JP2016161469A - Varnish inspection device and method for inspecting varnish - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a varnish inspection device that can inspect varnish for defects when printing transparent varnish on a piece of paper.SOLUTION: The varnish inspection device includes: a lighting unit 3 continuously emitting light to a piece of paper 1 diagonally from above; a line sensor 5 on an extension line of a specular reflection 4 to receive the specular reflection 4 of the light emitted from the lighting unit 3 to the paper 1; and a control unit 6 inspecting printed varnish for defects based on an image read by the line sensor 5.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a varnish inspection for inspecting whether there is a defect in printing of a transparent varnish.

  For example, a transparent varnish may be printed on a liner for a cardboard sheet. The purpose of printing the varnish is, for example, imparting slip resistance, gloss, abrasion resistance, waterproofness, and the like. In many cases, this varnish is printed after being subjected to normal printing with an opaque ink, and then overlaying the printing.

  Although defects (for example, varnish printing omission, fading, misalignment, etc.) may occur in this varnish printing, it is difficult to find the defects because the varnish is transparent and difficult to see. In particular, if the paper on which the varnish is printed is not a sheet of paper cut at right angles to the running direction, but continuous paper that is continuous in the running direction, it cannot be inspected until the printing lot is completed. When a varnish printing defect is sometimes found, the entire lot is disposed of as a defective product. The inventor of the present application examined whether it is possible to inspect whether or not there is a defect in the transparent varnish printing that is difficult to visually check while the paper is running.

  Here, what is described in Patent Document 1 is known as a print inspection apparatus for inspecting printing having a glossy portion. The print inspection apparatus of Patent Document 1 includes a strobe, an area sensor, and a half mirror. Light emitted instantaneously by the strobe is reflected by the half mirror and irradiated onto the printed material from above, and at the same time through the half mirror. The area sensor photographs the printed matter from directly above. By adopting this configuration, the print inspection apparatus of Patent Document 1 can capture glossy prints with a feeling close to the real thing. The area sensor is a two-dimensional camera that reads an image of a rectangular area.

  When the print inspection apparatus disclosed in Patent Document 1 is used, it is possible to capture a glossy print such as gold or silver with a feeling close to the real thing, and perform a print inspection based on the captured image. However, even if the printing inspection apparatus of Patent Document 1 is used, it is difficult to inspect whether or not there is a defect in the transparent varnish printing that is difficult to see.

JP-A-9-136403

  The problem to be solved by the present invention is to provide a varnish inspection apparatus capable of inspecting a defect of a varnish when a transparent varnish is printed on paper.

In order to solve the above problems, the present invention provides a varnish inspection apparatus having the following configuration.
A paper transport section for running paper on which a transparent varnish is printed,
An illumination device that continuously irradiates light from above obliquely onto the varnish printed area of the paper;
A line sensor that is arranged on an extension line of the specularly reflected light so as to receive specularly reflected light incident on the paper from the illumination device, and that reads an image of a linear region perpendicular to the traveling direction of the paper;
A control unit for inspecting whether there is a defect in the printing of the varnish based on an image read by the line sensor;
Varnish inspection device.

  In this case, since the line sensor receives the specularly reflected light from the varnish, the image read by the line sensor is greatly different in brightness between the area where the varnish is printed and the area where the varnish is not printed. The varnish can be inspected by comparing the image with the master image. Further, since the line sensor is adopted as the sensor for reading the image, the reflected light can be always received at the regular reflection angle at any position along the paper traveling direction. Therefore, it is possible to stably detect a varnish printing defect at any position along the paper traveling direction.

The illumination device and the line sensor are preferably arranged so that a difference between an incident angle θ ₁ of light from the illumination device to the paper and a reflection angle θ ₂ of the regular reflection light is within a range of ± 3 °. .

  In this way, regular reflection light from the paper can be reliably received by the line sensor, and stable varnish inspection can be performed.

It is preferable to arrange the line sensor so that the reflection angle θ2 of the regular reflection light is in the range of ₂ to 12 °.

Wherein said line sensor so that the reflected angle theta ₂ of the specular reflection light becomes 12 ° or less arranged, when smaller incident angle theta ₁ of light to the paper from the lighting device in response to this, printing of varnish In the formed region, total reflection of light (a phenomenon in which light is not reflected on the surface of the varnish but reflected entirely on the surface of the varnish) occurs. Therefore, the image read by the line sensor has significantly different brightness between the varnish printed area and the non-varnish printed area, and the varnish printed area can be detected more accurately. It becomes. Also, the when the reflection angle theta ₂ of the specular reflection light is disposed said line sensor so that the 2 ° or more, the lighting device and the layout of the line sensor becomes easy.

  For example, a fluorescent lamp may be used as the lighting device, but LED lighting arranged in a straight line in a direction orthogonal to the traveling direction of the paper is preferably used.

