JPH02277086A - Electrophotographic fluid developing device - Google Patents

Abstract

PURPOSE:To prevent toner adherence, contamination, etc., by providing a fluid toner supplying slit from which fluid toner is discharged upward and a fluid toner recovering slit which recovers the overall quantity of the fluid toner supplied on an image carrier surface. CONSTITUTION:By the operation of a fluid toner supplying pump 34, the fluid toner 36 with a positive electric charge is discharged from the fluid toner supplying slit 26 and supplied. Toner particles are made to adhere onto an organic photoconductor 18 in accordance with an electrostatic latent image and developed by supplying the toner 36. After being supplied to the photoconductor 18, the toner 36 is recovered from the fluid toner recovering slit 28 into a fluid toner tank 32. Since the sum total of the aperture area of the slit 28 is larger than the sum total of the aperture area of the slit 26 and recovering capacity is constantly kept higher than fluid toner supplying quantity, the recovery can prevent the toner adhesion inside the developing device or onto the back face of a photosensitive body.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic liquid developing device for developing an electrostatic latent image formed on an image carrier, and in particular to an electrophotographic liquid developing device suitable for reversal development. Regarding equipment.

[Prior art] Today, as lithographic offset printing plates, PS plates that use positive-working photosensitizers whose main components are diazo compounds and phenolic resins, and negative-working photosensitizers whose main components are acrylic monomers and prepolymers are in practical use. has been made into

On the other hand, due to advances in computer image processing, large-capacity data storage, and data communication technology, in recent years, everything from inputting, correcting, editing, and page layout to page composition has become computer-processed, and high-speed communication networks and satellite communications have enabled instantaneous remote location. An electronic editing system capable of outputting to the terminal block of is now in practical use. If this electronically edited data can be output directly to a lithographic printing plate, the plate-making process can be extremely shortened.

However, at present, a direct printing plate that can directly create a printing plate from the output of a terminal plotter has not been put into practical use. The reason for this is that direct printing plates require high sensitivity to enable scanning exposure within a practical time, and it is difficult to develop printing plates (direct printing plates) with this high sensitivity.

An electrophotographic method can be mentioned as a system having high sensitivity that can provide the above-mentioned direct printing plate. As a plate-making system that applied electrophotography,
No. 610, No. 48-40002, No. 48-18325
Plate-making systems for zinc oxide-resin dispersion offset printing plates described in Japanese Patent Publications No. 374-17162 and Japanese Patent Publication No. 38-7
No. 758, No. 4-39405, No. 52-2437,
JP 57-147656, JP 59-147335, JP 59-152456, JP 59-1678462, JP 58-145495, JP 59-168462,
Organic photoconductor described in Publication No. 58-145495 etc.
Resin-based offset printing plate systems are known. The printing plates used in these plate-making systems can be created as follows. After the zinc oxide-resin dispersion system is charged, exposed, developed, and fixed by a known electrophotographic process, the surface is treated with a desensitizing liquid to obtain an offset printing plate. In the latter organic photoconductor-resin system, after charging, fogging, development, and fixing, the toner layer acts as a resist;
The photosensitive layer in the non-image area is eluted. This exposes the substrate surface (usually hydrophilic) in the non-image area and is used as an offset printing plate.

As an exposure method, it is convenient to carry out scanning exposure using an Ar laser, a He-Ne laser, a semiconductor laser, etc. for boat fishing. Further, the toner phenomenon can be a positive-positive phenomenon due to a positive phenomenon or a negative-positive phenomenon due to a reversal phenomenon. Toners include so-called dry toners and liquid toners, but in order to create a printing plate with high resolution, it is preferable to develop with a liquid toner that can reduce the toner particle size.

Furthermore, many inventions have been made regarding developing devices that supply liquid toner to a photoreceptor that is an image carrier. For example, liquid toner can be dropped onto a roller that is in contact with the surface of the photoconductor, and liquid toner can be supplied to the surface of the photoconductor by the rotation of the roller, or sufficient liquid toner can be directly supplied to the surface of the photoconductor to remove excess liquid. There is a so-called metering method in which the toner is collected into a collection tank and then supplied again to the surface of the photoreceptor by means of circulation1, or a predetermined amount of liquid toner is supplied to the surface of the photoreceptor and the excess liquid toner is discarded. .

