JPH03194450A - Ink water content measuring instrument - Google Patents

Abstract

PURPOSE:To perform one-line automatic control in a short time by photodetecting the intensity distribution of diffracted light of projection light on an ink surface by a detector composed of plural photodetector and calculating ink water content. CONSTITUTION:The beam 2 which is projected by a laser device 1 is collimated by a collimator 3 into a parallel beam 4, which irradiates the ink surface of a roller 5 at an angle theta to the normal 7 of the irradiated surface 8. Then on a plane containing the beam 4 and normal 7, a photodetector 10 is placed on a straight line which has the same angle theta with the normal 7 and on the same straight line with a focus lens 9 at its focal distance position on the opposite side of the beam 4. The detector consists of plural photodetector 10 and photodetects the intensity distribution of the projection light on the ink surface 6. A computing element 5 calculates the ink water content according to the output of the detector. Then the water content is controlled automatically in a short time on an on-line basis.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ink moisture content measuring device that uses laser light to measure ink moisture content in a printing press.

[Conventional technology]

The configuration of the offset printing press is shown in Figure 4.

In offset printing, oil-based ink is applied from a group of ink supply rollers to a printing plate on which a lipophilic image area (the area where ink sticks) and a hydrophilic non-image area (the area where ink does not stick) are formed on the same plane. A method is adopted in which dampening water is supplied in a well-balanced manner from a group of water supply rollers, and ink is deposited on the image area due to the surface chemical action of both, which is then transferred to a blanket and then printed on paper. The water is mixed into the ink in an emulsified state.

In other words, by making use of the hydrophobicity of ink and applying this emulsified water to areas other than the halftone dots of the plate in advance, this prevents ink from adhering to those areas.

Therefore, if the amount of ink and dampening water becomes unbalanced in offset printing, printing problems such as smearing may occur.

This results in poor print quality such as poor halftone dot reproducibility and uneven density.

Therefore, the moisture content of ink is an important control parameter, but conventionally it has been measured by an off-line method using reagents. In other words, if you take a sample of ink containing water, put it in a solvent, and then add a reagent,
The method uses the fact that the color changes depending on the moisture content.

[Problem to be solved by the invention]

The conventional moisture content measurement described above is a manual offline method using reagents, and therefore has the following problems.

(1) It takes time.

(2) Requires manpower.

(3) Due to the above (II, T21), the moisture content cannot be controlled online.

[Failure to solve the problem]

A parallel laser beam is irradiated onto the ink surface of the roller surface. The diffracted light is focused by a condensing lens at a position that is in a plane that includes the normal to the irradiation surface and the laser beam and is at an angle equal to the angle between the laser beam and the normal, that is, in the direction of specular reflection. , the light is received by a plurality of light receiving elements placed on the focal plane of the condenser lens.

[Function] As shown in Figure 5, in an offset printing press, ink is supplied by rotating rollers that come into contact with each other, but the supply roller and the receiving roller that are in contact with it separate as they rotate. In the area where the ink is drawn, it is stretched into a string and protrusions (filaments are formed).The viscosity of the ink is high, 102 to 103 poise, although it varies depending on the water content, so it takes a long time for the stretched filaments to return to their original flat state. , which is at least 10 times longer than the normal rotation period of the roller.Therefore, during the rotation of the roller, traces of the filament remain on the ink surface as mesh-like granular irregularities as shown in FIG.

(For convenience, this is referred to as a mesh mark.) The size of the uneven grains of the mesh mark changes depending on the film thickness and water content. In other words, if the film thickness is constant and the water content is low, the viscosity of the ink is high, so the size of the uneven grains will be large; if the water content is thick, the viscosity will be small (and the grains of the network marks will be small. When the water content is constant and the film thickness is large, the uneven grains of the network marks become large, and when the film thickness is small, they become small.

However, the ink film thickness can be determined by the weight of the ink supplied or by other known measurement methods, so if the size of the grains of the mesh marks is known, the moisture content can be measured.

A parallel laser beam is irradiated onto this net-like mark, and the diffracted light is focused by a condensing lens in the direction of specular reflection and received by multiple photodetectors placed on the dot surface. The intensity distribution of the diffracted light obtained from this method allows us to determine the size of the grains in the network traces on the ink surface and measure the water content.

〔Example〕

In FIG. 1, 1 is a laser device, 2 is a laser beam,
3 is a collimator, 4 is a parallel laser beam, 5 is a roller,
6 is an ink surface, 7 is a normal line, 8 is an irradiation surface, 9 is a condensing lens, 10 is a plurality of light receiving elements, 1] is specularly reflected light, 12 is diffracted light, 13 is diffracted light and specularly reflected light The angle formed by 14 is A
/D converter, 15 is an arithmetic unit.