  In this way, since the LED illumination has higher light directivity than illumination such as a fluorescent lamp, it is possible to efficiently regularly reflect light in the direction of the line sensor.

The present invention also provides a varnish inspection method having the following configuration.
Run paper with transparent varnish printed on it,
Irradiate light continuously from diagonally above the varnish printed area of the paper,
With a line sensor arranged on the extended line of the specularly reflected light so as to receive the specularly reflected light incident on the paper, an image of a linear region orthogonal to the traveling direction of the paper is read.
Inspecting whether there is a defect in the printing of the varnish based on the image read by the line sensor,
Varnish inspection method.

  The varnish inspection apparatus according to the present invention reads an image having greatly different brightness between a varnish-printed area and a non-varnish-printed area with a line sensor, and compares the image with a master image to inspect the varnish. Can be performed. In addition, since a line sensor is used as a sensor for reading an image, the reflected light can always be received at a regular reflection angle at any position along the paper traveling direction, and any position along the paper traveling direction can be received. It is possible to stably detect defects in varnish printing even at the position.

The front view which shows typically the varnish inspection apparatus of embodiment of this invention Plan view of the varnish inspection device shown in FIG. The figure which showed typically the two-dimensional image synthesize | combined by a control part based on the output signal of a line sensor, and the pulse signal of a pulse generator. The figure which showed typically the two-dimensional image synthesize | combined by a control part, when a missing part arises in the part of the area | region where varnish should be printed originally The front view which shows the other example of the varnish inspection apparatus shown in FIG. Front view showing still another example of the varnish inspection apparatus shown in FIG.

  FIG. 1 schematically shows a varnish inspection apparatus according to an embodiment of the present invention. This varnish inspection device includes a paper transport unit 2 that travels a paper 1 on which a transparent varnish is printed, an illumination device 3 that irradiates light onto a region of the paper 1 on which the varnish is printed, and an incident on the paper 1. A line sensor 5 that images the paper 1 obliquely from above so as to receive the specularly reflected light 4 of the light, and a control unit that inspects whether there is a defect in varnish printing based on the image read by the line sensor 5 6. In FIG. 1, the varnish is printed on the upper surface of the paper 1.

  As shown in FIG. 2, the paper 1 is a continuous paper that is continuous in the running direction and is formed in a band shape with a constant width. The paper 1 is a liner for cardboard, for example. The paper 1 is subjected to normal printing with opaque ink, and then a transparent varnish is printed over the printing. The purpose of printing the varnish is, for example, imparting slip resistance, gloss, abrasion resistance, waterproofness, and the like.

  As shown in FIG. 1, the paper transport unit 2 includes an upstream roller 2A and a downstream roller 2B that are spaced apart in the traveling direction of the paper 1, and the upstream roller 2A and the downstream roller 2B. Paper 1 is stretched between them. A support roller 2C is provided between the upstream roller 2A and the downstream roller 2B in order to prevent the paper 1 from flapping. The traveling speed of the paper 1 is, for example, about 200 to 300 m / min. The upstream roller 2 </ b> A and the downstream roller 2 </ b> B are disposed so as to come into contact with the surface opposite to the surface on which the varnish of the paper 1 is printed. The support roller 2C is also disposed so as to support the paper 1 from the side opposite to the surface on which the varnish of the paper 1 is printed.

  As shown in FIG. 2, the illumination device 3 has a shape extending linearly in a direction orthogonal to the traveling direction of the paper 1, and a linear region L (dotted line in the drawing) orthogonal to the traveling direction of the paper 1. Irradiate light uniformly. The illuminating device 3 is not an illuminating device that irradiates light instantaneously like a strobe, but an illuminating device that irradiates light continuously. The illumination device 3 emits light having a wavelength in the visible region (for example, white light). If a fluorescent lamp extending in a direction orthogonal to the traveling direction of the paper 1 is adopted as the lighting device 3, the cost of the lighting device 3 can be reduced, but along the direction orthogonal to the traveling direction of the paper 1. Employing LED lighting in which a large number of LED elements are arranged is preferable because it has higher directivity of light than fluorescent lamps, and can efficiently regularly reflect light in the direction of the line sensor 5.

As shown in FIG. 1, the lighting device 3, the incident angle theta ₁ is 2 to 12 ° of the light with respect to the paper 1 (preferably 3 to 10 °) are arranged to be in the range of. Moreover, the illuminating device 3 is arrange | positioned so that the distance from the linear area | region L of the paper 1 may become the range of 50-350 mm (preferably 100-300 mm), for example.

The line sensor 5 is arranged so that the reflection angle θ ₂ of the regular reflected light 4 that is regularly reflected by the paper 1 and enters the line sensor 5 is in the range of ₂ to 12 ° (preferably 3 to 10 °). Here, the illuminating device 3 and the line sensor 5 include an incident angle θ ₁ of light from the illuminating device 3 to the paper 1, and a reflection angle θ ₂ of specularly reflected light 4 that is regularly reflected by the paper 1 and enters the line sensor 5. Are arranged within a range of ± 3 ° (preferably ± 2 °, more preferably ± 1 °). That is, when the light incident on the paper 1 from the illumination device 3 is reflected by the surface of the paper 1, the regular reflected light 4 reflected from the paper 1 at a reflection angle θ ₂ substantially equal to the incident angle θ _{1 of the} light, and the regular reflected light And diffusely reflected light that is reflected in all directions except for the direction 4 occurs. The line sensor 5 has a reflection angle θ _{2 that} is substantially equal to the incident angle θ ₁ of light from the illumination device 3 to the paper 1 (specifically, the difference from the incident angle θ ₁ is ± 3 ° (preferably ± 2 °). More preferably, it is arranged on the extended line of the regular reflection light 4 so as to receive the regular reflection light 4 reflected from the paper 1 at a reflection angle θ ₂ ) within a range of ± 1 °). As a result, the specularly reflected light 4 from the paper 1 can be reliably received by the line sensor 5, and the varnish inspection described later can be performed stably. The line sensor 5 is arranged such that the distance from the linear region L of the paper 1 is in the range of 800 to 2000 mm, for example.

  As shown in FIG. 2, the line sensor 5 is a one-dimensional camera that reads an image of a linear region L orthogonal to the traveling direction of the paper 1. The line sensor 5 includes one or two rows of image receiving elements arranged in a straight line perpendicular to the traveling direction of the paper 1. The line sensor 5 can be a monochrome type.

  As shown in FIG. 1, the paper transport unit 2 includes a pulse generator 7 (a rotary encoder that detects the amount of rotation of the downstream roller 2B in the figure) that outputs a pulse signal each time the paper 1 travels a certain distance. Is provided. As the pulse generator 7, a control pulse (pulse output from a servo amplifier) of a servo motor that drives the paper transport unit 2 may be used. The control unit 6 controls the varnish inspection based on the output signal of the line sensor 5 and the pulse signal of the pulse generator 7. The control unit 6 is connected to an abnormality notification device 8 for notifying varnish printing abnormality. As the abnormality notification device 8, for example, a monitor display, a warning light, a warning sound generation speaker, or the like arranged in parallel with the printing press can be adopted.

  FIG. 3 schematically shows a two-dimensional image synthesized by the control unit 6 based on the output signal of the line sensor 5 and the pulse signal of the pulse generator 7. That is, the control unit 6 captures an image read by the line sensor 5 in synchronization with the pulse signal of the pulse generator 7, and synthesizes the images in time series to obtain a two-dimensional image as shown in FIG.

  In FIG. 3, the traveling direction of the paper 1 is the vertical direction. The paper 1 is repeatedly subjected to varnish printing of the same pattern at regular intervals along the traveling direction of the paper 1. The varnish-printed area 10 is imaged as a pure white area where such a pattern does not appear even when a pattern is printed with an opaque ink under a transparent varnish, whereas the varnish print The area 11 that is not imaged is imaged as an area where light and dark appear according to printing (that is, an area where a pattern printed with opaque ink is imaged).

  And the control part 6 can test | inspect whether the printing of a varnish has a defect by comparing the image read by the line sensor 5 with the master image memorize | stored beforehand. For example, as shown in FIG. 4, when a missing portion occurs in a part of the region 10 where the varnish should be originally printed, the missing portion can be found. In this case, it can be determined that the varnish printing has a defect when the ratio of the size of the omission in the original varnish area is equal to or greater than a predetermined threshold (for example, 5%). In addition, in the same manner, it is possible to inspect varnish printing fading and varnish printing deviation.

  As the master image used in the varnish inspection, it is possible to use an image set in advance before starting the varnish printing, but after starting the varnish printing, when the varnish printing is stabilized, the line sensor 5 When the captured image is used, it is possible to prevent a malfunction of the inspection apparatus and perform a stable inspection. Furthermore, when a defect in varnish printing is detected continuously for a predetermined number of times (for example, five times) set in advance compared to the master image, serious abnormalities such as varnish cutting of the printing press and chipping of the varnish plate may occur. Since it is thought that it has occurred, the abnormality notification device 8 is activated to notify the operator who operates the printing press of the abnormality.

  In the above-described varnish inspection apparatus, the line sensor 5 receives the specularly reflected light 4 from the varnish, so that the image read by the line sensor 5 is an area 10 where the varnish is printed and an area 11 where the varnish is not printed. The brightness is greatly different, and it is possible to perform a varnish inspection by comparing the image with the master image. Further, since the line sensor 5 is employed as a sensor for reading an image, the reflected light can always be received at an angle of regular reflection at any position along the traveling direction of the paper 1. Therefore, it is possible to stably detect defects in varnish printing at any position along the traveling direction of the paper 1.

