment 2 Several other embodiments of the image forming head of the present invention are shown in FIG.
) to FIG. 3(f), FIGS. 3(a) to 3(f) are sectional views of the substrate at the tip of the head corresponding to FIG. 2 of the image forming head.

In the embodiment shown in FIG. 3(a), a glaze layer is formed on a ceramic insulating substrate at a position corresponding to the position of the image forming electrode to increase the amount of protrusion of the image forming electrode from the substrate. be. This makes it possible to increase the angle of inclination of the image forming head with respect to the surface of the image forming member, thereby increasing the pressure on the image forming member of the image forming head, achieving better head touch, and eliminating unnecessary contact between the image forming member and the head substrate. Excellent image quality is obtained since contact can be further reduced.

In the embodiment shown in FIG. 3(b), the effective distance between the common electrode and the image forming electrode is reduced by making the width of the upper part of the image forming electrode wider than that of the lower part. This further reduces image holes between the forming electrodes.

The embodiment shown in FIG. 3(c) is an example in which an insulating substrate in which insulating layers 1 and 0 are formed on a conductive substrate 9 is used as an insulating substrate. For example, in the case of six examples, which are stainless steel substrates coated with polyimide resin to make the surface insulating,
In this example, the insulating layer at the tip of the head is etched and removed to expose the conductive portion of the substrate, and the exposed conductive portion is used as a common electrode.

In the embodiment shown in FIG. 3(d), the common electrode is partially covered with an insulating glaze layer 11, and an image forming electrode is formed on the glaze layer 11. In this example, the image forming electrode can be formed very close to the substrate edge at the tip of the head, and the image forming electrode can be formed on the glaze layer, so that the inclination angle of the image forming head with respect to the image forming member can be increased. Therefore, the pressing force of the image forming member of the image forming head can be increased, a better head touch can be realized, and unnecessary contact of the image forming member with the head substrate can be further reduced, so that excellent image quality can be obtained.

The embodiment shown in FIG. 3(e) is an example in which a common electrode and an image forming electrode are formed on a substrate, the substrate is bent, and the common electrode and image forming electrode are arranged at the corners of the bent substrate. It is. Since each electrode is located at a corner, the pressure on the image forming member can be increased and a good head touch can be obtained. As the substrate, a stainless steel substrate coated with a resin such as polyimide resin can be used.

The embodiment shown in FIG. 3(f) is an example in which the substrate is a conductive substrate on which an insulating layer is formed, and the conductive portion of the substrate is exposed and used as a common electrode.

After the image forming electrodes are formed on the substrate, the substrate is bent so that the image forming electrodes are at the corners. As in FIG. 3(e), good head touch can be ensured.

Example 3゜ Images were compared using the image forming apparatus shown in FIG.

This image forming apparatus uses a conductive sleeve 14 that rotates in the direction of arrow 13 and has a built-in multipolar magnet as a member that supports and conveys the conductive powder 12. The first image forming member 15 is conveyed in the direction of arrow 16 in contact with the conductive powder 12 . An image forming pad 17 is arranged on the opposite side of the conductive powder 12 with the first image forming member 15 in between, and a bias voltage is applied to the image forming electrode of the image forming head from a power source 18 in accordance with an image signal. Ru. Charges corresponding to the bias voltage are injected into the first image forming member 15 that is in contact with the electrode to which the bias voltage is applied, or spontaneous polarization occurs. At the same time, the conductive powder 12 corresponding to the pixel to which the bias voltage is applied (that is, the portion of the first image forming member 15 on the opposite side of the pixel to which the bias voltage is applied) is charged with an opposite polarity. Injected. Therefore, the conductive powder 12 can be adhered onto the first image forming member 15 by electrostatic force. Note that a voltage of an appropriate value is applied to the common electrode of the image forming head to prevent the conductive powder 12 from adhering.

The conductive powder 12 attached to the first image forming member 15 according to the image is heated and pressurized by the fixing means 19, so that the conductive powder 12 fuses or joins together.
The bonded state is fixed onto the first image forming member 15. Examples of the fixing means 19 include a human roll fixing device, a flash fixing device, a pressure fixing device, etc., which are known in electrophotography.

