JPH0345381B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an electrophotographic method used in color press printing, in which a plurality of cylinders are used, each cylinder printing one color element of a color image to be printed on a substrate (substrate). It's about the body.

PRIOR ART A variety of color printing techniques are known in the art. The principle of conventional color printing technology is to first photograph color objects through separate filters to create so-called color-separated negatives. Halftone printing plates (printing plates) are produced using these negatives. However, in normal printing, four-color plates of black, yellow, cyan, and magenta are used to synthesize the color structure of the original image. These prints are mounted on a printing press or an intaglio printing press, and the substrate to be printed is moved against the press equipped with such printing plates, with careful synchronization to ensure perfect alignment. In this case, the ink is selected to achieve the desired result and is first applied to a printing plate, from which it is transferred directly or indirectly to a substrate.

For small size color printing or simple equipment color printing, each sheet is printed repeatedly with different printing plates and inks to achieve the desired result.

Traditionally used photocopying or photocopying has been replaced in recent years by electrostatic imaging methods.

At Xerox, the member for electrostatic printing is, for example, a metal drum coated with amorphous selenium. This drum is pressed against a substrate such as paper, an electric field is applied to transfer the image, and then the image is transferred to the paper using heat. Weld them together.
In electrofax, the electrostatic printing member is, for example, a sheet of electrically conductive paper coated with zinc oxide on an inorganic base, and this sheet itself becomes the reproduction product. The toner is welded to this sheet.

The principle of these previously known printing techniques is to produce a single copy from a given projected image. In a Xerox machine, a new exposure is made for each copy and the cycle repeats. Similarly, in electrofax, a new exposure and cycle are performed for each copy, but in this case, the electrostatic printing medium is not reused, but is sent out one after another from the device and becomes a copy.

Electrostatic image printing members of the electrofax system are used as temporary printing plates with appropriate processing, in which case the ink separates the image from the background. One of the members is made hydrophobic and the other is made hydrophilic by the above-described treatment, and in this state the member is placed on a press printing machine and used as a printing plate to make copies. The quality obtained with this method is low, and the number of copies obtained from one plate is considerably less than a few thousand copies. Various attempts have been made to perform electrostatic color printing using this method, but so far none have been successful in this process.
This is because, among other disadvantages, zinc oxide is not panchromatic.

DISCLOSURE OF THE INVENTION The present invention seeks to develop new uses for photoconductive coatings having the property of readily depositing on metal surfaces, such as those disclosed in US Pat. No. 4,025,339. The new application is inter alia to produce printing plates which can be used for press color printing.

U.S. Patent No. 2287122 and U.S. Patent No. 3354519
No. 6, 2003, describes a printing cylinder with an electrolytically deposited or electrolytically formed nickel sleeve having a thickness of a fraction of a millimeter. Such a cylinder of known construction has a diameter of approximately one-fifth of a meter and a length of several meters. Conventionally, this type of cylinder has been manufactured with a fine through hole in the shape of an image, so that ink is delivered from the inside of the cylinder through the cylinder and transferred onto a base body that rotates the cylinder. Optionally, uniform perforations are provided throughout, with some of the perforations being occluded to create an image pattern.

The advantages of using these cylinders are described in the aforementioned U.S. Pat.
Easy to handle, easy to install, etc.

However, it has been found that when using these electrostatic printing cylinders there are disadvantages in printing technology which must naturally be avoided. Such problems include the need to provide a through hole in the cylinder and the need to expel ink through the cylinder from within the cylinder. A further problem is the application of conventionally known photoconductors to the cylinder without bending, wrinkling, damaging or abrading the photoconductor. Obtaining the desired image characteristics requires an excessively thick coating, thus compromising the thin-walled properties and flexibility of the cylinder.

Therefore, in the present invention, a flexible metal sleeve having a thickness of a fraction of 1 mm and which can be made into a rigid cylindrical shape for printing is used, and a thin conductive film is coated on the outer surface of this sleeve. The coating is flexible, has a microcrystalline structure, is completely inorganic, and has a thickness of no more than the order of microns, so that it can be imaged at high speeds.

Example The present invention will be explained below with reference to the drawings.

