JPH027453B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a printing plate, and more particularly to a method of manufacturing a printing plate having minute dots in non-image areas.

Various methods have been used to prevent background smudge, that is, ink adhering to non-printing areas from staining the non-printing areas of the printed member.

The first is to use printing plates with relatively high relief. Conventionally, for example, letterpress printing plates have been made by casting lead alloys, etching metal plates, and photosensitive resins. In order to prevent the above-mentioned scumming, it is known to use a printing plate having a relatively high relief, generally 0.5 mm or more in height.

Printing plates with such a relatively high relief are, for example, difficult to handle, difficult to load onto a rotating printing cylinder, require a relatively large amount of material, and are expensive to manufacture. However, it has disadvantages such as increased manufacturing time.
In other words, printing plates with low relief are preferred in various respects.

A second method for preventing the above-mentioned scumming is to provide minute dots on the printing plate.

However, initially, the microdots or highlight dots had the same height as the printing relief and were provided over the entire printing surface of the printing plate. For this reason, anything printed using such a printing plate was dark overall.
Further, when printing using color ink, small color spots due to minute dots become noticeable and unacceptable.

As an improvement to the second method, it has been proposed to make the height of the microdots lower than the height of the printed relief.

According to this improved second method, if the printing operating conditions are favorable, the minute dots will not print, and even if the printing operating conditions are poor, the minute dots will cause ink to flow into the non-printing area. It is excellent in that it is only slightly attached.

In accordance with this improved second method, it has been proposed to utilize transparent or translucent supports.

This involves placing a photosensitive resin layer on a transparent or translucent support, irradiating a light beam from one side through a halftone image carrier for microdots, and passing the light beam through a printed image carrier from the other side. irradiation, thereby producing a printing plate with minute dots.

However, this method has the major limitation that the support must be formed from a transparent or translucent material. That is, as the transparent or translucent or translucent material, for example, plastics such as polyethylene, terephthalate, polystyrene, polycarbonate, polyvinyl chloride, polypropylene, polyvinyl alcohol, etc. may be used. However, sheets made of these materials are not necessarily stable in dimension, which poses a fatal problem, especially when accurate or precise printing is attempted. Furthermore, considering the heat generated during irradiation with light, this dimensional instability cannot be ignored even in general printing.

In addition, in the method using this transparent or translucent support, it is necessary to bring the halftone image carrier for minute dots into close contact with the photosensitive resin layer as much as possible. Therefore, this method has various problems in terms of work efficiency and the like.

Furthermore, in the methods using transparent or translucent supports, there are also problems with mounting the printing plate on the printing cylinder. That is, for example,
A suitable method for attaching printing plates to printing cylinders is known to utilize magnetic clamping. This attempts to attach a printing plate to a rotating printing cylinder using magnetic force. However, in the above method,
The magnetic clamp described above cannot be used because the support must be transparent or translucent, and transparent or translucent ferromagnetic materials are usually not considered.

Furthermore, in the method using the transparent or translucent support described above, there is also a problem regarding temperature control of the photosensitive resin. In order to accurately maintain dimensions such as the thickness of the photosensitive resin layer or to appropriately cure the photosensitive resin, the temperature of the photosensitive resin layer on the support must be accurately controlled. However, in the method using the transparent or translucent support described above, it is necessary to irradiate the support with light from both sides thereof. Therefore, it is not possible to provide a temperature control device in close proximity to the support. For this reason, accurate temperature control is difficult.

The present invention was made in the above-mentioned situation, and its purpose is to provide a new method for manufacturing a printing plate with minute dots.

Another object of the invention is to provide a method for producing printing plates in which there are no restrictions on the material of the support and therefore dimensionally stable supports can be used.

Another object of the present invention is to provide a method for manufacturing a printing plate with minute dots, which does not require the contact of a halftone image carrier with a photosensitive resin layer, and which has excellent working efficiency.

Another object of the invention is to provide a method for producing a printing plate with minute dots, the support of which can be made of ferromagnetic material, so that it can be mounted on a rotating printing cylinder by means of a magnetic clamp. It is.

Another object of the present invention is to provide a method for manufacturing a printing plate with minute dots, which allows accurate temperature control of a photosensitive resin.

These and other objects of the invention will become apparent from the following description of preferred embodiments of the invention, with reference to the accompanying drawings.

First, in FIG. 1, a support body 12 is placed on a support stand 10. As shown in FIG.

The support base 10 has a support body 12 disposed thereon.
A temperature control device (not shown) is provided to control the temperature.