[Problems to be Solved by the Invention] However, in the conventional developing device described above, peripheral devices such as rollers and developing electrodes, printing plates, etc. are stained with liquid toner, making cleaning difficult. In particular, during reversal development, a bias voltage is applied between the photoconductor and the developing electrode to develop the toner with the same polarity as the photoconductor's charge polarity, which causes a large amount of toner adhesion to the inside of the developing machine and the back surface of the photoconductor, causing contamination. It is a major cause of this.

Furthermore, maintenance of the dirty developing machine was troublesome.

Therefore, JP-A-63-163384 discloses a mechanism for preventing toner from adhering to the aperture roller, but since the photoreceptor passes through the toner, it is difficult to prevent toner from adhering to the back surface of the photoreceptor or the back electrode. I can't.

Also, US Patent No. 3,342,164 and British Patent No. 1
In Japanese Patent No. 099813, the recording paper is sucked by connecting the grooves at both ends of the developing section to a negative pressure source, and when the developing section becomes negative pressure, the developer is sucked through the slit in the center of the electrode, and the contact between the electrode and the paper is made. The developing section is made smaller and the back surface of the photoreceptor is prevented from becoming contaminated. However, this method has the disadvantage that the width of the photoreceptor is regulated and cannot be used when there are a wide variety of printing plates, such as lithographic printing plates.

In consideration of the above facts, the present invention can prevent toner from adhering to the inside of the developing machine or to the image carrier during reversal development, making maintenance easier and applicable to image carriers of various widths. It is an object of the present invention to provide an electrophotographic liquid developing device that can perform the following steps.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes one or more liquid toner supply slits provided in a liquid toner developing section and from which liquid toner is discharged upward, and a liquid toner supply slit. one or more liquid toner recovery slits capable of recovering more liquid toner than the amount of liquid toner supplied from the slits for recovering the entire amount of liquid toner supplied to the surface of the image carrier; It is characterized by having the following.

[Function] In the present invention having the above configuration, liquid toner is supplied from the liquid toner supply slit onto the image carrier on which the electrostatic latent image is formed. The electrostatic latent image on the image carrier is developed by the supplied liquid toner.

The supplied liquid toner is collected from the liquid toner collection slit. Since the liquid toner collection slit is capable of collecting more liquid toner than the amount of supplied liquid toner, the entire amount of the supplied liquid toner is collected. This prevents the liquid toner from scattering inside the developing machine and the peripheral equipment, so that the inside of the developing machine and the peripheral equipment are not contaminated, and maintenance becomes easy.

Furthermore, since the ejection port through which liquid toner is ejected is a slit, by adjusting the length of this slit to the maximum dimension of the image carrier, it is possible to develop many types of image carriers with different width dimensions. .

The electrophotographic liquid developing device of the present invention will be explained in more detail below.

[Example] This example mainly describes an electrophotographic offset printing plate in which an organic photoconductor is provided on an aluminum substrate, but it goes without saying that other configurations can be used for liquid development of an electrophotographic photoreceptor.

FIG. 1 shows an electrophotographic liquid developing apparatus 10 according to the present invention. Note that FIG. 1 is a schematic cross-sectional view of the electrophotographic liquid developing device IO.

As shown in FIG. 1, in the electrophotographic liquid developing device 10, two metal transport roller pairs 12 and 14 are arranged in sequence in the horizontal direction. These conveyor roller pairs 12
．． 14 is driven and rotated by the driving force of a driving means (not shown). Further, the conveyor roller pair 12, 14 is grounded by a ground terminal.

An offset printing plate 20 having an organic photoconductor 18 provided on an aluminum support 16 is inserted between the pair of conveyor rollers 12, and is sent out approximately horizontally toward the pair of conveyor rollers 14 (in the direction of the arrow in Figure 1). .

The conveyance speed of this offset printing plate 20 is 5 mm/s e
c ~2 Qmm/s e c (usually 10mm/
5ec).

A developing head 22 is located at the bottom of the conveyance path of the offset printing plate 20 that is conveyed between the conveyance roller pair 12 and the conveyance roller pair 14.
is located. A certain distance L (
(see Figure 2). This interval is set to 1 to 3 strokes. However, although it is set to 1 mm in design, it actually fluctuates to 1 to 2 buttons due to vibrations due to sagging or deformation of the offset printing plate 20, and the maximum is 3 mff1.
It fluctuates up to.

