JPS59208553A - Exposure for photomechanical process - Google Patents

Abstract

PURPOSE:To prevent the bending and breaking of the projections of a relief due to printing pressure and to enable clear printing by superposing a negative film having an image of letters or a figure on the surface of a synthetic resin plate for forming a relief, placing the resin plate opposite to a light source, and placing a light reflecting plate behind the resin plate. CONSTITUTION:A negative film 5 having an image of letters or a figure is superposed on the surface of a synthetic resin plate 4 for forming a relief, the plate 4 is placed opposite to a light source, and a light reflecting plate 6 is placed behind the plate 4. An ultraviolet light source 1 is used as the light source, a screen having many slits 2 for giving parallel rays of light is placed in front of the film 5, and a reflecting plate 3 is placed behind the source 1. Nearly parallel rays of light (t) are irradiated on the plate 4 through the slits 2 to form a photosensitive layer insoluble in water or alcohol on the support 7 of polyester or the like. The rays of light (t) enter the plate 4 at a small angle alpha of diffusion, and they are reflected by the plate 6. The resulting scattered rays of light (u) produce an insoluble part corresponding to the dotted part, and a curve (r) whose bottom has a circular cross-section is formed. The projections of the photosensitive layer are not easily bent or broken, and satisfactory halftone printing can be carried out.

Description

[Detailed Description of the Invention] A synthetic resin board is rotated by rotary printing [April: 1iIj When mounting a letterpress such as Yuzu, a negative film of desired characters or figures is polymerized on the synthetic resin board and exposed to ultraviolet rays, etc. The ray of light is 1i
Baking is performed by applying a lubricant, and the resin plate is washed with water or alcohol to dissolve and remove the portions that are not irradiated with light. If the synthetic resin letterpress plate made in this way is used to print halftone dots as shown in Figure 1, the cross section of the plate corresponding to the A-A section (2) is
Shape as shown in the figure (two.

In other words, the distance between the halftone dots @ the door is, for example, about 0.1 mm.
1-, when printing is performed using such a synthetic resin plate, the printing pressure causes the convex portion to bend as shown by the chain line p, staining the paper surface and f! #, R halftone dots cannot be printed. Another disadvantage is that the life of the plate is short because the protrusions break due to repeated bending. Furthermore, if the valley portions are made into a 7-shape as shown by the chain stitch q in Figure @2, clogging occurs due to N printing ink, the printing surface becomes stained, and the number of sheets that can be continuously printed is significantly reduced. Furthermore, if the depth of the troughs is made shallow as in chain 01r, the plate cannot be bent freely, which poses a problem when printing is carried out by attaching this to the plate cylinder of a rotary printing press. Accordingly, the present invention provides a printing apparatus capable of producing plates free of such defects.

FIG. 3 is a diagram showing the configuration of an embodiment of the present invention, in which a slit 2 for forming a parallel light gland consisting of a large number of cylindrical slits is arranged in front of an ultraviolet light source 1 such as a mercury lamp. The slit cage is swung in the direction of arrow S, and a reflective shade 3 is placed behind the light source 1. Therefore, as shown by the dotted arrow t, substantially parallel light rays pass through the slit 8. A synthetic resin plate 4 on which a plate is to be formed is placed opposite to this slit 2, and the above-mentioned parallel light beams are made incident thereon, and a negative film j of desired characters or figures is closely attached to the front surface of the synthetic resin plate 4, and A light reflecting plate 6 is arranged on the back surface. As shown in a partially enlarged view in Figure 4, the synthetic resin plate 4 has a photosensitive layer 8 made of nylon or the like that becomes insoluble in water or alcohol when irradiated with ultraviolet rays on a support substrate made of polyester or the like. This is a built-in structure. The reflecting plate 6 is a total reflecting plate or a white light scattering plate, and is placed either in close contact with the back surface of the synthetic resin powder 4 or at a distance of some distance.

In the above-mentioned apparatus, the light ray passing through the pickpocket 7) 2 forms a P+ substantially parallel light ray as shown by the dotted arrow in the diagram, but it has a certain degree of diffusion angle α. Therefore, a light beam passing through a small transparent part I of, for example, F1 shape in the negative film 5 gradually enlarges its cross section and enters the substrate. Since this substrate 7 is usually semi-transparent, part of the incident light is I
11! However, most of the light is incident on the light reflecting plate 6 after a few weeks. The reflector 6Fi is a mirror surface or a scattering surface, but in any case, it has a high reflectance of 1, so that the light rays scattered by the substrate W and further reflected by the reflector 6 or the rays U scattered by the reflector 6 reach the substrate 7. A wide range of the photosensitive layer 8 in the near part (
Two people shoot. In other words, this reflected light beam is diffused to the periphery of the ray l that has passed through the transparent part 1 of the film -1
The light rays enter the photosensitive layer 8 (2) into the recesses shown by the dotted areas in FIG. When the substrate 7 is washed with water or alcohol, the portion where the light beam does not enter is dissolved and removed, and the above-mentioned dot portion remains together with the substrate 7.

FIG. 5 is a cross-sectional view of the same portion as FIG. 2 in the case where a halftone dot plate as shown in FIG. 1 is manufactured using the above-described printing apparatus. In other words, a large amount of light scattered by the light reflecting plate 6 placed on the back side of the synthetic resin board enters the photosensitive layer 8 in the area close to the substrate, and the incident area becomes insoluble, thereby printing halftone dots. The base of the protrusion expands, and the cross section of the valley forms an arcuate curve r. Therefore, even if a large printing pressure is applied to the top υ of the protrusion, the protrusion will not easily bend and the area around the printed halftone dots will be smeared, resulting in extremely clear and good halftone dots and other printing. It can be carried out. And the convex part of the plate is as mentioned above.C: As the printing pressure bends and bends, the fine convex part like the halftone dots mentioned above will break in a short period of time [1■ζ2] and the life of the plate will be shortened. Such shortcomings are also removed. Furthermore, since the bottom of the valley forms an arc-shaped curve 9 as described above, the bottom of the valley (at the two-point point, etc.) becomes narrow, and the printing ink is captured and the This also excludes defects such as clogging and limiting the number of sheets that can be printed continuously.Moreover, the depth of the valley should be made deep enough so that the deepest part is exposed to light as shown in Figure I11@5. Ha
Since it is possible to completely dissolve and remove the particles, defects such as inhibiting the flexibility of the plate are also eliminated.

Note that the shape of the curve r in Figure 5 C2 can be adjusted appropriately depending on the distance M between the reflector and the synthetic resin plate of the printing plate and the reflectance.

[Brief explanation of the drawing]

Figure 9A1 is an enlarged view of the printed halftone dots Figure 2 is Figure 1C
A sectional view of a conventional letterpress plate for printing the A-A section of the second station, FIG. 3 is a diagram showing the initial production of an embodiment of the present invention, and FIG. FIG. 5 is a cross-sectional view of a part of a relief plate made using the printing apparatus of the present invention.
2 is a slit for forming parallel light beams, 3 is a reflecting shade, 4 synthetic resin plates S5 is a negative film, 6J' is a reflecting plate, F is a support substrate for the synthetic resin thicket 4, and 8 is also a photosensitive material. Patent applicant Fuku 1) Gaku○ ○ O ○ 0 0 Jit ta Shizai Z Kinunaka 3 td

Claims (1)

[Claims] A negative film of desired characters or figures is polymerized on the surface of the synthetic vernix plate on which the letterpress is to be formed to give it a glossy appearance ((two light reflecting plates are placed on the back side of the synthetic resin plate). Printing device for clothing