JPH0447311B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to an apparatus for making a lithographic printing plate by reversely developing an electrophotographic photoreceptor with a liquid developer.

(B) Prior art and its problems Image formation by electrophotography is easy and
It is widely used because of its speed, low cost, etc. Particularly in the printing field, the spread is remarkable. Electrophotographic photoreceptors used in the printing field have a photosensitive layer on a support, and are made into printing plates through a charging process, an exposure process, a developing process, and a fixing process. is used as a printing plate after a fixing process, an elution process, a rinsing process, and a gumming process.

A plate-making machine for obtaining a printing plate exposes a document and an electrophotographic photoreceptor in close contact with light, so-called contact printing, or projects the document onto an electrophotographic photoreceptor through a lens.
There are so-called photographing methods, and a laser method in which image information of a document is converted into an electrical signal and an electrophotographic photoreceptor is exposed to, for example, laser light. It goes without saying that in either method, there are positive exposure and negative exposure, and there are also normal development and reversal development in development.

FIG. 2 is a partial cross-sectional view showing reversal development performed using the electrophotographic photoreceptor 1. In FIG. 2, an electrophotographic photoreceptor having a photosensitive layer 4 provided on a support 6 is positively charged, and the electrophotographic photoreceptor is placed in a liquid developer 2 in which positively charged toner 3 is dispersed. 1 is immersed, and a developing bias is applied between the developing electrode 5 and the support 6 via a bias power source 9. Since the exposed portion 41 of the photosensitive layer 4 has lost its charge, the positively charged toner 3 is attracted by the developing bias and forms a toner image.

Since positive charges remain in the unexposed areas 42 of the photosensitive layer 4, the positively charged toner 3 is repelled and no toner sticks to them. Side surface 8 of electrophotographic photoreceptor
Since is the potential of the support 6 itself, the toner 3 is developed and adheres here.

When the developed electrophotographic photoreceptor 1 is fixed and the non-image area is eluted with alkali to form a printing plate for offset printing, toner remains attached to the side surface 8 of the electrophotographic photoreceptor. Therefore, during printing, ink adheres to this area, and when printed on printing paper larger than the printing plate, it is printed as linear stains on the printed matter, making it very unsightly.

Particularly in newspaper printing, in order to efficiently produce a large number of printed materials, it is common to attach multiple printing plates to the plate cylinder of a rotary press. This often results in ink stains and lowers the commercial value.

As a method for preventing ink stains from the sides of printing plates, Japanese Patent Application No. 11086/1986 discloses the following methods:
A method has been proposed to prevent toner from adhering by coating the side surfaces with an insulating resin layer, but this method is not only laborious and unsuitable for large-scale processing, but also the resin coating solution may damage the photosensitive layer. Penetrates the edges,
It still has the disadvantage that the edges become smudged.

(C) Purpose of the Invention The present invention is intended to solve the problems of the prior art described above, and its purpose is to prevent linear stains of ink from the side surface of an electrophotographic photoreceptor on printed matter.

As a result of intensive research, the present inventors have found that the above-mentioned object can be extremely well achieved by the following plate-making apparatus without the problems of the prior art.

(D) Structure of the Invention That is, the present invention is an apparatus for making a lithographic printing plate by reversing developing an electrophotographic photoreceptor, which includes at least a developing section for reversing developing, and a developing section for reversing the electrophotographic photoreceptor; a fixing section for fixing the toner image formed on the photoreceptor, and a means for removing developer attached to both sides of the photoreceptor due to development between the developing section and the fixing section. This is a plate-making device characterized by the following.

Hereinafter, the present invention will be explained in more detail using the drawings.

FIG. 1 is a schematic top view of a specific example showing the main parts of the plate making apparatus of the present invention.

After being charged and exposed, the electrophotographic photoreceptor 1 is subjected to liquid reversal development as described in FIG. As shown in FIG. 1, the electrophotographic photoreceptor 1 that has come out of the developing chamber has excess liquid developer 2 squeezed out by a pair of squeezing rollers 10, and is transported to the next fixing step.

Conventionally, the side surface 8 (second
The liquid developer 2 containing the toner 3 attached to the
Since it is fixed in the same manner as the liquid developer 2 on the photosensitive layer 4 in the fixing process, the above-mentioned drawbacks occur.