In the figure, a beam 2 emitted from a laser device 1 is converted into a parallel beam 4 with a diameter of about 3 to 2 Drrrm by a collimator 3. The parallel beam 4 is irradiated onto the ink surface 6 on the surface of the roller 5 (target roller shown in FIG. 4) at a certain angle θ with respect to the normal 7 of the irradiated surface 8. Then, on the plane including the parallel beam 4 and the normal line 7, and on the opposite side of the parallel beam 4, on a straight line having the same angle θ as the normal line 7, attach the condenser lens 9 on the same straight line and on the same line as the normal line 7. Multiple ring-shaped light receiving elements 10 placed at pointless positions are arranged to receive light.

In this case, the light 11 reflected by the smooth part of the ink surface 6, that is, the part without the ink trace, is specularly reflected light, so it is condensed to its focal point by the condensing lens 9, and is focused at the center of the multi-ring light-receiving element 10. The light is received at the

On the other hand, the light 12 diffracted by the particles of the net-like marks on the ink surface 6 similarly passes through the condenser lens 9 and reaches the light receiving element 10, but this diffracted light 12 forms a certain angle 13 with the specularly reflected light 11. (this angle is called a diffraction angle), so on the light receiving element 10 it reaches a position with a radius proportional to the size of the diffraction angle. This can be expressed as follows: S=f·ψ (1) S: Radius on the light receiving element f: Focal length ψ of the convex lens 9: Scattering angle 13.

Therefore, the intensity distribution of the diffracted light can be monitored from the strong threshold distribution of each ring excluding the center of the multi-ring light receiving element 10.

By the way, the size of the particles on the ink surface 6 and the light receiving element 1
The intensity distribution on 0 has the following relationship.

■(S)■2(Jl(X))2/X ・・・・・・・・・
・(2) ...Linear Bessel function This is shown in Figure 2.

As is clear from the figure, the distribution differs depending on the size of the particles of the network marks on the ink surface.

Note that the figure shows the case of one grain each with a radius of 10.50 μm and 100 μm; in reality, there are many grains with different sizes, but the output of the light receiving element 10 is the sum of them. Therefore, the total value indicates the average value of the grain size.

Therefore, the power of each ring of the light receiving element 10 is amplified.
By inputting the data to the arithmetic unit 15 through the A/D converter 14, analyzing and displaying the data, the size of the particles of the net-like marks on the ink surface can be determined, and the water content can be measured.

Figure 3 shows the results measured on the actual ink surface. The number of rings in the light-receiving element is (9), the innermost ring is 1 and the outermost ring is /1630, and the horizontal axis in FIG. 3 is the ring waste. The vertical axis in the figure is the output of each ring, that is, the optical force. In FIG. 3, (,) shows the case where the water content of the ink is small, and (b) shows the case where the water content is serious.

In Figure 3 (-), since the moisture content is small and the grains of the mesh marks on the surface are large, the output of the ring with a small radius is thick (becomes thick).
(b) is the opposite.

〔Effect of the invention〕

The ink moisture content measuring device according to the present invention includes a laser beam projection device that projects a parallel laser beam onto the ink surface of the roller surface, which is composed of a laser device and a collimator, and a laser beam projection device that projects a parallel laser beam onto the ink surface of the roller surface, and a laser beam projection device that is arranged in the direction of regular reflection of the projected light by the ink surface. A detector consisting of a condensing lens and a plurality of light-receiving elements placed on the focal plane of the condensing lens receives the intensity distribution of the diffracted light by the ink surface of the projected light, and a detector based on the output from the detector. Since the present invention is comprised of a calculator for calculating the ink moisture content, the following effects are obtained.

fil You can easily measure the ink moisture content,
And responsiveness is good.

(2) Therefore, it is possible to control the ink moisture content online, and it is possible to improve the performance of the printing press and save labor.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the configuration of an ink moisture content measuring device according to an embodiment of the present invention, Fig. 2 is a diagram showing the relationship between the particle size of the ink surface traces and scattered light, and Fig. 3 is a diagram showing the relationship between the ink moisture content measurement device and the scattered light by this device. The measurement results of the moisture content are shown, (a) the ink moisture content is low, (b)
indicates the case where the ink moisture content is high. FIG. 4 is a block diagram of an offset printing press, FIG. 5 is an explanatory diagram of a state in which filaments are produced, and FIG. 6 is a schematic diagram of the appearance of a mesh mark. 1...Laser device 3...Collimator 6...
Ink surface 9... Condensing lens 10... Light receiving element 15... Arithmetic unit agent

Claims (1)

[Claims] A laser beam projection device consisting of a laser device and a collimator projects parallel laser light onto the ink surface of the roller surface, a condenser lens disposed in the direction of specular reflection of the projected light by the ink surface, and a condenser lens arranged in the direction of specular reflection of the projected light by the ink surface a detector comprising a plurality of light-receiving elements placed on a focal plane and receiving the intensity distribution of the diffracted light by the ink surface of the projected light; and a calculator that calculates the ink moisture content based on the output from the detector. An ink moisture content measuring device comprising: