JPH07112756B2 - Paper - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a copy-preventing sheet in which a warning message or the like appears when a copy is made, and such a sheet can be widely used as a printing sheet or a copying sheet. .

[Conventional technology]

Today, electrostatic copiers are widespread and the equivalent of the original can be copied very easily. However, if the publication is copied without permission, the copyright may be infringed, and it is not preferable to copy the publication indefinitely from the viewpoint of preventing leakage of confidential information.

Therefore, conventionally, 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 halftone dots having different sizes are used to print characters and the like so that it is difficult to distinguish them so that the characters will appear when copied by an electrostatic copying machine. Examples of halftone dots having different sizes include combinations of 150 lines / inch, 85 lines / inch 130 lines / inch, 65 lines / inch 100 lines / inch and 100 lines / inch.

However, such hidden printing is not suitable for ordinary offset rotary printing. Because the halftone dots of such a line number are large enough, it is difficult to avoid double-printing (the original printing and the ink remaining on the blanket being transferred again) due to the bracket of the offset printing machine, and it is difficult to avoid it. The formation of halftone dots is difficult. Therefore, even if two types of areas having different halftone dots but the same density are formed, the size halftone dots have a higher probability of causing doubles, so that areas having different density are eventually found. It's just forming.

Moreover, in such hidden printing, the number of lines of halftone dots is changed to 2
Since the areas of different types are formed, their boundaries are easily visible even if the concentrations are the same. Therefore, it has been attempted to form halftone dots for camouflage juxtaposed in two different areas, but this is not only troublesome, but also the elimination of debris is rather bad.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved copy-preventing paper that is free from the influence of printing doublet and has the trouble of forming halftone dots for camouflage side by side.

[Means for solving problems]

As a result of the research conducted by the inventors, one of the two types of areas is printed by making fine elements that are much smaller than ordinary halftone dots contact each other, and the other is also much smaller than ordinary halftone dots. It has been found that by printing the fine elements apart from one another this time, the former is copyable, whereas it is not, and the invention is based on this.

The gist of the present invention is that "a first area and a second area are provided on paper by printing two different types of patterned halftone dots so that one forms a background and the other forms a pattern. In the paper, the two different types of patterned halftone dots have a structure in which substantially the same number of fine elements, which are much smaller than ordinary halftone dots, are arranged in different shapes, and the patterned halftone dot of the first area is formed. The dot structure has a higher proportion of fine elements in contact with each other than the structure of the patterned halftone dots in the second area. ].

First, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a first embodiment of the sheet of the present invention.
It is a plan view for explaining the second area, and shows an example in which the second area 2 exists in a character shape in the first area 1 occupying most of the paper A. The second area may be any pattern such as a figure or a symbol other than the character. As will be described later, the first and second areas are formed by printing two different types of patterned halftone dots, and the first and second areas may be interchanged.

FIG. 2 is a view for explaining an example of the first area, and shows a structure of one unit of the patterned halftone dots printed in the first area. In this example, one patterned halftone dot is composed of 146 black dot-shaped fine elements arranged on a 32 × 32 grid, and except for the four fine elements,
Fine elements are in contact with each other, and the size of one pattern dot is 25 per 25.4 mm (= 1 inch).
In other words, it is about 1 mm both vertically and horizontally.

FIG. 3 is a diagram for explaining an example of the second area, and shows the structure of one unit of the patterned halftone dots printed in the second area. In this example, the same number of 14
One patterned halftone dot is composed of six black dot-shaped fine elements, and the size and optical density of one patterned halftone dot are the same as those in FIG. Further, in this pattern halftone dot, fine elements are arranged in a shape different from that of FIG. 2, that is, the shape in which the fine elements are arranged is DNP.
With the exception of a few exceptions, 55 fine elements are separated from each other in the straight line portion and the remaining 91 fine elements are in contact with each other in the curved portion.

In the above example, the pattern halftone dots in FIG. 2 have a higher proportion of the fine elements in contact with each other, and the pattern halftone dots in FIG. 3 have a lower proportion of the fine elements in contact with each other.
When copying this example, the straight lines in the second area are not copied, only the curved parts are copied.

Therefore, in the duplicated copy, the one shown in FIG. 3 is reproduced with a lower density than the one shown in FIG. 2, and the area 2 in FIG. 1 (the portion printed with the patterned halftone dot shown in FIG. 3) is reproduced. ) Is reproduced in a density lower than that of the surrounding area 1 (the portion on which the patterned halftone dot shown in FIG. 2 is printed),
You can distinguish them, and you can see the characters. Moreover, each pattern halftone dot is not formed into a shape such as a circle or quadrangle with a line number of about several tens of lines / inch to 200 lines / inch like a normal halftone dot, and is composed of a finer set of fine elements. Therefore, the duplication of printing of fine elements is unlikely to occur stochastically, and the desired halftone dot can be printed.

In the present invention, the size of the fine elements constituting the patterned halftone dot is 25.4 mm ÷ 25 ÷ 32≈0.032 mm in the above example, which corresponds to 800 lines / 25.4 mm (25 × 32 = 80
0) is an example of a preferable size, but 500 lines / 25.4mm ~ 1
Within the range of 80 lines / 25.4 mm, the same effect as above can be exhibited. Outside this range, fine elements larger than 500 lines / inch are not preferable in terms of printing doublet, and fine elements smaller than 1800 lines / inch take into consideration the resolution limit of printing plates such as PS plates. Difficult to form,
In terms of the limit of resolution, 2300 lines / 25.4mm is possible.

In addition, although the patterned halftone dots are composed of the fine elements arranged on the 32 × 32 grid in the above example, it goes without saying that other numbers of grids may be used.

The numbers of lines of the two types of patterned halftone dots may be different from each other.

Since the densities (area ratios) of the two types of areas are determined by the number of fine elements forming each pattern-like halftone dot, if they are equal to each other, the densities will be equal, but even if they are slightly different, there is no practical problem.

Of the pattern dots printed in the two types of areas,
In the pattern halftone dot in which the proportion of the fine elements in contact with each other is low, 20% or more of the number of fine elements constituting one pattern halftone dot (about 146 in the above embodiment) (29 or more) are preferably separated from each other. That is, it is desirable that the number of fine elements in contact with each other is less than 80%.

On the other hand, the pattern-shaped halftone dot having a higher proportion of the fine elements in contact with each other does not need to have all the fine elements in contact with each other, and the proportion of the fine elements in contact with each other is lower in the proportion of the fine elements in contact with each other. It is preferable that the difference is 40 or more in terms of the percentage of fine elements in contact with each other in terms of clarity when copied.

The sheet of the present invention can be produced, for example, by using a layout scanner, as described below, directly or by producing and printing a printing plate through a photographic original plate.

FIG. 4 shows a layout scanner configuration. In FIG. 5, reference numeral 11 denotes an input scanner, which reads and obtains a manuscript (obtained by handwriting or typesetting) having a pattern as shown in FIG. The obtained image signal is stored in the magnetic disk 16 via the computer 12. Computer
Reference numeral 12 gives the captured image signal to the color monitor 14 via the image memory 13 for display. On the color monitor 14,
A keyboard 15 for interactively performing image processing is provided, and by operating the keyboard 15, desired image processing is performed.

Alternatively, instead of using the original, the keyboard 15 may be operated to generate predetermined characters, figures, and symbols inside the computer, and desired image processing may be performed in the same manner as described above.

The image processing data is stored on the magnetic disk 16 and is used as a look-up table via the computer 12 when forming dots.
Read out to 17. The look-up table 17 is one in which data corresponding to a pattern of halftone dots as shown in FIG. 2 or FIG. 3 is given by the computer 12 by operating the keyboard 15, and the magnetic disk 16 is used.
It has a function of selecting one of the halftone dot patterns and applying an output signal of the halftone dot to the modulator 18 as determined in advance based on the image data read from the.
The signal is then converted into a light beam by the modulator 18 and the photographic film on the output scanner 19 is exposed. After the exposure of the entire image is completed, development is carried out to obtain a photographic original plate of the paper of the present invention.

FIG. 5 shows in more detail the modulator 18 and the output scanner 19 in the device of the construction of FIG.
The beam from the laser 181 is dispersed by the splitter 182 and is controlled by the optical modulator 183 to the control signal from the modulation control unit 184. For example, the beam is given to the exposure head 186 via the optical fiber 185 that bundles 32 lines, thereby outputting the output scanner. 1
9 The above photographic film is to be exposed.

It is more preferable that the halftone dots are formed at an angle of 45 ° with respect to the paper, because the halftone dot duplication during printing can be further minimized.

[Operation and effect of invention]

The sheet of the present invention has the structure as described above, and since the dots are formed by the fine elements much smaller than the normal halftone dots, when the normal large halftone dots are used, Compared to printing, there is a low probability of double-printing.

Further, since the paper of the present invention is formed by fine elements much smaller than the normal halftone dots, the halftone dots having a far more delicate appearance than the case where the halftone dots of the normal size are used. Not only can they be formed, but they are also difficult to distinguish with the naked eye. Moreover, even if the paper of the present invention is to be reproduced using a scanner, the resolution of reading with a commercially available high image pickup tube such as a scanner is much coarser than that of resolving fine elements. Is also highly valuable.

Further, since the shape of each halftone dot can be changed quite freely, various characters, figures, symbols, etc., as well as trade names, trademarks, service marks, etc. can be halftone dots used.

[Use]

INDUSTRIAL APPLICABILITY The paper of the present invention is highly valuable when applied to printed matter paper that needs to be prohibited from copying, copying paper such as electrostatic copying, word processing paper, and notebook. You can hide it so that the advertisement appears when you copy it.

[Brief description of drawings]

FIG. 1 is a plan view of the sheet of the invention, FIG. 2 and FIG.
FIG. 4 is a diagram showing respective areas on a sheet, FIGS. 4 and 5 are diagrams showing an outline of an apparatus for making halftone dots of the sheet of the present invention, and FIG. 6 is a note of the present invention. It is a figure which shows the example applied to the book. A ... paper, 1 ... first area, 2 ... second area.

Claims (2)

[Claims] 1. A paper provided with first and second areas on a paper by printing two different types of patterned dots to form a background on one side and a pattern on the other side. The two types of different patterned halftone dots have a structure in which substantially the same number of fine elements, which are much smaller than ordinary halftone dots, are arranged in different shapes. The structure is characterized in that the proportion of fine elements in contact with each other is higher than that of the pattern-shaped halftone dot in the second area. 2. The paper according to claim 1, wherein the pattern partially formed by the first and second areas is a message that appears when copied.