As shown in FIG. 1, the plate-making apparatus of the present invention includes means 1 for removing unfixed liquid developer 2 adhering to the side surface of an electrophotographic photoreceptor 1 between a developing section and a fixing section.
1 to 14 are provided so that the liquid developer 2 on both sides of the electrophotographic photoreceptor 1 can be wiped off before the electrophotographic photoreceptor 1 enters the fixing process.

In FIG. 1, the wiping material 11 is brought into contact with the side surface of the electrophotographic photoreceptor 1 by a pressure roller 12,
It is made of a material that can adhere to or absorb the liquid developer 2, such as paper, cloth, leather, corpus cavernosum, and film. The rollers 13 and 14 are a feed roller and a take-up roller for the wiping material 11,
After the feeding is completed, it can be rotated in any direction to become a take-up roller. The wiping may be performed while the wiping material 11 is moving in a direction opposite to the traveling direction of the electrophotographic photoreceptor 1 (the direction shown in FIG. 1), or may be performed while moving in the opposite direction. When using the unwiped surface of the wiping material 11, it is preferable that each of the rollers 12, 13, and 14 can be moved up and down so as to move the wiping material 11 up and down.

Further, it is preferable that the pressure roller 12 is kept apart until the tip of the electrophotographic photoreceptor 1 comes between the rollers 12 on both sides, and when it comes between, it can be pressed against the side surface of the electrophotographic photoreceptor 1. .

In a modified embodiment of the present invention, the rollers 13 and 14 shown in FIG. 1 can be omitted, and the wiping material 11 wound around the pressure roller 12 can be used as a means for removing the liquid developer 2. It is preferable that the pressure roller 12 in this case also includes the above-described mechanism. Further, the pressure roller 12 itself may be made of a wiping material, and it can be used continuously by attaching something like a blade to the wiping material to scrape off the toner. In addition, the wiping material 11 is
Instead of the pressure roller 12, it is also possible to use a pressure plate facing parallel to the side surface of the electrophotographic photoreceptor 1, and the pressure plate itself may be made of a wiping material. The wiping material is replaceable and can be reused after cleaning the toner.

It is preferable to provide air blowing means (not shown) between the developing section and the fixing section in FIG. 1 for drying the liquid developer on the photosensitive layer.

The developing section used in the plate making machine of the present invention is
A liquid reversal developing device such as that described in US Pat. No. 62-2695 is preferably used. Further, the fixing section may be of a heat fixing type using a plurality of lamps.

Before the development step, there may be steps of plate feeding, charging, and exposure (for example, laser scanning exposure), and after the fixing step, there may be steps such as elution and gumming.

The electrophotographic photoreceptor 1 consists of an electrophotographic photosensitive layer provided on a metal plate support. For the metal plate support, metals such as aluminum, iron, copper, zinc, lead, or alloys of various metals can be used.

Alternatively, it substantially contains a good electrical conductor, such as a so-called composite support made by bonding aluminum, iron, etc. to a PET film.

The photosensitive layer of the electrophotographic photoreceptor 1 is made of, for example, an alkali-soluble resin such as a styrene-maleic anhydride copolymer, an acrylic resin having an acid value, a maleic acid ester resin, a vinyl acetate-maleic anhydride copolymer, Dispersing or dissolving various organic photoconductive materials such as inorganic or organic photoconductive substances such as zinc oxide, cadmium sulfide, azo pigments, phthalocyanines, and aromatic tertiary amino compounds in resins such as phenolic resins. It is obtained by coating and drying.

<Effects of the Invention> According to the plate-making machine of the present invention, the liquid developer attached to the side surface of the lithographic printing plate is easily removed while being conveyed until it is fixed, making it possible to continuously make large quantities of plates. This makes it possible to obtain printed matter without ink stains caused by the sides of the printing plate.

[Brief explanation of the drawing]

FIG. 1 is a schematic top view of a specific example showing the essential parts of the plate-making apparatus of the present invention, and FIG. 2 is a cross-sectional view of a model when reversal development is performed on an electrophotographic photoreceptor.

Claims (1)

[Claims] 1 An apparatus for making a lithographic printing plate by reversing development of an electrophotographic photoreceptor, which includes at least a developing section for reversal development and for fixing a toner image formed on the photoreceptor by development. 1. A plate-making apparatus comprising a fixing section, and a means for removing developer attached to both sides of the photoreceptor due to development between the developing section and the fixing section.