Further, the developing head 22 is connected to a bias power source 24, and reversal development is performed by applying a bias voltage during toner development.

As shown in FIG. 2, the developing head 22 has a liquid toner supply slit 26 and a liquid toner recovery slit 2.
8 is open facing the organic photoconductor 18 of the offset printing plate 20.

As shown in FIG. 3, the developing head 22 has a conduit 23 disposed inside a box body that opens upward.This conduit 23 has an opening along the longitudinal direction. Vertical walls 25 are erected from both edges in the width direction of this opening.A plurality of spacers 27 are arranged between these vertical walls 25, and the dimension between the vertical walls 25 is set to a predetermined dimension. As a result, a liquid toner supply slit 26 is formed between the upper ends of the vertical wall 25.Also, a liquid toner supply slit 26 provided adjacent to the vertical wall 25 forming the liquid toner supply slit 26 is formed between the upper ends of the vertical wall 25. 26 vertical wall 2 for formation
5 is a slit 28 for collecting liquid toner.

Each of these slits is formed long along the width direction of the offset printing plate 20, and is set to the maximum width dimension of the printing plate. Therefore, it is possible to accommodate printing plates having a wide variety of width dimensions.

Further, the total opening area of the liquid toner recovery slits 28 is set larger than the total opening area of the liquid toner supply slits 26. Therefore, all of the liquid toner discharged from the liquid toner supply slit 26 is recovered from the liquid toner recovery slit 28.

The liquid toner supply slit 26 is communicated with a liquid toner tank 32 via a conduit 30 via a conduit 23 . Further, a liquid toner supply pump 34 is disposed in the middle of the pipe line 30. By operating the liquid toner supply pump 34, the positively charged liquid toner 36 stored in the liquid toner tank 32 is sent to the developing head 22 and discharged from the liquid toner supply slit 26. This flow rate is approximately 91
/min is set.

Further, the developing head 22 is connected to a liquid toner tank 32 via a conduit 38.
It is communicated with. The liquid toner collected from the liquid toner collection slit 28 passes through this pipe line 38 and is collected into the liquid toner tank 32 .

Further, the offset printing plate 20 being transported is grounded by the aluminum support 16 coming into contact with the transport roller pair 12.14.

Next, the operation of this embodiment will be explained.

While the organic photoconductor 18 is being transported from the metal transport roller pair 12 to the transport roller pair 14, positively charged liquid toner 36 is discharged from the liquid toner supply slit 26 by the operation of the liquid toner supply pump 34. will be supplied.

This supply of liquid toner 36 causes toner particles in the liquid toner to adhere to the positive electrostatic latent image on the organic photoconductor 18 and develop it.

After being applied onto the organic photoconductor 18, the liquid toner 36 is collected into a liquid toner tank 32 through a liquid toner collection slit 28. In this collection, the total opening area of the liquid toner collecting slits 28 is larger than the total opening area of the liquid toner supplying slits 26, and the amount of liquid toner always collected is kept larger than the supplied amount.
It is possible to prevent toner from adhering to the inside of the developing machine or to the back surface of the photoreceptor, and maintenance of the apparatus becomes easy.

That is, by increasing the number of ways in which the supplied liquid toner can be collected, the upper part of the developing head 22 is always under-supplied of liquid toner.

When the offset printing plate 20 passes in this state, the liquid toner concentrates on the meniscus between the organic photoconductors 18, regardless of the size of the offset printing plate 20 in the width direction. Therefore, liquid toner does not go around to the back side of the offset printing plate 20. Also, at this time, since the liquid toner is supplied and discharged by the slit, the organic photoconductor 1
The toner liquid can be concentrated only in 8.

Further, when the offset printing plate 20 passes over the developing head 22, the flow of the liquid toner that has been uniformly discharged from the entire width of the liquid toner supply slit 26 is changed to the offset printing plate 20.
The liquid toner concentrates only on the lower surface of the liquid toner and flows out to the slit 28 for collecting liquid toner. Therefore, excess liquid toner does not flow out to the portion of the developing head 22 that does not face the organic photoconductor 180.
Liquid toner does not wrap around and come into contact with the aluminum support 16 of the offset printing plate 20. That is, the offset printing plate 20 can be developed by contacting only the surface of the organic photoconductor 18 of the offset printing plate 20 with liquid toner, regardless of its width, and toner adhesion to various parts of the developing machine or the photoreceptor that occurs during reversal development can be developed. Reversal development with no toner stains on the back side can be achieved.

