JP2570781B2 - Paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

 Purpose of the invention

[Industrial applications]

The present invention relates to a sheet having a copy protection function when a copy is made by an electrostatic copying machine.

2. Description of the Related Art A typical copying means today is an electrostatic copying machine, and it is extremely easy to make a precise copy by improving its performance. However, unauthorized copying of a publication causes copyright infringement, and it is not preferable to copy unrestricted copies without limitation from the viewpoint of confidentiality. Therefore, hidden printing is performed so that a warning message appears when copying. As an example of the hidden printing, there is a method in which characters and the like are printed using halftone dots having different sizes so as to be difficult to distinguish, and the characters and the like appear when copied by an electrostatic copying machine. Halftone dots of different sizes include, for example, the following combinations. 150 lines / inch, 85 lines / inch, 130 lines / inch, 65 lines / inch, 100 lines / inch, and 50 lines / inch. However, conventional offset rotary printing is not suitable as a means for performing such hidden printing. I mean,
If such a halftone dot having a large number of lines is used, it is difficult to avoid so-called double filing (the original printing and the transfer of the ink remaining on the blanket of the printing press again), and the halftone dot of a predetermined size is printed. Is difficult. Therefore, even if two types of areas having different dot sizes but the same density are to be formed, a large halftone dot that is liable to cause double printing is actually printed darker. Also, in hidden printing in which two areas are formed by changing the size of a halftone dot, even if the density can be made the same, the boundaries of the areas are often visible. Therefore, it has been attempted to form a camouflage halftone dot over two areas, but it is troublesome and ineffective, and is rather disadvantageous in terms of eliminating double.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION In view of the above-mentioned state of the art, it is an object of the present invention to reduce the occurrence of printing doubles even by means of inexpensive and efficient offset rotary printing, and to provide a troublesome method of forming halftone dots for camouflage side by side. The object of the present invention is to provide an improved paper for copy protection. Structure of the invention

[Means for solving the problems]

The paper of the present invention is a paper provided with a first area and a second area on the paper surface by printing two different types of halftone dots such that one forms a pattern and the other forms a background. Thus, the two types of halftone dots are star-shaped and have almost the same area, but the halftone dots in the first area 1 shown in FIG. 1 are elements arranged radially as shown in the center of FIG. Are connected to each other at the center, and the halftone dots of the second area 2 shown in FIG. 1 are such that the radially arranged elements are separated from each other at the center as shown in the center of FIG. It is. The halftone dot star is a type that radiates in all directions in the illustrated example, but any shape such as hexagon or ten can be selected. In order to form a halftone dot, an arbitrary star shape is created by using a layout scanner that has recently become a common practice, for example, by painting small sections of 32 × 32 in size. In the example shown in FIGS. 2 and 3, 32 × 32
A single halftone dot is constituted by the fine elements arranged on the grid, and the area ratio occupied by the colored portion in the area of the paper surface given to one halftone dot is made the same. The area ratio of the two types of halftone dots may not necessarily be the same depending on the combination of halftone dot shapes, the convenience of plate making, the effect on visual perception after printing, and the like. In short, since it is only necessary to make the first area and the second area indistinguishable after printing, do some trial and error if necessary,
Determine the optimal area ratio. The size of the halftone dot is preferably 50 to 150 lines / inch, more preferably 80 to 100 lines / inch. If a halftone dot of 50 lines / inch is composed of 32 × 32 fine elements, the size of one element is 25.4 mm ÷ 50 ÷ 32 = 0.015 mm, which is 1,600 lines / inch (50 × 32 = 1,600), and the size of the fine element is 25.4 mm ÷ 150 at the halftone dot of 150 lines / inch.
÷ 32 = 0.005 mm, which is equivalent to 4,800 lines (150 x 32 = 4,800). If the size of the fine element is larger than 1,600 lines / inch, printing dubble is likely to occur, and if it is smaller than 4,800 lines, the resolution of the printing plate is insufficient.

[Operation]

For example, as shown in FIG. 1, the paper of the present invention uses a halftone dot shown in the center of FIG. 2 and the center of FIG. Are almost the same, the printed portion looks to the naked eye as solid printing of the same density. When this sheet is used as an original for an electrostatic copying machine and is copied on the "light" side, the halftone dots in the first area are thinned as shown in step -1 in FIG. In the second area, the halftone dots are thinner and lighter than the halftone dots in the first area as shown in step -1 of FIG. Thus, the first area will have a gray background and the second area will appear as a lighter gray nuki character. When this sheet is copied under the "very light" condition, the halftone dots in the first area are made thinner as shown in step -2 in FIG. In the second area, the halftone dots are thin lines and dots as shown in step -2 in FIG. 3, and are not substantially copied. As a result, the first area has a lighter gray background, and the second area has white blank characters. When this sheet is copied on the “come” side, the halftone dots in the first area are thickened as shown in the +1 step in FIG. In the second area, the halftone dots are thicker than the halftone dots in the first area as shown in the +1 step in FIG. In this way, the first area has a gray background and the second area appears as dark gray text. When copying under the “very good” condition, the halftone dots in the first area become thicker as seen in the +2 level in FIG.
It is copied even darker. In the second area, the halftone dots are much thicker than the halftone dots in the first area as shown in the +2 stage of FIG. 3, and are copied very deeply. Thus, the first area will be dark gray, but within it the second area will appear as black text. Then, set the copy density selection key of the copier to
And what if you set it to "auto mode"? Even then, the appearance of characters will almost inevitably occur. Because the second area has a greater difference in shade than the first area, in order to eliminate the difference in density between the two areas, the copier sets a condition where the two areas have the same density. Because it must be possible, the above-described concentration selection can only be done stepwise, rather than continuously, and such conditions are rarely met at any concentration level. After all, at every density level, the characters will appear, whether darker or lighter than the background. As can be easily understood from the above description, the paper may be formed with the character portion as the first area and the background portion as the second area. Effect of the Invention The paper of the present invention prints two types of star-shaped halftone dots having substantially the same area ratio, and since these halftone dots are smaller than normal halftone dots, doubles may occur during printing. It is rare and appears to the naked eye to be the same concentration and does not interfere with use. Of course, a halftone dot for camouflage is unnecessary. This sheet is suitable as a sheet for printing a copy that must be prohibited, a copy sheet, a word processing sheet, or a notebook sheet. In addition to the use of copy protection, there is also a usage method in which the advertisement is hidden and printed so that it appears when copied.

[Brief description of the drawings]

FIG. 1 is a plan view showing first and second areas of an example of the sheet of the present invention. FIGS. 2 and 3 are enlarged views each illustrating a star shape forming two types of halftone dots to be printed on the paper of the present invention and how it looks when electrostatically copied. . 1 ... first area 2 ... second area

Claims (1)

(57) [Claims] 1. A paper provided with a first area and a second area on a sheet by printing two different types of halftone dots such that one forms a pattern and the other forms a background. The two types of halftone dots are both star-shaped and have almost the same area, but the halftone dots of the first area are composed of radially arranged elements connected to each other at the center, and the halftone dots of the second area Is a sheet in which radially arranged elements are released from each other at the center.