Support 12 may be opaque or transparent to actinic rays.
The material of the support body 12 may be metal or a fiber composition.
Preferred materials for support 12 are aluminum and paper fiber compositions. A particularly preferred material for the support 12 is a ferromagnetic material such as a steel alloy, in which case the printing plate can be mounted in a cylinder of a printing press by magnetic clamping. Support 12
is in the form of a thin plate, and its thickness is preferably 0.07 mm to 0.30 mm. An adhesive layer is preferably arranged on one side of the support 12 with which the layer of photosensitive resin comes into contact.

Next, the first photosensitive resin layer 16 is placed on the support 12 by the discharging and doctoring mechanism 14 .

The discharge and doctoring mechanism 14 discharges an amount of resin depending on its moving speed and the thickness of the resin layer to be placed. The discharge and doctoring mechanism 14 has a doctor blade 18, and the thickness of the resin layer arranged depends on the moving direction of the discharge and doctoring mechanism 14, that is, from left to right in FIG. 1 or from right to left in FIG. can be adjusted. The first photosensitive resin layer 16 is
The dispensing and doctoring mechanism 14 is positioned as it moves from left to right in FIG.

The resin for the first photosensitive resin layer 16 is one that is photosensitive to actinic radiation and cures, dissolves in various solutions, or has a relatively low viscosity and can be dispersed and removed by pressurized air. is preferred. Examples of such resins include resins containing a compound having an addition-polymerizable unsaturated group as a main ingredient and a photopolymerization initiator added thereto.

The thickness of the first photosensitive resin layer 16 is preferably
0.05mm to 0.13mm, particularly preferably about 0.08mm
mm (approximately 3 mils).

Next, in FIG. 2, the first photosensitive resin layer 1
6, a halftone image carrier 20 is arranged with a slight spacing thereon, and a light source 22 is arranged above it. Actinic radiation from light source 22 illuminates first photosensitive resin layer 16 through halftone image carrier 20, causing a portion of it to harden.

As the halftone image carrier 20, in addition to a negative film for photolithography with a silver salt image, materials that are substantially transparent to actinic radiation, such as plastic films and sheets, glass sheets, cellophane, paper, etc., on which a negative image is provided can be used. can be used. The transparent image areas of the halftone image carrier 20 are arranged to have a transmission density of less than 0.05 and the opaque emulsion areas have a blackening density of more than 3.5.

Preferably, the area ratio of the transparent area of the halftone image carrier 20 to the total area is between 1% and 10%. Such a halftone image carrier 20 can also be produced using a halftone screen. In this case, the number of lines of the screen used is 65
Lines/inch to 100 lines/inch are preferred. The halftone image carrier 20 can also be created using a mesh screen. In this case, the screen preferably has 100 to 144 meshes.

The halftone image carrier 20 is placed at a small distance from the first photopolymer layer 16, ie with an air gap. This interval is 0.25mm ~
It is preferably about 0.50 mm. With such a spacing, a film made of, for example, polypropylene, polycarbonate, polyethylene, acetyl cellulose, etc., which was used to separate the first photosensitive resin layer 16 and the halftone image carrier 20, can be used. A traditional intermediate layer is not required.

The light source 22 includes a lamp 24 and a parabolic reflector 2.
It is preferable to consist of 6. For example, by such an arrangement, the actinic radiation from the lamp 24 is made parallel and directed towards the halftone image carrier 2.
It can be made to hit 0 perpendicularly. By this,
The actinic radiation is directed at an angle to the halftone image carrier 20.
exposure and scattering of actinic radiation can be minimized. A member made of a matte, light-absorbing material can be placed, for example, around the light source to prevent undesirable actinic radiation from impinging on the first photopolymer 16. As the lamp 24 of the light source 22, an arc lamp, a mercury lamp, a xenon lamp, an ultraviolet fluorescent lamp, or the like can be used. Furthermore, sunlight can also be used as the light source 22. The light source 22 may be one that emits radiation such as X-rays depending on the characteristics of the photosensitive resin.

As mentioned above, in the specific example shown in FIG. 2, a planar halftone image carrier 20 and a light source 2
2, a part of the first photosensitive resin layer 16 is cured. Instead of this specific example, the halftone image carrier 20 is formed into a cylindrical shape, the light source 22 is disposed inside the halftone image carrier 20, and the halftone image carrier 20
and a light source 22 on a cylindrical halftone image carrier 2
0 is synchronized with the first photosensitive resin layer 16,
That is, the direction of movement (for example, from left to right in Figure 2)
In order to prevent relative movement between the cylindrical halftone image carrier 20 and the first photosensitive resin 16, the first photosensitive resin 16 may be moved while rotating the cylindrical halftone image carrier 20. A portion of the photosensitive resin layer 16 can be appropriately cured.