In FIG. 1, 10 indicates a cylinder, the base or base layer of which is a sleeve 12 made of metal such as nickel, copper-coated nickel, or copper. Nickel is preferred for this purpose because it is strong, thermally stable, and can be electrolytically refined to a uniform thickness with extremely high precision. This cylindrical sleeve is seamless. In a preferred embodiment, the sleeve has a wall thickness of about 0.15 mm, a circumference of about 1 m, and a length of 2 m or more.

The cylindrical sleeve 12 is mounted on a suitable sputtering machine and supported so as to present a smooth, uninterrupted surface against one or more targets of the sputtering machine, during which time the targets are supported during the sputtering process. This causes a uniform coating 14 of deposited photoconductive material to be formed on the sleeve when the sputtering process is completed.

The thickness of the photoconductive coating 14 is approximately 3,000 to 6,000 Angstroms (Å), and may be made of high purity cadmium sulfide. Slightly thicker coatings can also be used. This is because there is no special requirement for transparency. Dopants may be incorporated into the coating to selectively tune its spectral response to make the coating sensitive to different colors of light.

Sleeve 12 is maintained relatively rigid during the sputtering process by suitable means. The annular portions shown at 16 and 18 at the ends of the cylinder 10 formed do not need to be coated since the holder covers their surfaces.

The electrolytically finished sleeve 12 is highly flexible and bendable. The sleeve can be folded up into a very small container. For example, a cylindrical container of the same diameter as one sleeve may contain many other sleeves that are recessed inward and rolled to smaller diameters. Such a small rolled sleeve will not be damaged unless it is creased around it.

In order to function as a photoconductive material, a thick coating of zinc oxide with an organic material or an amorphous selenium matrix is required. If this is done, the properties described in the aforementioned U.S. patent
The properties of the coating of No. 4025339 cannot be approached. Coatings of this type cannot be placed on the sleeves 12 without completely changing their weight, flexibility and handling capacity of these sleeves. The coating does not adhere well and will crack and flake off when the cylinder is bent.

The photoconductive coating of the present invention has an extremely thin thickness;
The mechanical properties of the sleeve 12 are not affected in any way. The thickness of its coating is 300% of the thickness of the metal sleeve
1 times smaller, does not affect its flexibility in any way, does not actually increase its weight, and does not require special care in handling.

The thickness of the coating 14 can be about 3000 to 6000 Å, but since the transparency of the coating is determined only from the standpoint that it only needs to penetrate enough for photons to be absorbed, the thickness at the printing cylinder may be larger than 6000 Å. For example, this thickness can be about 1 micron (on the order of microns) or more.

In use, the cylinder 10 is supported sufficiently rigidly and in a cylindrical shape to enable it to act as a roller in a printing press.
For example, it is placed opposite to a backup drum, and a continuous substrate (imprinted object) is passed around the drum. Transfer ink or dye to a substrate by a roller.

The cylinder 10 is imaged before being mounted on the printing press. That is, the sleeve is loaded in the dark, exposed to a pattern or image, and then colored.
The exposed pattern forms an image on the cylinder,
The image has dots or small geometric shapes, creating a so-called "halftone" effect that differs from traditional halftone forms. The image may be a composite image derived from a programmed computer operated by a laser, or it may be a reproduction of a photograph or document scanned with a laser or other light source, and may be in the form of dots or other various shapes. It is converted into a geometric shape. Laser image is coated 14
It is convenient for exposing at high speed.

When the cylinder 10 is imaged and colored, a pattern of toner is deposited and positioned as shown at 20 in FIG. 3, thereby forming a fixed colored image on the coating 14. This toner must be insulating and uses a so-called "inductive donor". This prevents discharge from occurring from the non-colored portion 22 of the surface.

A cylinder provided with a colored pattern is mounted on a press printing machine. When this cylinder is used together with other cylinders of the same type, it is first charged to accumulate high-voltage charges on the surface of the colored image 20. This image is not sensitive to light. This means that when other parts of the surface are exposed to bright light or simply exposed to ambient light during use, the charge deposited by the corona discharge on the unpigmented portion 22 of the cylinder is immediately dissipated.
In this state, the cylinder is rotated into an ink bath called secondary toner. This secondary toner contains the desired dye or pigment, and the original primary toner may be free of facial dyes.

Since the pigment is deposited only on the charged portion of the cylinder, it adheres only to the toned image area 20. The cylinder rotates through the dye bath, adsorbing the pigment, and then moves to an adjacent substrate to transfer the pigment thereto. If a bias voltage is applied to this, electrostatic transfer occurs, so no actual physical contact is required. After the transfer is completed, this cycle is repeated. Post-transfer cleaning is not normally necessary, but there is no preclude from doing so.

A plurality of such cylinders or rollers are arranged around the drum. This drum serves as a guide and base for the substrate (printed object), and printing is performed on this substrate. Each cylinder transfers the images and colors on it to the substrate. It goes without saying that the registration (position alignment) of sequentially transferred images and the synchronization of the cylinders should be performed, thereby making it possible to achieve perfect color reproduction.

The manufacturer of this cylinder supplies this cylinder 10 to printers who own suitable printing presses.
It is supplied in either of the following two ways. That is, the manufacturer may supply a blank cylinder and a printer may print an image on the cylinder, or the manufacturer may supply a cylinder with an image formed using primary toner. In the latter case mentioned above, the printer supplies the specifications and the original images to be printed.

It is advantageous to provide an image printing device at the location where the press printing device is installed. However, most of the image printing using primary toner is performed off-line.

As described above, the electrophotographic photoreceptor that can be used as a printing cylinder according to the present invention can be used for color press printing using electrostatic technology. The printing cylinder according to the invention can also be used for black and white printing. However, this cylinder is advantageously used in press printing where multiple transfers are made on the same substrate.

It should be noted that the term "printing process" used in the present invention does not necessarily mean press printing, but merely indicates the function of the cylinder. In fact, there is no direct pressure or contact between the printing cylinder of the invention and the substrate. This space is an extremely small gap, and the ink or dye/pigment is simply transferred and transferred. This is expected to extend the life of the cylinder.

Effects of the Invention The present invention is based on the above-mentioned known example, that is, US Pat.
When compared with No. 4025339 (corresponding to JP-A-51-94826), it has the following advantages.

In known examples, polyester, which is easily sensitive to heat,
i.e. polyethylene phthalate (as an example,
It uses a board made from Mylar (product name). In a known example, a photoconductive layer is provided thereon by high frequency sputtering or the like. This known example is nothing but an improvement of the photoconductive layer.

The present invention uses an extremely thin seamless nickel sleeve as the substrate, instead of using a heat-sensitive polyester film as the substrate as in the known example. Moreover, the overlying photoconductive coating is completely inorganic so as not to impair the flexibility of the sleeve in addition to its photoconductive properties.

For this reason, the cylindrical electrophotographic photoreceptor according to the present invention uses a metal nickel sleeve, which is stronger than plastic, for the substrate, so it is strong, more thermally stable, and extremely high-performance. It has the advantages of precision and uniform thickness,
Furthermore, since it is provided with a completely inorganic coating, it has the advantage of being able to form images at high speed.

This sleeve is not only durable and convenient to use, but also flexible and will not be damaged unless creased, so it can be rolled up into small volumes and stored in small volumes, making it convenient for storage. has advantages.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view of a printing cylinder according to the present invention, FIG. 2 is an enlarged partial sectional view showing the coating of the cylinder, and FIG. 3 is the same view as FIG. FIG. 3 is a diagram showing a state in which a toner image is attached to the coating of the image forming apparatus. DESCRIPTION OF SYMBOLS 10...Cylinder, 12...Sleeve, 14...Coating, 20...Toner image pattern.

Claims (1)

[Scope of Claims] 1. A flexible, thin-walled, seamless nickel sleeve 12 having a thickness of about a fraction of 1 mm that can be firmly maintained in a cylindrical shape for printing purposes; Deposited thin film photoconductive coating 14
In an electrophotographic photoreceptor comprising: the photoconductive coating 14 is flexible, microcrystalline and completely inorganic, has a thickness of no more than an order of magnitude, and has a high speed The coating is capable of storing images and has microcrystals of high purity cadmium sulfide, the crystals being primarily oriented approximately perpendicular to the surface of the sleeve, and the coating is capable of accepting charges and retaining them for a sufficient length of time. This allows for image retention and image adhesion,
The coating surface is electronically anisotropic, its dark resistance is at least 10 ¹² Ωcm, the dark-to-light resistance ratio is on the order of 10 ⁴ , and the flexibility of the sleeve is hardly compromised by this coating. An electrophotographic photoreceptor. 2. The electrophotographic photoreceptor according to claim 1, wherein the cylinder has a welded image on the surface of the coating, and the welded image is formed of an insulating toner.