Further, the above-described varnish inspection apparatus arranges the line sensor 5 so that the reflection angle θ ₂ of the regular reflection light 4 entering the line sensor 5 is 12 ° or less (preferably 10 ° or less). Since the incident angle θ ₁ of the light from the illumination device 3 to the paper 1 is also reduced, the light is totally reflected in the region 10 where the varnish is printed (the light does not pass through the surface of the varnish and is totally reflected on the surface of the varnish). Phenomenon). For this reason, the image read by the line sensor 5 has significantly different brightness in the varnish-printed area 10 and the non-varnish-printed area 11, and the varnish-printed area 10 is detected with extremely high accuracy. Is possible.

Further, the above varnish inspection apparatus, since the fall reflection angle theta ₂ of the specular reflection light is 2 ° or more line sensor 5 (preferably 3 ° or more) line sensor 5 so as to be installed, the illumination device 3 Further, the line sensor 5 hardly interferes with the paper 1, and the layout of the illumination device 3 and the line sensor 5 is easy.

As shown in FIG. 5, the illumination device 3 and the line sensor 5 are configured such that light is emitted from the illumination device 3 to a portion where the traveling direction of the paper 1 is changed, and regular reflection light 4 from the portion is received by the line sensor 5. May be arranged. In this case, the incident angle θ ₁ of light from the illumination device 3 to the paper 1 and the reflection angle θ ₂ of light from the paper 1 to the line sensor 5 are defined with reference to the tangent line of the paper 1 as shown in FIG. The illumination device 3 and the line sensor 5 are arranged so that the incident angle θ ₁ and the reflection angle θ ₂ are the same. Even with this arrangement, it is possible to inspect the varnish, but if the central axis of the line sensor 5 changes in the running direction of the paper 1 due to vibration or the like, the specularly reflected light 4 from the paper 1 may not be received. There is. On the other hand, as shown in FIG. 1, the illumination device 3 and the light sensor 3 emit light from the illumination device 3 to a portion where the paper 1 travels flat, and the line sensor 5 receives the regular reflection light 4 from the portion. It is preferable to arrange the line sensor 5 because the regular reflected light 4 from the paper 1 can be stably received even if the central axis of the line sensor 5 changes in the traveling direction of the paper 1 due to vibration or the like.

  In the above embodiment, the example in which the support roller 2C is provided between the upstream roller 2A and the downstream roller 2B to prevent the paper 1 from flapping is described. However, as shown in FIG. When the interval between the downstream rollers 2B is narrow, the support roller 2C may be omitted.

DESCRIPTION OF SYMBOLS 1 Paper 2 Paper conveyance part 3 Illuminating device 4 Regular reflection light 5 Line sensor 6 Control part 10 Area | region L where varnish was printed Linear area | region (theta) ₁ Incident angle (theta) ₂ Reflection angle

Claims (5)

A paper transport section (2) for running paper (1) on which a transparent varnish is printed,
An illumination device (3) for continuously irradiating light from obliquely above the region (10) on which the varnish of the paper (1) is printed;
The traveling direction of the paper (1) is arranged on the extended line of the regular reflection light (4) so as to receive the regular reflection light (4) of the light incident on the paper (1) from the illumination device (3). A line sensor (5) for reading an image of a linear region (L) orthogonal to
A control unit (6) for inspecting whether or not the varnish printing is defective based on an image read by the line sensor (5);
Varnish inspection device. It said line sensor and the illumination device (3) (5), the difference between the reflection angle theta ₂ of the illumination device (3) from the incident angle theta ₁ of light to the paper (1) the specular reflection light is ± The varnish inspection apparatus according to claim 1, wherein the varnish inspection apparatus is disposed so as to be within a range of 3 °. The varnish inspection apparatus according to claim 1 or 2, wherein the line sensor (5) is arranged so that a reflection angle θ2 of the regular reflection light (4) is in a range of ₂ to 12 °.   The varnish inspection device according to any one of claims 1 to 3, wherein the illumination device (3) is an LED illumination that is linearly arranged in a direction orthogonal to a traveling direction of the paper (1). Run paper (1) with transparent varnish printed on it,
Irradiate light continuously from diagonally above the area (10) where the varnish of the paper (1) is printed,
The travel direction of the paper (1) is detected by a line sensor (5) arranged on an extension line of the regular reflection light (4) so as to receive the regular reflection light (4) of the light incident on the paper (1). Read the image of the linear region (L) orthogonal to
Inspecting whether there is a defect in the printing of the varnish based on the image read by the line sensor (5),
Varnish inspection method.

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