Next, in FIG. 3, after removing the halftone image carrier 20 and the light source 22 (FIG. 2), a second photosensitive resin layer is placed on the partially cured first photosensitive resin layer 16. 28 are arranged.

The second photosensitive resin layer 28 can be placed on the first photosensitive resin layer 16 by, for example, moving the discharge and doctoring mechanism 14 (FIG. 1) shown in FIG. 1 from right to left. can be done.

The resin for the second photosensitive resin layer 28 may be the same as or different from the resin for the first photosensitive resin layer 16. However, it is preferred that the resins be of the same type, for convenience, for example, when reusing uncured parts.

The thickness of the second photosensitive resin layer 28 is 0.38 mm (approx.
mil) is preferable. However, various changes can be made depending on, for example, the material of the member to be printed.

A printed image carrier 30 is then placed on the second photosensitive resin layer 28 with a slight spacing and actinic radiation is applied to the printed image carrier in a manner similar to that described with reference to FIG. The second photosensitive resin layer is irradiated through 30 to partially cure it.

Preferably, there is a spacing or air gap between the second photosensitive resin layer 28 and the printed image carrier 30, for example on the order of 0.38 mm (about 15 mils).

In the specific example described above, the second photosensitive resin layer 28 is placed on the first photosensitive resin layer 16 while leaving the uncured portion of the first photosensitive resin layer 28, and the printed image carrier is Actinic radiation is applied via 30. Therefore, by this irradiation, not only the second photosensitive resin layer 28 but also a part of the first photosensitive resin layer 16 is cured.

Instead of this specific example, the first photosensitive resin layer 16
After removing the uncured portion of the photosensitive resin layer 28, the second photosensitive resin layer 28 can be disposed.

The uncured resin portion can be removed as follows. For example, the uncured resin part can be treated with an aqueous solution of a surfactant, an aqueous alkaline solution,
Alternatively, it can be removed by dissolving it in an organic solution such as alcohol, acetone, benzene, or trichlene. Alternatively, if the photosensitive resin has a sufficiently low viscosity when uncured, it can be removed using vacuum suction, centrifugal force, or pressurized air.

After removing the uncured resin as described above, it is preferable to wipe off the remaining uncured resin with a blottening roller or blottening paper and to apply post-exposure to increase the strength of the cured resin.

Then, a printing plate having minute dots as shown in FIG. 4 can be obtained.

[Brief explanation of drawings]

FIG. 1 is a simplified diagram illustrating the step of disposing a first photosensitive resin layer on a support according to the present invention. Second
The figure is a simplified diagram illustrating the step of irradiating a first photosensitive resin layer with actinic radiation through a halftone image carrier in accordance with the present invention. FIG. 3 is a simplified diagram illustrating the step of irradiating the second photosensitive resin layer with actinic radiation through the printed image carrier in accordance with the present invention. FIG. 4 is a side view of a printing plate made according to the invention. 12... Support, 16... First photosensitive resin layer, 2
0... Halftone image carrier, 22... Light source, 28...
Second photosensitive resin layer, 30...Printed image carrier.

Claims (1)

[Scope of Claims] 1. Disposing a first photosensitive resin layer on a support; disposing a halftone image carrier in the vicinity of the first photosensitive resin layer without bringing it into close contact; irradiating the first photosensitive resin layer with actinic radiation via a carrier to cure a part of the first photosensitive resin layer; arranging a photosensitive resin layer; arranging a printed image carrier in the vicinity of the second photosensitive resin layer without bringing it into close contact; and disposing the second photosensitive resin layer through the printed image carrier;
irradiating the photosensitive resin layer with actinic radiation to cure a part of the second photosensitive resin layer to form a relief corresponding to the printed image; and removing the uncured portion. A method for producing a printing plate, comprising: 2. The method according to claim 1, wherein the support is made of a ferromagnetic material. 3. A method according to claim 1, wherein the area ratio of the transparent portion of the halftone image carrier to the total area is between 1% and 10%. 4. The method of claim 1, wherein the first photosensitive resin layer and the second photosensitive resin layer are disposed by the same dispensing and doctoring mechanism.