Furthermore, using a heat roll fixing device 20 as a transfer means, the first image forming member 15 is passed through the heat roll fixing device 20 together with the second image forming member 21, and the conductive powder 12 is heated and pressurized. The conductive powder is transferred all at once to the second image forming member 21 by utilizing their cohesive force.

Here, the conductive powder 12 is a so-called resin-based powder whose main component is a resin such as polystyrene, acrylic, or polyester, or a wax such as paraffin wax or carnauba wax, higher fatty acids, or a low-carbon powder. It is sufficient that the powder is a so-called wax-based powder mainly composed of polyolefins such as molecular weight polyethylene and polyethylene oxide, and has a specific resistance of 10 9 Ω or less, preferably 10 6 Ω or less, and The first image forming member 15 may be a flexible film with a specific resistance IQIIIΩ or more, preferably 10I2Ω or more, such as a polymer film such as polyethylene terephthalate (PET), polyphenylene sulfide (pps), polyimide, etc. In addition, a conductive layer with a specific resistance of 10'1 Ω or less formed on the electrode head side on a flexible film with a specific resistance of 101 gΩ or more is desirable because it can reduce the bias voltage. (The bias voltage required to obtain this conductive layer can be reduced.) This conductive layer is, for example, a material in which carbon black, metal powder, etc. are dispersed in an organic substance, and has a high resistivity in the horizontal direction and a low resistivity in the vertical direction. It is a so-called anisotropic conductive layer with a low conductivity.

The present inventor evaluated the effect of the electrode structure of the present invention by comparing toner images after development. Images produced by conventional heads without common electrodes had uneven background smudges and noticeable density unevenness.

On the other hand, in the image forming head of the present invention shown in Example 1.2 with a common electrode, no density unevenness was observed, and a uniform image was obtained over the entire surface of the image forming member. When the optical density had an average value of 1.45, the maximum variation width in an A4 size image forming area was about 0.06, which was extremely small. Furthermore, by changing the voltage applied to the common electrode, background smudge due to toner adhesion was reduced. Conventionally, the optical density in the non-print area was about 0.25, but with the head of the present invention, it can be reduced to 0.15 or less.

Furthermore, when examining images obtained with an image forming apparatus using a conventional conductive roller, the average value of 0 image immersion degree was 1.43, and the density unevenness was larger than that of images obtained by the present invention.
The difference between the maximum concentration and the minimum temperature was 0°12, and unevenness could be clearly discerned by visual inspection.

Furthermore, the background smudge was higher than that of the present invention, and overall the image quality obtained by the head of the present invention was much better.

[Effects of the Invention] As described above, the image forming head of the present invention can stabilize the surface potential of the image forming member and minimize disturbances in the formed image, so it can greatly contribute to improving image quality. In particular, the image forming head of the present invention can form high-quality images on flexible films with low tension, so it can be used in image forming devices such as new electrostatic printers and other devices that require image output, such as fascis, word processors, etc. Furthermore, it is possible to apply it to image displays using toner, and the field of application is extremely wide.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of an image forming head of the present invention. FIG. 2 is an enlarged cross-sectional view of the tip of the image forming head shown in FIG. 1; FIG. 4 is a schematic diagram of an image forming apparatus used for image formation evaluation. 1... Insulating substrate 2... Common electrode 3... Image forming electrode 4... Wire connection 5... Circuit board 6... IC driver 7... Connector 8... Glaze layer 9... Conductive substrate 10... Insulation Layer 1 toggle layer 12, conductive powder 13, arrow 14 indicating the rotation direction of the conductive sleeve, conductive sleeve 15, first image forming member 16, arrow indicating the transport direction of the first image forming member 17・
Image forming head power supply fixing means Heat roll fixing device Second image forming member Applicant Seiko Epson Co., Ltd. Agent Patent attorney Kizobe Suzuki (and one other person) Figure 3
(d-n-i Figure 3 and small

Claims (1)

[Claims] 1. An insulating substrate, a plurality of mutually separated electrode groups 1 formed on the insulating substrate, and an image forming member including at least a circuit for independently applying a voltage to each electrode of the electrode group 1 as a component; In an image forming head that moves while in contact with the image forming member and forms a charge image by an electrode group 1 on the image forming member, the insulating substrate is moved so that the image forming member contacts the common electrode and then contacts the electrode group 1. An image forming head characterized in that a common electrode is arranged on the top.