The offset printing plate 20 that has passed through the developing head 22 is squeezed out of excess liquid toner by a pair of transport rollers 14, and is transported to the next processing section.

Next, another embodiment will be described using FIGS. 4 and 5. Note that the same reference numerals are attached to the drawings for parts having the same configuration as those of the above embodiment, and the description thereof will be omitted.

FIG. 4 shows an example of an electrophotographic liquid developing device 50 to which the developing head 40 shown in FIG. 5 is attached. Here, unlike the previous embodiment, the total opening area of the liquid toner supply slit 42 and the liquid toner recovery slit 44 provided in the developing head 40 is the same. Furthermore, a suction pump 46 is provided in the middle of the conduit 38. by this,
The liquid toner 36 is sucked from the liquid toner recovery slit 44. This amount of suction is set to a value that allows suction to be greater than the amount of liquid toner 36 supplied.

Therefore, in this embodiment as well, it is possible to develop the back surface of the offset printing plate 20 without bringing the liquid toner into contact with it, regardless of the width of the offset printing plate 20.

Also shown in FIG. 4, in this embodiment the aluminum support 16 is grounded by spring-like ground terminals 52,54. The ground terminals 52 and 54 are arranged so that either one of them contacts the aluminum support plate 16 between the leading edge of the offset printing plate reaching the developing head 40 and the trailing edge of the offset printing plate passing through the pair of transport rollers 12. ing. In conventional reversal developing machines, these ground terminals 5 are
2.54, accumulation of toner particles occurred, often causing poor continuity. However, in this embodiment, the liquid toner does not come into contact with the offset printing plate, there is no failure as described above, and the maintainability can be significantly improved.

In each of the embodiments described above, liquid toner is uniformly supplied to the photosensitive surface in both the developing sections shown in FIG. 1 and FIG. 4, and a good reversal image can be formed by the developing bias voltage. In the above examples, it was shown that a reversal image can be formed by positively charging an organic photoconductor and applying a positive potential to the developing electrode using a positively charged voltage liquid toner. Similarly, reversal development can be performed using negatively charged toner and by applying a negative bias voltage.

It is also possible to positively (negatively) charge the photoreceptor and perform positive development using a negatively (positively) charged liquid toner.

Further, as a pre-processing step of the main developing section, a plate feeding section for an offset printing plate, a charging section, a scanning exposure section using a radar, a surface exposure section via a lens optical system, etc. are provided. Further, as post-processes, steps such as a drying section, a toner image fixing section, a toner non-image area elution section, a water washing section, a desensitizing section, and a pen part are provided as necessary.

[Effects of the Invention] The electrophotographic liquid developing device according to the present invention can be applied to image bearing members of various widths, and at the same time, it can prevent toner adhesion, dirt, etc. on the inside of the developing machine or on the back side of the image bearing member that occurs during reversal development. It is possible to prevent this, and the maintainability of the device can be significantly improved, which is an excellent effect.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an electrophotographic liquid developing device according to the present invention, FIG. 2 is a sectional view showing a developing head, FIG. 3 is a perspective view showing the developing head, and FIG. 4 is an electrophotographic FIG. 5 is a schematic configuration diagram showing another embodiment of the liquid developing device, and FIG. 5 is a sectional view showing another example of the developing head. 10.50... Electrophotographic liquid developing device, 16... Aluminum support, 18... Organic photoconductor, 20... Offset printing plate, 34... Liquid toner supply pump, 22.40 ...Development head, 26.42...Liquid toner supply slit, 28.4
4... Slit for collecting liquid toner, 36... Positively charged liquid toner 46... Pump for suction.

Claims (1)

[Claims] (1) A liquid toner developing section that develops the electrostatic latent image formed on the image carrier is disposed below the surface of the image carrier, and discharges liquid toner upward onto the surface of the image carrier. In an electrophotographic liquid developing device that supplies and develops, one or more liquid toner supply slits provided in the liquid toner developing section and from which the liquid toner is discharged upward; and from the liquid toner supply slits. one or more liquid toner collecting slits capable of collecting more liquid toner than the supplied amount of liquid toner and collecting the entire amount of liquid toner supplied to the surface of the image carrier; An electrophotographic liquid developing device characterized by: