JPH05269977A - Method for detecting register mark on opaque web - Google Patents

Abstract

PURPOSE:To make both of a visible register mark and a transparent register mark detectable without employing fluorescent material in the case where a web is of an opaque one. CONSTITUTION:A light source 1, capable of emitting visible light, is provided so that the light can be shed over an opaque web 3 at a specified angle, and a sensor 2 is provided in a position on which the light reflecting directly (regularly) on the opaque web 3 or a register mark 4 can be detected. The light to be shed over the opaque web 3 must be such that is in high directivity like laser beam or linear light transmitted through a lens system. In the case where the reflectance of the register mark 4 is bigger than that of the opaque web 3, the intensity of the reflection light shed on and reflected on the register mark 4 becomes certainly higher than that of the reflection light reflected directly on the surface of the opaque web 3. Therefore, the register mark 4 can be discerned by observing the variation in the reflected light. The shedding angle is desirable to be at 20-40 degrees.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a register mark detecting method on an opaque web capable of detecting register marks of both transparent ink and visible ink printed on the opaque web.

[0002]

2. Description of the Related Art As a registration method in printing,
A method of printing a register mark for each plate and controlling the positional relationship of these register marks is widely used. Therefore, it is necessary to accurately detect the printed register mark, but in the past, a method of visually identifying the mutual positional relationship was conventionally adopted. Here, the register marks include those printed with visible ink (visible registration marks) and those printed with transparent ink (transparent registration marks). In particular, when visually detecting a transparent register mark, an ultraviolet lamp was used to perform the operation at a low speed.

In recent years, a method of compensating for print misalignment by detecting register marks by an optical sensor and comparing their positions with each other has become widespread. Here, in the case of a visible register mark, the visible light source irradiates the plate with visible light vertically (diffuse reflected light detection method) or obliquely (direct reflected light detection method) to detect changes in the reflected light. The method of detection is adopted, and in the case of a transparent register mark, there are the following two methods and the like.

That is, one is Japanese Patent Publication No. 1-28575.
Which is described in Japanese Patent Application Laid-Open No. 1-283147, in which a register mark printed with a transparent ink containing a trace amount of a fluorescent whitening agent is irradiated with ultraviolet rays to cause luminescence to be detected. This is a method in which a register mark printed by adding an ultraviolet absorbing substance to transparent ink is irradiated with ultraviolet rays, and the register mark is detected from the change in the amount of reflected or transmitted light due to the absorption of ultraviolet rays.

[0005]

By the way, in order to eliminate the complexity of the visual detection method, the above-mentioned automation method using a light source and a sensor has been developed.
First, in the case of visible registration marks, the diffuse reflected light detection method does not stabilize the detection of diffused reflected light, and the direct reflected light detection method lacks the light amount, the straightness of the irradiation light (parallelism, directivity) is insufficient, and the irradiation and detection angles are inadequate. There was a problem.

Further, in the case of a transparent dragonfly, a fluorescing agent or the like must be mixed in the dragonfly, which is not preferable in food products and arts. In addition, it was impossible to detect if the web itself contained a fluorescent agent or the like.

Further, as described above, since a dedicated device is configured for each of the visible register mark and the transparent register mark, they must be shared when both are necessary, which is a problem of poor versatility. was there.

The present invention has been made under the circumstances described above, and an object of the present invention is to detect both visible and transparent registration marks in an opaque web without using a fluorescent agent or the like. It is to provide a method of detecting a register mark on an opaque web capable of performing the above.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a register mark detection method on an opaque web capable of detecting register marks of both transparent ink and visible ink printed on the opaque web. The above object of the present invention is directed to a register mark printed on the opaque web with an ink having a surface reflectance more than that of the opaque web, and the opaque web is irradiated with a strong directional visible light at a predetermined irradiation angle, This is achieved by detecting the register mark by receiving the specular reflection light and capturing the change.

[0010]

According to the present invention, the opaque web is irradiated with visible light having a strong directivity at a predetermined irradiation angle, and the specularly reflected light is received to detect the change, whereby the surface reflectance of the opaque web is determined. A register mark printed with an ink having a high surface reflectance can be detected with a register mark printed with either transparent ink or visible ink.

[0011]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing a configuration for realizing a register mark detection method on an opaque web according to the present invention. A light source 1 capable of irradiating visible light is provided with an opaque web 3
The sensor 2 is arranged so that it can be irradiated at a predetermined angle with respect to, and the sensor 2 is arranged at a position where the direct reflected light (regular reflected light) on the opaque web 3 or the register mark 4 can be detected. Here, the irradiation light to the opaque web 3 has strong directivity, such as laser light or straight light passing through a lens system.

Next, the principle and conditions under which the register mark 4 can be detected by detecting specularly reflected light with such a configuration will be described. 2A and 2B are views for explaining the principle and the condition that the register mark 4 can be detected. Here, the intensity of the irradiation light from the light source 1 is I, the surface reflectance of the opaque web 3 is R _p , and the surface reflectance of the register mark 4 is R _i, and the incident light to the register mark 4 is from its upper surface to its lower surface. The light absorption rate at the time of transmission is α. Therefore, first, when the light is reflected on the opaque web 3 as shown in FIG. 3A, the intensity of the reflected light is R _p × I. Next, when the light is reflected on the register mark 4 as shown in FIG. 3B, the intensity at each point on the optical path is as shown in the figure, and the intensity of the reflected light (up to the second order) is { (1-R _i ) × (1-R _p ) × R _p × α ² + R _i } ×
It becomes I. Further, the difference F between the intensity of the reflected light on the register mark 4 and the intensity of the reflected light on the opaque web 3 is as shown in Formula 1.

[0013]

## EQU1 ## F = {(1-R _i ) × (1-R _p ) × R _p × α ² + R _i } × I-R _p × I = {(1-R _i ) × (1-R _p ) × R _p × α ² + (R _i −R _p )} × I In the formula 1, (1-R _i ), (1-R _p ), R _p , α
^Since all ² are positive, the difference F is always positive if the condition R _i ≧ R _p is satisfied. That is, R _i ≧ R
_If the condition of _p is satisfied, the intensity of the reflected light on the register mark 4 is always greater than the intensity of the reflected light on the opaque web 3. Therefore, if the condition of R _i ≧ R _p is satisfied, the register mark 4 can be identified by its change by observing the reflected light. At this time, R _i
The greater the difference between R _p and R _p, the easier the identification. This does not depend on whether the ink of the register mark 4 is transparent or visible.

Next, the irradiation angle with respect to the opaque web 3 will be described. FIG. 3 is a diagram for explaining the irradiation angle. According to physical theory, the smaller the angle formed by the opaque web 3 and the irradiation light, the higher the detection sensitivity.
It is preferable to use the one shown in FIG. 7B instead of the one shown in FIG. 2, but if the remaining angle is too small, the influence of the flapping of the opaque web 3 will occur. Therefore, as shown in FIG. 20 degrees to 40 degrees is preferable, and about 30 degrees is the best.

As described above, if the register mark 4 having a reflectance higher than that of the opaque web 3 is selected, visible light is irradiated at an angle of 20 to 40 degrees, and the specular reflection light is observed, the ink is ink. Regardless of the type, the register mark 4 on the opaque web can be detected.

[0016]

As described above, according to the method for detecting a register mark on an opaque web of the present invention, if the register mark is printed with an ink having a surface reflectance higher than its surface reflectance on the opaque web, a transparent ink is used. It is possible to detect any of the registration marks of the visible ink and the visible ink. For example, when the registration mark is used for registration, the entire apparatus can be downsized. Also, when the surface reflectance of the web is higher than the surface reflectance of the ink,
The registration mark can be detected under the condition that the expression 1 is positive.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration for realizing a method for detecting a register mark on an opaque web according to the present invention.

FIG. 2 is a diagram for explaining the principle and conditions under which the register mark 4 can be detected.

FIG. 3 is a diagram for explaining an irradiation angle.

[Explanation of symbols]

 1 light source 2 sensor 3 opaque web 4 register mark

Claims (2)

[Claims] 1. A register mark printed on an opaque web with an ink having a surface reflectance higher than the surface reflectance of the opaque web is irradiated with visible light having a strong directivity at a predetermined irradiation angle. A method for detecting a register mark on an opaque web, characterized in that the register mark is detected by receiving specularly reflected light and detecting the change. 2. The method for detecting a register mark on an opaque web according to claim 1, wherein the predetermined irradiation angle is 20 degrees to 40 degrees.